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Sample records for heavy ga-doped zno

  1. Effect of gallium concentrations on the morphologies, structural and optical properties of Ga-doped ZnO nanostructures.

    PubMed

    Algarni, H; El-Gomati, M M; Al-Assiri, M S

    2014-07-01

    The effect of gallium ion concentrations (0.5 and 2%) on the morphologies, structural and optical properties of Ga-doped ZnO nanostructures are presented. Ga-doped ZnO nanostructures were synthesized on silicon substrates by simple thermal evaporation process using metallic zinc and Ga powders in the presence of oxygen. Interestingly, it was observed that Ga-ions incorporation in ZnO nanomaterials play an important role on the growth kinetics and hence on the morphologies of as-grown Ga-doped ZnO nanostructures. It was seen that at low Ga-concentration, needle-shaped Ga-doped ZnO nanostructures are formed, presumably by subsequent stacking of hexagonal plates. However, when increasing the Ga-concentration, multipods of Ga-doped ZnO were grown. In addition to the morphologies, incorporating Ga-ions into ZnO also affect the room-temperature photoluminescence properties. Therefore, at lower Ga-ion concentration, an intense UV emission was observed while at high Ga-concentration a deep level emission was seen in the room-temperature photoluminescence spectra. This research demonstrates that by controlling the Ga-ion concentration the morphologies and optical properties of ZnO nanomaterials can be tailored.

  2. Effect of Ga-doping on the properties of ZnO nanowire

    SciTech Connect

    Ishiyama, Takeshi Nakane, Takaya Fujii, Tsutomu

    2015-02-27

    Arrays of single-crystal zinc oxide (ZnO) nanowires have been synthesized on silicon substrates by vapor-liquid-solid growth techniques. The effect of growth conditions including substrate temperature and Ar gas flow rate on growth properties of ZnO nanowire arrays were studied. Structural and optical characterization was performed using scanning electron microscopy (SEM) and photoluminescence (PL) spectroscopy. SEM images of the ZnO nanowire arrays grown at various Ar gas flow rates indicated that the alignment and structural features of ZnO nanowires were affected by the gas flow rate. The PL of the ZnO nanowire arrays exhibited strong ultraviolet (UV) emission at 380 nm and green emission around 510 nm. Moreover, the green emission reduced in Ga-doped sample.

  3. Demonstration of hyperbolic metamaterials at telecommunication wavelength using Ga-doped ZnO.

    PubMed

    Kalusniak, Sascha; Orphal, Laura; Sadofev, Sergey

    2015-12-14

    Hyperbolic metamaterials (HMMs) have attracted much attention because they allow for broadband enhancement of spontaneous emission and imaging below the diffraction limit. However, HMMs with traditional metals as metallic component are not suitable for applications in the infrared spectral range. Using Ga-doped ZnO, we demonstrate monolithic HMMs operating at infrared wavelengths. We identify the material's hyperbolic character by various optical measurements in combination with theoretical calculations. In particular, negative refraction of the extraordinary wave and propagation of light with wave vector values exceeding that of free-space are demonstrated in the entire telecommunication window. These findings reveal a considerable potential for creating novel functional elements at telecommunication wavelengths.

  4. Low Sheet Resistivity of Transparent Ga-Doped ZnO Film Grown by Atmospheric Spray Pyrolysis

    NASA Astrophysics Data System (ADS)

    Takemoto, Yujin; Oshima, Minoru; Yoshino, Kenji; Toyota, Kouji; Inaba, Koichiro; Haga, Ken-ichi; Tokudome, Koichi

    2011-08-01

    Ga-doped ZnO film on polyethylene terephthalate film was successfully grown at 150 °C by conventional atmospheric spray pyrolysis using diethylzinc-based solution. The samples had an average optical transmittance of more than 80% and were strongly a-axis orientated according to the result of optical transmittance and X-ray diffraction analyses, respectively. The n-type Ga-doped ZnO films had a low sheet resistivity of 250 Ω/square at an optimal Ga content of 1 at. % upon UV irradiation.

  5. CO sensing properties under UV radiation of Ga-doped ZnO nanopowders

    NASA Astrophysics Data System (ADS)

    Dhahri, R.; Hjiri, M.; Mir, L. El.; Bonavita, A.; Iannazzo, D.; Leonardi, S. G.; Neri, G.

    2015-11-01

    In this study, the effect of Ga-doping and UV radiation on CO sensing of ZnO nano-powders has been investigated. GZO nanoparticles with different Ga loadings were prepared using a modified sol-gel route and charaterized by means of trasmission electron microscopy (TEM), X-ray diffraction (XRD) and photoluminescence (PL) analysis. Electrical and CO-sensing tests were performed on resistive planar devices consisting of thick films of GZO deposited on interdigitated alumina substrates in both dark and illumination condition by exposing the samples to UV radiation (λ = 400 nm). The baseline resistance in dark decreases strongly with the increase of Ga loading. This effect is reinforced by using UV radiation at low temperature in samples containing up to 3 at.% of Ga, which suggests also an effect of the microstructure of GZO on UV light promoting mechanism. The combined effect of Ga doping and UV irradiation allowed to monitor CO in air at low concentration with high sensitivity and lower operating temperature than on unpromoted ZnO sensor.

  6. Fabrication and characterization of pristine and annealed Ga doped ZnO thin films using sputtering

    NASA Astrophysics Data System (ADS)

    Mishra, Abhisek; Mohapatra, Saswat; Gouda, Himanshu Sekhar; Singh, Udai P.

    2016-05-01

    ZnO is a wide-band gap, transparent, polar semiconductor with unparalleled optoelectronic, piezoelectric, thermal and transport properties, which make it the material of choice for a wide range of applications such as blue/UV optoelectronics, energy conversion, transparent electronics, spintronic, plasmonic and sensor devices. We report, three sets of Ga doped Zinc Oxide (GZO) were fabricated in different sputtering power (100 watt, 200 watt and 300 watt). Thereafter films were annealed in nitrogen ambient for 30 minutes at 400° C. From the optical absorption spectroscopy it was found that pristine films are showing a 75% transmittance in the visible region of light and it increases after the annealing. However, for 300 W grown sample opposite trend has been achieved for the post annealed sample. X-ray diffraction pattern of all the pristine and annealed films showed a preferable growth orientation at (002) phase. Some other weak peaks were also appeared in different angle which indicates that films are polycrystalline in nature. XRD data also reveals that crystallite size increases with sputtering power up to 200 W and thereafter it decreases with the deposition power. It also noted that the crystallite size of the annealed film increases with compare to the non annealed films. At room temperature an enhancement in electrical properties of Ga doped ZnO thin films was noted for the annealed ZnO films except for the film deposited at 300 watt. More significantly, it was found that annealed thin films showed the resistivity in the range of 10-3 ˜ 10-4 ohm-cm. Such a high optical transmittance and conducting zinc-oxide thin film can be used as a window layer in solar cell.

  7. Mid-infrared extraordinary transmission through Ga-doped ZnO films with 2D hole arrays

    NASA Astrophysics Data System (ADS)

    Cleary, Justin W.; Nader Esfahani, Nima; Vangala, Shiva; Guo, Junpeng; Hendrickson, Joshua R.; Leedy, Kevin D.; Look, David C.

    2014-03-01

    Extraordinary optical transmission (EOT), through highly conductive ZnO films with sub-wavelength hole arrays is investigated in the long-wavelength infrared regime. EOT is facilitated by the excitation of surface plasmon polaritons (SPPs) on Ga-Doped ZnO films and can be tuned utilizing the physical parameters such as film thickness, period, hole size, and hole shape, as well as doping of the film. Analytical and finite-difference time-domain calculations are completed for 1 micron thick films with square, circular, and triangular hole arrays demonstrating SPP coupling and EOT. The fundamental plasmonic modes are observed in each of these hole shapes at wavelengths that correspond to strong EOT peaks. Doping tunability for these structures is also observed. Ga-doped ZnO films are grown via pulsed laser deposition (PLD) on silicon with plasma frequencies in the near-infrared. The sub-wavelength 2D hole arrays are fabricated in the Ga-doped ZnO films via standard lithography and etching processes. This highly conductive ZnO EOT structure may prove useful in novel integrated components such as tunable biosensors or surface plasmon coupling mechanisms.

  8. A computational study on the experimentally observed sensitivity of Ga-doped ZnO nanocluster toward CO gas

    NASA Astrophysics Data System (ADS)

    Derakhshandeh, Maryam; Anaraki-Ardakani, Hossein

    2016-10-01

    Metal doped ZnO nanostructures have attracted extensive attention as chemical sensors for toxic gases. An experimental study has previously shown that Ga-doped ZnO nanostructures significantly show a higher electronic response than the undoped sample toward CO gas. Here, the electronic sensitivity of pristine and Ga-doped ZnO nanoclusters to CO gas is explored using density functional theory computations (at B3LYP, PBE, M06-2X, and ωB97XD levels). Our results reproduce and clarify the electrical behavior which has been observed experimentally from the ZnO nanoparticles after the exposure to CO gas. We showed that the calculated change of HOMO-LUMO gap may be a proper index for the change of electrical conductance which is measurable experimentally. It was found that, in contrast to the pristine ZnO nanocluster, the electronic properties of Ga-doped cluster are sharply sensitive to the presence of CO gas which is in good accordance with the results of the experimental study.

  9. Hot-electron energy relaxation time in Ga-doped ZnO films

    SciTech Connect

    Šermukšnis, E. Liberis, J.; Ramonas, M.; Matulionis, A.; Toporkov, M.; Liu, H. Y.; Avrutin, V.; Özgür, Ü.; Morkoç, H.

    2015-02-14

    Hot-electron energy relaxation time is deduced for Ga-doped ZnO epitaxial layers from pulsed hot-electron noise measurements at room temperature. The relaxation time increases from ∼0.17 ps to ∼1.8 ps when the electron density increases from 1.4 × 10{sup 17 }cm{sup −3} to 1.3 × 10{sup 20 }cm{sup −3}. A local minimum is resolved near an electron density of 1.4 × 10{sup 19 }cm{sup −3}. The longest energy relaxation time (1.8 ps), observed at the highest electron density, is in good agreement with the published values obtained by optical time-resolved luminescence and absorption experiments. Monte Carlo simulations provide a qualitative interpretation of our observations if hot-phonon accumulation is taken into account. The local minimum of the electron energy relaxation time is explained by the ultrafast plasmon-assisted decay of hot phonons in the vicinity of the plasmon–LO-phonon resonance.

  10. The electrical properties of low pressure chemical vapor deposition Ga doped ZnO thin films depending on chemical bonding configuration

    NASA Astrophysics Data System (ADS)

    Jung, Hanearl; Kim, Doyoung; Kim, Hyungjun

    2014-04-01

    The electrical and chemical properties of low pressure chemical vapor deposition (LP-CVD) Ga doped ZnO (ZnO:Ga) films were systematically investigated using Hall measurement and X-ray photoemission spectroscopy (XPS). Diethylzinc (DEZ) and O2 gas were used as precursor and reactant gas, respectively, and trimethyl gallium (TMGa) was used as a Ga doping source. Initially, the electrical properties of undoped LP-CVD ZnO films depending on the partial pressure of DEZ and O2 ratio were investigated using X-ray diffraction (XRD) by changing partial pressure of DEZ from 40 to 140 mTorr and that of O2 from 40 to 80 mTorr. The resistivity was reduced by Ga doping from 7.24 × 10-3 Ω cm for undoped ZnO to 2.05 × 10-3 Ω cm for Ga doped ZnO at the TMG pressure of 8 mTorr. The change of electric properties of Ga doped ZnO with varying the amount of Ga dopants was systematically discussed based on the structural crystallinity and chemical bonding configuration, analyzed by XRD and XPS, respectively.

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

    NASA Astrophysics Data System (ADS)

    Temizer, Namik Kemal

    Recently there is tremendous interest in Transparent conducting oxide (TCO) research due to the unlimited and exciting application areas. Current research is mostly focused on finding alternative low cost and sustainable materials in order to replace indium tin oxide (ITO), which caused serious concern due to the increasing cost of indium and chemical stability issues of ITO. The primary aim of this research is to develop alternative TCO materials with superior properties in order to increase the efficiency in optoelectronic applications, as well as to study the properties of these materials to fully characterize them. We have grown Al and Ga-doped ZnO films with an optimized composition under different deposition conditions in order to understand the effect of processing parameters on the film properties. We report a detailed investigation on the structure-property correlations in Ga and Al codoped ZnO films on c-sapphire substrates where the thin film microstructure varies from nanocrystalline to single crystal. We have achieved highly epitaxial films with very high optical transmittance (close to 90%) and low resistivity (˜110muO-cm) values. The films grown in an ambient oxygen partial pressure (PO2 ) of 50 mTorr and at growth temperatures from room temperature to 600°C showed semiconducting behavior, whereas samples grown at a Po2 of 1 mTorr showed metallic nature. The most striking feature is the occurrence of resistivity minima at relatively high temperatures around 110 K in films deposited at high temperatures. The structure-property correlations reveal that point defects play an important role in modifying the structural, optical, electrical and magnetic properties and such changes in physical properties are controlled predominantly by the defect content. To gain a better understanding of the conduction processes in doped ZnO thin films, we have studied the temperature variation of resistivity of some selected samples that showed some interesting behavior

  12. Large-scale preparation of porous ultrathin Ga-doped ZnO nanoneedles from 3D basic zinc carbonate superstructures.

    PubMed

    Du, Shangfeng; Liu, Haidi; Chen, Yunfa

    2009-02-25

    A facile procedure for large-scale preparation of porous ZnO 1D nanomaterials with good electrical conductivity has been demonstrated for the first time. Porous ultrathin Ga-doped ZnO nanoneedles can be prepared by calcining the precursor of ultrathin Ga-doped basic zinc carbonate (BZC) nanoneedles obtained from BZC 3D superstructures, which are synthesized by a simple chemical co-precipitation method at room temperature, without using any catalyst, template or surfactant. There is evidence that the growth mechanisms of the BZC 3D superstructures and nanoneedles are correlated with the concentrations of ammonium ions and ethanol in the synthesis solution. The as-prepared porous Ga-doped ZnO nanoneedles have a thickness of only a couple of nanometers, consisting of many fine nanoparticles in a few nanometers. Electrical conductivity measurements indicate that porous ultrathin ZnO nanoneedles have a volume resistivity similar to that of the spherical Ga-doped ZnO nanoparticles. The porous nanostructures and good electrical conductivity make the porous ultrathin ZnO 1D nanoneedles promising candidates for applications in electrochemical fields.

  13. Synthesis of nano-dimensional ZnO and Ga doped ZnO thin films by vapor phase transport and study as transparent conducting oxide.

    PubMed

    Ghosh, S; Saurav, M; Pandey, B; Srivastava, P

    2008-05-01

    We report synthesis of polycrystalline ZnO and Ga doped ZnO (ZnO:Ga) thin films (approximately 80 nm) on Si and quartz substrates in a non-vacuum muffle furnace, a simple and cost-effective route, without any catalyst/reactive carrier gases, at relatively low processing temperature of 550 degrees C. The crystalline phases of the films are identified by grazing angle X-ray diffraction (GAXRD). The growth of ZnO films is examined with scanning electron microscope (SEM) as a function of deposition time. An optical transmission of approximately 90% is observed for pure ZnO film having a resistivity of approximately 2.1 Omega-cm as measured by van der Pauw technique. Doping with Ga results in single phase ZnO:Ga films, retaining an optical transmission of about 80% and three orders of magnitude decrease in resistivity as compared to pure ZnO film. PMID:18572702

  14. ZnO nanowires array grown on Ga-doped ZnO single crystal for dye-sensitized solar cells

    PubMed Central

    Hu, Qichang; Li, Yafeng; Huang, Feng; Zhang, Zhaojun; Ding, Kai; Wei, Mingdeng; Lin, Zhang

    2015-01-01

    High quality ZnO nanowires arrays were homoepitaxial grown on Ga-doped ZnO single crystal (GZOSC), which have the advantages of high conductivity, high carrier mobility and high thermal stability. When it was employed as a photoanode in the DSSCs, the cell exhibited a 1.44% power-conversion efficiency under the illumination of one sun (AM 1.5G). The performance is superior to our ZnO nanowires/FTO based DSSCs under the same condition. This enhanced performance is mainly attributed to the perfect interface between the ZnO nanowires and the GZOSC substrate that contributes to lower carrier scattering and recombination rates compared with that grown on traditional FTO substrate. PMID:26099568

  15. CONDENSED MATTER: STRUCTURE, MECHANICAL AND THERMAL PROPERTIES: Structural and Electrical Properties of Single Crystalline Ga-Doped ZnO Thin Films Grown by Molecular Beam Epitaxy

    NASA Astrophysics Data System (ADS)

    Lu, Zhong-Lin; Zou, Wen-Qin; Xu, Ming-Xiang; Zhang, Feng-Ming; Du, You-Wei

    2009-11-01

    High-quality Ga-doped ZnO (ZnO:Ga) single crystalline films with various Ga concentrations are grown on a-plane sapphire substrates using molecular-beam epitaxy. The site configuration of doped Ga atoms is studied by means of x-ray absorption spectroscopy. It is found that nearly all Ga can substitute into ZnO lattice as electrically active donors, a generating high density of free carriers with about one electron per Ga dopant when the Ga concentration is no more than 2%. However, further increasing the Ga doping concentration leads to a decrease of the conductivity due to partial segregation of Ga atoms to the minor phase of the spinel ZnGa2O4 or other intermediate phase. It seems that the maximum solubility of Ga in the ZnO single crystalline film is about 2 at.% and the lowest resistivity can reach 1.92 × 10-4 Ω·cm at room temperature, close to the best value reported. In contrast to ZnO:Ga thin film with 1% or 2% Ga doping, the film with 4% Ga doping exhibits a metal semiconductor transition at 80 K. The scattering mechanism of conducting electrons in single crystalline ZnO:Ga thin film is discussed.

  16. Electronic structure of Al- and Ga-doped ZnO films studied by hard X-ray photoelectron spectroscopy

    SciTech Connect

    Gabás, M.; Ramos Barrado, José R.; Torelli, P.; Barrett, N. T.

    2014-01-01

    Al- and Ga-doped sputtered ZnO films (AZO, GZO) are semiconducting and metallic, respectively, despite the same electronic valence structure of the dopants. Using hard X-ray photoelectron spectroscopy we observe that both dopants induce a band in the electronic structure near the Fermi level, accompanied by a narrowing of the Zn 3d/O 2p gap in the valence band and, in the case of GZO, a substantial shift in the Zn 3d. Ga occupies substitutional sites, whereas Al dopants are in both substitutional and interstitial sites. The latter could induce O and Zn defects, which act as acceptors explaining the semiconducting character of AZO and the lack of variation in the optical gap. By contrast, mainly substitutional doping is consistent with the metallic-like behavior of GZO.

  17. Long-wavelength infrared surface plasmons on Ga-doped ZnO films excited via 2D hole arrays for extraordinary optical transmission

    NASA Astrophysics Data System (ADS)

    Cleary, Justin W.; Esfahani, Nima Nader; Vangala, Shivashankar; Guo, Junpeng; Hendrickson, Joshua R.; Leedy, Kevin D.; Thomson, Darren; Look, David C.

    2013-09-01

    Extraordinary optical transmission (EOT) through highly conductive ZnO films with sub-wavelength hole arrays is investigated in the long-wavelength infrared regime. EOT is facilitated by the excitation of surface plasmon polaritons (SPPs) and can be tuned utilizing the physical structure size such as period. Pulse laser deposited Ga-doped ZnO has been shown to have fluctuations in optical and electrical parameters based on fabrication techniques, providing a complimentary tuning means. The sub-wavelength 2D hole arrays are fabricated in the Ga-doped ZnO films via standard lithography and etching processes. Optical reflection measurements completed with a microscope coupled FTIR system contain absorption resonances that are in agreement with analytical theories for excitation of SPPs on 2D structures. EOT through Ga-doped ZnO is numerically demonstrated at wavelengths where SPPs are excited. This highly conductive ZnO EOT structure may prove useful in novel integrated components such as tunable biosensors or surface plasmon coupling mechanisms.

  18. SEMICONDUCTOR DEVICES: A Ga-doped ZnO transparent conduct layer for GaN-based LEDs

    NASA Astrophysics Data System (ADS)

    Zhen, Liu; Xiaofeng, Wang; Hua, Yang; Yao, Duan; Yiping, Zeng

    2010-09-01

    An 8 μm thick Ga-doped ZnO (GZO) film grown by metal-source vapor phase epitaxy was deposited on a GaN-based light-emitting diode (LED) to substitute for the conventional ITO as a transparent conduct layer (TCL). Electroluminescence spectra exhibited that the intensity value of LED emission with a GZO TCL is markedly improved by 23.6% as compared to an LED with an ITO TCL at 20 mA. In addition, the forward voltage of the LED with a GZO TCL at 20 mA is higher than that of the conventional LED. To investigate the reason for the increase of the forward voltage, X-ray photoelectron spectroscopy was performed to analyze the interface properties of the GZO/p-GaN heterojunction. The large valence band offset (2:24 ± 0:21 eV) resulting from the formation of Ga2O3 in the GZO/p-GaN interface was attributed to the increase of the forward voltage.

  19. Fabrication and resistive switching characteristics of high compact Ga-doped ZnO nanorod thin film devices

    NASA Astrophysics Data System (ADS)

    Yao, I.-Chuan; Lee, Dai-Ying; Tseng, Tseung-Yuen; Lin, Pang

    2012-04-01

    This study investigates the resistive switching behavior of Ga-doped ZnO (GZO) nanorod thin films with various Ga/Zn molar ratios. Vertically well-aligned and uniform GZO nanorod thin films were successfully grown on Au/Ti/SiO2/p-Si substrates using an aqueous solution method. X-ray diffraction (XRD) results indicate that GZO nanorods have [0001] highly preferred orientation. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations show the formation of highly ordered and dense nanorod thin films. These compact GZO nanorod thin films can be used to make resistive switching memory devices. Such memory devices can be reversibly switched between ON and OFF states, with a stable resistance ratio of ten times, narrow dispersion of ON and OFF voltages, and good endurance performance of over 100 cycles. The resistive switching mechanism in these devices is related to the formation and rupture of conducting filaments consisting of oxygen vacancies, occurring at interfaces between GZO nanorods (grain boundaries). Results show that the resulting compact GZO nanorod thin films have a high potential for resistive memory applications.

  20. Mechanical and transparent conductive properties of ZnO and Ga-doped ZnO films sputtered using electron-cyclotron-resonance plasma on polyethylene naphtalate substrates

    SciTech Connect

    Akazawa, Housei

    2014-03-15

    Transparent conductive ZnO and Ga-doped ZnO (GZO) films were deposited on polyethylene naphtalate (PEN) sheet substrates using electron cyclotron resonance plasma sputtering. Both ZnO and GZO films were highly adhesive to the PEN substrates without inserting an intermediate layer in the interface. When compared at the same thickness, the transparent conductive properties of GZO films on PEN substrates were only slightly inferior to those on glass substrates. However, the carrier concentration of ZnO films on PEN substrates was 1.5 times that of those on glass substrates, whereas their Hall mobility was only 60% at a thickness of 300 nm. The depth profile of elements measured by secondary ion mass spectroscopy revealed the diffusion of hydrocarbons out of the PEN substrate into the ZnO film. Hence, doped carbons may act as donors to enhance carrier concentration, and the intermixing of elements at the interface may deteriorate the crystallinity, resulting in the lower Hall mobility. When the ZnO films were thicker than 400 nm, cracks became prevalent because of the lattice mismatch strain between the film and the substrate, whereas GZO films were free of cracks. The authors investigated how rolling the films around a cylindrical pipe surface affected their conductive properties. Degraded conductivity occurred at a threshold pipe radius of 10 mm when tensile stress was applied to the film, but it occurred at a pipe radius of 5 mm when compressive stress was applied. These values are guidelines for bending actual devices fabricated on PEN substrates.

  1. Comparative studies of Al-doped ZnO and Ga-doped ZnO transparent conducting oxide thin films

    PubMed Central

    2012-01-01

    We have investigated the influences of aluminum and gallium dopants (0 to 2.0 mol%) on zinc oxide (ZnO) thin films regarding crystallization and electrical and optical properties for application in transparent conducting oxide devices. Al- and Ga-doped ZnO thin films were deposited on glass substrates (corning 1737) by sol–gel spin-coating process. As a starting material, AlCl3⋅6H2O, Ga(NO3)2, and Zn(CH3COO)2⋅2H2O were used. A lowest sheet resistance of 3.3 × 103 Ω/□ was obtained for the GZO thin film doped with 1.5 mol% of Ga after post-annealing at 650°C for 60 min in air. All the films showed more than 85% transparency in the visible region. We have studied the structural and microstructural properties as a function of Al and Ga concentrations through X-ray diffraction and scanning electron microscopy analysis. In addition, the optical bandgap and photoluminescence were estimated. PMID:23173885

  2. Structural, morphological, optical and compositional characterization of spray deposited Ga doped ZnO thin film for Dye-Sensitized Solar Cell application

    NASA Astrophysics Data System (ADS)

    Amala Rani, A.; Ernest, Suhashini

    2014-11-01

    Zinc Oxide and Gallium doped Zinc Oxide films have been deposited by the Spray Pyrolysis method onto preheated glass substrates using Zinc acetate and Gallium (III) acetyl acetonate as precursors for Zn and Ga ions, respectively. The effect of ZnO and Ga doping on the structural, morphological, optical and chemical properties of sprayed ZnO and Gallium doped ZnO thin films were investigated. XRD studies reveal that the films are crystalline with hexagonal (wurtzite) crystal structure. The average transparency in the visible range was around 75% for the thin film deposited using Gallium doping. X-ray Photoelectron Spectroscopy (XPS) was utilized to view the changes in the oxidation state of ZnO and Gallium doped ZnO thin films. The ZnO and Gallium doped ZnO thin film has been deposited above the Indium Tin Oxide (ITO) coated glass substrate. The efficiency of the obtained DSSC measured for 0.1 M ZnO thin film by sensitizing for 12 h was, ŋ = 2.5%. Similarly for Gallium doped Zinc Oxide, the efficiency ŋ is found to be 3.9%, 4.1% and 4.3% for every increase in doping of Gallium concentrations which is utilized for the application of Dye-Sensitized Solar Cell.

  3. Band alignment and photon extraction studies of Na-doped MgZnO/Ga-doped ZnO heterojunction for light-emitter applications

    NASA Astrophysics Data System (ADS)

    Pandey, Sushil Kumar; Awasthi, Vishnu; Sengar, Brajendra Singh; Garg, Vivek; Sharma, Pankaj; Kumar, Shailendra; Mukherjee, C.; Mukherjee, Shaibal

    2015-10-01

    Ultraviolet photoelectron spectroscopy is carried out to measure the energy discontinuity at the interface of p-type Na-doped MgZnO (NMZO)/n-type Ga-doped ZnO (GZO) heterojunction grown by dual ion beam sputtering. The offset values at valence band and conduction band of NMZO/GZO heterojunction are calculated to be 1.93 and -2.36 eV, respectively. The p-type conduction in NMZO film has been confirmed by Hall measurement and band structure. Moreover, the effect of Ar+ ion sputtering on the valence band onset values of NMZO and GZO thin films has been investigated. This asymmetric waveguide structure formed by the lower refractive index of GZO than that of NMZO indicates that easy extraction of photons generated in GZO through the NMZO layer into free space. The asymmetric waveguide structure has potential applications to produce ZnO-based light emitters with high extraction efficiency.

  4. Stress-induced anomalous shift of optical band gap in Ga-doped ZnO thin films: Experimental and first-principles study

    SciTech Connect

    Wang, Yaqin; Tang, Wu E-mail: lan.zhang@mail.xjtu.edu.cn; Liu, Jie; Zhang, Lan E-mail: lan.zhang@mail.xjtu.edu.cn

    2015-04-20

    In this work, highly c-axis oriented Ga-doped ZnO thin films have been deposited on glass substrates by RF magnetron sputtering under different sputtering times. The optical band gap is observed to shift linearly with the electron concentration and in-plane stress. The failure of fitting the shift of band gap as a function of electron concentration using the available theoretical models suggests the in-plane stress, instead of the electron concentration, be regarded as the dominant cause to this anomalous redshift of the optical band gap. And the mechanism of stress-dependent optical band gap is supported by the first-principles calculation based on density functional theory.

  5. Thermoelectric and Magneto-Thermoelectric Properties of Ga-DOPED ZnO Thin Films by RF Magnetron Sputtering

    NASA Astrophysics Data System (ADS)

    Liu, H.; Fang, L.; Wu, F.; Tian, D. X.; Li, W. J.; Lu, Y.; Kong, C. Y.; Zhang, S. F.

    2014-04-01

    Zn(1-x)GaxO thin films (x = 0.01, 0.03, 0.05, 0.07 named as GZO1, GZO2, GZO3, GZO4, respectively) were deposited on glass substrates by RF magnetron sputtering. The crystal structure, electrical, thermoelectric and magneto-thermoelectric properties of GZO films were investigated. It is found that all the GZO films are polycrystalline and preferentially oriented in the c-axis. The electrical resistivity of GZO films decreased first with increasing Ga doping content before it reached a minimum at x = 0.05, and then increased with further increasing Ga doping content. The magnetic fields (B) ranging from 0 to 1.5 T are perpendicularly applied to the films to study the magneto-thermoelectric properties. It is observed that the absolute values of Seebeck coefficients (|S|) of GZO1, GZO2, GZO3 show marked variation with magnetic field and obtain the maximum value at B = 0.5 T. Whereas the |S| value of GZO4 fluctuates slightly with magnetic field and reaches its peak at B = 1.0 T. The magneto-thermoelectric properties are analyzed and we propose that this behavior is mainly attributed to the effect of magnetic field on the electron transport.

  6. Optical, electrical and mechanical properties of Ga-doped ZnO thin films under different sputtering powers

    NASA Astrophysics Data System (ADS)

    Chang, Sheng Hsiung; Cheng, Hsin-Ming; Tien, Chuen-Lin; Lin, Shih-Chin; Chuang, Kie-Pin

    2014-12-01

    We present the optical, electrical and mechanical properties of Ga-doped zinc oxide (GZO) thin films prepared by radio-frequency (RF) magnetron sputtering at room temperature under different RF powers (80-180 W). The thickness, electron concentration, and electron mobility of the GZO thin film were determined by fitting the visible-to-near-infrared transmittance spectrum of GZO film/glass using the transfer matrix method. The bending force per unit width was measured by a home-made Twyman-Green interferometer with the fast Fourier transform method. The obtained results show that the optical, electrical and mechanical properties of GZO thin film are subject to the RF power. At an RF power of 140 W, the local minimum of bending force per unit width corresponds to the highest electron mobility in GZO thin film. This study demonstrates that the optical, electrical and mechanical properties of GZO thin film can be fully resolved by non-contact optical methods.

  7. Band alignment and photon extraction studies of Na-doped MgZnO/Ga-doped ZnO heterojunction for light-emitter applications

    SciTech Connect

    Pandey, Sushil Kumar; Awasthi, Vishnu; Sengar, Brajendra Singh; Garg, Vivek; Sharma, Pankaj; Mukherjee, Shaibal; Kumar, Shailendra; Mukherjee, C.

    2015-10-28

    Ultraviolet photoelectron spectroscopy is carried out to measure the energy discontinuity at the interface of p-type Na-doped MgZnO (NMZO)/n-type Ga-doped ZnO (GZO) heterojunction grown by dual ion beam sputtering. The offset values at valence band and conduction band of NMZO/GZO heterojunction are calculated to be 1.93 and −2.36 eV, respectively. The p-type conduction in NMZO film has been confirmed by Hall measurement and band structure. Moreover, the effect of Ar{sup +} ion sputtering on the valence band onset values of NMZO and GZO thin films has been investigated. This asymmetric waveguide structure formed by the lower refractive index of GZO than that of NMZO indicates that easy extraction of photons generated in GZO through the NMZO layer into free space. The asymmetric waveguide structure has potential applications to produce ZnO-based light emitters with high extraction efficiency.

  8. Growth Behavior of Ga-Doped ZnO Thin Films Deposited on Au/SiN/Si(001) Substrates by Radio Frequency Magnetron Sputtering

    NASA Astrophysics Data System (ADS)

    Seo, Seon Hee; Kang, Hyon Chol

    2013-11-01

    This paper reports the growth behavior of Ga-doped ZnO (ZnO:Ga) thin films deposited on Au/SiN/Si(001) substrates by radio-frequency magnetron sputtering. The microstructures of the overgrown ZnO:Ga thin films were investigated by performing X-ray diffraction, scanning electron microcopy, and transmission electron microscopy analyses. It was confirmed that the growth process proceeds through three stages. In the first stage, nano-scale ZnO:Ga islands were grown on the SiN layer, while a fairly continuous flat structure was formed on the Au nanoparticles (NPs). In the second stage of the growth process, ZnO:Ga domains with different growth orientations, depending strongly on the crystalline planes of the host Au NPs, were nucleated. These domains then grew at different rates, resulting in a change in the morphology from the initial shape reflecting that of the Au NPs to a sunflower-type shape. In the final stage, columnar growth with a preferred (0002) orientation along the surface normal direction became dominant.

  9. The effects of dopant concentration and deposition temperature on the structural, optical and electrical properties of Ga-doped ZnO thin films

    NASA Astrophysics Data System (ADS)

    Mahdhi, H.; Ben Ayadi, Z.; Alaya, S.; Gauffier, J. L.; Djessas, K.

    2014-08-01

    In the present work, we have deposited Ga-doped ZnO (GZO) thin films by magnetron sputtering technique using nanocrystalline particles elaborated by sol-gel method as a target material. The gallium doping concentration was varied from 1.0 to 5.0 at.%. The effect of the deposition temperature and the dopant concentration, on the physical properties of the GZO thin films was analyzed. The as-deposited films with a thickness of about 300 nm were polycrystalline with a hexagonal wurtzite structure and preferentially oriented in the (0 0 2) crystallographic direction. The crystallite size ranged from 25 to 32 nm, depending on the deposition temperature and Ga at.%. A minimum electrical resistivity value of 2.2 × 10-3 Ω cm and a maximum mobility of 16.42 cm2/V s were obtained under the optimal deposition conditions. The optical transmittance measurements show that all films are highly transparent in the visible wavelength region with an average transmittance of about 90%.

  10. Effects of oxygen plasma post-treatment on the structural, electrical and optical properties of Ga-doped ZnO films

    NASA Astrophysics Data System (ADS)

    Lee, Eunji; Kim, Sungik; Heo, Sujin; Lee, Jewon

    2015-11-01

    The effects of O2 plasma post-treatment on the electrical behavior of Ga-doped ZnO (GZO) films were characterized. GZO films were spin-coated onto glass and post-treated in an O2 plasma at a 0- to 100-W radio-frequency (RF) power and a 0- to 60-s process times in a capacitively-coupled plasma system. Atomic force microscopy, X-ray diffraction, Hall, UV-Vis spectroscopy, photoluminescence, and photocurrent measurements were used to study the influence of the O2 plasma post-treatment on the surface morphological, electrical, and optical properties of the GZO films. With increasing RF power during the O2 plasma post-treatment, the electrical properties of the GZO films improved significantly. The carrier concentration of the GZO films increased by a factor of approximately 52 from 5.89 × 1017 to 3.08 × 1019 cm -3 for a 30-s O2 plasma exposure at 100-W RF power. The electrical improvement was attributed to the GZO films' high crystallinity, caused by the O2 plasma post-treatment reducing the number of oxygen defects. The plasma treatment had little effect on the transmittance of the GZO films. The optical band gap of the film increased with increasing RF power. An enhanced UV photocurrent was obtained for the GZO film after a 30-s O2 plasma post-treatment at a 100-W RF power, and the recovery was slow.

  11. Optimization of process parameters for the electrical properties in Ga-doped ZnO thin films prepared by r.f. magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Zhu, D. L.; Wang, Q.; Han, S.; Cao, P. J.; Liu, W. J.; Jia, F.; Zeng, Y. X.; Ma, X. C.; Lu, Y. M.

    2014-04-01

    Ga-doped ZnO (GZO) transparent conductive thin films have been deposited on quartz substrates by r.f. magnetron sputtering. The optimization of four process parameters (i.e., vacuum annealing temperature, r.f. power, sputtering pressure, and Ar flow rate) based on Taguchi method has been systematically studied in order to obtain the minimum resistivity. Compared to the optimal parameter set selected from orthogonal array by Taguchi method, the optimal prediction design can receive an improvement of 22.3% in electrical resistivity, and the corresponding resistivity is 8.08 × 10-4 Ω cm. The analysis of variance shows that vacuum annealing temperature is the most significant influencing parameter on the electrical properties in GZO films. X-ray photoelectron spectroscopy and photoluminescence results exhibit that the enhancement in electrical conductivity after vacuum annealing is ascribed to the variation of the chemical states of oxygen in GZO films. With the increase in annealing temperature, the content of absorbed oxygen and interstitial oxygen as acceptors will decrease.

  12. Degradation of transparent conductive properties of undoped ZnO and Ga-doped ZnO films left in atmospheric ambient for several years and trials to recover initial conductance

    SciTech Connect

    Akazawa, Housei

    2014-03-15

    This study evaluated the long-term stability of the transparent conductive properties of undoped ZnO and Ga-doped ZnO (GZO) films that had been left in an atmospheric ambient environment for 5 to 6 yr. When ZnO films are stored in a clean room with a controlled temperature and humidity of 23 °C and 45%, respectively, throughout the year, the increases in sheet resistance are less than 5% of their initial value. The ZnO films stored in a non-air-conditioned laboratory room, whose temperature varies between 5 and 35 °C and humidity varies between 30% and 70% per year, suffer from increases in the sheet resistance by almost 13%, which is associated with a slight rise in the near-infrared transmittance level. Postannealing of these degraded ZnO films at 150–200 °C recovers the initial conductance by removing the H{sub 2}O molecules that have penetrated the film. One hour of irradiation with electron cyclotron resonance Ar plasma effectively restores the conductive surfaces while maintaining a temperature below 70 °C. The GZO films containing a few weight percent of Ga{sub 2}O{sub 3} are stable even when stored in a non-air-conditioned laboratory room, with changes in the sheet resistance of less than 3%. The GZO films with a Ga{sub 2}O{sub 3} content larger than 10 wt. %, however, exhibit serious degradation probably due to the strong affinity of segregated Ga{sub 2}O{sub 3} domains with H{sub 2}O vapor molecules. Neither postannealing nor Ar plasma irradiation can recover the initial sheet resistance of these GZO films.

  13. Effect of RF power on the optical, electrical, mechanical and structural properties of sputtering Ga-doped ZnO thin films

    NASA Astrophysics Data System (ADS)

    Tien, Chuen-Lin; Yu, Kuo-Chang; Tsai, Tsung-Yo; Liu, Ming-Chung

    2015-11-01

    We present the influences of radio-frequency (RF) power on the optical, electrical, mechanical, and structural properties of Ga-doped zinc oxide (GZO) thin films by RF magnetron sputtering at room temperature. GZO thin films were grown on unheated glass and silicon substrates using radio-frequency (RF) magnetron sputtering method with different RF powers (from 60 W to 160 W). The optical properties of the GZO thin film were determined by a UV-vis spectrophotometer. The residual stress in GZO films were measured by a home-made Twyman-Green interferometer with the fast Fourier transform (FFT) method. The surface roughness of GZO films were measured by a microscopic interferometry. The microstructure, composition and crystal orientation of the GZO films were determined by scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). This paper revealed that the optical, electrical, mechanical, and structural properties of GZO thin film are subject to the RF power. For the optical spectrum measurement, an average optical transmittance in the visible region of the spectra of 85% was obtained. For the characteristic measurements, all the GZO thin films deposited by RF magnetron sputtering have compressive stress at different RF powers. A minimum residual stress of 0.24 GPa is found at the RF power of 140 W. A four-point probe method was used to measure the resistivity of the GZO thin films with different powers, the results indicate that the resistivity increases with increasing of RF power. In addition, the root-mean-square (RMS) surface roughness of GZO thin films slightly increases as the RF power is increasing. We have also compared the results with the relevant literatures.

  14. Growth characteristics and properties of Ga-doped ZnO (GZO) thin films grown by thermal and plasma-enhanced atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Nam, Taewook; Lee, Chang Wan; Kim, Hyun Jae; Kim, Hyungjun

    2014-03-01

    The growth characteristics and electrical and optical properties of gallium-doped ZnO (GZO) grown by thermal atomic layer deposition (Th-ALD) and plasma-enhanced atomic layer deposition (PE-ALD) were investigated as a function of key growth parameters including the growth temperature. While GZO films are generally deposited at high growth temperatures above 300 °C, room temperature deposition is possible using PE-ALD. The chemical properties of the films were analyzed by X-ray photoelectron spectroscopy and their electrical properties including the carrier concentration, mobility, and resistivity were investigated by Hall measurements. The lowest resistivity of 1.49 × 10-3 Ω cm was obtained for the Th-ALD GZO film grown at 300 °C. The transmittance was enhanced to over 85% in the visible light range when Ga was doped on a ZnO film. In addition, a GZO bottom-gated thin film transistor (TFT) was fabricated and exhibited good electrical properties.

  15. Growth of Cu{sub 2}O on Ga-doped ZnO and their interface energy alignment for thin film solar cells

    SciTech Connect

    Wong, L. M.; Chiam, S. Y.; Wang, S. J.; Pan, J. S.; Huang, J. Q.; Chim, W. K.

    2010-08-15

    Cu{sub 2}O thin films are deposited by direct current reactive magnetron sputtering on borofloat glass and indium tin oxide (ITO) coated glass at room temperature. The effect of oxygen partial pressure on the structures and properties of Cu{sub 2}O thin films are investigated. We show that oxygen partial pressure is a crucial parameter in achieving pure phases of CuO and Cu{sub 2}O. Based on this finding, we fabricate heterojunctions of p-type Cu{sub 2}O with n-type gallium doped ZnO (GZO) on ITO coated glass substrates by pulsed laser deposition for GZO thin films. The energy band alignment for thin films of Cu{sub 2}O/GZO on ITO glass is characterized using high-resolution x-ray photoelectron spectroscopy. The energy band alignment for the Cu{sub 2}O/GZO heterojunctions is determined to be type II with a valence band offset of 2.82 eV and shows negligible effects of variation with gallium doping. The higher conduction band of the Cu{sub 2}O relative to that of GZO in the obtained band alignment shows that the heterojunctions are suitable for solar cell application based on energy levels consideration.

  16. Growth of Cu2O on Ga-doped ZnO and their interface energy alignment for thin film solar cells

    NASA Astrophysics Data System (ADS)

    Wong, L. M.; Chiam, S. Y.; Huang, J. Q.; Wang, S. J.; Pan, J. S.; Chim, W. K.

    2010-08-01

    Cu2O thin films are deposited by direct current reactive magnetron sputtering on borofloat glass and indium tin oxide (ITO) coated glass at room temperature. The effect of oxygen partial pressure on the structures and properties of Cu2O thin films are investigated. We show that oxygen partial pressure is a crucial parameter in achieving pure phases of CuO and Cu2O. Based on this finding, we fabricate heterojunctions of p-type Cu2O with n-type gallium doped ZnO (GZO) on ITO coated glass substrates by pulsed laser deposition for GZO thin films. The energy band alignment for thin films of Cu2O/GZO on ITO glass is characterized using high-resolution x-ray photoelectron spectroscopy. The energy band alignment for the Cu2O/GZO heterojunctions is determined to be type II with a valence band offset of 2.82 eV and shows negligible effects of variation with gallium doping. The higher conduction band of the Cu2O relative to that of GZO in the obtained band alignment shows that the heterojunctions are suitable for solar cell application based on energy levels consideration.

  17. Effect of a ga-doped ZnO thin film with a ZTO buffer layer fabricated by using pulsed DC magnetron sputter for dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Song, Sang-Woo; Lee, Kyung-Ju; Roh, Ji-Hyung; Park, On-Jeon; Kim, Hwan-Sun; Moon, Byung-Moo; Ji, Min-Woo

    2014-08-01

    The electrical property of a Ga-doped ZnO(GZO) thin film is well known to be similar that of commercialized fluorine-doped tin oxide(FTO). However GZO is limited for use at high process temperatures for solar cells because of its unstable resistivity at temperatures above 300 °C. A GZO thin film compared to zinc tin oxide(ZTO)-GZO multilayer can be used at high process temperatures. A GZO thin film was deposited on glass by using pulsed DC magnetron sputter. Then, a ZTO buffer layer was deposited on the GZO surface. During the deposition, the working pressure was 5 mTorr (Z-1 glass) and 1 mTorr (Z-2 glass). Dye-sensitized solar cells (DSSCs) were fabricated using Z-1, Z-2 and commercialized FTO glasses. Z-2 showed a conversion efficiency of 4.265%, which was enhanced by 0.399% compared to that of the DSSCs using FTO(3.784%). The conversion efficiency for Z-1 (3.889%) was a little higher than that of FTO. Thus, the ZTO-GZO electrode showed better characteristics than those obtained using the FTO electrode, which can be attributed to the reduced charge recombination and series resistance.

  18. Effects of Al, Ga-DOPING on Transparent Conducting Properties of Amorphous ZnO-SnO2 Films

    NASA Astrophysics Data System (ADS)

    Moriga, Toshihiro; Nishimura, Yusuke; Suketa, Hiroshi; Murai, Kei-Ichiro; Nogami, Kazuhiro; Tominaga, Kikuo; Nakabayashi, Ichiro

    ZnOSnO2 thin films were deposited on glass substrates (Corning#1737) by DC magnetron sputtering. In this works, we examined a doping effect on a ZnO target on transparent conducting properties. ZnO:Al(4wt%), and ZnO:Ga(6wt%) targets were used for a dopant-free ZnO target. Substrate temperature was held at 250°C. The current ratio δ was defined as IZn/IZ+ISn (ZnO target current divided by the sum of ZnO and SnO2 target currents). Compositions of as-deposited films were changed with the current ratio δ. In the ZnO-SnO2 system, amorphous transparent films appeared over the range of 0.33≤δ≤0.73. On the other hand, in the ZnO:Al(4wt%)-SnO2 and ZnO:Ga(6wt%)-SnO2 systems, they appeared over the range of 0.20≤δ≤0.80 and 0.33≤δ≤0.80, ≤δ≤ respectively. The minimum resistivity of amorphous films was about 3.0×10-2 Ωcm for all the systems. Al, Ga doping effect on film resistivity was not clear very much. But optical transparencies were 80-90% in visible region, 10% higher than those of ZnO-SnO2 system at average. Optical band gap for the films with the same current ratio δ also was enhanced by the Al, Ga doping.

  19. Magnetic properties of Ga doped cobalt ferrite: Compton scattering study

    NASA Astrophysics Data System (ADS)

    Sharma, Arvind; Sahariya, Jagrati; Mund, H. S.; Itou, M.; Sakurai, Y.; Ahuja, B. L.

    2014-04-01

    We present the spin momentum density of Ga doped CoFe2O4 at 100 K using magnetic Compton scattering. The measurement has been performed using circularly polarized synchrotron radiations of 182.65 keV at SPring8, Japan. The experimental profile is decomposed into its constituent profile to determine the spin moment at individual sites. Co atom has the maximum contribution (about 58%) in the total spin moment of the doped CoFe2O4.

  20. Transparent conductive and near-infrared reflective Ga-doped ZnO/Cu bilayer films grown at room temperature

    SciTech Connect

    Lu, J. G.; Bie, X.; Wang, Y. P.; Gong, L.; Ye, Z. Z.

    2011-05-15

    Bilayer films consisting of Ga-doped ZnO (GZO) and Cu layers were grown at room temperature by magnetron sputtering. The structural, electrical, and optical properties of GZO/Cu bilayer films were investigated in detail. The crystallinity and transparent-conductive properties of the films were correlated with the Cu layer thickness. The GZO/Cu bilayer film with the Cu layer thickness of 7.8 nm exhibited a low resistivity of 7.6x10{sup -5} {Omega} cm and an average visible transmittance of 74%. The reflectance was up to 65% in the near-infrared region for this film. The transparent conductive and near-infrared reflective GZO/Cu bilayer films could be readily deposited at room temperature. The GZO/Cu bilayer films were thermally stable when annealed at temperatures as high as 500 deg. C.

  1. Swift heavy ion irradiation of ZnO nanoparticles embedded in silica: Radiation-induced deoxidation and shape elongation

    SciTech Connect

    Amekura, H.; Tsuya, D.; Mitsuishi, K.; Nakayama, Y.; Okubo, N.; Ishikawa, N.; Singh, U. B.; Khan, S. A.; Avasthi, D. K.; Mohapatra, S.

    2013-11-11

    ZnO nanoparticles (NPs) embedded in amorphous SiO{sub 2} were irradiated with 200 MeV Xe{sup 14+} swift heavy ions (SHIs) to a fluence of 5.0 × 10{sup 13} ions/cm{sup 2}. Optical linear dichroism was induced in the samples by the irradiation, indicating shape transformation of the NPs from spheres to anisotropic ones. Transmission electron microscopy observations revealed that some NPs were elongated to prolate shapes; the elongated NPs consisted not of ZnO but of Zn metal. The SHI irradiation induced deoxidation of small ZnO NPs and successive shape elongation of the deoxidized metal NPs.

  2. Ga doping to significantly improve the performance of all-electrochemically fabricated Cu2O-ZnO nanowire solar cells.

    PubMed

    Xie, Jiale; Guo, Chunxian; Li, Chang Ming

    2013-10-14

    Cu2O-ZnO nanowire solar cells have the advantages of light weight and high stability while possessing a large active material interface for potentially high power conversion efficiencies. In particular, electrochemically fabricated devices have attracted increasing attention due to their low-cost and simple fabrication process. However, most of them are "partially" electrochemically fabricated by vacuum deposition onto a preexisting ZnO layer. There are a few examples made via all-electrochemical deposition, but the power conversion efficiency (PCE) is too low (0.13%) for practical applications. Herein we use an all-electrochemical approach to directly deposit ZnO NWs onto FTO followed by electrochemical doping with Ga to produce a heterojunction solar cell. The Ga doping greatly improves light utilization while significantly suppressing charge recombination. A 2.5% molar ratio of Ga to ZnO delivers the best performance with a short circuit current density (Jsc) of 3.24 mA cm(-2) and a PCE of 0.25%, which is significantly higher than in the absence of Ga doping. Moreover, the use of electrochemically deposited ZnO powder-buffered Cu2O from a mixed Cu(2+)-ZnO powder solution and oxygen plasma treatment could reduce the density of defect sites in the heterojunction interface to further increase Jsc and PCE to 4.86 mA cm(-2) and 0.34%, respectively, resulting in the highest power conversion efficiency among all-electrochemically fabricated Cu2O-ZnO NW solar cells. This approach offers great potential for a low-cost solution-based process to mass-manufacture high-performance Cu2O-ZnO NW solar cells. PMID:23945632

  3. Structural and optical properties of Ga-doped CdO nanocrystalline thin films

    NASA Astrophysics Data System (ADS)

    Thambidurai, M.; Muthukumarasamy, N.; Ranjitha, A.; Velauthapillai, Dhayalan

    2015-10-01

    In the present work, a systematic study has been carried out to understand the effect of gallium doping on the various properties of the CdO nanocrystalline thin films. Ga-doped CdO nanocrystalline thin films with different gallium concentrations (0.01 M, 0.03 M, 0.05 M, 0.07 M and 0.09 M) have been synthesized by sol-gel method. The X-ray diffraction (XRD) patterns show that the CdO and Ga-doped CdO films exhibit cubic structure. The chemical composition of the Ga-doped CdO films was studied using X-ray photoelectron spectroscopy (XPS). XPS results clearly showed the existence of Ga as a doping element in the CdO crystal lattice. Optical absorption spectra of Ga-doped CdO films shows that absorption edge is slightly shifted toward longer wavelength side (red shift) when compared to that of CdO. The optical band gap of CdO film was found to decrease with increasing Ga-doping concentration.

  4. Enhanced Thermoelectric Properties of Cu2ZnSnSe4 with Ga-doping

    DOE PAGESBeta

    Wei, Kaya; Beauchemin, Laura; Wang, Hsin; Porter, Wallace D.; Martin, Joshua; Nolas, George S.

    2015-08-10

    Gallium doped Cu2ZnSnSe4 quaternary chalcogenides with and without excess Cu were synthesized by elemental reaction and densified using hot pressing in order to investigate their high temperature thermoelectric properties. The resistivity, , and Seebeck coefficient, S, for these materials decrease with increased Ga-doping while both mobility and effective mass increase with Ga doping. The power factor (S2/ρ) therefore increases with Ga-doping. The highest thermoelectric figure of merit (ZT = 0.39 at 700 K) was obtained for the composition that had the lowest thermal conductivity. Our results suggest an approach to achieving optimized thermoelectric properties and are part of the continuingmore » effort to explore different quaternary chalcogenide compositions and structure types, as this class of materials continues to be of interest for thermoelectrics applications.« less

  5. Write-once memory effects observed in Ga-doped ZnO/organic semiconductor/MoO3/Au structures

    NASA Astrophysics Data System (ADS)

    Hasegawa, Junya; Nagase, Takashi; Kobayashi, Takashi; Naito, Hiroyoshi

    2016-03-01

    Electrical switching phenomena in a device configuration of inverted organic light-emitting diodes have been observed. The device structure was Ga-doped ZnO (GZO)/N,N‧-dicarbazolyl-3,5-benzene (m-CP)/MoO3 (10 nm)/Au (50 nm) fabricated by solution coating. The devices are write-once-read-many-times (WORM) memory devices with low switching voltage (<3 V) and long retention time (>700 h). Equivalent circuits in OFF and ON states are determined from the Cole-Cole plots measured by impedance spectroscopy. The switching phenomena and nonvolatile memory behavior are attributable to the formation conductive Au filaments in the m-CP layer of the ON state.

  6. Highly transparent low resistance Ga doped ZnO/Cu grid double layers prepared at room temperature

    NASA Astrophysics Data System (ADS)

    Jang, Cholho; Zhizhen, Ye; Jianguo, Lü

    2015-12-01

    Ga doped ZnO (GZO)/Cu grid double layer structures were prepared at room temperature (RT). We have studied the electrical and optical characteristics of the GZO/Cu grid double layer as a function of the Cu grid spacing distance. The optical transmittance and sheet resistance of the GZO/Cu grid double layer are higher than that of the GZO/Cu film double layer regardless of the Cu grid spacing distance and increase as the Cu grid spacing distance increases. The calculated values for the transmittance and sheet resistance of the GZO/Cu grid double layer well follow the trend of the experimentally observed transmittance and sheet resistance ones. For the GZO/Cu grid double layer with a Cu grid spacing distance of 1 mm, the highest figure of merit (ΦTC = 6.19 × 10-3 Ω-1) was obtained. In this case, the transmittance, resistivity and filling factor (FF) of the GZO/Cu grid double layer are 83.74%, 1.10 × 10-4 Ω·cm and 0.173, respectively. Project supported by the Key Project of the National Natural Science Foundation of China (No. 91333203), the Program for Innovative Research Team in University of Ministry of Education of China (No. IRT13037), the National Natural Science Foundation of China (No. 51172204), and the Zhejiang Provincial Department of Science and Technology of China (No. 2010R50020).

  7. Excellent low-field magnetoresistance effect in Ga-doped MnZn ferrites

    SciTech Connect

    Kim, Hyo-Jin; Yoo, Sang-Im

    2014-12-15

    An excellent low field magnetoresistance (LFMR) property was achieved from the Ga-doped (Mn{sub 0.8}Zn{sub 0.2})Fe{sub 2}O{sub 4} (MnZn) ferrites at room temperature (RT). For this study, undoped and Ga-doped MnZn ferrites with the nominal compositions of (Mn{sub 0.8}Zn{sub 0.2}){sub 1−x}Ga{sub x}Fe{sub 2}O{sub 4} (x = 0 ∼ 0.1) were prepared by the conventional solid state reaction at 1400°C for 2 h in air. From the magneto-transport measurements, Ga-doped MnZn ferrites were found to have not only much lower resistivity values but also greatly improved LFMR ratios in comparison with undoped sample. The highest maximum LFMR ratio of 2.5% at 290 K in 0.5 kOe was achievable from 2 mol% Ga-doped MnZn ferrite. This large LFMR effect is attributable to an increase in spin electrons by Ga{sup 3+} ion substitution for the (Mn, Zn){sup 2+} site.

  8. Low-temperature processed Ga-doped ZnO coatings from colloidal inks.

    PubMed

    Della Gaspera, Enrico; Bersani, Marco; Cittadini, Michela; Guglielmi, Massimo; Pagani, Diego; Noriega, Rodrigo; Mehra, Saahil; Salleo, Alberto; Martucci, Alessandro

    2013-03-01

    We present a new colloidal synthesis of gallium-doped zinc oxide nanocrystals that are transparent in the visible and absorb in the near-infrared. Thermal decomposition of zinc stearate and gallium nitrate after hot injection of the precursors in a mixture of organic amines leads to nanocrystals with tunable properties according to gallium amount. Substitutional Ga(3+) ions trigger a plasmonic resonance in the infrared region resulting from an increase in the free electrons concentration. These nanocrystals can be deposited by spin coating, drop casting, and spray coating resulting in homogeneous and high-quality thin films. The optical transmission of the Ga-ZnO nanoparticle assemblies in the visible is greater than 90%, and at the same time, the near-infrared absorption of the nanocrystals is maintained in the films as well. Several strategies to improve the films electrical and optical properties have been presented, such as UV treatments to remove the organic compounds responsible for the observed interparticle resistance and reducing atmosphere treatments on both colloidal solutions and thin films to increase the free carriers concentration, enhancing electrical conductivity and infrared absorption. The electrical resistance of the nanoparticle assemblies is about 30 kΩ/sq for the as-deposited, UV-exposed films, and it drops down to 300 Ω/sq after annealing in forming gas at 450 °C, comparable with state of the art tin-doped indium oxide coatings deposited from nanocrystal inks. PMID:23394063

  9. Enhanced Thermoelectric Properties of Cu2ZnSnSe4 with Ga-doping

    SciTech Connect

    Wei, Kaya; Beauchemin, Laura; Wang, Hsin; Porter, Wallace D.; Martin, Joshua; Nolas, George S.

    2015-08-10

    Gallium doped Cu2ZnSnSe4 quaternary chalcogenides with and without excess Cu were synthesized by elemental reaction and densified using hot pressing in order to investigate their high temperature thermoelectric properties. The resistivity, , and Seebeck coefficient, S, for these materials decrease with increased Ga-doping while both mobility and effective mass increase with Ga doping. The power factor (S2/ρ) therefore increases with Ga-doping. The highest thermoelectric figure of merit (ZT = 0.39 at 700 K) was obtained for the composition that had the lowest thermal conductivity. Our results suggest an approach to achieving optimized thermoelectric properties and are part of the continuing effort to explore different quaternary chalcogenide compositions and structure types, as this class of materials continues to be of interest for thermoelectrics applications.

  10. Annealing-induced interfacial reactions and the effects on the electrical properties of Ga doped ZnO/CuxS contacts to p-GaN

    NASA Astrophysics Data System (ADS)

    Gu, Wen; Wu, Xingyang; Song, Peng; Zhang, Jianhua

    2015-03-01

    Ga-doped ZnO (GZO) contacts to p-GaN were investigated by using CuxS interlayers under different annealing temperatures. It is shown that the GZO/CuxS contacts annealed at 300 and 400 °C for 3 min in air exhibited non-ohmic characteristics. However, annealing the contacts at 500 and 600 °C in air resulted in linear current-voltage characteristics. The lowest specific contact resistivity of 1.66 × 10-2 Ω cm2 was obtained for the contact annealed at 500 °C. To account for the formation mechanism of the ohmic contact, AES and XPS were used to analyze the interfacial properties of the GZO/CuxS/p-GaN and CuxS/p-GaN interfaces, respectively. The possible reasons were discussed in detail, suggesting that the interfacial reactions and atomic diffusions are thought to be responsible for forming such a low contact resistance.

  11. Adsorption of sugars on Al- and Ga-doped boron nitride surfaces: A computational study

    NASA Astrophysics Data System (ADS)

    Darwish, Ahmed A.; Fadlallah, Mohamed M.; Badawi, Ashraf; Maarouf, Ahmed A.

    2016-07-01

    Molecular adsorption on surfaces is a key element for many applications, including sensing and catalysis. Non-invasive sugar sensing has been an active area of research due to its importance to diabetes care. The adsorption of sugars on a template surface study is at the heart of matter. Here, we study doped hexagonal boron nitride sheets (h-BNNs) as adsorbing and sensing template for glucose and glucosamine. Using first principles calculations, we find that the adsorption of glucose and glucosamine on h-BNNs is significantly enhanced by the substitutional doping of the sheet with Al and Ga. Including long range van der Waals corrections gives adsorption energies of about 2 eV. In addition to the charge transfer occurring between glucose and the Al/Ga-doped BN sheets, the adsorption alters the size of the band gap, allowing for optical detection of adsorption. We also find that Al-doped boron nitride sheet is better than Ga-doped boron nitride sheet to enhance the adsorption energy of glucose and glucosamine. The results of our work can be potentially utilized when designing support templates for glucose and glucosamine.

  12. Photovoltaic performance of Gallium-doped ZnO thin film/Si nanowires heterojunction diodes

    NASA Astrophysics Data System (ADS)

    Akgul, Guvenc; Aksoy Akgul, Funda; Emrah Unalan, Husnu; Turan, Rasit

    2016-04-01

    In this work, photovoltaic performance of Ga-doped ZnO thin film/Si NWs heterojunction diodes was investigated. Highly dense and vertically well-aligned Si NW arrays were successfully synthesised on a p-type (1 0 0)-oriented Si wafer through cost-effective metal-assisted chemical etching technique. Ga-doped ZnO thin films were deposited onto Si NWs via radio frequency magnetron sputtering to construct three-dimensional heterostructures. Photovoltaic characteristics of the fabricated diodes were determined with current density (J)-voltage (V) measurements under simulated solar irradiation of AM 1.5 G. The optimal open-circuit voltage, short-circuit current density, fill factor and power conversion efficiency were found to be 0.37 V, 3.30 mA cm-2, 39.00 and 0.62%, respectively. Moreover, photovoltaic diodes exhibited relatively high external quantum efficiency over the broadband wavelengths between 350 and 1100 nm interval of the spectrum. The observed photovoltaic performance in this study clearly indicates that the investigated device structure composed of Ga-doped ZnO thin film/Si NWs heterojunctions could facilitate an alternative pathway for optoelectronic applications in future, and be a promising alternative candidate for high-performance low-cost new-generation photovoltaic diodes.

  13. Deep levels in Ga-doped ZnSe grown by molecular-beam epitaxy

    NASA Astrophysics Data System (ADS)

    Venkatesan, S.; Pierret, R. F.; Qiu, J.; Kobayashi, M.; Gunshor, R. L.; Kolodziejski, L. A.

    1989-10-01

    Results of a deep-level transient spectroscopy study of Ga-doped ZnSe thin films grown by molecular-beam epitaxy are presented. Two prominent deep levels were observed in all the samples investigated. The concentration of the trap detected at 0.34 eV below the conduction-band edge was essentially independent of the doping concentration and is attributed to native defects arising from Se vacancies in the ZnSe films. The second level with an activation energy of 0.26 eV shows a very strong doping dependence and is tentatively identified as arising from dopant-site (gallium-on-zinc-site) defects complexed with selenium vacancies. Preliminary results also indicate that planar doping of ZnSe significantly reduces the concentration of the Ga-vacancy complex.

  14. The enhanced spontaneous dielectric polarization in Ga doped CuFeO{sub 2}

    SciTech Connect

    Shi, Liran; Wei, Meng; Huang, Junwei; Chen, Borong; Shang, Cui; Xia, Zhengcai Long, Zhuo; Ouyang, Zhongwen; Xia, Nianming

    2014-11-07

    The magnetic and dielectric polarization properties of the single crystal samples of CuFe{sub 1−x}Ga{sub x}O{sub 2} (x = 0 and 0.02) are investigated. Experimental results show that the magnetization and dielectric polarizations are anisotropy and coupled together. Compared with pure CuFeO{sub 2}, in the case with the magnetic field parallel to the c axis, a field-induced phase transition with a hysteresis is clearly observed between the five-sublattice (5SL) and three-sublattice (3SL) phases. Specially, an obvious spontaneous dielectric polarization is observed in CuFe{sub 0.98}Ga{sub 0.02}O{sub 2} in a lower magnetic field region, indicating that the Ga doping has an effect on the enhancement of spontaneous dielectric polarization. Based on the dilution effect, change of exchange interaction, and partial release of the spin frustration due to the structural modulation of the Ga ion dopant, the origin of the magnetization, and spontaneous polarization characteristics are discussed and the complete dielectric polarization diagrams are assumed.

  15. CORRIGENDUM: Spin-coated Ga-doped ZnO transparent conducting thin films for organic light-emitting diodes Spin-coated Ga-doped ZnO transparent conducting thin films for organic light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Nayak, Pradipta K.; Kim, Jinwoo; Chung, Seungjun; Jeong, Jaewook; Lee, Changhee; Hong, Yongtaek

    2009-07-01

    Two corrections should be made to the previously published version of this article. On page 1, right-hand column, the radius of Zn should be read as 0.074 nm. This value is taken from Lide D R 1991 Handbook of Chemistry and Physics 71st edn (Boca Raton, FL: CRC Press). In the first paragraph of section 2, Diethanolammine and its acronym DEA should be corrected to Monoethanolamine and MEA.

  16. Aging effects of the precursor solutions on the properties of spin coated Ga-doped ZnO thin films

    SciTech Connect

    Serrao, Felcy Jyothi Dharmaprakash, S. M.

    2015-06-24

    In this study, gallium doped zinc oxide thin films (GZO) were grown on a glass substrate by a simple sol-gel process and spin coating technique using zinc acetate and gallium nitrate (3at%) as precursors for Zn and Ga ions respectively. The effects of aging time of the precursor solution on the structural and optical properties of the GZO films were investigated. The surface morphology, grain size, film thickness and optical properties of the GZO films were found to depend directly on the sol aging time. XRD studies reveal that the films are polycrystalline with a hexagonal wurtzite structure and show the c-axis grain orientation. Optical transmittance spectra of all the films exhibited transmittance higher than about 82% within the visible wavelength region. A sharp fundamental absorption edge with a slight blue shifting was observed with an increase in sol aging time which can be explained by Burstein-Moss effect. The result indicates that an appropriate aging time of the sol is important for the improvement of the structural and optical properties of GZO thin films derived from sol-gel method.

  17. Aging effects of the precursor solutions on the properties of spin coated Ga-doped ZnO thin films

    NASA Astrophysics Data System (ADS)

    Serrao, Felcy Jyothi; Dharmaprakash, S. M.

    2015-06-01

    In this study, gallium doped zinc oxide thin films (GZO) were grown on a glass substrate by a simple sol-gel process and spin coating technique using zinc acetate and gallium nitrate (3at%) as precursors for Zn and Ga ions respectively. The effects of aging time of the precursor solution on the structural and optical properties of the GZO films were investigated. The surface morphology, grain size, film thickness and optical properties of the GZO films were found to depend directly on the sol aging time. XRD studies reveal that the films are polycrystalline with a hexagonal wurtzite structure and show the c-axis grain orientation. Optical transmittance spectra of all the films exhibited transmittance higher than about 82% within the visible wavelength region. A sharp fundamental absorption edge with a slight blue shifting was observed with an increase in sol aging time which can be explained by Burstein-Moss effect. The result indicates that an appropriate aging time of the sol is important for the improvement of the structural and optical properties of GZO thin films derived from sol-gel method.

  18. Effect of deposition times on structure of Ga-doped ZnO thin films as humidity sensor

    SciTech Connect

    Khalid, Faridzatul Shahira; Awang, Rozidawati

    2014-09-03

    Gallium doped zinc oxide (GZO) has good electrical property. It is widely used as transparent electrode in photovoltaic devices, and sensing element in gas and pressure sensors. GZO thin film was prepared using magnetron sputtering. Film deposition times were set at 10, 15, 20, 25 and 30 minutes to get samples of different thickness. X-ray diffraction (XRD) was used to determine the structure of GZO thin films. Structure for GZO thin film is hexagonal wurtzite structure. Morphology and thickness of GZO thin films was observed from FESEM micrographs. Grain size and thickness of thin films improved with increasing deposition times. However, increasing the thickness of thin films occur below 25 minutes only. Electrical properties of GZO thin films were studied using a four-point probe technique. The changes in the structure of the thin films lead to the changed of their electrical properties resulting in the reduction of the film resistance. These thin films properties significantly implying the potential application of the sample as a humidity sensor.

  19. Single phase formation of Co-implanted ZnO thin films by swift heavy ion irradiation: Optical studies

    SciTech Connect

    Kumar, Ravi; Singh, Fouran; Angadi, Basavaraj; Choi, Ji-Won; Choi, Won-Kook; Jeong, Kwangho; Song, Jong-Han; Khan, M. Wasi; Srivastava, J. P.; Kumar, Ajay; Tandon, R. P.

    2006-12-01

    Low temperature photoluminescence and optical absorption studies on 200 MeV Ag{sup +15} ion irradiated Co-implanted ZnO thin films were studied. The Co clusters present in as implanted samples were observed to be dissolved using 200 MeV Ag{sup +15} ion irradiation with a fluence of 1x10{sup 12} ions/cm{sup 2}. The photoluminescence spectrum of pure ZnO thin film was characterized by the I{sub 4} peak due to the neutral donor bound excitons and the broad green emission. The Co-doped ZnO films show three sharp levels and two shoulders corresponding to 3t{sub 2g} and 2e{sub g} levels of crystal field splitted Co d orbitals, respectively. The ultraviolet-visible absorption spectroscopy also shows the systematic variation of band gap after 200 MeV Ag{sup +15} ion irradiation.

  20. Investigation of thermal resistance and power consumption in Ga-doped indium oxide (In{sub 2}O{sub 3}) nanowire phase change random access memory

    SciTech Connect

    Jin, Bo; Lee, Jeong-Soo E-mail: ljs6951@postech.ac.kr; Lim, Taekyung; Ju, Sanghyun; Latypov, Marat I.; Pi, Dong-Hai; Seop Kim, Hyoung; Meyyappan, M. E-mail: ljs6951@postech.ac.kr

    2014-03-10

    The resistance stability and thermal resistance of phase change memory devices using ∼40 nm diameter Ga-doped In{sub 2}O{sub 3} nanowires (Ga:In{sub 2}O{sub 3} NW) with different Ga-doping concentrations have been investigated. The estimated resistance stability (R(t)/R{sub 0} ratio) improves with higher Ga concentration and is dependent on annealing temperature. The extracted thermal resistance (R{sub th}) increases with higher Ga-concentration and thus the power consumption can be reduced by ∼90% for the 11.5% Ga:In{sub 2}O{sub 3} NW, compared to the 2.1% Ga:In{sub 2}O{sub 3} NW. The excellent characteristics of Ga-doped In{sub 2}O{sub 3} nanowire devices offer an avenue to develop low power and reliable phase change random access memory applications.

  1. Electrical properties and stability of p-type ZnO film enhanced by alloying with S and heavy doping of Cu

    SciTech Connect

    Pan, H. L.; Yang, T.; Xu, Y.; Yao, B.; Zhang, B. Y.; Liu, W. W.; Shen, D. Z.

    2010-10-04

    Single wurtzite p-type Zn{sub 1-y}Cu{sub y}O{sub 1-x}S{sub x} alloy films with 0.081{<=}x{<=}0.186 and 0.09{<=}y{<=}0.159 were grown on quartz reproducibly by magnetron sputtering. The alloys show very stable p-type conductivity with a hole concentration of 4.31-5.78x10{sup 19} cm{sup -3}, a resistivity of 0.29-0.34 {Omega} cm and a mobility of 0.32-0.49 cm{sup 2} V{sup -1} s{sup -1}. The p-type conductivity is attributed to substitution of Cu{sup +1} for the Zn site, and the ionization energy of the Cu{sup +1} acceptor is measured to be 53 meV, much less than that of Cu-doped ZnO reported previously. The small ionization energy is due to Cu heavy doping and increase in valence band maximum of ZnO induced by alloying with S.

  2. Enhancement of photo sensor properties of nanocrystalline ZnO thin film by swift heavy ion irradiation

    SciTech Connect

    Mahajan, S. V.; Upadhye, D. S.; Bagul, S. B.; Shaikh, S. U.; Birajadar, R. B.; Siddiqui, F. Y.; Huse, N. P.; Sharma, R. B. E-mail: rps.phy@gmail.com

    2015-06-24

    Nanocrystalline Zinc Oxide (ZnO) thin film prepared by Low cost Successive Ionic Layer Adsorption and Reaction (SILAR) method. This film was irradiated by 120 MeV Ni{sup 7+} ions with the fluence of 5x10{sup 12}ions/cm{sup 2}. The X-ray diffraction study was shows polycrystalline nature with wurtzite structure. The optical properties as absorbance were determined using UV-Spectrophotometer and band gap was also calculated. The Photo Sensor nature was calculated by I-V characteristics with different sources of light 40W, 60W and 100W.

  3. Enhanced role of Al or Ga-doped graphene on the adsorption and dissociation of N2O under electric field.

    PubMed

    Lv, Yong-an; Zhuang, Gui-lin; Wang, Jian-guo; Jia, Ya-bo; Xie, Qin

    2011-07-21

    To find an effective strategy for the capture and decomposition of nitrous oxide (N(2)O) is very important in order to protect the ozone layer and control the effects of global warming. Based on first-principles calculations, such a strategy is proposed by the systemic study of N(2)O interaction with pristine and Al (or Ga)-doped graphene, and N(2)O dissociation on the surface of Al (or Ga)-doped graphene in an applied electric field. The calculated adsorption energy value shows the N(2)O molecule more firmly adsorbs on the surface of Al (or Ga)-doped graphene than that of pristine graphene, deriving from a stronger covalent bond between the N(2)O molecule and the Al (or Ga) atom. Furthermore, our study suggests that N(2)O molecules can be easily decomposed to N(2) and O(2) with the appropriate electric field, which reveals that Al-doped graphene may be a new candidate for control of N(2)O.

  4. Plasmon generation in sputtered Ga-doped MgZnO thin films for solar cell applications

    NASA Astrophysics Data System (ADS)

    Awasthi, Vishnu; Pandey, Sushil Kumar; Garg, Vivek; Sengar, Brajendra S.; Sharma, Pankaj; Kumar, Shailendra; Mukherjee, C.; Mukherjee, Shaibal

    2016-06-01

    The crystalline, electrical, morphological, optical properties and plasmonic behaviour of Ga doped MgZnO (GMZO) thin films grown at different substrate temperatures (200-600 °C) by a dual ion beam sputtering (DIBS) system are investigated. Transmittance value of more than ˜94% in 400-1000 nm region is observed for all GMZO films. The particle plasmon features can be detected in the absorption coefficient spectra of GMZO grown at 500 and 600 °C in the form of a peak at ˜4.37 eV, which corresponds to a plasmon resonance peak of nanoclusters formed in GMZO. The presence of such plasmonic features is confirmed by ultraviolet photoelectron spectroscopy measurements. The values of particle plasmon resonance energy of various nanoclusters are in the range of solar spectrum, and these can easily be tuned and excited at the desirable wavelengths while optimizing the efficiency of solar cells (SCs) by simple alteration of DIBS growth temperature. These nanoclusters are extremely promising to enhance the optical scattering and trapping of the incident light, which increases the optical path length in the absorber layer of cost-effective SCs and eventually increases its efficiency.

  5. Effects of annealing temperature on the properties of Ga-doped In2O3 Thin Films

    NASA Astrophysics Data System (ADS)

    Cho, Shinho

    2015-10-01

    Ga-doped In2O3 (GIO) thin films were deposited on glass substrates at a growth temperature of 300 °C by using radio-frequency magnetron sputtering. The deposited films were then subjected to rapid thermal annealing (RTA) at various temperatures. The annealed films were characterized by using X-ray diffraction (XRD), ultraviolet-visible spectrophotometry, scanning electron microscopy, and Hall-effect measurements. The optical bandgap, electrical resistivity, and figure of merit of the GIO thin films were found to depend significantly on the RTA temperature. The XRD patterns of the films indicated that all the films had a body-centered cubic structure, with the primary peak being the (222) diffraction peak. The average optical transmittance of the GIO thin films for wavelengths of 500 - 1100 nm increased from 44.5% before annealing to 87.2% after annealing at 450 °C; the figure of merit was also the highest after annealing at this temperature. These results indicate that the properties of GIO thin films can be varied by controlling the RTA temperature.

  6. Effects of rapid thermal annealing on properties of Ga-doped MgxZn1-xO films and Ga-doped MgxZn1-xO/AlGaN heterojunction diodes

    NASA Astrophysics Data System (ADS)

    Hsueh, Kuang-Po; Cheng, Po-Wei

    2014-08-01

    This study investigated the thermal annealing effects of Ga-doped MgxZn1-xO (GMZO) films and GMZO/AlGaN heterojunction diodes. GMZO films were deposited using a radio-frequency magnetron sputtering system with a 4-in. ZnO/MgO/Ga2O3 target. In addition, the Hall results, X-ray diffraction, transparent performance, and X-ray photoelectron spectroscopy (XPS) spectra were measured. The as-grown GMZO film deposited in this study exhibited a high transparency with transmittances over 95% in the visible region (360-700 nm) and a sharp absorption edge in the UV region (275-350 nm). The phenomenon of phase separation in the GMZO films was investigated based on the XPS spectra, revealing that an increase in the O-Zn signal accompanied a decline in the O-Ga signal after the thermal annealing. Moreover, the current-voltage (I-V) characteristics of the GMZO/AlGaN n-p junction diodes were examined at different annealing temperatures. The light emission derived from the forward-biased junction and near-ultraviolet (near-UV) light emission was evident at all p-n junctions. The n-GMZO/p-AlGaN diode annealed at 800 °C exhibited a brighter near-UV emission compared with the other diodes. In addition, the spectrum of diode annealed at 800 °C exhibited a broad peak at 474 nm (2.62 eV) and a tail of the emission spectrum extending to 850 nm. Based on these findings, the GMZO films are suitable for forming transparent contact layers in optoelectronic devices, and the n-GMZO/p-AlGaN junction diode is a feasible alternative in near-UV light emission devices.

  7. 266  nm ultraviolet light generation in Ga-doped BaAlBO3F2 crystals.

    PubMed

    Yang, Lei; Yue, Yinchao; Yang, Feng; Hu, Zhanggui; Xu, Zuyan

    2016-04-01

    BaAlBO3F2 (BABF) crystals are a recently developed and promising nonlinear optical material, notably for the third harmonic generation of ultraviolet (UV) light at 355 nm. However, the fourth harmonic generation of UV light at 266 nm has never been obtained by using a BABF crystal due to its relatively small birefringence. We demonstrate that the birefringence of BABF can be effectively increased by doping it with Ga3+. The fourth harmonic generation of UV light at 266 nm was achieved for the first time in a Ga-doped BABF crystal. PMID:27192296

  8. Significant mobility enhancement in extremely thin highly doped ZnO films

    SciTech Connect

    Look, David C.; Heller, Eric R.; Yao, Yu-Feng; Yang, C. C.

    2015-04-13

    Highly Ga-doped ZnO (GZO) films of thicknesses d = 5, 25, 50, and 300 nm, grown on 160-nm ZnO buffer layers by molecular beam epitaxy, had 294-K Hall-effect mobilities μ{sub H} of 64.1, 43.4, 37.0, and 34.2 cm{sup 2}/V-s, respectively. This extremely unusual ordering of μ{sub H} vs d is explained by the existence of a very high-mobility Debye tail in the ZnO, arising from the large Fermi-level mismatch between the GZO and the ZnO. Scattering theory in conjunction with Poisson analysis predicts a Debye-tail mobility of 206 cm{sup 2}/V-s at the interface (z = d), falling to 58 cm{sup 2}/V-s at z = d + 2 nm. Excellent fits to μ{sub H} vs d and sheet concentration n{sub s} vs d are obtained with no adjustable parameters.

  9. Direct measurement of defect and dopant abruptness at high electron mobility ZnO homojunctions

    NASA Astrophysics Data System (ADS)

    Foster, G. M.; Faber, G.; Yao, Y.-F.; Yang, C. C.; Heller, E. R.; Look, D. C.; Brillson, L. J.

    2016-10-01

    Due to a strong Fermi-level mismatch, about 10% of the electrons in a 5-nm-thick highly Ga-doped ZnO (GZO) layer grown by molecular beam epitaxy at 250 °C on an undoped ZnO buffer layer transfer to the ZnO (Debye leakage), causing the measured Hall-effect mobility (μH) of the GZO/ZnO combination to remarkably increase from 34 cm2/V s, in thick GZO, to 64 cm2/V s. From previous characterization of the GZO, it is known that ND = [Ga] = 1.04 × 1021 and NA = [VZn] = 1.03 × 1020 cm-3, where ND, NA, and [VZn] are the donor, acceptor, and Zn-vacancy concentrations, respectively. In the ZnO, ND = 3.04 × 1019 and NA = 8.10 × 1018 cm-3. Assuming the interface is abrupt, theory predicts μH = 61 cm2/V s, with no adjustable parameters. The assumption of abruptness in [Ga] and [VZn] profiles is confirmed directly with a differential form of depth-resolved cathodoluminescence spectroscopy coupled with X-ray photoelectron spectroscopy. An anneal in Ar at 500 °C for 10 min somewhat broadens the profiles but causes no appreciable degradation in μH and other electrical properties.

  10. Characteristics of Ga-Rich Cu(In, Ga)Se2 Solar Cells Grown on Ga-Doped ZnO Back Contact.

    PubMed

    Sun, Qian; Kim, Kyoung-Bo; Jeon, Chan-Wook

    2016-05-01

    Wide bandgap Cu(In,Ga)Se2 (CIGS) thin films were deposited on Ga-rich Ga:ZnO (GZO) or MoN/GZO by single-stage co-evaporation. CIGS/TCO interface phases, such as resistive n-type Ga2O3, which are likely to have formed during the high temperature growth of Ga-rich CIGS, can deteriorate the solar cell performance. Although some Ga accumulation was observed in both of the CIGS/GZO and CIGS/MoN/GZO interfaces formed at 520 degrees C, the Ga oxide layer was absent. On the other hand, their current-voltage characteristics showed strong roll-over behavior regardless of the MoN diffusion barrier. The strong Schottky barrier formation at the CLGS/GZO junction due to the low work function of GZO, was attributed to current blocking at a high forward bias.

  11. Characteristics of Ga-Rich Cu(In, Ga)Se2 Solar Cells Grown on Ga-Doped ZnO Back Contact.

    PubMed

    Sun, Qian; Kim, Kyoung-Bo; Jeon, Chan-Wook

    2016-05-01

    Wide bandgap Cu(In,Ga)Se2 (CIGS) thin films were deposited on Ga-rich Ga:ZnO (GZO) or MoN/GZO by single-stage co-evaporation. CIGS/TCO interface phases, such as resistive n-type Ga2O3, which are likely to have formed during the high temperature growth of Ga-rich CIGS, can deteriorate the solar cell performance. Although some Ga accumulation was observed in both of the CIGS/GZO and CIGS/MoN/GZO interfaces formed at 520 degrees C, the Ga oxide layer was absent. On the other hand, their current-voltage characteristics showed strong roll-over behavior regardless of the MoN diffusion barrier. The strong Schottky barrier formation at the CLGS/GZO junction due to the low work function of GZO, was attributed to current blocking at a high forward bias. PMID:27483870

  12. Ab-initio study on electronic and magnetic properties of (Ga,Co) co-doped ZnO

    NASA Astrophysics Data System (ADS)

    González-García, A.; Mendoza-Estrada, V.; López-Pérez, W.; Pinilla-Castellanos, C.; González-Hernández, R.

    2016-08-01

    Using first-principles calculations based on density functional theory within GGA formalism, we have studied the electronic structure and magnetic properties of (Ga,Co) co-doped ZnO system. The effect of impurity distances on ferromagnetic and antiferromagnetic ground state in Co0.056Zn0.944O has been studied. For the closest Co-Co distance, a ferromagnetic ground state with total magnetic moment of ∼⃒3.00μB per Co atom has been found. The electronic structure also displays a nearly halfmetallic order. Conversely, for the farthest Co-Co distance an antiferromagnetic ground state was found for Co0.056Zn0.944O. When Zn2+ ions are replaced by Ga ions in Co0.056Zn0.944O, the new (Ga,Co) co-doped ZnO system is more energetically stable. It has also been found that Ga-doping reduces the Co0.056Zn0.944O band gap due to the sp-d exchange interactions, which is in good agreement with the experimental data. Moreover, the Ga-doping changes the nearly halmetallic order of Co0.056Zn0944O to metallic. Results also show that Ga0.029Co0.056Zn0.915O is still ferromagnetic with a total magnetic moment of ∼⃒3.00μB per Co atom. It was also found that the ferromagnetic ground state in (Ga,Co) co-doped ZnO vanishes as Ga concentration increases.

  13. Effect of the microstructural characteristics of a Ga-doped TiO2 hole block layer on an inverted structure organic solar cell

    NASA Astrophysics Data System (ADS)

    Lee, Eun Ju; Ryu, Sang Ouk

    2016-09-01

    Inverted-structure organic solar cells (OSCs) were fabricated using atomic-layer-deposition (ALD) processed Ga-doped TiO2 as hole blocking layer (HBL). Measured photovoltaic efficiencies were greatly related to the crystallinity of the TiO2 films. However, the efficiencies of the OSCs and the crystallinity of the HBL did not show a linear relationship. The HBL was fully crystallized at a deposition temperature of 200 °C or above, and the power conversion efficiency was measured to be 2.7% with for the HBL processed at 200 °C, but the efficiency decreased to 2.4% for the HBL processed at 250 °C. On the other hand, the surface roughness of the crystallized films was found be increased to two fold in the studied temperature range. Once the HBL had been fully crystallized, the major factor that determined the overall performance of OSCs was the surface roughness of the HBL.

  14. Improvement in the optical and electrical properties of Ga-doped zinc-oxide films by using nano-imprinted pattern arrays and post-annealing

    NASA Astrophysics Data System (ADS)

    Lee, Su Yeon; Lee, Seong Eui; Lee, Hee Chul; Lee, Ho Nyun; Kim, Hyun Jong

    2015-01-01

    The effects of nano-imprinted arrays and post-annealing on the optical and the electrical properties of sputtered Ga-doped zinc-oxide (GZO) films were intensively investigated to develop suitable electrodes for photonic applications. We fabricated nano-structures with a GZO circular pattern with a diameter of 250 nm by using UV nano-imprinting lithography and the lift-off process. The nano-structured GZO/glass substrate showed a high optical transmittance of 91.0% at a wavelength of 550 nm, which was increased by about 2.2% compared to that of unprocessed GZO/glass. Then nano-structured GZO/glass substrate was rapidly annealed under different conditions to acquire a high optical transmittance and a low resistivity. The optimized nano-structured GZO film post-annealed at 400 °C showed the highest optical transmittance of 92.0% and an improved resistivity of 1.3 × 10-3 Ω·cm.

  15. Sol-gel derived Al-Ga co-doped transparent conducting oxide ZnO thin films

    NASA Astrophysics Data System (ADS)

    Serrao, Felcy Jyothi; Sandeep, K. M.; Bhat, Shreesha; Dharmaprakash, S. M.

    2016-05-01

    Transparent conducting ZnO doped with Al, Ga and co-doped Al and Ga (1:1) (AGZO) thin films were grown on glass substrates by cost effective sol-gel spin coating method. The XRD results showed that all the films are polycrystalline in nature and highly textured along the (002) plane. Enhanced grain size was observed in the case of AGZO thin films. The transmittance of all the films was more than 83% in the visible region of light. The electrical properties such as carrier concentration and mobility values are increased in case of AGZO compared to that of Al and Ga doped ZnO thin films. The minimum resistivity of 2.54 × 10-3 Ω cm was observed in AGZO thin film. The co-doped AGZO thin films exhibited minimum resistivity and high optical transmittance, indicate that co-doped ZnO thin films could be used in transparent electronics mainly in display applications.

  16. 100 MeV Ni{sup +7} swift heavy ion induced magnetism in cobalt doped ZnO thin films

    SciTech Connect

    Kumar, Sunil Singh, D. P.; Kumar, Ravi

    2014-04-24

    Zn{sub 0.90}Co{sub 0.10}O thin films were prepared using Sol-Gel spin coating method. Films were irradiated with 100 MeV Ni{sub +7} Swift Heavy Ions (SHI) with fluences 1× 10{sup 13} ions/cm{sup 2} using 15 UD tandem accelerator at IUAC New Delhi and its effect were studied on the structural, optical and magnetic properties of irradiated thin films. X-ray diffraction studies show single phase films with preferred c-axis orientation after irradiation. Ultraviolet-visible absorption spectroscopy shows red shift in the band gap of irradiated thin films. Magnetic field dependence of magnetization reveals weak ferromagnetism in irradiated thin films. AFM studies shows significant increase in the grain size and the surface roughness of the films after irradiation.

  17. Investigation of Ga substitution in ZnO powder and opto-electronic properties.

    PubMed

    Serier, Hélène; Demourgues, Alain; Gaudon, Manuel

    2010-08-01

    Two sets of Ga-doped ZnO powders were synthesized via solid-state and Pechini routes with a substitution rate varying from 0 to 4 mol %. The gallium solubility limit is strongly dependent on the synthesis history. Indeed, a low temperature annealing allows incorporating about 1.5 mol % (X-ray diffraction (XRD), inductive coupled plasma spectroscopy (ICP), optical properties) whereas under 0.1% of dopant is introduced after thermal treatment at high temperature: 1500 degrees C (from XRD and pellets conductivity). The incorporation of gallium leads to an anisotropic distortion of the zincite crystal lattice (a and c parameters increase and decrease, respectively, versus the Ga content leading to a decrease of the c/a ratio) which can be explained from the valence bond model. XRD analysis, chemical titration by ICP, and conductivity measurements (on pellets obtained at high temperature) allow determining accurately the maximum Ga content in the zincite. The optical properties (IR absorption efficiency) linked to electron carriers are directly correlated to the gallium rate introduced in ZnO oxide; nevertheless, the non linear correlation between these two parameters tends to show that the concentration of charge carriers in the system is not equal to the amount of Ga(3+) atoms inserted per ZnO volume unit. A saturation regime is observed and was here explained once again on the basis of the valence band model by the increase of inhibiting p type defects with the increase of (n-type donors) Ga(3+) concentration. PMID:20593782

  18. Effects of rapid thermal annealing on properties of Ga-doped Mg{sub x}Zn{sub 1−x}O films and Ga-doped Mg{sub x}Zn{sub 1−x}O/AlGaN heterojunction diodes

    SciTech Connect

    Hsueh, Kuang-Po E-mail: kphsueh@mail.vnu.edu.tw; Cheng, Po-Wei

    2014-08-14

    This study investigated the thermal annealing effects of Ga-doped Mg{sub x}Zn{sub 1−x}O (GMZO) films and GMZO/AlGaN heterojunction diodes. GMZO films were deposited using a radio-frequency magnetron sputtering system with a 4-in. ZnO/MgO/Ga{sub 2}O{sub 3} target. In addition, the Hall results, X-ray diffraction, transparent performance, and X-ray photoelectron spectroscopy (XPS) spectra were measured. The as-grown GMZO film deposited in this study exhibited a high transparency with transmittances over 95% in the visible region (360–700 nm) and a sharp absorption edge in the UV region (275–350 nm). The phenomenon of phase separation in the GMZO films was investigated based on the XPS spectra, revealing that an increase in the O-Zn signal accompanied a decline in the O-Ga signal after the thermal annealing. Moreover, the current-voltage (I-V) characteristics of the GMZO/AlGaN n-p junction diodes were examined at different annealing temperatures. The light emission derived from the forward-biased junction and near-ultraviolet (near-UV) light emission was evident at all p-n junctions. The n-GMZO/p-AlGaN diode annealed at 800 °C exhibited a brighter near-UV emission compared with the other diodes. In addition, the spectrum of diode annealed at 800 °C exhibited a broad peak at 474 nm (2.62 eV) and a tail of the emission spectrum extending to 850 nm. Based on these findings, the GMZO films are suitable for forming transparent contact layers in optoelectronic devices, and the n-GMZO/p-AlGaN junction diode is a feasible alternative in near-UV light emission devices.

  19. Evaluation of the band alignment and valence plasmonic features of a DIBS grown Ga-doped Mg0.05Zn0.95O/CIGSe heterojunction by photoelectron spectroscopy

    NASA Astrophysics Data System (ADS)

    Awasthi, Vishnu; Pandey, Sushil Kumar; Kumar, Shailendra; Mukherjee, C.; Gupta, Mukul; Mukherjee, Shaibal

    2015-12-01

    The bandgap alignment of a Ga-doped MgZnO (GMZO)/CIGSe heterojunction exposed to short duration Ar+  ion beam sputtering has been investigated by ultraviolet photoelectron spectroscopy measurement. The offset values at the valence and conduction band of the GMZO/CIGSe hetrojunction are calculated to be 2.69 and  -0.63 eV, respectively. Moreover, the valence band onsets of GMZO and CIGSe thin films before and after few minutes Ar+ ion sputtering have been investigated. The presented study demonstrates the photoelectron-induced generation of resonant valence bulk and surface plasmonic features of various metal and metal oxide nanoclusters embedded within a GMZO matrix. The presence of such nanoclusters is proven to be beneficial in realizing cost-effective, ultra-thin, and high-performance photovoltaics based on the heterojunction.

  20. High-Hall-Mobility Al-Doped ZnO Films Having Textured Polycrystalline Structure with a Well-Defined (0001) Orientation

    NASA Astrophysics Data System (ADS)

    Nomoto, Junichi; Makino, Hisao; Yamamoto, Tetsuya

    2016-06-01

    Five hundred-nanometer-thick ZnO-based textured polycrystalline films consisting of 490-nm-thick Al-doped ZnO (AZO) films deposited on 10-nm-thick Ga-doped ZnO (GZO) films exhibited a high Hall mobility ( μ H) of 50.1 cm2/Vs with a carrier concentration ( N) of 2.55 × 1020 cm-3. Firstly, the GZO films were prepared on glass substrates by ion plating with dc arc discharge, and the AZO films were then deposited on the GZO films by direct current magnetron sputtering (DC-MS). The GZO interface layers with a preferential c-axis orientation play a critical role in producing AZO films with texture development of a well-defined (0001) orientation, whereas 500-nm-thick AZO films deposited by only DC-MS showed a mixture of the c-plane and the other plane orientation, to exhibit a μ H of 38.7 cm2/Vs with an N of 2.22 × 1020 cm-3.

  1. A-site compositional effects in Ga-doped hollandite materials of the form BaxCsyGa2x+yTi8−2x−yO16: implications for Cs immobilization in crystalline ceramic waste forms

    PubMed Central

    Xu, Yun; Wen, Yi; Grote, Rob; Amoroso, Jake; Shuller Nickles, Lindsay; Brinkman, Kyle S.

    2016-01-01

    The hollandite structure is a promising crystalline host for Cs immobilization. A series of Ga-doped hollandite BaxCsyGa2x+yTi8−2x−yO16 (x = 0, 0.667, 1.04, 1.33; y = 1.33, 0.667, 0.24, 0) was synthesized through a solid oxide reaction method resulting in a tetragonal hollandite structure (space group I4/m). The lattice parameter associated with the tunnel dimension was found to increases as Cs substitution in the tunnel increased. A direct investigation of cation mobility in tunnels using electrochemical impedance spectroscopy was conducted to evaluate the ability of the hollandite structure to immobilize cations over a wide compositional range. Hollandite with the largest tunnel size and highest aspect ratio grain morphology resulting in rod-like microstructural features exhibited the highest ionic conductivity. The results indicate that grain size and optimized Cs stoichiometry control cation motion and by extension, the propensity for Cs release from hollandite. PMID:27273791

  2. A-site compositional effects in Ga-doped hollandite materials of the form BaxCsyGa2x+yTi8-2x-yO16: implications for Cs immobilization in crystalline ceramic waste forms

    NASA Astrophysics Data System (ADS)

    Xu, Yun; Wen, Yi; Grote, Rob; Amoroso, Jake; Shuller Nickles, Lindsay; Brinkman, Kyle S.

    2016-06-01

    The hollandite structure is a promising crystalline host for Cs immobilization. A series of Ga-doped hollandite BaxCsyGa2x+yTi8-2x-yO16 (x = 0, 0.667, 1.04, 1.33; y = 1.33, 0.667, 0.24, 0) was synthesized through a solid oxide reaction method resulting in a tetragonal hollandite structure (space group I4/m). The lattice parameter associated with the tunnel dimension was found to increases as Cs substitution in the tunnel increased. A direct investigation of cation mobility in tunnels using electrochemical impedance spectroscopy was conducted to evaluate the ability of the hollandite structure to immobilize cations over a wide compositional range. Hollandite with the largest tunnel size and highest aspect ratio grain morphology resulting in rod-like microstructural features exhibited the highest ionic conductivity. The results indicate that grain size and optimized Cs stoichiometry control cation motion and by extension, the propensity for Cs release from hollandite.

  3. A-site compositional effects in Ga-doped hollandite materials of the form BaxCsyGa2x+yTi8-2x-yO16: implications for Cs immobilization in crystalline ceramic waste forms.

    PubMed

    Xu, Yun; Wen, Yi; Grote, Rob; Amoroso, Jake; Shuller Nickles, Lindsay; Brinkman, Kyle S

    2016-01-01

    The hollandite structure is a promising crystalline host for Cs immobilization. A series of Ga-doped hollandite BaxCsyGa2x+yTi8-2x-yO16 (x = 0, 0.667, 1.04, 1.33; y = 1.33, 0.667, 0.24, 0) was synthesized through a solid oxide reaction method resulting in a tetragonal hollandite structure (space group I4/m). The lattice parameter associated with the tunnel dimension was found to increases as Cs substitution in the tunnel increased. A direct investigation of cation mobility in tunnels using electrochemical impedance spectroscopy was conducted to evaluate the ability of the hollandite structure to immobilize cations over a wide compositional range. Hollandite with the largest tunnel size and highest aspect ratio grain morphology resulting in rod-like microstructural features exhibited the highest ionic conductivity. The results indicate that grain size and optimized Cs stoichiometry control cation motion and by extension, the propensity for Cs release from hollandite. PMID:27273791

  4. A-site compositional effects in Ga-doped hollandite materials of the form BaxCsyGa2x+yTi8‑2x‑yO16: implications for Cs immobilization in crystalline ceramic waste forms

    NASA Astrophysics Data System (ADS)

    Xu, Yun; Wen, Yi; Grote, Rob; Amoroso, Jake; Shuller Nickles, Lindsay; Brinkman, Kyle S.

    2016-06-01

    The hollandite structure is a promising crystalline host for Cs immobilization. A series of Ga-doped hollandite BaxCsyGa2x+yTi8‑2x‑yO16 (x = 0, 0.667, 1.04, 1.33; y = 1.33, 0.667, 0.24, 0) was synthesized through a solid oxide reaction method resulting in a tetragonal hollandite structure (space group I4/m). The lattice parameter associated with the tunnel dimension was found to increases as Cs substitution in the tunnel increased. A direct investigation of cation mobility in tunnels using electrochemical impedance spectroscopy was conducted to evaluate the ability of the hollandite structure to immobilize cations over a wide compositional range. Hollandite with the largest tunnel size and highest aspect ratio grain morphology resulting in rod-like microstructural features exhibited the highest ionic conductivity. The results indicate that grain size and optimized Cs stoichiometry control cation motion and by extension, the propensity for Cs release from hollandite.

  5. ZnO nanowire lasers.

    PubMed

    Vanmaekelbergh, Daniël; van Vugt, Lambert K

    2011-07-01

    The pathway towards the realization of optical solid-state lasers was gradual and slow. After Einstein's paper on absorption and stimulated emission of light in 1917 it took until 1960 for the first solid state laser device to see the light. Not much later, the first semiconductor laser was demonstrated and lasing in the near UV spectral range from ZnO was reported as early as 1966. The research on the optical properties of ZnO showed a remarkable revival since 1995 with the demonstration of room temperature lasing, which was further enhanced by the first report of lasing by a single nanowire in 2001. Since then, the research focussed increasingly on one-dimensional nanowires of ZnO. We start this review with a brief description of the opto-electronic properties of ZnO that are related to the wurtzite crystal structure. How these properties are modified by the nanowire geometry is discussed in the subsequent sections, in which we present the confined photon and/or polariton modes and how these can be investigated experimentally. Next, we review experimental studies of laser emission from single ZnO nanowires under different experimental conditions. We emphasize the special features resulting from the sub-wavelength dimensions by presenting our results on single ZnO nanowires lying on a substrate. At present, the mechanism of lasing in ZnO (nanowires) is the subject of a strong debate that is considered at the end of this review. PMID:21552596

  6. Properties of double-layered Ga-doped Al-zinc-oxide/titanium-doped indium-tin-oxide thin films prepared by dc magnetron sputtering applied for Si-based thin film solar cells

    SciTech Connect

    Wang, Chao-Chun; Wuu, Dong-Sing; Lin, Yang-Shih; Lien, Shui-Yang; Huang, Yung-Chuan; Liu, Chueh-Yang; Chen, Chia-Fu; Nautiyal, Asheesh; Lee, Shuo-Jen

    2011-11-15

    In this article, Ga-doped Al-zinc-oxide (GAZO)/titanium-doped indium-tin-oxide (ITIO) bi-layer films were deposited onto glass substrates by direct current (dc) magnetron sputtering. The bottom ITIO film, with a thickness of 200 nm, was sputtered onto the glass substrate. The ITIO film was post-annealed at 350 deg. C for 10-120 min as a seed layer. The effect of post-annealing conditions on the morphologies, electrical, and optical properties of ITIO films was investigated. A GAZO layer with a thickness of 1200 nm was continuously sputtered onto the ITIO bottom layer. The results show that the properties of the GAZO/ITIO films were strongly dependent on the post-annealed conditions. The spectral haze (T{sub diffuse}/T{sub total}) of the GAZO/ITIO bi-layer films increases upon increasing the post-annealing time. The haze and resistivity of the GAZO/ITIO bi-layer films were improved with the post-annealed process. After optimizing the deposition and annealing parameters, the GAZO/ITIO bi-layer film has an average transmittance of 83.20% at the 400-800 nm wavelengths, a maximum haze of 16%, and the lowest resistivity of 1.04 x 10{sup -3}{Omega} cm. Finally, the GAZO/ITIO bi-layer films, as a front electrode for silicon-based thin film solar cells, obtained a maximum efficiency of 7.10%. These encouraging experimental results have potential applications in GAZO/ITIO bi-layer film deposition by in-line sputtering without the wet-etching process and enable the production of highly efficient, low-cost thin film solar cells.

  7. Highly Conducting Gallium-Doped ZnO Thin Film as Transparent Schottky Contact for Organic- Semiconductor-Based Schottky Diodes

    NASA Astrophysics Data System (ADS)

    Singh, Budhi; Ghosh, Subhasis

    2015-08-01

    Highly conducting and transparent Ga-doped ZnO (GZO) thin films have been grown on transparent substrates at different growth temperatures with Ga content varying from 0.01% to 10%. All films showed pronounced c-axis orientation corresponding to hexagonal wurtzite structure. The minimum resistivity of 4.3 × 10-4 Ω cm was reproducibly obtained in GZO thin film doped with 2% Ga and grown at 600°C. We have further shown that highly conducting transparent GZO thin film can be used as a Schottky contact in copper phthalocyanine (CuPc)-based Schottky diodes. The capacitance-voltage characteristics of the Al/CuPc/Au and GZO/CuPc/Au Schottky diodes show similar built-in potential ( V bi) of 0.98 V, which is close to the difference in work function between Au (5.2 eV) and Al or GZO (4.2 eV), establishing that GZO behaves as a metal electrode with work function similar to Al. Similar values of acceptor concentration (˜1015 cm-3) in CuPc were obtained from the capacitance-voltage characteristics of the Al/CuPc/Au and GZO/CuPc/Au Schottky diodes. These observations indicate the absence of interface states at the metal/organic interface in CuPc-based Schottky diodes.

  8. Defects in ZnO

    NASA Astrophysics Data System (ADS)

    McCluskey, M. D.; Jokela, S. J.

    2009-10-01

    Zinc oxide (ZnO) is a wide band gap semiconductor with potential applications in optoelectronics, transparent electronics, and spintronics. The high efficiency of UV emission in this material could be harnessed in solid-state white lighting devices. The problem of defects, in particular, acceptor dopants, remains a key challenge. In this review, defects in ZnO are discussed, with an emphasis on the physical properties of point defects in bulk crystals. As grown, ZnO is usually n-type, a property that was historically ascribed to native defects. However, experiments and theory have shown that O vacancies are deep donors, while Zn interstitials are too mobile to be stable at room temperature. Group-III (B, Al, Ga, and In) and H impurities account for most of the n-type conductivity in ZnO samples. Interstitial H donors have been observed with IR spectroscopy, while substitutional H donors have been predicted from first-principles calculations but not observed directly. Despite numerous reports, reliable p-type conductivity has not been achieved. Ferromagnetism is complicated by the presence of secondary phases, grain boundaries, and native defects. The famous green luminescence has several possible origins, including Cu impurities and Zn vacancies. The properties of group-I (Cu, Li, and Na) and group-V (N, P, As, and Sb) acceptors, and their complexes with H, are discussed. In the future, doping of ZnO nanocrystals will rely on an understanding of these fundamental properties.

  9. Impurity-doped ZnO Thin Films Prepared by Physical Deposition Methods Appropriate for Transparent Electrode Applications in Thin-film Solar Cells

    NASA Astrophysics Data System (ADS)

    Minami, Tadatsugu; Miyata, Toshihiro; Nomoto, Jun-ichi

    2012-04-01

    This paper describes the development of transparent conducting impurity-doped ZnO thin films that would be appropriate for applications as transparent electrodes in thin-film solar cells. Transparent conducting Al-, B- and Ga-doped ZnO (AZO, BZO and GZO) thin films were prepared in a thickness range from 500 to 2000 nm on glass substrates at 200°C using various physical deposition methods: BZO films with vacuum arc plasma evaporation, AZO and GZO films with different types of magnetron sputtering depositions (MSDs) and all films with pulsed laser deposition (PLD). The suitability and stability of the electrical properties and, in addition, the suitability of the light scattering characteristics and surface texture formation were investigated in the prepared thin films. In particular, the suitability and stability evaluation was focused on the use of AZO, BZO and GZO thin films prepared by doping each impurity at an appropriate content to attain the lowest resistivity. The higher Hall mobility obtained in impurity-doped ZnO thin films with a resistivity on the order of 10-4 Ωcm was related more to the content, i.e., the obtained carrier concentration, rather than the kind of impurity doped into the films. The stability of resistivity of the BZO thin films in long-term moisture-resistance tests (in air at 85% relative humidity and 85°C) was found to be lower than that of the AZO and GZO thin films. The surface texture formation was carried out by wet-chemical etching (in a 0.1% HCl solution at 25°C) conducted either before or after being heat-treated either with rapid thermal annealing (RTA) or without RTA. The suitability of the light scattering characteristics and the surface texture formation obtainable by wet-chemical etching (for use in transparent electrode applications) was considerably dependent on the deposition method used as well as whether the wet-chemical etching was conducted with or without RTA. A significant improvement of both transmittance and

  10. A Comparison of ZnO and ZnO(-)

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Partridge, Harry; Arnold, James (Technical Monitor)

    1998-01-01

    Ab initio electronic structure calculations are performed to support and to help interpret the experimental work reported in the proceeding manuscript. The CCSD(T) approach, in conjunction with a large basis set, is used to compute spectroscopic constants for the X(exp 1)Epsilon(+) and (3)II states of ZnO and the X(exp 2)Epsilon(+) state of ZnO(-). The spectroscopic constants, including the electron affinity, are in good agreement with experiment. The ZnO EA is significantly larger than that of O, thus relative to the atomic ground state asymptotes, ZnO(-) has a larger D(sub o) than the (1)Epsilon(+) state, despite the fact that the extra electron goes into an antibonding orbital. The changes in spectroscopic constants can be understood in terms of the X(exp 1)Epsilon(+) formally dissociating to Zn (1)S + O (1)D while the (3)II and (2)Epsilon(+) states dissociate to Zn (1)S + O (3)P and Zn (1) and O(-) (2)P, respectively.

  11. Acceptors in ZnO

    SciTech Connect

    Mccluskey, Matthew D.; Corolewski, Caleb; Lv, Jinpeng; Tarun, Marianne C.; Teklemichael, Samuel T.; Walter, Eric D.; Norton, M. G.; Harrison, Kale W.; Ha, Su Y.

    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 peak 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.

  12. Acceptors in ZnO

    SciTech Connect

    McCluskey, Matthew D. Corolewski, Caleb D.; Lv, Jinpeng; Tarun, Marianne C.; Teklemichael, Samuel T.; Walter, Eric D.; Norton, M. Grant; Harrison, Kale W.; Ha, Su

    2015-03-21

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

  13. Homoepitaxial ZnO Film Growth

    NASA Technical Reports Server (NTRS)

    Zhu, Shen; Su, C-H; Lehoczky, S. L.; Harris, M. T.; Callahan, M. J.; McCarty, P.; George, M. A.; Rose, M. Franklin (Technical Monitor)

    2000-01-01

    ZnO films have high potential for many applications, such as surface acoustic wave filters, UV detectors, and light emitting devices due to its structural, electrical, and optical properties. High quality epitaxial films are required for these applications. The Al2O3 substrate is commonly used for ZnO heteroepitaxial growth. Recently, high quality ZnO single crystals are available for grow homoepitaxial films. Epitaxial ZnO films were grown on the two polar surfaces (O-face and Zn-face) of (0001) ZnO single crystal substrates using off-axis magnetron sputtering deposition. As a comparison, films were also deposited on (0001) Al2O3 substrates. It was found that the two polar ZnO surfaces have different photoluminescence (PL) spectrum, surface structure and morphology, which strongly influence the epitaxial film growth. The morphology and structure of homoepitaxial films grown on the ZnO substrates were different from heteroepitaxial films grown on the Al2O3. An interesting result shows that high temperature annealing of ZnO single crystals will improve the surface structure on the O-face surface rather than the opposite surface. The measurements of PL, low-angle incident x-ray diffraction, and atomic force microscopy of ZnO films indicate that the O-terminated surface is better for ZnO epitaxial film growth.

  14. Preparation of new morphological ZnO and Ce-doped ZnO

    SciTech Connect

    Chelouche, A.; Djouadi, D.; Aksas, A.

    2013-12-16

    ZnO micro-tori and cerium doped hexangulars ZnO have been prepared by the sol-gel method under methanol hypercritical conditions of temperature and pressure. X-ray diffraction (XRD) measurement has revealed the high crystalline quality and the nanometric size of the samples. Scanning electron microscopy (SEM) has shown that the ZnO powder has a torus-like shape while that of ZnO:Ce has a hexangular-like shape, either standing free or inserted into the cores of ZnO tori. Transmission electron microscopy (TEM) has revealed that the ZnO particles have sizes between 25 and 30 nm while Ce-doped ZnO grains have diameters ranging from 75 nm to 100 nm. Photoluminescence spectra at room temperature of the samples have revealed that the introduction of cerium in ZnO reduces the emission intensity lines, particularly the ZnO red and green ones.

  15. Gold coated ZnO nanorod biosensor for glucose detection

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Anuradha; Jain, Chhavi; Rao, V. Padmanapan; Banerjee, S.

    2012-06-01

    Gold coated ZnO nanorod based biosensor has been fabricated for its glucose detecting abilities and compared with that of ZnO nanorod based biosensor. SEM images of electrochemically grown ZnO nanorods show hexagonally grown ZnO nanorods on an ITO substrate. Electrochemical analysis show that gold coated ZnO based biosensors have higher sensitivity, lower limit of detection and a wider linear range for glucose detection. The results demonstrate that gold coated ZnO nanorod based biosensors are a promising material for biosensor applications over single component ZnO nanorod based biosensor.

  16. Heavy flavors

    SciTech Connect

    Cox, B.; Gilman, F.J.; Gottschalk, T.D.

    1986-11-01

    A range of issues pertaining to heavy flavors at the SSC is examined including heavy flavor production by gluon-gluon fusion and by shower evolution of gluon jets, flavor tagging, reconstruction of Higgs and W bosons, and the study of rare decays and CP violation in the B meson system. A specific detector for doing heavy flavor physics and tuned to this latter study at the SSC, the TASTER, is described. 36 refs., 10 figs.

  17. Stability studies of commercial ZnO engineered nanoparticles in domestic wastewater

    NASA Astrophysics Data System (ADS)

    Chaúque, E. F. C.; Zvimba, J. N.; Ngila, J. C.; Musee, N.

    Most wastewater treatment plants (WWTPs) employ activated sludge processes to treat wastewater. The bacteria found in these systems degrade organic matter but are very sensitive to toxic compounds such as heavy metals, among others. The impact of emerging contaminants, such as engineered nanoparticles (ENPs) on the treatment efficiency of WWTPs is yet to be fully elucidated. The effects of physicochemical parameters; the pH and ionic strength on ZnO ENPs in domestic wastewater were investigated to establish their fate and behavior in wastewater treatment systems, as well as potential release into the environment if they pass untreated. Our findings showed a decrease in zinc concentration in the filtrate as pH and ionic strength increased which indicated its possible removal through the abiotic, biosorption, and biosolid settling mechanisms. This phenomenon was further confirmed by transmission electron microscopy (TEM) images which showed agglomerates of ZnO ENPs in wastewater compared with de-ionized water. The dynamic light scattering (DLS) analysis of ZnO ENPs suspension in the wastewater showed their stability over a period of 2 h, with energy dispersive X-ray (EDS) analysis showing the presence of zinc on the sludge surface, while X-ray diffraction (XRD) analysis confirmed the presence of ZnO ENPs in the sludge over typical wastewater pH ranges. The results of this study will inform the integrated water management on the impact of nanotechnology based industries and the best approach in handling wastewater treatment products.

  18. Rocksalt ZnO nanocrystal formation by beam irradiation of wurtzite ZnO in a transmission electron microscope

    NASA Astrophysics Data System (ADS)

    Lee, Sung Bo

    2016-10-01

    Under ambient conditions, ZnO crystallizes in a hexagonal wurtzite structure, but undergoes a phase transformation into a rocksalt structure with increasing hydrostatic pressure. However, in the present study, I have successfully demonstrated that intense beam irradiation of a wurtzite ZnO specimen in a transmission electron microscope produces nanoparticles of rocksalt ZnO as well as wurtzite ZnO, suggesting that the application of pressures is not a necessary condition for the formation of rocksalt ZnO.

  19. Multifunctional transparent ZnO nanorod films

    NASA Astrophysics Data System (ADS)

    Kwak, Geunjae; Jung, Sungmook; Yong, Kijung

    2011-03-01

    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.

  20. Persistent photoconductivity of ZnO

    NASA Astrophysics Data System (ADS)

    Laiho, R.; Stepanov, Yu. P.; Vlasenko, M. P.; Vlasenko, L. S.

    2009-12-01

    Persistent photoconductivity is observed in ZnO single crystals and ceramics together with persistence of electron paramagnetic resonance (EPR) spectra of defects and impurity centers. It is shown that when the light is switched on and off the microwave conductivity detected from absorption of the microwave field is well correlated with the dc-conductivity measured with electrical contacts applied to the sample. The microwave photoconductivity arises together with light-induced EPR spectra and persists after switching off the light. Coexistence of the conductivity and EPR spectra shows that the photoexcited electrons cannot return back to paramagnetic centers. The persistent photoconductivity in ZnO ceramics is large in comparison with the effect observed in powders prepared from the same material and in ZnO single crystals. This suggests that surface conductivity is the dominant mechanism of persistent photoconductivity in ZnO.

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

    PubMed Central

    2011-01-01

    A hydrothermal method to grow vertical-aligned ZnO nanorod arrays on ZnO films obtained by atomic layer deposition (ALD) is presented. The growth of ZnO nanorods is studied as function of the crystallographic orientation of the ZnO films deposited on silicon (100) substrates. Different thicknesses of ZnO films around 40 to 180 nm were obtained and characterized before carrying out the growth process by hydrothermal methods. A textured ZnO layer with preferential direction in the normal c-axes is formed on substrates by the decomposition of diethylzinc to provide nucleation sites for vertical nanorod growth. Crystallographic orientation of the ZnO nanorods and ZnO-ALD films was determined by X-ray diffraction analysis. Composition, morphologies, length, size, and diameter of the nanorods were studied using a scanning electron microscope and energy dispersed x-ray spectroscopy analyses. In this work, it is demonstrated that crystallinity of the ZnO-ALD films plays an important role in the vertical-aligned ZnO nanorod growth. The nanorod arrays synthesized in solution had a diameter, length, density, and orientation desirable for a potential application as photosensitive materials in the manufacture of semiconductor-polymer solar cells. PACS 61.46.Hk, Nanocrystals; 61.46.Km, Structure of nanowires and nanorods; 81.07.Gf, Nanowires; 81.15.Gh, Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.) PMID:21899743

  2. Polymer assisted preparation and characterization of ZnO and Sn doped ZnO nanostructures

    NASA Astrophysics Data System (ADS)

    Santhosh Kumar, A.; Nagaraja, K. K.; Nagaraja, H. S.

    2015-02-01

    Zinc oxide (ZnO) and tin doped ZnO are wide band gap semiconducting materials with excellent optoelectronic properties. In the present study ZnO and Sn: ZnO films are prepared using polymer assisted sol gel process. The thermal behaviour of the dried gel sample studied using DTA and TG analysis. TG-DTA result shown that most of the organic of PVA and CH3COO group of zinc acetate and other volatiles are removed below 500°C. The effect of Sn on the crystallinity, microstructral properties of the deposited films was investigated. XRD patterns of undoped and Sn doped ZnO films indicate enhanced intensities for the peak corresponding to (002) plane, resulting preferential orientation along the c-axis. The SEM images confirm that the grown films are composed of nanorods.

  3. Great blue-shift of luminescence of ZnO nanoparticle array constructed from ZnO quantum dots

    PubMed Central

    2011-01-01

    ZnO nanoparticle array has been fabricated on the Si substrate by a simple thermal chemical vapor transport and condensation without any metal catalysts. This ZnO nanoparticles array is constructed from ZnO quantum dots (QDs), and half-embedded in the amorphous silicon oxide layer on the surface of the Si substrate. The cathodoluminescence measurements showed that there is a pronounced blue-shift of luminescence comparable to those of the bulk counterpart, which is suggested to originate from ZnO QDs with small size where the quantum confinement effect can work well. The fabrication mechanism of the ZnO nanoparticle array constructed from ZnO QDs was proposed, in which the immiscible-like interaction between ZnO nuclei and Si surface play a key role in the ZnO QDs cluster formation. These investigations showed the fabricated nanostructure has potential applications in ultraviolet emitters. PMID:21711864

  4. Synthesis and antibacterial properties of ZnO brush pens

    NASA Astrophysics Data System (ADS)

    Wang, Dan; Zhang, Rong; Li, Yilin; Weng, Yuan; Liang, Weiquan; Zhang, Wenfeng; Zheng, Weitao; Hu, Haimei

    2015-12-01

    In this paper, ZnO with a novel hierarchical nanostructure has been synthesized by a new solution method. The novel hierarchical structure is named a ‘brush pen’. The biocompatibility and antibacterial properties of ZnO brush pens have been evaluated. The results demonstrate that ZnO brush pens show good antibacterial activity against Staphylococcus aureus.

  5. Complex and oriented ZnO nanostructures

    NASA Astrophysics Data System (ADS)

    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.

  6. ZnO nanolasers on graphene films

    NASA Astrophysics Data System (ADS)

    Baek, Hyeonjun; Park, Jun Beom; Park, Jong-woo; Hyun, Jerome K.; Yoon, Hosang; Oh, Hongseok; Yoon, Jiyoung

    2016-06-01

    We grew and characterized zinc oxide (ZnO) nanolasers on graphene films. By using graphene as a growth medium, we were able to prepare position-controlled and vertically aligned ZnO nanotube lasers. The ZnO nanolasers grown on graphene films showed good optical characteristics, evidenced by a low lasing threshold. Furthermore, the nanolaser/graphene system was easily lifted off the original substrate and transferred onto foreign substrates. The lasing performance was observed to be significantly enhanced by depositing a layer of silver on the back of the graphene film during this transfer process, which was quantitatively investigated using finite-difference time-domain simulations. Due to the wide selection of substrates enabled by the use of graphene films, our results suggest promising strategies for preparing practical nanolasers with improved performance.

  7. Dye-Sensitization Of Nanocrystalline ZnO Thin Films

    SciTech Connect

    Ajimsha, R. S.; Tyagi, M.; Das, A. K.; Misra, P.; Kukreja, L. M.

    2010-12-01

    Nannocrystalline and nanoporus thin films of ZnO were synthesized on glass substrates by using wet chemical drop casting method. X-ray diffraction measurements on these samples confirmed the formation of ZnO nanocrystallites in hexagonal wurtzite phase with mean size of {approx}20 nm. Photo sensitization of these nanostructured ZnO thin films was carried out using three types of dyes Rhodamine 6 G, Chlorophyll and cocktail of Rhodamine 6 G and Chlorophyll in 1:1 ratio. Dye sensitized ZnO thin films showed enhanced optical absorption in visible spectral region compared to the pristine ZnO thin films.

  8. 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.

  9. 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

  10. PAC investigations of radiation damage annealing in 111In implanted ZnO

    NASA Astrophysics Data System (ADS)

    Dogra, R.; Byrne, A. P.; Ridgway, M. C.

    2009-08-01

    The structural and electronic environment about implanted radioactive 111In(→ 111Cd) probe atoms as a function of annealing temperature in a single crystal of ZnO(0 0 0 1) has been monitored on an atomic scale using perturbed angular correlation technique, a nuclear hyperfine method. This technique is based upon the hyperfine interaction of the nuclear electric quadrupole moment or magnetic moment of the probes, respectively, with the electric field gradient or magnetic hyperfine field arising from the extra-nuclear electronic charges and spin distributions. The probe atoms 111In were recoil-implanted at room temperature following heavy-ion nuclear reactions. The electric quadrupole interaction was measured at room temperature for as-implanted and annealed samples. The thermal annealing in ambient nitrogen up to 1000 °C showed a progressive reduction of disorder around the probe atom as evidenced via continual decrease in width of the distribution of quadrupole interaction frequencies. Present measurements suggested that annealing at 800 °C for 30 min in flowing nitrogen is enough to produce an optimum recovery of crystallinity. After annealing of radiation damage at 1000 °C we observed an axially symmetric electric field gradient which is characterized by the unique quadrupole interaction frequency of 30.6(3) MHz and a frequency distribution of width nearly zero. The observed electric field gradient was attributed to substitutional incorporation of probe atoms at cation-sites of ZnO. In contrast to annealing in ambient nitrogen at 1000 °C, air annealing of 111In implanted ZnO samples revealed change in local stoichiometry about probe atoms which is attributed to the internal oxidation of the indium probes. The measured electric field gradient and asymmetry parameter at cation-sites of ZnO have been compared with theoretical calculations using a simple point charge model.

  11. Growth of a Novel Nanostructured ZnO Urchin: Control of Cytotoxicity and Dissolution of the ZnO Urchin.

    PubMed

    Imani, Roghayeh; Drašler, Barbara; Kononenko, Veno; Romih, Tea; Eleršič, Kristina; Jelenc, Janez; Junkar, Ita; Remškar, Maja; Drobne, Damjana; Kralj-Iglič, Veronika; Iglič, Aleš

    2015-12-01

    The applications of zinc oxide (ZnO) nanowires (NWs) in implantable wireless devices, such as diagnostic nanobiosensors and nanobiogenerators, have recently attracted enormous attention due to their unique properties. However, for these implantable nanodevices, the biocompatibility and the ability to control the behaviour of cells in contact with ZnO NWs are demanded for the success of these implantable devices, but to date, only a few contrasting results from their biocompatibility can be found. There is a need for more research about the biocompatibility of ZnO nanostructures and the adhesion and viability of cells on the surface of ZnO nanostructures. Here, we introduce synthesis of a new nature-inspired nanostructured ZnO urchin, with the dimensions of the ZnO urchin's acicula being controllable. To examine the biocompatibility and behaviour of cells in contact with the ZnO urchin, the Madin-Darby canine kidney (MDCK) epithelial cell line was chosen as an in vitro experimental model. The results of the viability assay indicated that, compared to control, the number of viable cells attached to the surface of the ZnO urchin and its surrounding area were reduced. The measurements of the Zn contents of cell media confirmed ZnO dissolution, which suggests that the ZnO dissolution in cell culture medium could lead to cytotoxicity. A purposeful reduction of ZnO cytotoxicity was achieved by surface coating of the ZnO urchin with poly(vinylidene fluorid-co-hexafluoropropylene) (PVDF-HFP), which changed the material matrix to slow the Zn ion release and consequently reduce the cytotoxicity of the ZnO urchin without reducing its functionality.

  12. Growth of a Novel Nanostructured ZnO Urchin: Control of Cytotoxicity and Dissolution of the ZnO Urchin

    NASA Astrophysics Data System (ADS)

    Imani, Roghayeh; Drašler, Barbara; Kononenko, Veno; Romih, Tea; Eleršič, Kristina; Jelenc, Janez; Junkar, Ita; Remškar, Maja; Drobne, Damjana; Kralj-Iglič, Veronika; Iglič, Aleš

    2015-11-01

    The applications of zinc oxide (ZnO) nanowires (NWs) in implantable wireless devices, such as diagnostic nanobiosensors and nanobiogenerators, have recently attracted enormous attention due to their unique properties. However, for these implantable nanodevices, the biocompatibility and the ability to control the behaviour of cells in contact with ZnO NWs are demanded for the success of these implantable devices, but to date, only a few contrasting results from their biocompatibility can be found. There is a need for more research about the biocompatibility of ZnO nanostructures and the adhesion and viability of cells on the surface of ZnO nanostructures. Here, we introduce synthesis of a new nature-inspired nanostructured ZnO urchin, with the dimensions of the ZnO urchin's acicula being controllable. To examine the biocompatibility and behaviour of cells in contact with the ZnO urchin, the Madin-Darby canine kidney (MDCK) epithelial cell line was chosen as an in vitro experimental model. The results of the viability assay indicated that, compared to control, the number of viable cells attached to the surface of the ZnO urchin and its surrounding area were reduced. The measurements of the Zn contents of cell media confirmed ZnO dissolution, which suggests that the ZnO dissolution in cell culture medium could lead to cytotoxicity. A purposeful reduction of ZnO cytotoxicity was achieved by surface coating of the ZnO urchin with poly(vinylidene fluorid-co-hexafluoropropylene) (PVDF-HFP), which changed the material matrix to slow the Zn ion release and consequently reduce the cytotoxicity of the ZnO urchin without reducing its functionality.

  13. ZnO quantum dots-decorated ZnO nanowires for the enhancement of antibacterial and photocatalytic performances

    NASA Astrophysics Data System (ADS)

    Wu, Jyh Ming; Tsay, Li-Yi

    2015-10-01

    We demonstrate highly antibacterial activities for killing off Staphylococcus aureus and Escherichia coli using ZnO nanowires decorated with ZnO quantum dots (so-called ZnO QDs/NWs) under visible-light irradiation and dark conditions. The average size of the ZnO QDs is in the range of 3-5 nm; these were uniformly dispersed on the ZnO nanowires’ surface to form the ZnO QDs/NWs. A significant blue-shift effect was observed using photoluminescence (PL) spectra. The size of the ZnO QDs is strongly dependent on the material’s synthesis time. The ZnO QDs/NWs exhibited an excellent photocatalytic activity under visible-light irradiation. The ZnO QDs’ active sites (i.e. the O-H bond and Zn2+) accelerate the photogenerated-carrier migration from the QDs to the NWs. As a consequence, the electrons reacted with the dissolved oxygen to form oxygen ions and produced hydroperoxyl radicals to enhance photocatalytic activity. The antibacterial activities (as indicated by R-factor-inhibiting activity) of the ZnO QDs/NWs for killing off Staphylococcus aureus and Escherichia coli is around 4.9 and 5.5 under visible-light irradiation and dark conditions, respectively. The hydroxyl radicals served as an efficient oxidized agent for decomposing the organic dye and microorganism species. The antibacterial activities of the ZnO QDs/NWs in the dark may be attributed to the Zn2+ ions that were released from the ZnO QDs and infused into the microbial solution against the growth of bacteria thus disrupting the microorganism. The highly antibacterial and photocatalytic activity of the ZnO QDs/NWs can be well implanted on a screen window, thus offering a promising solution to inhibit the spread of germs under visible-light and dark conditions.

  14. Heavy loads

    SciTech Connect

    Metz, D.

    1982-01-01

    The extreme pressures on the roof and walls of an earth-sheltered residential home are discussed and the need for careful planning is stressed. Pertinent terms are defined. Footings and wall structure (reinforced concrete walls and concrete block walls) are described. Roofing systems are discussed in detail and illustrated: (1) poured-in-place concrete roof slabs; (2) pre-cast concrete planks; and (3) heavy timber roofs. Insulation of earth-sheltered homes is reviewed in terms of using: (1) urethanes; (2) extruded polystyrene; and (3) expanded polystyrene. Advantages, disadvantages, R-factors, costs, and installation are discussed. (MJJ)

  15. Synthesis and characterization of ZnO thin films

    NASA Astrophysics Data System (ADS)

    Anilkumar T., S.; Girija M., L.; Venkatesh, J.

    2016-05-01

    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 conductivity 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.

  16. Growing ZnO crystals on magnetite nanoparticles.

    PubMed

    Turgeman, Rachel; Tirosh, Shay; Gedanken, Aharon

    2004-04-01

    We report herein on the oriented growth of ZnO crystals on magnetite nanoparticles. The ZnO crystals were grown by hydrolyzing a supersaturated aqueous solution of zinc nitrate. The seeds for the growth were magnetite nanoparticles with a diameter of 5.7 nm and a narrow size distribution. Hollowed ZnO hexagons of 0.15 microm width and 0.5 microm length filled with Fe(3)O(4) particles were obtained. HR-TEM (high-resolution transmission electron microscopy) and selected-area EDS (energy-dispersive spectroscopy) show that the nanoparticles are homogenously spread in the ZnO tubes. Zeta potential measurements were employed to understand the relationship between the nanoparticles and the oriented growth of the ZnO crystals. The results show that the surfactants induced the directional growth of the ZnO crystals.

  17. Homoepitaxial regrowth habits of ZnO nanowire arrays

    PubMed Central

    2011-01-01

    Synthetic regrowth of ZnO nanowires [NWs] under a similar chemical vapor transport and condensation [CVTC] process can produce abundant ZnO nanostructures which are not possible by a single CVTC step. In this work, we report three different regrowth modes of ZnO NWs: axial growth, radial growth, and both directions. The different growth modes seem to be determined by the properties of initial ZnO NW templates. By varying the growth parameters in the first-step CVTC process, ZnO nanostructures (e.g., nanoantenna) with drastically different morphologies can be obtained with distinct photoluminescence properties. The results have implications in guiding the rational synthesis of various ZnO NW heterostructures. PMID:22151820

  18. Cu-doping induced ferromagnetism in ZnO nanowires.

    PubMed

    Xu, Congkang; Yang, Kaikun; Huang, Liwei; Wang, Howard

    2009-03-28

    Cu-doped and undoped ZnO nanowires have been successfully fabricated at 600 degrees C using a vapor transport approach. Comprehensive structural analyses on as-fabricated nanowires reveal highly crystalline ZnO nanowires with 0.5 at. % of substitutional Cu doping. Ferromagnetism has been observed in Cu-doped ZnO nanowires but not in undoped ones, which is probably associated with defects involving both Cu dopants and Zn interstitials.

  19. UV response of cellulose ZnO hybrid nanocomposite

    NASA Astrophysics Data System (ADS)

    Mun, Seongcheol; Ko, Hyun-U.; Min, Seung-Ki; Kim, Hyun-Chan; Kim, Jaehwan

    2016-04-01

    ZnO nanorods grown cellulose film is a fascinating inorganic-organic hybrid nanocomposite in terms of synergistic properties with semiconductive functionality of ZnO and renewability and flexibility of cellulose film. This paper reports the fabrication and evaluation of cellulose ZnO hybrid nanocomposite (CEZOHN). ZnO nanorod is well grown on a cellulose film by simple chemical reaction with direct seeding and hydrothermal growing. CEZOHN has unique electric, electro-mechanical and photo-electrical behaviors. The performance of CEZOHN is estimated by measuring induced photocurrent under UV exposure. Mechanism of UV sensing and its possible applications for flexible and wearable UV sensor are addressed.

  20. Photophysics and photochemistry of quantized ZnO colloids

    SciTech Connect

    Kamat, P.V.; Patrick, B.

    1992-08-06

    The photophysical and photochemical behavior of quantized ZnO colloids in ethanol has been investigated by time-resolved transient absorption and emission measurements. Trapping of electrons at the ZnO surface resulted in broad absorption in the red region. The green emission of ZnO colloids was readily quenched by hole scavengers such as SCN{sup -} and I{sup -}. The photoinduced charge transfer to these hole scavengers was studied by laser flash photolysis. The yield of oxidized product increased considerably when ZnO colloids were coupled with ZnSe. 36 refs., 11 figs., 1 tab.

  1. Development of latent fingerprint by ZnO deposition.

    PubMed

    Yu, I-Heng; Jou, Shyankay; Chen, Chin-Min; Wang, Kuang-Chuan; Pang, Lei-Jang; Liao, Jeh Shane

    2011-04-15

    Vacuum metal deposition (VMD) utilizing sequential Au and Zn depositions has been an effective technique to develop latent fingerprint on plastic surfaces. A simplified vacuum deposition process was conducted to develop fingerprint in this study. While pure ZnO was thermally evaporated in a vacuum system, ZnO could condense on polyethylene terephthalate (PET) surface. Direct deposition of ZnO, without applying Au seeding, yielded normal development of latent fingerprint. The development of aged fingerprint by ZnO deposition was more effective than that by Au/Zn VMD.

  2. Buffer layer effect on ZnO nanorods growth alignment

    NASA Astrophysics Data System (ADS)

    Zhao, Dongxu; Andreazza, Caroline; Andreazza, Pascal; Ma, Jiangang; Liu, Yichun; Shen, Dezhen

    2005-06-01

    Vertical aligned ZnO nanorods array was fabricated on Si with introducing a ZnO thin film as a buffer layer. Two different nucleation mechanisms were found in growth process. With using Au catalyst, Zn vapor could diffuse into Au nanoclusters with forming a solid solution. Then the ZnO nucleation site is mainly on the catalyst by oxidation of Au/Zn alloy. Without catalyst, nucleation could occur directly on the surface of buffer layer by homoepitaxy. The density and the size of ZnO nanorods could be governed by morphological character of catalyst and buffer layer. The nanorods growth is followed by vapor-solid mechanism.

  3. Sodium doping in ZnO crystals

    SciTech Connect

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

    2015-01-12

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

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

    SciTech Connect

    Mohan, R. Raj; Rajendran, K.; Sambath, K.

    2014-01-28

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

  5. Microstructural properties at the interfaces of ZnO nanorods and ZnO homo-buffer layers.

    PubMed

    Kwak, Changha; Kim, Byung-Hyuk; Park, Chang-In; Park, Sun-Hong; Seo, Soo-Young; Kim, Seon-Hyo; Han, Sang-Wook

    2010-02-01

    Uniformly and vertically well-aligned ZnO nanorods were fabricated in-situ and ex-situ on ZnO films using a catalyst-free metal-organic chemical vapor process. Microstructural properties of the initial growth of ZnO nanorods on ZnO films with different surface roughnesses were investigated. We observed that the ZnO nanorods grown on ZnO films with surface roughness of less than 1.0 nm were well-aligned along the c-axis and in the ab-plane. When the nanorods grew on ZnO films with a large surface roughness, they had three different growth directions of 28 degrees, 62 degrees, and 90 degrees to the film surface. The slant angle of 62 degrees corresponds to the angle between the ZnO(001) and (101) planes. The initial growth direction difference caused structural disorder at the interface of the ZnO nanorod and film, and prevented epitaxial growth and the alignment of the nanorods. PMID:20352736

  6. Synthesis, characterization and photocatalytic activity of PVP stabilized ZnO and modified ZnO nanostructures

    NASA Astrophysics Data System (ADS)

    Bandekar, Gauri; Rajurkar, N. S.; Mulla, I. S.; Mulik, U. P.; Amalnerkar, D. P.; Adhyapak, P. V.

    2013-01-01

    In the present study, ZnO nanostructures have been successfully synthesized by hydrothermal, sonochemical and precipitation methods using polyvinyl pyrrolidone (PVP) as the capping agent. The ZnO nanoparticles were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), UV-Visible spectroscopy and photoluminescence (PL) techniques. The XRD results revealed the hexagonal wurtzite structure of the ZnO nanostructures for all the samples. Furthermore, the morphology of the ZnO particles was obtained from FESEM micrographs. Particles prepared by hydrothermal method were found to be rice grain shaped and that prepared by precipitation and sonochemical methods were spherical shaped. Sunlight driven photocatalytic degradation of methylene blue (MB) was studied for ZnO nanostructures synthesized by various methods. The ZnO nanostructures were further decorated with Ag nanoparticles to enhance its dye degradation efficiency. The Ag decorated ZnO nanoparticles exhibited a higher degradation rate as compared to pure ZnO nanoparticles which was independent of pH. Since this process of dye degradation relies on the degradation of dye due to oxidation by highly reactive hydroxyl radicals, there are many factors which affect the efficiency of this process. Hence a study was conducted on the effect of various parameters on ZnO viz amount of catalyst, reaction pH and concentration of MB dye.

  7. Root uptake and phytotoxicity of ZnO nanoparticles.

    PubMed

    Lin, Daohui; Xing, Baoshan

    2008-08-01

    Increasing application of nanotechnology highlights the need to clarify nanotoxicity. However, few researches have focused on phytotoxicity of nanomaterials; it is unknown whether plants can uptake and transport nanoparticles. This study was to examine cell internalization and upward translocation of ZnO nanoparticles by Lolium perenne (ryegrass). The dissolution of ZnO nanoparticles and its contribution to the toxicity on ryegrass were also investigated. Zn2+ ions were used to compare and verify the root uptake and phytotoxicity of ZnO nanoparticles in a hydroponic culture system. The root uptake and phytotoxicity were visualized by light scanning electron, and transmission electron microscopies. In the presence of ZnO nanoparticles, ryegrass biomass significantly reduced, root tips shrank, and root epidermal and cortical cells highly vacuolated or collapsed. Zn2+ ion concentrations in bulk nutrient solutions with ZnO nanoparticles were lower than the toxicity threshold of Zn2+ to the ryegrass; shoot Zn contents under ZnO nanoparticle treatments were much lower than that under Zn2+ treatments. Therefore, the phytotoxicity of ZnO nanoparticles was not directly from their limited dissolution in the bulk nutrient solution or rhizosphere. ZnO nanoparticles greatly adhered on to the rootsurface. Individual ZnO nanoparticles were observed present in apoplast and protoplast of the root endodermis and stele. However, translocation factors of Zn from root to shoot remained very low under ZnO nanoparticle treatments, and were much lower than that under Zn2+ treatments, implying that little (if any) ZnO nanoparticles could translocate up in the ryegrass in this study.

  8. Role of ZnO thin film in the vertically aligned growth of ZnO nanorods by chemical bath deposition

    NASA Astrophysics Data System (ADS)

    Son, Nguyen Thanh; Noh, Jin-Seo; Park, Sungho

    2016-08-01

    The effect of ZnO thin film on the growth of ZnO nanorods was investigated. ZnO thin films were sputter-deposited on Si substrate with varying the thickness. ZnO nanorods were grown on the thin film using a chemical bath deposition (CBD) method at 90 °C. The ZnO thin films showed granular structure and vertical roughness on the surface, which facilitated the vertical growth of ZnO nanorods. The average grain size and the surface roughness of ZnO film increased with an increase in film thickness, and this led to the increase in both the average diameter and the average length of vertically grown ZnO nanorods. In particular, it was found that the average diameter of ZnO nanorods was very close to the average grain size of ZnO thin film, confirming the role of ZnO film as a seed layer for the vertical growth of ZnO nanorods. The CBD growth on ZnO seed layers may provide a facile route to engineering vertically aligned ZnO nanorod arrays.

  9. ZnO nanorods: growth mechanism and anisotropic functionalization

    NASA Astrophysics Data System (ADS)

    Pacholski, Claudia; Kornowski, Andreas; Weller, Horst

    2004-10-01

    We report on the wet-chemical synthesis of ZnO nanoparticles and their functionalization with metal colloids by photocatalytic reduction of metal ions. Different morphologies of ZnO nanoparticles were prepared by using different precursor concentrations and zinc sources such as zinc acetate, zinc propanoate and zinc decanoate. Spherical ZnO nanoparticles were produced at low concentrations and with zinc precursors having long alkylchains. The formation of elongated particles was achieved by using zinc acetate and high precursor concentrations. We found that ZnO nanorods were grown via oriented attachment of pre-formed quasi-spherical particles. This growth mechanism occurs at almost ambient temperature and in the first step, pearl chain like structures of 5 nm particles are formed, which coarse by condensation and finally grow - assisted by Ostwald ripening - to almost perfect single crystalline rods with length up to 300 nm. These nanorods were metallizied with silver and platinum by photocatalytic reduction of the appropriate metal ions on pre-formed ZnO nanorods. The deposition of metal took place at different locations of the ZnO nanorods and depended on the metal source. Positively charged silver ions were preferentially reduced to silver colloids at one end of the ZnO nanorods and led to anisotropic functionalized nanoparticles. Using a negatively charged platinum complex instead of silver ions generated a statistical coverage of the ZnO nanorods.

  10. Magnetism in dopant-free ZnO nanoplates.

    PubMed

    Hong, Jung-Il; Choi, Jiil; Jang, Seung Soon; Gu, Jiyeong; Chang, Yangling; Wortman, Gregory; Snyder, Robert L; Wang, Zhong Lin

    2012-02-01

    It is known that bulk ZnO is a nonmagnetic material. However, the electronic band structure of ZnO is severely distorted when the ZnO is in the shape of a very thin plate with its dimension along the c-axis reduced to a few nanometers while keeping the bulk scale sizes in the other two dimensions. We found that the chemically synthesized ZnO nanoplates exhibit magnetism even at room temperature. First-principles calculations show a growing asymmetry in the spin distribution within the distorted bands formed from Zn (3d) and O (2p) orbitals with the reduction of thickness of the ZnO nanoplates, which is suggested to be responsible for the observed magnetism. In contrast, reducing the dimension along the a- or b-axes of a ZnO crystal does not yield any magnetism for ZnO nanowires that grow along c-axis, suggesting that the internal electric field produced by the large {0001} polar surfaces of the nanoplates may be responsible for the distorted electronic band structures of thin ZnO nanoplates.

  11. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

  13. Fabrication and photoluminescence studies of porous ZnO nanorods

    NASA Astrophysics Data System (ADS)

    Cho, Min Young; Kim, Min Su; Kim, Soaram; Leem, Jae-Young; Kim, Do Yeob; Kim, Sung-O.; Nam, Giwoong

    2012-07-01

    Zinc-oxide (ZnO) nanorods were grown using the hydrothermal method, and nanosized pores were formed on their surfaces by thermal annealing at 700 °C for 20 min under an argon atmosphere. The structural and the optical properties of the porous ZnO nanorods were investigated using scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and temperature-dependent photoluminescence. The average diameter and density of the nanosized pores were 32 nm and 7 × 1010 cm-2, respectively. The crystal quality, stoichiometry, and optical properties of the porous ZnO nanorods were enhanced in comparison with those of the as-prepared ZnO nanorods. The activation energies for the exciton with increasing temperature in the as-prepared and the porous ZnO nanorods were 27.0 and 37.8 meV, respectively. At temperatures of 50 K < T < 125 K, the free exciton emission peak energy of the porous ZnO nanorods exhibited an anomalous behavior. The values of the fitting parameters in Varshni's empirical formula were α = 1 × 10-3 eV/K and β = 720 K for the as-prepared ZnO nanorods and α = 1 × 10-3 eV/K and β = 710 K for the porous ZnO nanorods. With increasing temperature, the exciton radiative lifetime of the porous ZnO nanorods exhibited an inverted S-shape while that of the as-prepared ZnO nanorods increased linearly.

  14. Gold as an intruder in ZnO nanowires.

    PubMed

    Méndez-Reyes, José M; Monroy, B Marel; Bizarro, Monserrat; Güell, Frank; Martínez, Ana; Ramos, Estrella

    2015-09-01

    Several techniques for obtaining ZnO nanowires (ZnO NWs) have been reported in the literature. In particular, vapour-liquid-solid (VLS) with Au as a catalyst is widely used. During this process, Au impurities in the ZnO NWs can be incorporated accidentally, and for this reason we named these impurities as intruders. It is thought that these intruders may produce interesting alterations in the electronic characteristics of nanowires. In the experiment, it is not easy to detect either Au atoms in these nanowires, or the modification that intruders produce in different electrical, optical and other properties. For this reason, in this density functional theory investigation, the effect of Au intruders on ZnO NWs is analysed. Au extended (thread) and point defects (atoms replacing Zn or O, or Au interstitials) are used to simulate the presence of gold atoms. Optimised geometries, band-gaps and density of states indicate that the presence of small amounts of Au drastically modifies the electronic states of ZnO NWs. The results reported here clearly indicate that small amounts of Au have a strong impact on the electronic properties of ZnO NWs, introducing states in the band edges that may promote transitions in the visible spectral region. The presence of Au as an intruder in ZnO NWs enhances the potential use of this system for photonic and photovoltaic applications. PMID:26219752

  15. Hugely enhanced electroluminescence from mesoporous ZnO particles

    NASA Astrophysics Data System (ADS)

    Ning, Guang-hui; Zhao, Xiao-peng; Li, Jia; Zhang, Chang-qing

    2006-03-01

    Using octadecylamine (ODA) and dodecylamine (DDA) as template, nanostructured porous ZnO particles were synthesized by sol-gel method. The results of experiments show that the density of ZnO processed with ODA, DDA and without template is 5.31, 5.37 and 5.42 cm2/g respectively. The surface analysis proves that the ZnO particles processed with ODA and DDA hold porous structure. Hugely enhanced electroluminescence (EL) was observed from the porous ZnO particles under direct current electric field from 2-4.66 V/μm. Comparing with the low emission intensity of the ZnO without porous structure, the emission intensity of the ZnO sample processed with DDA and DDA were enhanced 12 times and 20 times respectively at the voltage of 4.66 V/μm. The EL spectrum shows mainly broad peak emission feature with a peak at 556 nm. The threshold voltage is just 2 V/μm. The results indicate that the porous structure in ZnO particles can enhance EL intensity.

  16. Synthesis and characterization of ZnO tetrapods

    NASA Astrophysics Data System (ADS)

    Zahran, H. Y.; Yahia, I. S.

    2015-06-01

    ZnO was prepared by direct combustion method of pure zinc metal at 1000 °C for 30 min. After combustion, ZnO was formed as a fumed powder. The as-synthesized ZnO was characterized by means of different techniques such as: X-ray diffraction (XRD), scanning electron microscope (SEM), diffused reflectance and the electrical conductivity measurements. XRD showed that ZnO has a nanocrystalline hexagonal phase with lattice constants a = 3.24982 Å and c = 5.20661 Å as compared to JCDPS card. From the analysis of the diffused reflectance spectra, the optical band gap was calculated and equals 3.2 eV which is in the same range for commercial ZnO and the reported ZnO prepared by other techniques. SEM micrographs showed the nanotetrapods structure of ZnO with highly uniform distribution of tetrapods. The DC electrical conductivity measurement was carried out in the temperature range 293-473 K, and it was found to be increased with increasing temperature forming three different conduction mechanisms associated with three activation energies.

  17. Growth of Homoepitaxial ZnO Semiconducting Films

    NASA Technical Reports Server (NTRS)

    Zhu, Shen; Su, Ching-Hua; Lehoczky, S. L.; Harris, M. T.; George, Michael A.; McCarty, P.

    1999-01-01

    As a high temperature semiconductor, ZnO has been used for many applications such as wave-guide, solar cells, and surface acoustic wave devices. Since the ZnO material has an energy gap of 3.3 eV at room temperature and an excitonic binding energy (60 meV) that is possible to make excitonic lasering at room temperature a recent surge of interest is to synthesize ZnO films for electro-optical devices. These applications require films with a smooth surface, good crystal quality, and low defect density. Homoepitaxial films have been studied in terms of morphology, crystal structure, and electrical and optical properties. ZnO single crystals are grown by the hydrothermal method. Substrates are mechanically polished and annealed in air for four hours before deposited films. The annealing temperature-dependence of ZnO substrates is studied. Films are synthesized by the off-axis reactive sputtering deposition. The films have very smooth surface with a roughness ZnO films grown of (0001) ZnO and (0001) sapphire substrates will be also compared and discussed in the presentation.

  18. Superhydrophobic ZnO networks with high water adhesion

    PubMed Central

    2014-01-01

    ZnO structures were deposited using a simple chemical bath deposition technique onto interdigitated electrodes fabricated by a conventional photolithography method on SiO2/Si substrates. The X-ray diffraction studies show that the ZnO samples have a hexagonal wurtzite crystalline structure. The scanning electron microscopy observations prove that the substrates are uniformly covered by ZnO networks formed by monodisperse rods. The ZnO rod average diameter and length were tuned by controlling reactants' concentration and reaction time. Optical spectroscopy measurements demonstrate that all the samples display bandgap values and emission bands typical for ZnO. The electrical measurements reveal percolating networks which are highly sensitive when the samples are exposed to ammonia vapors, a variation in their resistance with the exposure time being evidenced. Other important characteristics are that the ZnO rod networks exhibit superhydrophobicity, with water contact angles exceeding 150° and a high water droplet adhesion. Reproducible, easily scalable, and low-cost chemical bath deposition and photolithography techniques could provide a facile approach to fabricate such ZnO networks and devices based on them for a wide range of applications where multifunctionality, i.e., sensing and superhydrophobicity, properties are required. PACS 81.07.-b; 81.05.Dz; 68.08.Bc PMID:25136286

  19. High pressure and high temperature behaviour of ZnO

    SciTech Connect

    Thakar, Nilesh A.; Bhatt, Apoorva D.; Pandya, Tushar C.

    2014-04-24

    The thermodynamic properties with the wurtzite (B4) and rocksalt (B1) phases of ZnO under high pressures and high temperatures have been investigated using Tait's Equation of state (EOS). The effects of pressures and temperatures on thermodynamic properties such as bulk modulus, thermal expansivity and thermal pressure are explored for both two structures. It is found that ZnO material gradually softens with increase of temperature while it hardens with the increment of the pressure. Our predicted results of thermodynamics properties for both the phases of ZnO are in overall agreement with the available data in the literature.

  20. 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.

  1. Green emission in carbon doped ZnO films

    SciTech Connect

    Tseng, L. T.; Yi, J. B. Zhang, X. Y.; Xing, G. Z.; Luo, X.; Li, S.; Fan, H. M.; Herng, T. S.; Ding, J.; Ionescu, M.

    2014-06-15

    The emission behavior of C-doped ZnO films, which were prepared by implantation of carbon into ZnO films, is investigated. Orange/red emission is observed for the films with the thickness of 60–100 nm. However, the film with thickness of 200 nm shows strong green emission. Further investigations by annealing bulk ZnO single crystals under different environments, i.e. Ar, Zn or C vapor, indicated that the complex defects based on Zn interstitials are responsible for the strong green emission. The existence of complex defects was confirmed by electron spin resonance (ESR) and low temperature photoluminescence (PL) measurement.

  2. 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.

  3. Spectroscopic studies on photoelectron transfer from 2-(furan-2-yl)-1-phenyl-1H-phenanthro[9,10-d]imidazole to ZnO, Cu-doped ZnO and Ag-doped ZnO.

    PubMed

    Thanikachalam, V; Arunpandiyan, A; Jayabharathi, J; Karunakaran, C; Ramanathan, P

    2014-09-01

    The 2-(furan-2-yl)-1-phenyl-1H-phenanthro[9,10-d]imidazole [FPI] has been designed and synthesized as fluorescent sensor for nanoparticulate ZnO. The present work investigates the photoelectron transfer (PET) from FPI to ZnO, Cu-doped ZnO and Ag- doped ZnO nanoparticles using electronic and life time spectral measurements. Broad absorption along with red shift indicates the formation of charge-transfer complex [FPI-Nanoparticles]. The photophysical studies indicate lowering of HOMO and LUMO energy levels of FPI on adsorption on ZnO due to FPI- ZnO interaction. The obtained binding constant implies that the binding of FPI with nanoparticles was influenced by the surface modification of ZnO nanoparticles with Cu and Ag.

  4. Nanowire Array Gratings with ZnO Combs

    SciTech Connect

    Pan, Zhengwei; Mahurin, Shannon Mark; Dai, Sheng; Lowndes, Douglas H

    2005-01-01

    Diffraction gratings are mainly manufactured by mechanical ruling, interference lithography, or resin replication, which generally require expensive equipment, complicated procedures, and a stable environment. We describe the controlled growth of self-organized microscale ZnO comb gratings by a simple one-step thermal evaporation and condensation method. The ZnO combs consist of an array of very uniform, perfectly aligned, evenly spaced and long single-crystalline ZnO nanowires or nanobelts with periods in the range of 0.2 to 2 {mu}m. Diffraction experiments show that the ZnO combs can function as a tiny three-beam divider that may find applications in miniaturized integrated optics such as three-beam optical pickup systems.

  5. 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.

  6. Solution synthesis and optimization of ZnO nanowindmills

    NASA Astrophysics Data System (ADS)

    Yu, Lijie; Qu, Fengyu; Wu, Xiang

    2011-06-01

    In this work, novel windmill-like ZnO structures were fabricated through a solution route at low reaction temperature. The as-synthesized ZnO nanowindmill has a central trunk of nanorod and six symmetrical nanorods grown epitaxially on the surface of the ZnO trunk along [0 0 0 1] direction. Each nanorod forming the windmill with a smooth top is about 6 μm in length and about 700 nm in diameter. Several control experiments were conducted to study the formation of the nanowindmills of ZnO in detail. Cathodoluminescence (CL) property of the as-obtained product was investigated, which shows there are three emission peaks centered at 384, 616 and 753 nm in CL spectrum.

  7. Synthesis, characterization, and green luminescence in ZnO nanocages.

    PubMed

    Snure, Michael; Tiwari, Ashutosh

    2007-02-01

    In this paper, we report the synthesis, characterization and observation of green luminescence in ZnO nanocages. A novel low temperature solution-based technique has been developed for growing highly porous ZnO nano-cages from coarse ZnO precursor powders. Various samples, prepared in this study, were characterized using several different characterization tools such as X-ray diffraction, Scanning Electron Microscopy, Energy Dispersive X-ray Spectroscopy, Raman, Photoluminescence and Optical Transmission Spectroscopy. It has been shown that ZnO nanocages exhibit green luminescence, with PL data showing a broad green peak at 510 nm. The shift and broadening in the luminescence peaks are understood to arise because of the onset of deep level defects in the system.

  8. Li doped ZnO thin films for optoelectronic applications

    NASA Astrophysics Data System (ADS)

    Sandeep, K. M.; Bhat, Shreesha; Serrao, F. J.; Dharmaprakash, S. M.

    2016-05-01

    We have prepared undoped (ZnO) and Li doped ZnO (LZO) thin films using cost effective sol gel spin coating method.The structural properties were analyzed by X-ray diffraction, and it showed that Li ions occupied interstitial positions in the LZO film. The optical properties like band bending effect, absorption length, band edge sharpness, which have direct impact on solar cell performance has been calculated. The room temperature photoluminescence spectra of the films showed dominant blue emission with CIE coordinate numbers (0.1384, 0.0836) for ZnO and (0.1356, 0.0910) for LZO. The dominating wavelength of the blue emission is present at 470.9 nm and 472.3 nm for ZnO and LZO films respectively. The structural and optical parameters determined in the present study could be used in LED applications.

  9. 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. PMID:26807679

  10. Colloidal transition-metal-doped ZnO quantum dots.

    PubMed

    Radovanovic, Pavle V; Norberg, Nick S; McNally, Kathryn E; Gamelin, Daniel R

    2002-12-25

    Methods for introducing new magnetic, optical, electronic, photophysical, or photochemical properties to semiconductor nanocrystals are attracting intense applications-oriented interest. In this communication, we report the preparation and electronic absorption spectroscopy of colloidal ZnO DMS-QDs. Our synthetic procedure involves modification of literature methods known to yield highly crystalline and relatively monodisperse nanocrystals of pure ZnO to allow introduction of transition-metal dopants. We use ligand-field electronic absorption spectroscopy as a dopant-specific optical probe to monitor dopant incorporation during nanocrystal growth and to verify internal substitutional doping in Co2+:ZnO and Ni2+:ZnO DMS-QDs. To the best of our knowledge, these are the first free-standing oxide DMS-QDs reported. The synthesis of colloidal oxide DMS-QDs introduces a new category of magnetic semiconductor materials available for detailed physical study and application in nanotechnology.

  11. What is atomic structures of (ZnO) 34 magic cluster?

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoqiu; Wang, Baolin; Tang, Lingli; Sai, Linwei; Zhao, Jijun

    2010-01-01

    Recent experiment on the mass spectrum of ZnO clusters revealed a (ZnO) 34 magic cluster with enhanced stability [A. Dmytruk, et al., Microelect. J. 40 (2009) 218]. We have performed an extensive search for the most stable structure of (ZnO) 34 using gradient-corrected density-functional theory. Instead of the previously nominated onion-like nested cage of (ZnO) 6@(ZnO) 28, we found that the hollow cage structures satisfying the isolated six square rule constitute the most preferred structural motif for (ZnO) 34 cluster.

  12. Key Materials Aspects for Valence Control of ZnO.

    NASA Astrophysics Data System (ADS)

    Tsukazaki, Atsushi

    2006-03-01

    ZnO has significant advantages for light emitting diodes (LEDs) and lasers from the following reasons; 1) exciton binding energy in ZnO is 60 meV and can be enhanced over 100 meV in superlattices, 2) it is possible to tune the bandgap from 3 eV to 4.5 eV in Zn1-xCdxO and MgxZn1-xO alloy films having quite small lattice mismatch, and 3) large and high-quality single-crystal wafers are commercially available. In order to harvest these advantages in real devices, reliable technique for fabricating p-type ZnO has to be properly established. Recently we have reported on the improvements of undoped ZnO film quality with inserting a ZnO self-buffer layer onto lattice matched ScAlMgO4 substrate [1]. In view of point defect formation during the epitaxy, we have carefully optimized the growth conditions. We selected nitrogen as an acceptor, because the ionic radius is close to that of oxygen. Here we propose a repeated temperature modulation (RTM) technique for efficient nitrogen doping into ZnO with keeping high crystallinity [2]. By carefully optimizing the conditions, p-type ZnO with a hole concentration of 10^16 - 10^17 cm-3 can be reproducibly fabricated. We also demonstrated blue electroluminescence from p-i-n homojunction LED [3]. The details of thin film growth, characteristics of p-type ZnO and device performance will be presented. [1] A. Tsukazaki et al. Nature Mater. 4, 42 (2005). [2] A. Tsukazaki et al. Appl. Phys. Lett.83, 2784 (2003). [3]A. Tsukazaki et al. Jpn. J. Appl. Phys.Lett.44, L643 (2005).

  13. High efficient ZnO nanowalnuts photocatalyst: A case study

    SciTech Connect

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

    2014-11-15

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

  14. Synthesis, characteristics and antimicrobial activity of ZnO nanoparticles.

    PubMed

    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. PMID:25748589

  15. Controlled modification of multiwalled carbon nanotubes with Zno nanostructures

    SciTech Connect

    Wang Xiuying; Xia Baiying; Zhu Xingfu; Chen Jiesheng; Qiu Shilun; Li Jixue

    2008-04-15

    Multiwalled carbon nanotubes (MWNTs) have been successfully modified with ZnO nanostructures by zinc-ammonitum complex ion covalently attached to the MWNTs through the C-N bonds. Flower-like ZnO on the tips of MWNTs and ZnO nanoparticles on the surface of MWNTs have been obtained, respectively, via adjusting the reaction time. The modified MWNTs have been characterized with X-ray diffraction, scanning electron and transmission electron microscopy. A growth mechanism has been proposed in which the soaking time plays a key role in controlling the size, morphology, and site of ZnO nanostructures. Photoluminescence properties of the as-synthesized products have also been investigated. - Multiwalled carbon nanotube (MWNT)/flower-like ZnO heterojunctions and MWNT/ZnO nanoparticle composites were prepared by zinc-ammonitum complex ion covalently attached to the MWNTs through the C-N bonds via adjusting the reaction time. A growth mechanism has been proposed in which the soaking time plays a key role in controlling the size, morphology, and site of ZnO nanostructures.

  16. 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.

  17. Luminescence mechanisms of defective ZnO nanoparticles.

    PubMed

    Camarda, Pietro; Messina, Fabrizio; Vaccaro, Lavinia; Agnello, Simonpietro; Buscarino, Gianpiero; Schneider, Reinhard; Popescu, Radian; Gerthsen, Dagmar; Lorenzi, Roberto; Gelardi, Franco Mario; Cannas, Marco

    2016-06-28

    ZnO nanoparticles (NPs) synthesized by pulsed laser ablation (PLAL) of a zinc plate in deionized water were investigated by time-resolved photoluminescence (PL) and complementary techniques (TEM, AFM, μRaman). HRTEM images show that PLAL produces crystalline ZnO NPs in wurtzite structure with a slightly distorted lattice parameter a. Consistently, optical spectra show the typical absorption edge of wurtzite ZnO (Eg = 3.38 eV) and the related excitonic PL peaked at 3.32 eV with a subnanosecond lifetime. ZnO NPs display a further PL peaking at 2.2 eV related to defects, which shows a power law decay kinetics. Thermal annealing in O2 and in a He atmosphere produces a reduction of the A1(LO) Raman mode at 565 cm(-1) associated with oxygen vacancies, accompanied by a decrease of defect-related emission at 2.2 eV. Based on our experimental results the emission at 2.2 eV is proposed to originate from a photo-generated hole in the valence band recombining with an electron deeply trapped in a singly ionized oxygen vacancy. This investigation clarifies important aspects of the photophysics of ZnO NPs and indicates that ZnO emission can be controlled by thermal annealing, which is important in view of optoelectronic applications. PMID:27251452

  18. Hierarchical ZnO Superstructures: Nanoflake-Decorated Nanonail Arrays.

    PubMed

    Hu, Anzheng; Wang, Jingyang; Liang, Guiji; Wang, Song; Zhan, Dan; Yang, Han

    2016-01-01

    By using metallic Zn powders as zinc source, we synthesized unusual hierarchical ZnO superstructures, nanoflake-decorated nanonail arrays, on a large scale via a simple low-temperature thermal evaporation method. The hierarchical superstructures were characterized by using X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, high resolution transmission electron microscopy as well as selected area electron diffraction. Studies found that both the ZnO nanonails and the decorated ZnO nanoflakes are single-crystals, with the preferred growth orientations along the (001) direction. The possible formation mechanism for the interesting hierarchical superstructures has been discussed. It was found that the deposition of indium films on a Si substrate and the heterogeneous nucleation of ZnO nanoflakes on the main ZnO nanonails play key roles in the fabrication of ZnO superstructures. Moreover, these special hierarchical superstructures showed much strong and complicated photoluminescent emissions in the visible region. PMID:27398581

  19. Stabilization principles for polar surfaces of ZnO.

    PubMed

    Lauritsen, Jeppe V; Porsgaard, Soeren; Rasmussen, Morten K; Jensen, Mona C R; Bechstein, Ralf; Meinander, Kristoffer; Clausen, Bjerne S; Helveg, Stig; Wahl, Roman; Kresse, Georg; Besenbacher, Flemming

    2011-07-26

    ZnO is a wide band gap metal oxide with a very interesting combination of semiconducting, transparent optical and catalytic properties. Recently, an amplified interest in ZnO has appeared due to the impressive progress made in nanofabrication of tailored ZnO nanostructures and functional surfaces. However, the fundamental principles governing the structure of even the clean low-index ZnO surfaces have not been adequately explained. From an interplay of high-resolution scanning probe microscopy (SPM), X-ray photoelectron spectroscopy (XPS), near edge X-ray absorption fine structure (NEXAFS) spectroscopy experiments, and density functional theory (DFT) calculations, we identify here a group of hitherto unresolved surface structures which stabilize the clean polar O-terminated ZnO(0001) surface. The found honeycomb structures are truly remarkable since their existence deviates from expectations using a conventional electrostatic model which applies to the opposite Zn-terminated (0001) surface. As a common principle, the differences for the clean polar ZnO surfaces are explained by a higher bonding flexibility of the exposed 3-fold coordinated surface Zn atoms as compared to O atoms. PMID:21671628

  20. 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.

  1. Self-assembled ZnO nanoparticles on ZnO microsheet: ultrafast synthesis and tunable photoluminescence properties

    NASA Astrophysics Data System (ADS)

    Brahma, Sanjaya; Khatei, Jayakrishna; Sunkara, S.; Lo, K.-Y.; Shivashankar, S. A.

    2015-06-01

    We report on the tunable photoluminescence characteristics of porous ZnO microsheets fabricated within 1-5 min of microwave irradiation in the presence of a capping agent such as citric acid, and mixture of citric acid with polyvinylpyrrolidone (PVP). The UV emission intensity reduces to 60% and visible emission increases tenfold when the molar concentration of citric acid is doubled. Further diminution of the intensity of UV emission (25%) is observed when PVP is mixed with citric acid. The addition of nitrogen donor ligands to the parent precursor leads to a red shift in the visible luminescence. The deep level emission covers the entire visible spectrum and gives an impression of white light emission from these ZnO samples. The detailed luminescence mechanism of our ZnO samples is described with the help of a band diagram constructed by using the theoretical models that describe the formation energy of the defect energy levels within the energy band structure. Oxygen vacancies play the key role in the variation of the green luminescence in the ZnO microsheets. Our research findings provide an insight that it is possible to retain the microstructure and simultaneously introduce defects into ZnO. The growth of the ZnO microsheets may be due to the self assembly of the fine sheets formed during the initial stage of nucleation.

  2. Local transformation of ZIF-8 powders and coatings into ZnO nanorods for photocatalytic application

    NASA Astrophysics Data System (ADS)

    Wee, Lik H.; Janssens, Nikki; Sree, Sreeprasanth P.; Wiktor, Christian; Gobechiya, Elena; Fischer, Roland A.; Kirschhock, Christine E. A.; Martens, Johan A.

    2014-01-01

    Silver nitrate induces spontaneous room temperature transformation of ZIF-8 into a composite of ZnO nanorods embedded in a ZIF-8 matrix. This first example of reverse transformation of ZIF-8 into ZnO is a convenient method for generating fixed ZnO nanoparticles in powders as well as films and coatings. The fabricated ZnO nanorod@ZIF-8 is photocatalytically active.Silver nitrate induces spontaneous room temperature transformation of ZIF-8 into a composite of ZnO nanorods embedded in a ZIF-8 matrix. This first example of reverse transformation of ZIF-8 into ZnO is a convenient method for generating fixed ZnO nanoparticles in powders as well as films and coatings. The fabricated ZnO nanorod@ZIF-8 is photocatalytically active. Electronic supplementary information (ESI) available: Experimental details, XRD patterns and XRD quantitative phase analysis. See DOI: 10.1039/c3nr05289c

  3. 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.

  4. Growth of Homoepitaxial ZnO Semiconducting Films

    NASA Technical Reports Server (NTRS)

    Zhu, Shen; Su, C.-H.; Lehoczky, S. L.; Harris, M. T.; George, M. A.; McCarty, P.

    1999-01-01

    As a high temperature wide-band-gap (3.3 eV at room temperature) semiconductor, ZnO has been used for many applications such as wave-guides, solar cells, and surface acoustic wave devices, Since ZnO has a 60 meV excitonic binding energy that makes it possible to produce excitonic lasing at room temperature, a recent surge of interest is to synthesize ZnO films for UV/blue/green laser diodes. These applications require films with a smooth surface, good crystal quality, and low defect density. Thus, homoepitaxial film growth is the best choice. Homoepitaxial films have been studied in terms of morphology, crystal structure, and electrical and optical properties. ZnO single crystal substrates grown by the hydrothermal method are mechanically polished and annealed in air for four hours before the films are deposited. The annealing temperature-dependence on ZnO substrate morphology and electrical properties is investigated. Films are synthesized by off-axis reactive sputtering deposition. This produces films that have very smooth surfaces with roughness less than or equal to 5 nm on a 5 microns x 5 microns area. The full width at half maximum of film theta rocking curves measured by the x-ray diffraction is slightly larger than that of the crystal substrate. Films are also characterized by measuring resistivity, optical transmittance, and photoluminescence. The properties of ZnO films grown on (0001) ZnO and (0001) sapphire substrates will also be compared and discussed.

  5. Photoluminescence characterization of ZnO nanowires functionalization

    NASA Astrophysics Data System (ADS)

    Politi, Jane; Gioffrè, Mariano; Rea, Ilaria; De Stefano, Luca; Rendina, Ivo

    2015-05-01

    Nanostructured photoluminescent materials are optimal transducers for optical biosensors due to their capacity to convert molecular interactions in light signals without contamination or deterioration of the samples. In recent years, nanostructured biosensors with low cost and readily available properties have been developed for such applications as therapeutics, diagnostic and environmental. Zinc oxide nanowires (ZnO NWs) is material with unique properties and due to these they were widely studied in many fields as electronics, optics, and photonics. ZnO NWs can be either grown independently or deposited on solid support, such as glass, gold substrates and crystalline silicon. Vertical aligned ZnO forest on a substrate shows specific advantages in photonic device fabrication. ZnO NWs are typically synthesized by such techniques classified as vapour phase and solution phase synthesis. In particular, hydrothermal methods have received a lot of attention and have been widely used for synthesis of ZnO NWs. This technique shows more crystalline defects than others due to oxygen vacancies, so as the material shows intense photoluminescence emission under laser irradiation. ZnO NWs surface is highly hydrolysed, so it is covered by OH reactive groups, and standard biomodification chemistry can be used in order to bind bioprobes on the surface. In this work, we present our newest results on synthetic nanostructured materials characterization for optical biosensors applications. In particular, we characterize the ZnO NWs structure grown on crystalline silicon by SEM images and the biomodification by photoluminesce technique, fluorescence microscopy, water contact angle and FT-IR measurements.

  6. Tuning magnetism by biaxial strain in native ZnO.

    PubMed

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

    2015-07-01

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

  7. Solution precursor plasma deposition of nanostructured ZnO coatings

    SciTech Connect

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

    2011-08-15

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

  8. Influence of Al-, Co-, Cu-, and In-doped ZnO buffer layers on the structural and the optical properties of ZnO thin films

    NASA Astrophysics Data System (ADS)

    Kim, Younggyu; Choe, Jongyun; Nam, Giwoong; Kim, Ikhyun; Leem, Jae-Young; Lee, Sang-heon; Kim, Soaram; Kim, Do Yeob; Kim, Sung-O.

    2015-01-01

    Zinc oxide (ZnO) thin films without a buffer layer and with Al-, Co-, Cu-, and In-doped ZnO buffer layers were prepared by using the sol-gel spin-coating method. For the first time, the effects of the ZnO buffer layers doped with different metal materials on the structural and the optical properties of the ZnO thin films are investigated. The surface morphologies of the ZnO thin films having wrinkle structures significantly depended on the type of buffer layer. The largest crystallite size and the highest c-axis orientation were observed for the ZnO thin film with a Co-doped ZnO buffer layer. However, the transmittance for the ZnO thin films with metal-doped buffer layers was slightly decreased compared to that without the buffer layer, and metal-doped ZnO buffer layers hardly affected the optical band gap of the ZnO thin films.

  9. One-pot synthesis of ZnO2/ZnO composite with enhanced photocatalytic performance for organic dye removal.

    PubMed

    Liu, Wei; Wang, Mingliang; Xu, Chunxiang; Chen, Shifu; Fu, Xianliang

    2013-01-01

    The ZnO2/ZnO photocatalysts with various ZnO2 contents were prepared by one-pot synthesis method using ZnO and H2O2 as raw materials. The photocatalysts were characterized by XRD, UV-vis DRS, SEM, EDS, FT-IR spectra, fluorescence emission spectra, and BET specific area. The photocatalytic performance of the photocatalyst was evaluated by photocatalytic degradation of methyl orange (MO) and rhodamine B (RhB). The results showed that the photocatalytic activity of the ZnO2/ZnO was much higher than that of single-phase ZnO or ZnO2. The optimum ZnO2 content was 1.0 wt.%. The maximal degradation rate constant of MO and RhB was 4.1 times and 2.2 times that observed for pure ZnO, respectively. The stability of the prepared photocatalyst in the photocatalytic process was also investigated. The active species in dye degradation were examined by adding a series of scavengers. The possible mechanisms involved in the photocatalytic degradation of dye were also discussed.

  10. 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

  11. 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.

  12. Genomic DNA binding to ZnO microrods

    NASA Astrophysics Data System (ADS)

    Guzmán-Embús, D. A.; Cardozo, M. Orrego; Vargas-Hernández, C.

    2015-08-01

    In this work, ZnO microrods were produced by hydrothermal synthesis. DNA was extracted from pork spleen cells by cellular lysis, deproteinization and precipitation. The analysis of the DNA binding to the ZnO was performed using Raman spectroscopy a technique that allowed for the evaluation of the effect that the presence of the ZnO in the complex has on the DNA structure. Vibrational spectral bands from the DNA molecule and hexagonal wurtzite ZnO were observed and classified as E2(M), A1(TO), E2(High), E1(LO) and 2LO. The Raman signals from the vibrational bands corresponding to the phosphodiester bond 5‧-C-O-P-O-C-3‧ and bond stretching of the PO2- group, as well as ring vibrations of the nitrogenous bases of the DNA, were enhanced by the presence of the ZnO microrods. The bands from the modes corresponding to the C-O and Odbnd Psbnd O- molecules of the DNA backbone were observed to exhibit larger spectral shifts due to the compression and tensile stresses generated at the ZnO/DNA interface, respectively. In addition, the relative vibrational mode intensities of the nitrogenous bases increased.

  13. Heavy quark masses

    NASA Technical Reports Server (NTRS)

    Testa, Massimo

    1990-01-01

    In the large quark mass limit, an argument which identifies the mass of the heavy-light pseudoscalar or scalar bound state with the renormalized mass of the heavy quark is given. The following equation is discussed: m(sub Q) = m(sub B), where m(sub Q) and m(sub B) are respectively the mass of the heavy quark and the mass of the pseudoscalar bound state.

  14. Mutagenicity of heavy metals

    SciTech Connect

    Wong, P.K.

    1988-04-01

    Certain heavy metals are required, as trace elements for normal cellular functions. However, heavy metals are toxic to cells once their levels exceed their low physiological values. The toxicity of heavy metals on microorganisms, and on animals has been well-documented. These interactions may induce the alteration of the primary as well as secondary structures of the DNA and result in mutation(s). The present communication reports the results in determining the mutagenicity and carcinogenicity of ten heavy metals commonly found in polluted areas by using the Salmonella/mammalian-microsome mutagenicity test.

  15. Heavy-Quark Production

    NASA Astrophysics Data System (ADS)

    Frixione, Stefano; Mangano, Michelangelo L.; Nason, Paolo; Ridolfi, Giovanni

    The following sections are included: * INTRODUCTION * FIXED-TARGET PRODUCTION * Total cross sections * Single-inclusive distributions * Double-differential distributions * HEAVY-FLAVOUR PRODUCTION AT HERA * Photoproduction cross sections * Charm photoproduction * Bottom photoproduction * Deep-inelastic production * Future physics * Determination of f^{(p)}_{g} * Polarization asymmetries * HERA-B * HEAVY-QUARK PRODUCTION AT HADRON COLLIDERS * Inclusive bottom production * Preliminaries * The effect of higher-order corrections * Comparison with experimental results * boverline{b} correlations * Heavy-quark jets in perturbative QCD * Preliminaries * The structure of heavy-quark jets at the Tevatron * Associated production of heavy quarks with W or γ * Photon plus heavy quarks * W bosons plus heavy quarks * Production of top quarks * Total toverline{t} production cross sections * Top kinematical distributions * HIGHER ORDERS AND RESUMMATION * What are soft-gluon effects * Problems with the x-space resummation formula * Phenomenological applications * HEAVY-FLAVOUR PRODUCTION IN e+e- COLLISIONS * Preliminaries * Fragmentation function * Heavy-quark production via gluon splitting * Correlations * CONCLUSIONS AND OUTLOOK * Acknowledgements * REFERENCES

  16. 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.

  17. High mobility ZnO nanowires for terahertz detection applications

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

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

  18. Nitrogen is a deep acceptor in ZnO

    DOE PAGESBeta

    Tarun, M. C.; Iqbal, M. Zafar; McCluskey, M. D.

    2011-04-14

    Zinc oxide is a promising material for blue and UV solid-state lighting devices, among other applications. Nitrogen has been regarded as a potential p-type dopant for ZnO. However, recent calculations indicate that nitrogen is a deep acceptor. This paper presents experimental evidence that nitrogen is, in fact, a deep acceptor and therefore cannot produce p-type ZnO. A broad photoluminescence (PL) emission band near 1.7 eV, with an excitation onset of ~2.2 eV, was observed, in agreement with the deep-acceptor model of the nitrogen defect. Thus the deep-acceptor behavior can be explained by the low energy of the ZnO valence bandmore » relative to the vacuum level.« less

  19. Enhanced Photoluminescence in Acetylene-Treated ZnO Nanorods.

    PubMed

    Jäppinen, Luke; Jalkanen, Tero; Sieber, Brigitte; Addad, Ahmed; Heinonen, Markku; Kukk, Edwin; Radevici, Ivan; Paturi, Petriina; Peurla, Markus; Shahbazi, Mohammad-Ali; Santos, Hélder A; Boukherroub, Rabah; Santos, Hellen; Lastusaari, Mika; Salonen, Jarno

    2016-12-01

    Zinc oxide (ZnO) nanorods were manufactured using the aqueous chemical growth (ACG) method, and the effect of thermal acetylene treatment on their morphology, chemical composition, and optical properties was investigated. Changes in the elemental content of the treated rods were found to be different than in previous reports, possibly due to the different defect concentrations in the samples, highlighting the importance of synthesis method selection for the process. Acetylene treatment resulted in a significant improvement of the ultraviolet photoluminescence of the rods. The greatest increase in emission intensity was recorded on ZnO rods treated at the temperature of 825 °C. The findings imply that the changes brought on by the treatment are limited to the surface of the ZnO rods.

  20. Nitrogen is a deep acceptor in ZnO

    SciTech Connect

    Tarun, M. C.; Iqbal, M. Zafar; McCluskey, M. D.

    2011-04-14

    Zinc oxide is a promising material for blue and UV solid-state lighting devices, among other applications. Nitrogen has been regarded as a potential p-type dopant for ZnO. However, recent calculations indicate that nitrogen is a deep acceptor. This paper presents experimental evidence that nitrogen is, in fact, a deep acceptor and therefore cannot produce p-type ZnO. A broad photoluminescence (PL) emission band near 1.7 eV, with an excitation onset of ~2.2 eV, was observed, in agreement with the deep-acceptor model of the nitrogen defect. Thus the deep-acceptor behavior can be explained by the low energy of the ZnO valence band relative to the vacuum level.

  1. Enhanced Photoluminescence in Acetylene-Treated ZnO Nanorods

    NASA Astrophysics Data System (ADS)

    Jäppinen, Luke; Jalkanen, Tero; Sieber, Brigitte; Addad, Ahmed; Heinonen, Markku; Kukk, Edwin; Radevici, Ivan; Paturi, Petriina; Peurla, Markus; Shahbazi, Mohammad-Ali; Santos, Hélder A.; Boukherroub, Rabah; Santos, Hellen; Lastusaari, Mika; Salonen, Jarno

    2016-09-01

    Zinc oxide (ZnO) nanorods were manufactured using the aqueous chemical growth (ACG) method, and the effect of thermal acetylene treatment on their morphology, chemical composition, and optical properties was investigated. Changes in the elemental content of the treated rods were found to be different than in previous reports, possibly due to the different defect concentrations in the samples, highlighting the importance of synthesis method selection for the process. Acetylene treatment resulted in a significant improvement of the ultraviolet photoluminescence of the rods. The greatest increase in emission intensity was recorded on ZnO rods treated at the temperature of 825 °C. The findings imply that the changes brought on by the treatment are limited to the surface of the ZnO rods.

  2. Electrical Property of Conventionally Sintered ZnO

    NASA Astrophysics Data System (ADS)

    Tak, S. K.; Shekhwat, M. S.; Mangal, R.

    ZnO powder was synthesized by solid state reaction method. The synthesized powder was granulated and pressed using uni-axial press for preparing the pallets. The prepared pellets were sintered in conventional furnace at different temperatures (900-1300° C). The phase study was done by powder X-ray diffraction and it was found that the there is no other phase present in the synthesized material but the peak intensity is increasing with temperature. The crystallite size of the synthesized ZnO powder was found to be increase with temperature. The effect of sintering on grain growth is investigated by scanning electron microscopy (SEM). SEM revels that the average grain size is increases with increase in sintering temperature. AC impedance of these samples was decreased markedly with increased sintering temperature. In present work the effect of sintering temperatures and hold time on micro structural and electrical properties of ZnO ceramics is carried out.

  3. Excellent acetone sensing properties of porous ZnO

    NASA Astrophysics Data System (ADS)

    Liu, Chang-Bai; Liu, Xing-Yi; Wang, Sheng-Lei

    2015-01-01

    Porous ZnO was obtained by hydrothermal method. The results of scanning electron microscope revealed the porous structure in the as-prepared materials. The acetone sensing test results of porous ZnO show that porous ZnO possesses excellent acetone gas sensing properties. The response is 35.5 at the optimum operating temperature of 320 °C to 100 ppm acetone. The response and recovery times to 50 ppm acetone are 2 s and 8 s, respectively. The lowest detecting limit to acetone is 0.25 ppm, and the response value is 3.8. Moreover, the sensors also exhibit excellent selectivity and long-time stability to acetone. Projected supported by the Project of Challenge Cup for College Students, China (Grant No. 450060497053).

  4. Mobility of indium on the ZnO(0001) surface

    SciTech Connect

    Heinhold, R.; Reeves, R. J.; Allen, M. W.; Williams, G. T.; Evans, D. A.

    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 unintentional In adlayers may form during the epitaxial growth of ZnO on indium-bonded substrates.

  5. Enhanced Photoluminescence in Acetylene-Treated ZnO Nanorods.

    PubMed

    Jäppinen, Luke; Jalkanen, Tero; Sieber, Brigitte; Addad, Ahmed; Heinonen, Markku; Kukk, Edwin; Radevici, Ivan; Paturi, Petriina; Peurla, Markus; Shahbazi, Mohammad-Ali; Santos, Hélder A; Boukherroub, Rabah; Santos, Hellen; Lastusaari, Mika; Salonen, Jarno

    2016-12-01

    Zinc oxide (ZnO) nanorods were manufactured using the aqueous chemical growth (ACG) method, and the effect of thermal acetylene treatment on their morphology, chemical composition, and optical properties was investigated. Changes in the elemental content of the treated rods were found to be different than in previous reports, possibly due to the different defect concentrations in the samples, highlighting the importance of synthesis method selection for the process. Acetylene treatment resulted in a significant improvement of the ultraviolet photoluminescence of the rods. The greatest increase in emission intensity was recorded on ZnO rods treated at the temperature of 825 °C. The findings imply that the changes brought on by the treatment are limited to the surface of the ZnO rods. PMID:27644239

  6. Optoelectronic properties of (ZnO)60 isomers.

    PubMed

    Caddeo, Claudia; Malloci, Giuliano; De Angelis, Filippo; Colombo, Luciano; Mattoni, Alessandro

    2012-11-01

    We studied the optoelectronic properties of six possible structures of the (ZnO)(60) cluster using density functional theory (DFT). Vertical ionization energies and electron affinities are calculated through total energy differences, while the optical absorption spectra are obtained by using hybrid time-dependent DFT. The (ZnO)(60) cluster has been proven to be particularly stable and it is of potential interest for future applications in nanoelectronics, but its ground-state configuration has been unknown to date. Since the relative stability inferred from total energy calculations suffers from a strong dependence on the computational scheme adopted, we combined it with optical spectroscopy to identify the most abundant geometrical structure of this cluster. The calculated optical spectra are different for each isomer and they could be thus used in comparison with experimental data to explain the ground state of (ZnO)(60). PMID:23000945

  7. ZnO layers deposited by Atomic Layer Deposition

    NASA Astrophysics Data System (ADS)

    Pécz, B.; Baji, Zs; Lábadi, Z.; Kovács, A.

    2013-11-01

    The structure of 40 nm thick epitaxial ZnO layers grown on single crystalline sapphire and GaN substrates by atomic layer deposition has been studied using transmission electron microscopy. The growth is carried out between 150°C and 300°C without any buffer layer using di-ethyl zinc and water precursors. The ZnO layer on sapphire is found to be polycrystalline, which is probably due to the large misfit (~15 %) and the relatively low deposition temperature. However, the small misfit (~1.8 %) between the ZnO layer that is deposited on GaN at 300°C resulted in a high quality single crystalline layer.

  8. Structural and optical properties of ZnO and ZnO:Fe nanoparticles under dense electronic excitations

    SciTech Connect

    Kumar, Shiv; Singh, Ranjan Kr.; Ghosh, Anup K.; Asokan, K.; Kanjilal, D.; Chatterjee, S.

    2013-10-28

    We report on the changes in structural, morphological, and optical properties of sol-gel derived ZnO and ZnO:Fe nanoparticles due to dense electronic excitations produced by heavy ion irradiations using 200 MeV Ag{sup +15} ion beams. X-ray diffraction studies with Rietveld refinement show that the samples are single phase and tensile strain has been developed in the ion-irradiated samples. The Raman spectroscopy measurements show that ion-irradiation results in microscopic structural disorders and breaking of translational symmetry giving rise to local distortions in the lattice. Atomic force microscopy studies show that roughness of the pellets increases strongly for pure ZnO as compared with Fe-doped ZnO due to ion-irradiation. Fourier transform infrared analysis confirms tetrahedral coordination of O ions surrounding the Zn-ions and surface modification of the nanoparticles. The UV-Vis spectroscopy measurements show that the band gap increases on Fe doping which may be due to 4s–3d and 2p–3d interactions and the Burstein-Moss band filling effect. The band gap decreases after irradiation which can be interpreted on the basis of creation of some new localized energy states above the valence band. Photoluminescence (PL) intensity is enhanced and two new emission bands viz. a blue band at ∼480 nm (related to surface defects) and a green band at ∼525 nm (related to O vacancies) are observed in ion-irradiated nanoparticles. The enhancement of PL-intensity in irradiated samples is attributed to the increase of different defect states and Zn−O bonds on the surfaces of the irradiated nanoparticles arising from surface modification.

  9. Design of Shallow p-type Dopants in ZnO (Presentation)

    SciTech Connect

    Wei, S.H.; Li, J.; Yan. Y.

    2008-05-01

    ZnO is a promising material for short wave-length opto-electronic devices such as UV lasers and LEDs due to its large exciton binding energy and low material cost. ZnO can be doped easily n-type, but the realization of stable p-type ZnO is rather difficult. Using first-principles band structure methods the authors address what causes the p-type doping difficulty in ZnO and how to overcome the p-type doping difficulty in ZnO.

  10. Effect of gamma irradiation on DC electrical conductivity of ZnO nanoparticles

    SciTech Connect

    Swaroop, K.; Somashekarappa, H. M.; Naveen, C. S.; Jayanna, H. S.

    2015-06-24

    The temperature dependent dc electrical conductivity of gamma irradiated Zinc oxide (ZnO) nanoparticles is presented in this paper. The X-ray diffraction (XRD) pattern shows hexagonal wurtzite structure of ZnO. Fourier Transform Infrared Spectroscopy (FTIR) confirms Zn-O stretching vibrations. UV-Visible spectroscopy studies show that the energy band gap (E{sub g}) of the prepared ZnO nanoparticles increases with respect to gamma irradiation dose, which can be related to room temperature dc electrical conductivity. The result shows significant variation in the high temperature dc electrical conductivity of ZnO nanoparticles due to gamma irradiation.

  11. Growth and characterization of periodically polarity-inverted ZnO structures on sapphire substrates

    SciTech Connect

    Park, Jinsub; Yao, Takafumi

    2012-10-15

    We report on the fabrication and characterization of periodically polarity inverted (PPI) ZnO heterostructures on (0 0 0 1) Al{sub 2}O{sub 3} substrates. For the periodically inverted array of ZnO polarity, CrN and Cr{sub 2}O{sub 3} polarity selection buffer layers are used for the Zn- and O-polar ZnO films, respectively. The change of polarity and period in fabricated ZnO structures is evaluated by diffraction patterns and polarity sensitive piezo-response microscopy. Finally, PPI ZnO structures with subnanometer scale period are demonstrated by using holographic lithography and regrowth techniques.

  12. Structural and electrical properties of electric field assisted spray deposited pea structured ZnO film

    NASA Astrophysics Data System (ADS)

    Chaturvedi, Neha; Swami, Sanjay Kumar; Dutta, Viresh

    2016-05-01

    Spray deposition of ZnO film was carried out. The uneven growth of ZnO nanostructures is resulted for spray deposited ZnO film. Application of DC voltage (1000V) during spray deposition provides formation of pea like structures with uniform coverage over the substrate. Electric field assisted spray deposition provides increased crystallinity with reduced resistivity and improved mobility of the ZnO film as compared to spray deposited ZnO film without electric field. This with large area deposition makes the process more efficient than other techniques.

  13. Resistive switching characteristics of a compact ZnO nanorod array grown directly on an Al-doped ZnO substrate

    NASA Astrophysics Data System (ADS)

    Yoo, E. J.; Shin, J. Y.; Yoon, T. S.; Kang, C. J.; Choi, Y. J.

    2016-07-01

    ZnO’s resistive switching properties have drawn much attention because ZnO has a simple chemical composition and is easy to manipulate. The propulsion mechanism for resistive switching in ZnO is based on a conducting filament that consists of oxygen vacancies. In the case of film structure, the random formation of the conducting filaments occasionally leads to unstable switching characteristics. Limiting the direction in which the conducting filaments are formed is one way to solve this problem. In this study, we demonstrate reliable resistive switching behavior in a device with an Au/compact ZnO nanorod array/Al-doped ZnO structure with stable resistive switching over 105 cycles and a long retention time of 104 s by confining conducting filaments along the boundaries between ZnO nanorods. The restrictive formation of conducting filaments along the boundaries between ZnO nanorods is observed directly using conductive atomic force microscopy.

  14. Assembly of ordered ZnO porous thin films by cooperative assembly method using polystyrene spheres and ultrafine ZnO particles

    SciTech Connect

    Liu Zhifeng; Jin Zhengguo . E-mail: zhgjin@tju.edu.cn; Li Wei; Qiu Jijun

    2006-01-05

    Ordered ZnO porous thin films were fabricated by cooperative assembly method using polystyrene sphere (PS) and ultrafine ZnO particles, in which ultrafine ZnO particles were directly assembled in the voids of PS while the template was being assembled by capillary forces. The influence of experimental parameters, such as evaporation temperature, ZnO concentration and the concentration ratio of PS/ZnO on morphology of the porous structure was mainly studied. The results showed that an ordered porous structure could be obtained by this method. X-ray diffraction (XRD) spectra indicated the porous ZnO thin film was wurtzite structure. The transmissivity decreased with the decrease of wavelength, but still kept above 80% beyond the wavelength of 550 nm. Optical band gap of the ZnO thin film was 3.13 eV.

  15. A high power ZnO thin film piezoelectric generator

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

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

  16. 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.

  17. Structure of graphene oxide dispersed with ZnO nanoparticles

    SciTech Connect

    Yadav, Rishikesh Pandey, Devendra K.; Khare, P. S.

    2014-10-15

    Graphene has been proposed as a promising two-dimensional nanomaterial with outstanding electronic, optical, thermal and mechanical properties for many applications. In present work a process of dispersion of graphene oxide with ZnO nanoparticles in ethanol solution with different pH values, have been studied. Samples have been characterized by XRD, SEM, PL, UV-visible spectroscopy and particles size measurement. The results analysis indicates overall improved emission spectrum. It has been observed that the average diameter of RGO (Reduced Graphene Oxide) decreases in presence of ZnO nanoparticles from 3.8μm to 0.41μm.

  18. Kinetics of Congruent Vaporization of ZnO Islands

    SciTech Connect

    Kim, B.J.; Stach, E.; Garcia, R.E.

    2011-09-28

    We examine the congruent vaporization of ZnO islands using in situ transmission electron microscopy. Correlating quantitative measurements with a theoretical model offers a comprehensive understanding of the equilibrium conditions of the system, including equilibrium vapor pressure and surface free energy. Interestingly, the surface energy depends on temperature, presumably due to a charged surface at our specific condition of low P and high T. We find that the vaporization temperature decreases with decreasing system size, a trend that is more pronounced at higher T. Applying our results of island decay towards the growth of the ZnO provides new insights into the cooperative facet growth of anisotropic nanocrystals.

  19. Optical characterization of ZnO nanomaterial with praseodymium ions

    NASA Astrophysics Data System (ADS)

    Sharma, Y. K.; Pal, Sudha; Goyal, Priyanka; Bind, Umesh Chandra

    2016-05-01

    ZnO nanomaterial with praseodymium ions was prepared by chemical synthesis method. The ZnO nanomaterial was characterized by XRD, SEM and TEM. Their absorption in UV-VIS/NIR regions was measured at room temperature. The experimental oscillator strengths were calculated from the areas under the absorption bands. Eight absorption bands have been observed. From these spectral data various energy interaction parameters like Slater-Condon, Lande, Racah, Nephelauxetic ratio and bonding parameters have been computed. Judd-Ofelt analysis has been carried out using the absorption spectra to evaluate the radiative properties for luminescent levels of the praseodymium ion and discussed. The observed nano particle size is 2nm.

  20. Hopping conduction in single ZnO nanowires

    NASA Astrophysics Data System (ADS)

    Ma, Yong-Jun; Zhang, Ze; Zhou, Feng; Lu, Li; Jin, Aizi; Gu, Changzhi

    2005-06-01

    ZnO nanowires were synthesized by chemical vapour deposition (CVD). The dc electrical conductivity of a single ZnO nanowire was investigated over a wide temperature range from 300 to 6 K. It is found that the temperature dependence of conductivity follows the relation \\ln \\rho \\sim T^{-1/2} . The conductivity data suggest that the dominant conduction mechanism is Efros-Shklovskii variable-range hopping conduction. The strong electron-electron interaction in the nanowire is also proved by the I-V and d I/d V curves, on which there emerges a Coulomb gap-like structure at low temperatures.

  1. Reducing ZnO nanoparticle cytotoxicity by surface modification

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  2. 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

    2011-05-01

    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.

  3. Electron-hole quantum physics in ZnO

    NASA Astrophysics Data System (ADS)

    Versteegh, M. A. M.

    2011-09-01

    This dissertation describes several new aspects of the quantum physics of electrons and holes in zinc oxide (ZnO), including a few possible applications. Zinc oxide is a II-VI semiconductor with a direct band gap in the ultraviolet. Experimental and theoretical studies have been performed, both on bulk ZnO and on ZnO nanowires. Chapter 2 presents a new technique for an ultrafast all-optical shutter, based on two-photon absorption in a ZnO crystal. This shutter can be used for luminescence experiments requiring extremely high time-resolution. Chapter 3 describes a time-resolved study on the electron-hole many-body effects in highly excited ZnO at room temperature, in particular band-filling, band-gap renormalization, and the disappearance of the exciton resonance due to screening. In Chapter 4, the quantum many-body theory developed and experimentally verified in Chapter 3, is used to explain laser action in ZnO nanowires, and compared with experimental results. In contrast to current opinion, the results indicate that excitons are not involved in the laser action. The measured emission wavelength, the laser threshold, and the spectral distance between the laser modes are shown to be excellently explained by our quantum many-body theory. Multiple scattering of light in a forest of nanowires can be employed to enhance light absorption in solar cells. Optimization of this technique requires better understanding of light diffusion in such a nanowire forest. In Chapter 5 we demonstrate a method, based on two-photon absorption, to directly measure the residence time of light in a nanowire forest, and we show that scanning electron microscope (SEM) images can be used to predict the photon mean free path. In Chapter 6 we present a new ultrafast all-optical transistor, consisting of a forest of ZnO nanowires. After excitation, laser action in this forest causes rapid recombination of the majority of the electrons and holes, limiting the amplification to 1.2 picoseconds only

  4. Single photon emission from ZnO nanoparticles

    SciTech Connect

    Choi, Sumin; Ton-That, Cuong; Phillips, Matthew R.; Aharonovich, Igor; Johnson, Brett C.; Castelletto, Stefania

    2014-06-30

    Room temperature single photon emitters are very important resources for photonics and emerging quantum technologies. In this work, we study single photon emission from defect centers in 20 nm zinc oxide (ZnO) nanoparticles. The emitters exhibit bright broadband fluorescence in the red spectral range centered at 640 nm with polarized excitation and emission. The studied emitters showed continuous blinking; however, bleaching can be suppressed using a polymethyl methacrylate coating. Furthermore, hydrogen termination increased the density of single photon emitters. Our results will contribute to the identification of quantum systems in ZnO.

  5. Improved Response of ZnO Films for Pyroelectric Devices

    PubMed Central

    Hsiao, Chun-Ching; Yu, Shih-Yuan

    2012-01-01

    Increasing the temperature variation rate is a useful method for enhancing the response of pyroelectric devices. A three-dimensional ZnO film was fabricated by the aerosol deposition (AD) rapid process using the shadow mask method, which induces lateral temperature gradients on the sidewalls of the responsive element, thereby increasing the temperature variation rate. To enhance the quality of the film and reduce the concentration of defects, the film was further treated by laser annealing, and the integration of a comb-like top electrode enhanced the voltage response and reduced the response time of the resulting ZnO pyroelectric devices. PMID:23235444

  6. Growth modes of ZnO nanostructures from laser ablation

    NASA Astrophysics Data System (ADS)

    Amarilio-Burshtein, I.; Tamir, S.; Lifshitz, Y.

    2010-03-01

    ZnO nanowires (NWs) and other nanostructures were grown by laser ablation of a ZnO containing target onto different substrates with and without the presence of an Au catalyst. The morphology and structure of the NWs were studied using high resolution scanning and transmission electron microscopes [including imaging, selected area electron diffraction (SAED), and energy dispersive x-ray spectroscopy (EDS)]. The different growth modes obtainable could be tuned by varying the Zn concentration in the vapor phase keeping other growth parameters intact. Possible growth mechanisms of these nanowires are suggested and discussed.

  7. Fabrication and characterization of ZnO nanowire structure on flexible substrate with different solution molarities

    NASA Astrophysics Data System (ADS)

    Lee, Kyu-Hang; Hur, Shin; Kim, Wan-Doo; Choi, Hongsoo

    2010-08-01

    Zinc Oxide nanostructures are capable of applying numerous applications such as optoelectronics, sensors, varistors, and electronic devices. There are several techniques to gorw ZnO nanostructures, including vapor-liquid-solid method, chemical vapor deposition, physical vapor deposition, metal organic chemical vapor deposition and solution process. Recently reported solution method is a simple way to grow ZnO nanowires at a low temperature. One distinctive advantage with the solution method is low processing temperature so that flexible polymer materials can be used as a substrate to grow ZnO nanowires. In this study, ZnO nanowires have been fabricated on PET film by solution method with various molarities to see the effect of different molarities on ZnO nanowire growth. The solution temperature was 80°C and ZnO nanowires were grown for 6 hours for each case. The ZnO seed layer was sputtered at room temperature for 33 min. prior to ZnO nanowire growth. These ZnO nanowires were characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), and photoluminescence (PL) measurements at room temperature using a He-Cd 325-nm laser as the excitation source. We also measured the current using current Atomic Force Microscopy (I-AFM) and presented the possibility to use ZnO nanowires as a power source for micro/nano scale devices. As a result, we found that the characterization of ZnO nanowires changes according to the solution molarity.

  8. Control of optical and electrical properties of ZnO nanocrystals by nanosecond-laser annealing

    NASA Astrophysics Data System (ADS)

    Shimogaki, T.; Ofuji, T.; Tetsuyama, N.; Kawahara, H.; Higashihata, M.; Ikenoue, H.; Nakamura, D.; Okada, T.

    2014-03-01

    Effects of laser annealing on electrical and optical properties of Zinc oxide (ZnO) nanocrystals, which are expected as building blocks for optoelectronic devices, have been investigated in this study. In the case of fabricating p-n junction in single one-dimensional ZnO nanocrystal, phosphorus-ions implanted p-type ZnO nanocrystals were recrystallized and recovered in the optical properties by nanosecond-laser annealing using a KrF excimer laser. Antimony-doped p-type ZnO nanocrystals were synthesized by irradiating laminated structure which antimony thin film were deposited on ZnO nanocrystals with the laser beam. Additionally, it is possible to control the growth rate of ZnO nanowires by using laser annealing. Irradiating with pulsed laser a part of ZnO buffer layer deposited on the a-cut sapphire substrate, then ZnO nanowires were grown on the ZnO buffer layer by the nanoparticle assisted pulsed laser deposition method. As a result, the clear boundary of the laser annealed and non-laser annealed area was appeared. It was observed that ZnO nanowires were grown densely at non-laser annealed area, on the other hand, sparse ones were grown at the laser-annealed region. In this report, the possibility of laser annealing techniques to establish the stable and reliable fabrication process of ZnO nanowires-based LD and LED are discussed on the basis of experimental results.

  9. Morphology dependent photocatalytic and magnetic properties of ZnO nanostructures

    NASA Astrophysics Data System (ADS)

    Gupta, Jagriti; Bhargava, Parag; Bahadur, D.

    2014-09-01

    Zinc oxide (ZnO) nanostructures of different morphology are synthesized by simple soft-chemical approaches. X-ray diffraction and Raman spectra reveal the formation of highly crystalline single-phase hexagonal wurtzite nanostructures of ZnO. TEM micrographs indicate that ZnO nanoparticles are spherical in shape having a size of about 8 nm whereas the length of ZnO nanorods are about 30-40 nm. SEM micrographs show that ZnO nanoassembly is spherical and porous and is about 100-400 nm in size whereas the length of the ZnO microrods are about 4-5 μm having a diameter of about 150 nm. The ZnO microdiscs are 2-3 μm in size. Photoluminescence spectra of the various ZnO nanostructures show that the near band edge emission of ZnO is strongly dependent on their size and shape. Furthermore, the sharp decrease in the intensity of green emission as shape and size changes from nano to microstructures undoubtedly indicates the suppression of oxygen vacancies due to change in the surface to volume ratio i.e. decrease in the surface area from nano to microstructures. Thus, photocatalytic performance of ZnO nanostructures strongly depends on the presence of oxygen vacancies as well as higher surface area. ZnO nanostructures show size, shape and defect concentration dependent ferromagnetic behavior and photocatalytic activity.

  10. Tunable Lattice Constant and Band Gap of Single- and Few-Layer ZnO.

    PubMed

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

    2016-04-01

    Single and few-layer ZnO(0001) (ZnO(nL), n = 1-4) grown on Au(111) have been characterized via scanning tunneling microscopy (STM), scanning tunneling spectroscopy (STS), and density functional theory (DFT) calculations. We find that the in-plane lattice constants of the ZnO(nL, n ≤ 3) are expanded compared to that of the bulk wurtzite ZnO(0001). The lattice constant reaches a maximum expansion of 3% in the ZnO(2L) and decreases to the bulk wurtzite ZnO value in the ZnO(4L). The band gap decreases monotonically with increasing number of ZnO layers from 4.48 eV (ZnO(1L)) to 3.42 eV (ZnO(4L)). These results suggest that a transition from a planar to the bulk-like ZnO structure occurs around the thickness of ZnO(4L). The work also demonstrates that the lattice constant and the band gap in ultrathin ZnO can be tuned by controlling the number of layers, providing a basis for further investigation of this material. PMID:27003692

  11. ZnO hierarchical nanostructures: simple solvothermal synthesis and growth mechanism.

    PubMed

    Dev, Apurba; Kar, Soumitra; Chaudhuri, Subhadra

    2008-09-01

    Hierarchical nano/micro structures of ZnO have been fabricated by solvothermal approach on sol-gel derived ZnO thin films. Paintbrush like nano/micro rod assembly, double-sided brush and windmill type architectures of ZnO are obtained when the ZnO thin film coated substrates were treated solvothermally in water at pH 10. Aligned nanorods are obtained at pH approximately 13.5 in water. In ethylenediamine-water solvent divergent micro/nanorod assemblies such as hemispherical dandelion, rice plant type bush of ZnO are obtained. Increase in the percentage of ethyelendiamine resulted in the formation of smaller assemblies of relatively thin nanorods. Initial slow reaction caused by the slow increase of the temperature inside the reaction medium and the different growth kinetics of the ZnO crystals are supposed to be the reason behind the architectural assemblies of the ZnO crystals.

  12. Transparent conductivity modulation of ZnO by group-IVA doping

    NASA Astrophysics Data System (ADS)

    Liu, J.; Fan, X. F.; Sun, C. Q.; Zhu, W.

    2016-04-01

    We examined the effect of group-IVA doping on the electronic structure and transmittance of ZnO using first-principle calculations. All these doped ZnO materials are found to perform n-type conductive behavior. Si-doped ZnO and Pb-doped ZnO are found to have larger optical band gap than those of Ge-doped ZnO and Sn-doped ZnO. The transmittance of Si-doped ZnO is found to be high in both UV and visible region. The enhancement of UV region transmittance can be attributed to the enhanced optical band gap, while the reduction of visible region transmittance is due to the intraband optical transition.

  13. Synthesis of ZnO nanosheets via electrodeposition method and their optical properties, growth mechanism

    NASA Astrophysics Data System (ADS)

    Yang, Jun; Wang, Yongqian; Kong, Junhan; Jia, Hanxiang; Wang, Zhengshu

    2015-08-01

    ZnO nanosheets were prepared by electrochemical deposition method at 80 °C on seeded Indium Tin Oxide conducting glass substrates. The seed layer was coated on ITO by spin coating and annealed at 350 °C for 30 min prior to electrochemical deposition growth. X-ray diffraction patterns (XRD) and field emission scanning electron microscope (FESEM) images confirmed that the ZnO nanosheets consist of polycrystalline structures. Room temperature photoluminescence spectra (PL) of the ZnO nanosheets exhibited band-edge ultraviolet (UV) and visible emission (blue) indicating the ZnO nanosheets had excellent optical properties. The UV-Vis absorption spectrum of ZnO nanosheets was shown a strong absorption at 300 nm. The ZnO nanosheets structure demonstrated higher photocatalytic activity during degradation of aqueous methylene blue under visible-light irradiation. Moreover, the growth mechanism of the ZnO nanosheets had been discussed.

  14. Mutagenicity of heavy metals

    SciTech Connect

    Wong, P.K. )

    1988-05-01

    Certain heavy metals are required, as trace elements for normal cellular functions. However, heavy metals are toxic to cells once their levels exceed their low physiological values. The toxicity of heavy metals on microorganisms, on plants and on animals has been well-documented. These interactions may induce the alteration of the primary as well as secondary structures of the DNA and result in mutation(s). Though the rec assay with Bacillus subtilis and the reversion assay with Escherichia coli were used to assess the mutagenicity of some heavy metals, the present communication reports the results in determining the mutagenicity and carcinogenicity of ten heavy metals commonly found in polluted areas by using the Salmonella/mammalian-microsome mutagenicity test.

  15. Study of ZnO and Mg doped ZnO nanoparticles by sol-gel process

    SciTech Connect

    Ansari, Mohd Meenhaz Arshad, Mohd; Tripathi, Pushpendra

    2015-06-24

    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 absorption spectra was obtained and the band gap of the samples calculated.

  16. Dynamics of ZnO nanoparticles formed in the high-pressure phase during growth of ZnO nanocrystals

    NASA Astrophysics Data System (ADS)

    Nakamura, D.; Shimogaki, T.; Takao, S.; Nakao, S.; Harada, K.; Higashihata, M.; Okada, T.

    2015-03-01

    The dynamics of zinc oxide (ZnO) nanoparticles formed in Ar gas of 200 Torr by laser ablation are visualized by ultraviolet Rayleigh scattering imaging. The time-resolved imaging of the ZnO nanoparticles are presented for several conditions of single-pulse ablation and 10 Hz ablation at room temperature. Scattering light from the nanoparticles appeared at 1-2 ms after ablation, and the spatial distribution was a mushroom like swirling cloud. The cloud propagates forward about 2.6 m/s without lateral expansion. In addition, nanoparticle distribution at a substrate heating condition, which is growth condition of ZnO nanocrystals is investigated. The nanoparticles under heating condition formed almost the same spatial distribution as that of room temperature and their speed was increased to 3.2 m/s at 750 °C.

  17. Built-in electric field in ZnO based semipolar quantum wells grown on (1012) ZnO substrates

    SciTech Connect

    Chauveau, J.-M.; Xia, Y.; Roland, B.; Vinter, B.; Ben Taazaet-Belgacem, I.; Teisseire, M.; Nemoz, M.; Brault, J.; Damilano, B.; Leroux, M.

    2013-12-23

    We report on the properties of semipolar (Zn,Mg)O/ZnO quantum wells homoepitaxially grown by molecular beam epitaxy on (1012) R-plane ZnO substrates. We demonstrate that atomically flat interfaces can be achieved with fully relaxed quantum wells because the mismatch between (Zn,Mg)O and ZnO is minimal for this growth orientation. The photoluminescence properties evidence a quantum confined Stark effect with an internal electric field estimated to 430 kV/cm for a 17% Mg content in the barriers. The quantum well emission is strongly polarized along the 1210 direction and a comparison with the semipolar bulk ZnO luminescence polarization points to the effect of the confinement.

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

    PubMed

    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

  19. 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.

  20. 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

  1. Transformation of ZnO polycrystalline sheets into hexagon-like mesocrystalline ZnO rods (tubes) under ultrasonic vibration.

    PubMed

    Ding, Jianning; Fang, Xiang; Yang, Rong; Kan, Biao; Li, Xiazhang; Yuan, Ningyi

    2014-01-01

    The mesoscale assembly process is sensitive to additives that can modify the interactions of the crystal nucleus and the developing crystals with solid surfaces and soluble molecules. However, the presence of additives is not a prerequisite for the mesoscale transformation process. In this study, ZnO sheet networks were synthesized on Al foils by a hydrothermal process. Scanning electron microscopy and transmission electron microscopy images confirmed that under ultrasonic vibration, monolithic polycrystalline ZnO sheets transformed into hexagon-like mesocrystalline tubes or rods. The formation mechanism was discussed.

  2. Heavy-ion dosimetry

    SciTech Connect

    Schimmerling, W.

    1980-03-01

    This lecture deals with some of the more important physical characteristics of relativistic heavy ions and their measurement, with beam delivery and beam monitoring, and with conventional radiation dosimetry as used in the operation of the BEVALAC biomedical facility for high energy heavy ions (Lyman and Howard, 1977; BEVALAC, 1977). Even so, many fundamental aspects of the interaction of relativistic heavy ions with matter, including important atomic physics and radiation chemical considerations, are not discussed beyond the reminder that such additional understanding is required before an adequte perspective of the problem can be attained.

  3. ZnO nanowire-based CO sensor

    NASA Astrophysics Data System (ADS)

    Ho, Mon-Shu; Chen, Wei-Hao; Chen, Yu-Lin; Chang, Meng-Fan

    This study applied ZnO nanowires to the fabrication of a CO gas sensor operable at room temperature. Following the deposition of a seed layer by spin coating, an aqueous solution method was used to grow ZnO nanowires. This was followed by the self-assembly of an electrode array via dielectrophoresis prior to the fabrication of the CO sensing device. The material characteristics were analyzed using FE-SEM, EDS, GIXRD, FE-TEM, and the measurement of photoluminescence (PL). Our results identified the ZnO nanowires as a single crystalline wurtzite structure. Extending the growth period from 30 min to 360 min led to an increase in the length and diameter of the nanowires. After two hours, the ZnO presented a preferred crystal orientation of [002]. Sensor chips were assembled using 60 pairs of electrodes with gaps of 2 μm, over which were lain nanowires to complete the sensing devices. The average sensing response was 48.37 s and the average recovery time was 65.61 s, with a sensing response magnitude of approximately 6.8% at room temperature.

  4. 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.

  5. Aerogel tempelated ZnO dye-sensitized solar cells.

    SciTech Connect

    Hamann, T. W.; Martinson , A. B. E.; Elam, J. W.; Pellin, M. J.; Hupp, J. T.; Materials Science Division; Northwestern Univ.

    2008-01-01

    Atomic layer deposition is employed to conformally coat low density, high surface area aerogel films with ZnO. The ZnO/aerogel membranes are incorporated as photoanodes in dye-sensitized solar cells, which exhibit excellent power efficiencies of up to 2.4% under 100 mW cm{sup -2} light intensity.

  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. Self-focused ZnO transducers for ultrasonic biomicroscopy

    SciTech Connect

    Cannata, J. M.; Williams, J. A.; Zhou, Q. F.; Sun, L.; Shung, K. K.; Yu, H.; Kim, E. S.

    2008-04-15

    A simple fabrication technique was developed to produce high frequency (100 MHz) 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 18 {mu}m thick ZnO layer on 2 mm diameter aluminum rods with ends shaped and polished to produce a 2 mm 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 4 {mu}m 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 101 MHz with a -6 dB bandwidth of 49%. The measured two way insertion loss was 44 dB. A tungsten wire phantom and an adult zebrafish eye were imaged to show the capability of these transducers.

  8. ZnO for photocatalytic air purification applications

    NASA Astrophysics Data System (ADS)

    Tudose, I. V.; Suchea, M.

    2016-06-01

    Nano and micro-structured ZnO coatings onto various substrates were grown by chemical methods and optimized with respect to their photocatalytic activity against in-doors common air pollutants. Excellent quality coatings with high stability and photocatalytic efficiency were obtained with the scope to be integrated in a novel air-purification system.

  9. Photoluminescence of spray pyrolysis deposited ZnO nanorods

    PubMed Central

    2011-01-01

    Photoluminescence of highly structured ZnO layers comprising well-shaped hexagonal rods is presented. The ZnO rods (length 500-1,000 nm, diameter 100-300 nm) were grown in air onto a preheated soda-lime glass (SGL) or ITO/SGL substrate by low-cost chemical spray pyrolysis method using zinc chloride precursor solutions and growth temperatures in the range of 450-550°C. We report the effect of the variation in deposition parameters (substrate type, growth temperature, spray rate, solvent type) on the photoluminescence properties of the spray-deposited ZnO nanorods. A dominant near band edge (NBE) emission is observed at 300 K and at 10 K. High-resolution photoluminescence measurements at 10 K reveal fine structure of the NBE band with the dominant peaks related to the bound exciton transitions. It is found that all studied technological parameters affect the excitonic photoluminescence in ZnO nanorods. PACS: 78.55.Et, 81.15.Rs, 61.46.Km PMID:21711895

  10. Synthesis of ZnO flowers and their photoluminescence properties

    SciTech Connect

    Wu Changle; Qiao Xueliang Luo Langli; Li Haijun

    2008-07-01

    Flower-like ZnO nano/microstructures have been synthesized by thermal treatment of Zn(NH{sub 3}){sub 4}{sup 2+} precursor in aqueous solvent, using ammonia as the structure directing agent. A number of techniques, including X-ray diffraction (XRD), field emission scan electron microscopy (FESEM), transmission electron microscopy (TEM), thermal analysis, and photoluminescence (PL) were used to characterize the obtained ZnO structures. The photoluminescence (PL) measurements indicated that the as-synthesized ZnO structures showed UV ({approx}375 nm), blue ({approx}465 nm), and yellow ({approx}585 nm) emission bands when they were excited by a He-Gd laser using 320 nm as the excitation source. Furthermore, it has been interestingly found that the intensity of light emission at {approx}585 nm remarkably decreased when the obtained ZnO nanocrystals were annealed at 600 deg. C for 3 h in air. The reason might be the possible oxygen vacancies and interstitials in the sample decreased at high temperature.

  11. Computer simulation of ZnO varistors failures

    SciTech Connect

    Bartkowiak, M.; Mahan, G.D. |; Comber, M.G.; Alim, M.A.

    1997-11-01

    Zinc oxide varistors are multi-component ceramic devices produced by sintering ZnO powder together with small amounts of other oxides. Highly nonlinear current-voltage (I-V) characteristics of ZnO varistors are used in electrical surge arresters. They protect electrical equipment from damage by limiting overvoltages and dissipating the associated energy. Therefore, the energy handling capability is crucial. It is defined as the amount of energy that a varistor can absorb before it fails. Here, a simple thermo-mechanical model is applied to evaluate the influence of the nonuniformity of ZnO varistor disks used in surge arresters on their energy handling capability. By solving heat transfer equations for a varistor disk with nonuniform electrical properties, the authors compute the time dependence of the temperature profile and the distribution of thermal stresses. The model can identify the energy handling limitations of ZnO varistors imposed by three different failure modes: puncture, thermal runaway, and cracking. It conforms to the available failure data, and explains the observation that energy handling improves at high current densities.

  12. ZnO coated nanospring-based chemiresistors

    NASA Astrophysics Data System (ADS)

    Dobrokhotov, Vladimir; Oakes, Landon; Sowell, Dewayne; Larin, Alexander; Hall, Jessica; Kengne, Alex; Bakharev, Pavel; Corti, Giancarlo; Cantrell, Timothy; Prakash, Tej; Williams, Joseph; McIlroy, D. N.

    2012-02-01

    Chemiresistors were constructed using 3-D silica nanospring mats coated with a contiguous film of ZnO nanocrystals. Chemiresistors with an average ZnO nanocrystal radius <3 nm, or >20 nm, were found to exhibit a relative change in conductance of a factor of 50 upon exposure to a gas flow of 20% O2 and 80% N2 with ˜500 ppm of toluene and an operational temperature of 400 °C. Samples with an average ZnO nanocrystal radius of 15 nm were found to be the most responsive with a relative conductance change of a factor of 1000. The addition of metal nanoparticles (average radius equal to 2.4 nm) onto the surface of the ZnO nanocrystals (average radius equal to 15 nm) produced a relative change in conductance of a factor of 1500. For the optimum conditions (T = 400 °C, grain size ˜15 nm) well-defined spikes in conductance to explosive vapors (TNT, TATP) were obtained for 0.1 ms exposure time at ppb levels.

  13. Co doped ZnO nanowires as visible light photocatalysts

    NASA Astrophysics Data System (ADS)

    Šutka, Andris; Käämbre, Tanel; Pärna, Rainer; Juhnevica, Inna; Maiorov, Mihael; Joost, Urmas; Kisand, Vambola

    2016-06-01

    High aspect ratio cobalt doped ZnO nanowires showing strong photocatalytic activity and moderate ferromagnetic behaviour were successfully synthesized using a solvothermal method and characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), vibrating sample magnetometry (VSM) and UV-visible absorption spectroscopy. The photocatalytic activities evaluated for visible light driven degradation of an aqueous methylene orange (MO) solution were higher than for Co doped ZnO nanoparticles at the same doping level and synthesized by the same synthesis route. The rate constant for MO visible light photocatalytic degradation was 1.9·10-3 min-1 in case of nanoparticles and 4.2·10-3 min-1 in case of nanowires. We observe strongly enhanced visible light photocatalytic activity for moderate Co doping levels, with an optimum at a composition of Zn0.95Co0.05O. The enhanced photocatalytic activities of Co doped ZnO nanowires were attributed to the combined effects of enhanced visible light absorption at the Co sites in ZnO nanowires, and improved separation efficiency of photogenerated charge carriers at optimal Co doping.

  14. Memristive switching of ZnO nanorod mesh

    NASA Astrophysics Data System (ADS)

    Yevgeniy, Puzyrev; Shen, Xiao; Ni, Kai; Zhang, Xuan; Hachtel, Jordan; Choi, Bo; Chisholm, Matthew; Fleetwood, Daniel; Schrimpf, Ronald; Pantelides, Sokrates

    We present a combined experimental and theoretical study of memristive switching in a self-assembled mesh of ZnO nanorods. A ZnO nanorod mesh spans the area between Ag contacts in a device that exhibits hysteresis with large ON/OFF ratio, reaching ION/IOFF values of 104. We show that switching behavior depends critically on the geometry of the nanorod mesh. We employ density functional theory (DFT) calculations to deduce the mechanism for resistive switching for the nanorod mesh. Redistribution of Ag atoms, driven by an electrical field, leads to the formation and evolution of a conducting path through nanorods. Field-induced migration of Ag atoms changes the doping level of nanorods and modulates their conductivity. Using static DFT and nudged-elastic-band calculations, we investigate the energy of interaction between Ag clusters and a ZnO surface, including migration barriers of Ag atoms. Current-voltage (I-V) characteristics are modeled using percolation theory in a nanorod mesh. To describe the dynamics of SET/RESET phenomena, model parameters include the experimentally observed nanorod geometry and the energetics of Ag on ZnO surfaces, obtained from DFT calculations. This work was supported by NSF Grant DMR-1207241, DOE Grant DE-FG02-09ER46554, and the McMinn Endowment at Vanderbilt University. Computational support was provided by the NSF XSEDE under Grant #DMR TG-DMR130121.

  15. ZnO doped sodium silicate preionize N2 laser

    NASA Astrophysics Data System (ADS)

    M, Montaser; F, Sabry; S, A. Ibrahim

    1989-11-01

    An experimental study of the effect of ZnO doped sodium silicate thin film, used as a semiconductive preionizer on the output energy is presented. The output energy of the nitrogen laser increased by two folds. The performance of the preionizer can be controlled to match the discharge requirements.

  16. Hydrogen in Ag-doped ZnO: theoretical calculations.

    PubMed

    He, H Y; Hu, J; Pan, B C

    2009-05-28

    Based on density functional theory calculations, we systematically investigate the behaviors of a H atom in Ag-doped ZnO involving the preference sites, diffusion behaviors, the electronic structures, and vibrational properties. We find that a H atom can migrate to the doped Ag to form a Ag-H complex by overcoming energy barriers of 0.3-1.0 eV. The lowest-energy site for H location is the bond center of a Ag-O in the basal plane. Moreover, H can migrate between this site and its equivalent sites with energy cost of less than 0.5 eV. In contrast, dissociation of such a Ag-H complex needs energy of about 1.1-1.3 eV. This implies that the Ag-H complexes can commonly exist in the Ag-doped ZnO, which have a negative effect on the desirable p-type carrier concentrations of Ag-doped ZnO. In addition, based on the frozen phonon calculation, the vibrational properties of ZnO with a Ag-H complex are predicted. Some new vibrational modes associated with the Ag-H complex present in the vibrational spectrum of the system.

  17. 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.

  18. Preparation and characteristics of ZnO varistors

    NASA Astrophysics Data System (ADS)

    Wei, C. C.; Tsai, Y. L.; Huang, C. L.

    The nonohmic properties of ZnO varistors having additives of Bi, Sb, and several other three-valence metal oxides were investigated. It is determined that the very high nonlinearity of the electrical properties of these varistors is related to the additive content, sintering temperature, and ambient temperature. Results of scanning electron microscopy indicate that the characteristics of ZnO varistors can be attributed to the electrical barriers in the vicinity of the grain boundary within the ZnO grains, which are mostly found in direct contact with each other. The barrier height at zero bias was found to be 1.57 V and the donor concentration of ZnO grains was determined to equal 3 x 10 to the 18th/cu cm. The V-I characteristics in the prebreakdown region at very low voltage are shown to be temperature sensitive, which is consistent with thermionic emission. The breakdown field in the depletion layer is found to be above 10 to the 6th V/cm. In addition, it is determined that tunneling through the barrier dominates in the breakdown regions and can adequately account for values of alpha in excess of 60.

  19. Ferromagnetism in Co- and Mn-doped ZnO

    NASA Astrophysics Data System (ADS)

    Theodoropoulou, N. A.; Hebard, A. F.; Norton, D. P.; Budai, J. D.; Boatner, L. A.; Lee, J. S.; Khim, Z. G.; Park, Y. D.; Overberg, M. E.; Pearton, S. J.; Wilson, R. G.

    2003-12-01

    Bulk single crystals of Sn-doped ZnO were implanted with Co or Mn at doses designed to produce transition metal concentrations of 3-5 at.% in the near-surface (˜2000 Å) region. The implantation was performed at ˜350 °C to promote dynamic annealing of ion-induced damage. Following annealing at 700 °C, temperature-dependent magnetization measurements showed ordering temperatures of ˜300 K for Co- and ˜250 K for Mn-implanted ZnO. Clear hysteresis loops were obtained at these temperatures. The coercive fields were ⩽100 Oe for all measurement temperatures. X-ray diffraction showed no detectable second phases in the Mn-implanted material. One plausible origin for the ferromagnetism in this case is a carrier-induced mechanism. By sharp contrast, the Co-implanted material showed evidence for the presence of Co precipitates with hexagonal symmetry, which is the cause of the room temperature ferromagnetism. Our results are consistent with the stabilization of ferromagnetic states by electron doping in transition metal-doped ZnO predicted by Sato and Katayama-Yoshida [Jpn. J. Appl. Phys. 40 (2001) L334]. This work shows the excellent promise of Mn-doped ZnO for potential room temperature spintronic applications.

  20. Influence of homo buffer layer thickness on the quality of ZnO epilayers.

    PubMed

    Eid, E A; Fouda, A N

    2015-10-01

    ZnO buffer layers with different thicknesses were deposited on a-plane sapphire substrates at 300 °C. ZnO epilayers were grown on ZnO buffers at 600 °C by radio-frequency magnetron sputtering and vacuum annealed at 900 °C for an hour. Influence of nucleation layer thickness on the structural and quality of ZnO thin films was investigated using X-ray diffraction (XRD), atomic force microscopy (AFM), and Raman spectroscopy. The best ZnO film quality was obtained with the ZnO buffer layer of 45 nm thick which provided the smoothest surface with RMS value of 0.3 nm. X-ray diffraction measurements reveal that the films have a single phase wurtzite structure with (0001) preferred crystal orientation. As evident from narrow FWHM of ZnO (0002) rocking curve, ZnO buffer can serve as a good template for the growth of high-quality ZnO films with little tilt. In addition, the micro-Raman scattering measurements at room temperature revealed the existence of Raman active phonon modes of ZnO; A1(TO), A1(LO) and E2(high). The latter two modes were not observed in thin buffer layer beside the dis-appearance of E2(low) mode in all films. PMID:25950638

  1. Selective area growth of well-ordered ZnO nanowire arrays with controllable polarity.

    PubMed

    Consonni, Vincent; Sarigiannidou, Eirini; Appert, Estelle; Bocheux, Amandine; Guillemin, Sophie; Donatini, Fabrice; Robin, Ivan-Christophe; Kioseoglou, Joseph; Robaut, Florence

    2014-05-27

    Controlling the polarity of ZnO nanowires in addition to the uniformity of their structural morphology in terms of position, vertical alignment, length, diameter, and period is still a technological and fundamental challenge for real-world device integration. In order to tackle this issue, we specifically combine the selective area growth on prepatterned polar c-plane ZnO single crystals using electron-beam lithography, with the chemical bath deposition. The formation of ZnO nanowires with a highly controlled structural morphology and a high optical quality is demonstrated over large surface areas on both polar c-plane ZnO single crystals. Importantly, the polarity of ZnO nanowires can be switched from O- to Zn-polar, depending on the polarity of prepatterned ZnO single crystals. This indicates that no fundamental limitations prevent ZnO nanowires from being O- or Zn-polar. In contrast to their catalyst-free growth by vapor-phase deposition techniques, the possibility to control the polarity of ZnO nanowires grown in solution is remarkable, further showing the strong interest in the chemical bath deposition and hydrothermal techniques. The single O- and Zn-polar ZnO nanowires additionally exhibit distinctive cathodoluminescence spectra. To a broader extent, these findings open the way to the ultimate fabrication of well-organized heterostructures made from ZnO nanowires, which can act as building blocks in a large number of electronic, optoelectronic, and photovoltaic devices.

  2. 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.

  3. Radio-frequency magnetron sputtering and wet thermal oxidation of ZnO thin film

    NASA Astrophysics Data System (ADS)

    Liu, H. F.; Chua, S. J.; Hu, G. X.; Gong, H.; Xiang, N.

    2007-08-01

    The authors studied the growth and wet thermal oxidation (WTO) of ZnO thin films using a radio-frequency magnetron sputtering technique. X-ray diffraction reveals a preferred orientation of [101¯0]ZnO(0002)//[112¯0]Al2O3(0002) coexisted with a small amount of ZnO (101¯1) and ZnO (101¯3) crystals on the Al2O3 (0001) substrate. The ZnO (101¯1) and ZnO (101¯3) crystals, as well as the in-plane preferred orientation, are absent from the growth of ZnO on the GaAs(001) substrate. WTO at 550 °C improves the crystalline and the photoluminescence more significantly than annealing in air, N2 and O2 ambient; it also tends to convert the crystal from ZnO (101¯1) and ZnO (101¯3) to ZnO (0002). The evolution of the photoluminescence upon WTO and annealing reveals that the green and orange emissions, centered at 520 and 650 nm, are likely originated from oxygen vacancies and oxygen interstitials, respectively; while the 420 nm emission, which is very sensitive to the postgrowth thermal processing regardless of the substrate and the ambient gas, is likely originated from the surface-state related defects.

  4. The Antibacterial Activity of Ta-doped ZnO Nanoparticles

    NASA Astrophysics Data System (ADS)

    Guo, Bing-Lei; Han, Ping; Guo, Li-Chuan; Cao, Yan-Qiang; Li, Ai-Dong; Kong, Ji-Zhou; Zhai, Hai-Fa; Wu, Di

    2015-08-01

    A novel photocatalyst of Ta-doped ZnO nanoparticles was prepared by a modified Pechini-type method. The antimicrobial study of Ta-doped ZnO nanoparticles on several bacteria of Gram-positive Bacillus subtilis ( B. subtilis) and Staphylococcus aureus ( S. aureus) and Gram-negative Escherichia coli ( E. coli) and Pseudomonas aeruginosa ( P. aeruginosa) were performed using a standard microbial method. The Ta-doping concentration effect on the minimum inhibitory concentration (MIC) of various bacteria under dark ambient has been evaluated. The photocatalytical inactivation of Ta-doped ZnO nanoparticles under visible light irradiation was examined. The MIC results indicate that the incorporation of Ta5+ ions into ZnO significantly improve the bacteriostasis effect of ZnO nanoparticles on E. coli, S. aureus, and B. subtilis in the absence of light. Compared to MIC results without light irradiation, Ta-doped ZnO and pure ZnO nanoparticles show much stronger bactericidal efficacy on P. aeruginosa, E. coli, and S. aureus under visible light illumination. The possible antimicrobial mechanisms in Ta-doped ZnO systems under visible light and dark conditions were also proposed. Ta-doped ZnO nanoparticles exhibit more effective bactericidal efficacy than pure ZnO in dark ambient, which can be attributed to the synergistic effect of enhanced surface bioactivity and increased electrostatic force due to the incorporation of Ta5+ ions into ZnO. Based on the antibacterial tests, 5 % Ta-doped ZnO is a more effective antimicrobial agent than pure ZnO.

  5. Electronic structure of Co-doped ZnO nanorods

    NASA Astrophysics Data System (ADS)

    Neffati, Ahmed; Souissi, Hajer; Kammoun, Souha

    2012-10-01

    The optical transmission spectra, the photoluminescence (PL), and the photoluminescence excitation (PLE) spectra of the cobalt doped zinc oxide nanorods Zn1-xCoxO (x = 0.01, 0.10) were measured by Loan et al. [J. Phys. D: Appl. Phys. 42, 065412 (2009)] in the region 1.5-4 eV. These spectra exhibit a group of ultraviolet narrow lines in the region of 3.0-3.4 eV related to the near-band-edge emission of the host ZnO materials and a group of emission lines in the red region of 1.8-1.9 eV assigned to the radiative transitions within the tetrahedral Co2+ ions in the ZnO host crystal. The group of lines in the visible region provides important information about the electronic structure of the cobalt doped zinc oxide nanorods. This work investigates a theoretical crystal-field analysis of the visible lines associated to the Co2+ ion transition occupying a Td site symmetry in ZnO host crystal. A satisfactory correlations were obtained between experimental and calculated energy levels. The electronic structure was compared with the reported for cobalt transition ion doped in ZnO nanoparticles and bulk crystals [Volbers et al., Appl. Phys. A 88, 153 (2007) and H. J. Schulz and M. Thiede, Phys. Rev. B 35, 18 (1987)]. In order to explain the existence of excitation peaks observed near the band edge of the ZnO host, an energy transfer mechanism is proposed.

  6. CMOS Alcohol Sensor Employing ZnO Nanowire Sensing Films

    NASA Astrophysics Data System (ADS)

    Santra, S.; Ali, S. Z.; Guha, P. K.; Hiralal, P.; Unalan, H. E.; Dalal, S. H.; Covington, J. A.; Milne, W. I.; Gardner, J. W.; Udrea, F.

    2009-05-01

    This paper reports on the utilization of zinc oxide nanowires (ZnO NWs) on a silicon on insulator (SOI) CMOS micro-hotplate for use as an alcohol sensor. The device was designed in Cadence and fabricated in a 1.0 μm SOI CMOS process at XFAB (Germany). The basic resistive gas sensor comprises of a metal micro-heater (made of aluminum) embedded in an ultra-thin membrane. Gold plated aluminum electrodes, formed of the top metal, are used for contacting with the sensing material. This design allows high operating temperatures with low power consumption. The membrane was formed by using deep reactive ion etching. ZnO NWs were grown on SOI CMOS substrates by a simple and low-cost hydrothermal method. A few nanometer of ZnO seed layer was first sputtered on the chips, using a metal mask, and then the chips were dipped in a zinc nitrate hexahydrate and hexamethylenetramine solution at 90° C to grow ZnO NWs. The chemical sensitivity of the on-chip NWs were studied in the presence of ethanol (C2H5OH) vapour (with 10% relative humidity) at two different temperatures: 200 and 250° C (the corresponding power consumptions are only 18 and 22 mW). The concentrations of ethanol vapour were varied from 175-1484 ppm (pers per million) and the maximum response was observed 40% (change in resistance in %) at 786 ppm at 250° C. These preliminary measurements showed that the on-chip deposited ZnO NWs could be a promising material for a CMOS based ethanol sensor.

  7. Zn2NF and Related Analogues of ZnO.

    PubMed

    Lingampalli, Srinivasa Rao; Manjunath, Krishnappa; Shenoy, Sandhya; Waghmare, Umesh V; Rao, C N R

    2016-07-01

    Substitution of aliovalent N(3-) and F(-) anions in place of O(2-) in ZnO brings about major changes in the electronic structure and properties, the composition, even with 10 atomic percent or less of the two anions, rendering the material yellow colored with a much smaller band gap. We have examined the variation of band gap of ZnO with progressive substitution of N and F and more importantly prepared Zn2NF which is the composition one obtains ultimately upon complete replacement of O(2-) ions. In this article, we present the results of a first complete study of the crystal and electronic structures as well as of properties of a stable metal nitride fluoride, Zn2NF. This material occurs in two crystal forms, tetragonal and orthorhombic, both with a band gap much smaller than that of ZnO. Electronic structures of Zn2NF as well as ZnO0.2N0.5F0.3 investigated by first-principles calculations show that the valence bands of these are dominated by the N (2p) states lying at the top. Interestingly, the latter is a p-type material, a property that has been anticipated for long time. The calculations predict conduction and valence band edges in Zn2NF to be favorable for water splitting. Zn2NF does indeed exhibit good visible-light-induced hydrogen evolution activity unlike ZnO. The present study demonstrates how aliovalent anion substitution can be employed for tuning band gaps of materials. PMID:27299368

  8. Capped ZnO (3, 0) nanotubes as building blocks of bare and H passivated wurtzite ZnO nanocrystals

    NASA Astrophysics Data System (ADS)

    Abdulsattar, Mudar Ahmed

    2015-09-01

    In the present work we propose building blocks of hexagonal type crystals and nanocrystals of zinc oxide including wurtzite structure that are called wurtzoids. These molecules are ZnO (3, 0) nanotubes capped at their two terminals with Zn or O atoms. Hexagonal part of these molecules is included in the central part of these molecules. This part can be repeated to increase hexagonal structure ratio. Hydrogen passivated and bare ZnO wurtzoids are investigated. Results show bare wurtzoids have shorter and stronger surface sp2 bonds than H passivated sp3 bonded wurtzoids. The calculated energy gap of these molecules shows the expected trend of gaps. Calculated binding energy per atom shows that wurtzoids are tight and stable structures which are not the case of ZnO diamondoids. Vibrational frequencies manifest the expected trends of hexagonal type structures. Reduced mass and force constant of these vibrations are investigated to illustrate the sp2 and sp3 bonding effects of bare and H passivated ZnO nanocrystals respectively.

  9. Aerodynamics of Heavy Vehicles

    NASA Astrophysics Data System (ADS)

    Choi, Haecheon; Lee, Jungil; Park, Hyungmin

    2014-01-01

    We present an overview of the aerodynamics of heavy vehicles, such as tractor-trailers, high-speed trains, and buses. We introduce three-dimensional flow structures around simplified model vehicles and heavy vehicles and discuss the flow-control devices used for drag reduction. Finally, we suggest important unsteady flow structures to investigate for the enhancement of aerodynamic performance and future directions for experimental and numerical approaches.

  10. Process for removing heavy metal compounds from heavy crude oil

    DOEpatents

    Cha, Chang Y.; Boysen, John E.; Branthaver, Jan F.

    1991-01-01

    A process is provided for removing heavy metal compounds from heavy crude oil by mixing the heavy crude oil with tar sand; preheating the mixture to a temperature of about 650.degree. F.; heating said mixture to up to 800.degree. F.; and separating tar sand from the light oils formed during said heating. The heavy metals removed from the heavy oils can be recovered from the spent sand for other uses.

  11. Effect of ZnO buffer layer on the cathodoluminescence of ZnGa 2O 4/ZnO phosphor screen for FED

    NASA Astrophysics Data System (ADS)

    Yang, Su-Hua; Hsueh, Ting-Jen; Chang, Shoou-Jinn

    2006-01-01

    A ZnGa 2O 4/ZnO phosphor screen for FED was prepared by RF magnetron sputtering. The ZnO buffer layer has a reasonable resistivity of about 5.2×10 3 Ω cm and a high transparency larger than 85%. The ZnGa 2O 4 phosphor was polycrystalline on ITO, yet it was amorphous on ZnO. If the ZnGa 2O 4/ZnO phosphor screen was annealed at temperatures above 300 °C, then ZnGa 2O 4 was crystallized. Owing to the lattice mismatch between ZnGa 2O 4 and ZnO, the grain size of ZnGa 2O 4 on ZnO was small. As a result, the effective emission area and luminescence of the ZnGa 2O 4/ZnO phosphor screen were enhanced. Auger electron spectroscopy (AES) examination showed that atoms in ZnO did not diffuse into ZnGa 2O 4 film, and the ZnGa 2O 4 was Zn-deficient. For charge balance, oxygen vacancy defects in the phosphor film were formed to compensate Zn deficiencies; consequently, the probability for electrons transfer from 2E B to 4A 2 of Ga energy levels was improved and the luminescence of the phosphor was increased.

  12. Ohmic-Rectifying Conversion of Ni Contacts on ZnO and the Possible Determination of ZnO Thin Film Surface Polarity

    PubMed Central

    Saw, Kim Guan; Tneh, Sau Siong; Tan, Gaik Leng; Yam, Fong Kwong; Ng, Sha Shiong; Hassan, Zainuriah

    2014-01-01

    The current-voltage characteristics of Ni contacts with the surfaces of ZnO thin films as well as single crystal (0001) ZnO substrate are investigated. The ZnO thin film shows a conversion from Ohmic to rectifying behavior when annealed at 800°C. Similar findings are also found on the Zn-polar surface of (0001) ZnO. The O-polar surface, however, only shows Ohmic behavior before and after annealing. The rectifying behavior observed on the Zn-polar and ZnO thin film surfaces is associated with the formation of nickel zinc oxide (Ni1-xZnxO, where x = 0.1, 0.2). The current-voltage characteristics suggest that a p-n junction is formed by Ni1-xZnxO (which is believed to be p-type) and ZnO (which is intrinsically n-type). The rectifying behavior for the ZnO thin film as a result of annealing suggests that its surface is Zn-terminated. Current-voltage measurements could possibly be used to determine the surface polarity of ZnO thin films. PMID:24466144

  13. 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.

  14. Effect of ZnO seed layer on the morphology and optical properties of ZnO nanorods grown on GaN buffer layers

    SciTech Connect

    Nandi, R. Mohan, S. Major, S. S.; Srinivasa, R. 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 and 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.

  15. Synthesis, structural and optical properties of pure ZnO and Co doped ZnO nanoparticles prepared by the co-precipitation method

    NASA Astrophysics Data System (ADS)

    Devi, P. Geetha; Velu, A. Sakthi

    2016-09-01

    Pure ZnO and Cobalt (Co) doped ZnO nanoparticles (NPs) were synthesized by the co-precipitation method. The synthesized nanoparticles retained the wurtzite hexagonal structure, which was confirmed by X-ray diffraction studies. From FESEM studies, ZnO and Co doped ZnO NPs showed Spherical and nanorod mixed phase and Spherical like morphology, respectively. The amount of dopant (Co2+) incorporated into ZnO sample was determined by EDAX. The FT-IR spectra confirmed the Zn-O stretching bands at 438 and 427 cm-1 for ZnO and Co doped ZnO NPs. From the UV-VIS spectroscopic measurements, the excitonic pecks were found around 376 and 370 nm for the respective samples. The photoluminescence measurements revealed that the broad emission was composed of seven different bands due to zinc vacancies, oxygen vacancies and surface defects. The dynamic light scattering (DLS) and Zeta potential measurements were used to find out the size and surface charges.

  16. Optimal Zn/O ratio in vapor phase for the synthesis of high quality ZnO tetrapod nanocrystals via thermal evaporation of Zn in Air

    NASA Astrophysics Data System (ADS)

    Lee, Geun-Hyoung

    2012-10-01

    Tetrapod-shaped ZnO nanocrystals were synthezised via thermal evaporation of Zn powder in air. The Zn powder was oxidized at 930 °C for 60 min. To investigate the optimal Zn/O molar ratio in such vapor phase synthesis, the Zn content was varied in range of 0.1-0.75 g. When the Zn content was 0.1 g, no nanocrystals were formed. Above 0.25 g Zn, growth of ZnO nanocrystals started without clear tetrapod like morphology. Beyond Zn content of 0.50 g, clear tetrapod-shaped ZnO nanocrystals were detected. These results establish that there is a certain required ratio of zinc and oxygen in vapor phase for generation of tetrapod-shaped ZnO nanocrystals. Such Zn:O ratio is also calculated theoretically from the ideal gas law. Clear tetrapod type ZnO nanocrystals prepared with Zn content of 0.5 g exhibited the highest intensity of the ultraviolet emission centered at 380 nm which also confirms the high crystalline quality of such ZnO nanocrystals.

  17. Thermodynamic Study of Interactions Between ZnO and ZnO Binding Peptides Using Isothermal Titration Calorimetry.

    PubMed

    Limo, Marion J; Perry, Carole C

    2015-06-23

    While material-specific peptide binding sequences have been identified using a combination of combinatorial methods and computational modeling tools, a deep molecular level understanding of the fundamental principles through which these interactions occur and in some instances modify the morphology of inorganic materials is far from being fully realized. Understanding the thermodynamic changes that occur during peptide-inorganic interactions and correlating these to structural modifications of the inorganic materials could be the key to achieving and mastering control over material formation processes. This study is a detailed investigation applying isothermal titration calorimetry (ITC) to directly probe thermodynamic changes that occur during interaction of ZnO binding peptides (ZnO-BPs) and ZnO. The ZnO-BPs used are reported sequences G-12 (GLHVMHKVAPPR), GT-16 (GLHVMHKVAPPR-GGGC), and alanine mutants of G-12 (G-12A6, G-12A11, and G-12A12) whose interaction with ZnO during solution synthesis studies have been extensively investigated. The interactions of the ZnO-BPs with ZnO yielded biphasic isotherms comprising both an endothermic and an exothermic event. Qualitative differences were observed in the isothermal profiles of the different peptides and ZnO particles studied. Measured ΔG values were between -6 and -8.5 kcal/mol, and high adsorption affinity values indicated the occurrence of favorable ZnO-BP-ZnO interactions. ITC has great potential in its use to understand peptide-inorganic interactions, and with continued development, the knowledge gained may be instrumental for simplification of selection processes of organic molecules for the advancement of material synthesis and design.

  18. Fundamental understanding of the growth, doping and characterization of aligned ZnO nanowires

    NASA Astrophysics Data System (ADS)

    Shen, Gang

    Zinc oxide (ZnO) is a II-VI semiconductor whose wide direct bandgap (3.37 eV) and large exciton binding energy (60 meV) make it compelling for optoelectronic devices such as light emitting diodes, lasers, photodetectors, solar cells, and mechanical energy harvesting devices. One dimensional structures of ZnO (nanowires) have become significant due to their unique physical properties arising from quantum confinement, and they are ideal for studying transport mechanisms in one-dimensional systems. In this doctoral research work, ZnO nanowire (NW) arrays were synthesized on sapphire substrates through carbo-thermal reduction of ZnO powders, and the effects of growth parameters on the properties of ZnO NW arrays were studied by scanning and transmission electron microscopy, X-ray diffraction, photoluminescence and Raman spectroscopy. Based on the phonon mode selection rules in wurtzite ZnO, confocal Raman spectroscopy was used to assess the alignment of ZnO NWs in an array, thereby complementing X-ray diffraction. Al doped ZnO NW arrays were achieved by mixing Al powder into the ZnO and graphite source mixture, and the presence of Al was confirmed by Energy-dispersive X-ray spectroscopy. The incorporation of Al had the effects of lowering the electrical resistivity, slightly deteriorating crystal quality and suppressing defect related green emission. Two models of ZnO NW growth were developed by establishing the relationship between NW length and diameter for undoped and Al doped ZnO NWs separately. The growth of undoped ZnO NWs followed the diffusion-induced model which was characterized by thin wires being longer than thick wires, while the growth of Al doped ZnO was controlled by Gibbs-Thomson effect which was characterized by thin wires being shorter than thin wires. Local electrode atom probe analysis of ZnO NWs was carried out to study the crystal stoichiometry and Al incorporation. Undoped ZnO NWs were found to be high purity with no detectable impurities

  19. 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

  20. 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

  1. Atomic layer deposition of ZnO on Cu-nanoclusters for methanol synthesis

    SciTech Connect

    Zhang Ziyu; Patterson, Matthew; Ren Maoming; Wang Ying; Flake, John C.; Sprunger, Phillip T.; Kurtz, Richard L.

    2013-01-15

    The properties of ALD-grown ZnO thin films on Cu clusters supported on ZnO(1010) have been studied with scanning tunneling and scanning electron microscopy in combination with angle-resolved x-ray photoelectron spectroscopy. Deposition at room temperature of two monolayers of Cu on ZnO(1010) results in metallic Cu{sup 0} clusters {approx}8 nm wide by 1.4 nm high. Higher coverages of 15 ML results in a similar morphology, with slightly larger cluster sizes. Following air-exposure and ALD-growth of two cycles of ZnO, the Cu exhibits Cu{sup +} species characteristic of Cu{sub 2}O and the thin ZnO coating is hydroxylated. Electrochemical studies of ALD ZnO coatings on Cu suggest that they are more active for CO{sub 2} reduction.

  2. Ab inito study of Ag-related defects in ZnO

    NASA Astrophysics Data System (ADS)

    Wan, Qixin; Xiong, Zhihua; Li, Dongmei; Liu, Guodong

    2008-12-01

    Using first-principles calculations, we investigated the structure and electronic properties of Ag-related defects in ZnO. The calculation results indicate that AgZn behaves as acceptor. Simultaneously, by comparing the formation energy and electronic structure of Ag-related defects in ZnO, Oi-AgZn behaves as acceptor in Ag-doped ZnO and it is better to gain p-type ZnO. However, Hi-AgZn complex has the lowest formation energy. Thus, the formation of the other point defects is greatly suppressed by the formation of Hi in Ag-doped ZnO. Moreover, the H atoms can be easily dissociated from hydrogen-passivated complexes by post-annealing at moderate temperatures, thus, codoping Ag with H may be a good method to achieve p-type in Ag-doped ZnO.

  3. Hydrothermal synthesis and dielectric properties of chrysanthemum-like ZnO particles

    NASA Astrophysics Data System (ADS)

    Yan, Jun-Feng; Zhang, Zhi-Yong; You, Tian-Gui; Zhao, Wu; Yun, Jiang-Ni

    2009-09-01

    By orthogonal design theory, technological parameters of chrysanthemum-like ZnO particles prepared in a hydrothermal process are optimized. This paper reports a set of technological parameters for growing chrysanthemum-like ZnO particles on a large scale. It investigates the morphologies and crystalline structures of the as-synthesized three-dimensional ZnO particles with a scanning electron microscope, x-ray diffractometer and transmission electron microscope, and the possible growth mechanism on the three-dimensional ZnO particles. The experimental results indicate that the values of in', in″ and tan δe gradually increase in the X band with the improvement of the developmental level of chrysanthemum-like ZnO particles, implying that the electromagnetic wave absorbing property depends on the morphologies of three-dimensional ZnO particles.

  4. Nanoantenna-like properties of sea-urchin shaped ZnO as a nanolight filter

    NASA Astrophysics Data System (ADS)

    Husn Su, Yen; Chen, Wei-Yu

    2012-09-01

    A light scattering peak of ZnO rods is presented at 543.2 nm. The radiation peaks of ZnO nanospines correspond to 496.6 nm and 630.6 nm due to the breaking of the symmetry of the ZnO rods. The radiation peaks of sea-urchin shaped ZnO was observed and confirmed by utilizing the dipole approximation. Sea-urchin shaped ZnO can tune and then filter different frequencies of light by utilizing incident light to illuminate at the different positions of sea-urchin shaped ZnO which works like a nanolight filter device and has potential applications in photonic computers, bio-light emission device, and solar cells.

  5. Fabrication and gas-sensing properties of hierarchical ZnO replica using down as template

    NASA Astrophysics Data System (ADS)

    Bai, Zikui; Li, Songzhan; Xu, Jie; Zhou, Yingshan; Gu, Shaojin; Tao, Yongzhen; Liu, Li; Fang, Dong; Xu, Weilin

    2016-06-01

    Hierarchical ZnO replica using down as template fabricated by a combination of low-temperature plasma treatment and sonochemical method was used in gas sensor for the detection of ethanol and formaldehyde. The morphologies and crystal structures of the hierarchical ZnO replica were characterized by field-emission scanning electron microscopy and X-ray diffraction, respectively. Results showed that the hierarchical ZnO replica retained the initial down morphology and consisted of hexagonal wurtzite structure ZnO nanocrystals. The results of resistance-temperature characteristics and responses to ethanol and formaldehyde indicated that the hierarchical ZnO film had low activation energy (0.1118 eV) and a low optimum operating temperature and that the response time was longer than recovery time. These behaviors were well explained in relation to three-dimensional network structures and the high specific surface area of the hierarchical ZnO replica.

  6. Surface Defects Control for ZnO Nanorods Synthesized Through a Gas-Assisted Hydrothermal Process

    NASA Astrophysics Data System (ADS)

    Zhao, Limin; Shu, Changhua; Jia, Zhengfeng; Wang, Changzheng

    2016-08-01

    Oxygen vacancies in crystal have an important impact on the electronic properties of zinc oxide (ZnO). In this paper, ZnO nanorods with rich oxygen vacancies were prepared through a novel gas-assisted hydrothermal growth process. X-ray diffraction data showed that single-phase ZnO with the wurtzite crystal structure was obtained and the crystallite size decreased as the reaction atmosphere pressure increased. The oxygen vacancies of ZnO were confirmed using x-ray photoelectron spectroscopy and photoluminescence spectroscopy. The results showed that the concentration of oxygen vacancies could be regulated by both the atmosphere pressure and the atmosphere properties. The oxygen vacancies in ZnO samples were reduced when the pressure increase in the hydrogen reaction environment (reducing atmosphere) and the oxygen vacancies in ZnO samples were increased when the pressure increased in the oxygen reaction environment (oxidizing atmosphere).

  7. The effects of addition of citric acid on the morphologies of ZnO nanorods

    SciTech Connect

    Yang Zao . E-mail: yangzao888@tom.com; Liu Quanhui; Yang Lei

    2007-02-15

    ZnO nanorods of 25-100 nm in diameter and 0.2-1 {mu}m in length were fabricated through citric acid assisted annealing process. The microstructure of ZnO nanorods was characterized by X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy and field-emission scanning electron microscopy, respectively. As a result, it was found that ZnO nanorods were single crystalline and pure. The effects of the growth conditions such as addition of citric acid, annealing temperature on the morphologies of ZnO nanostructures have also been investigated. At the given temperature the length decreased but the diameter increased with addition of the mass of citric acid. With the rising of the calcining heat, the shape of ZnO changed from rod to granule for a given amount of citric acid. Finally, the mechanism for citric acid assisted annealing synthesis of the ZnO nanostructure is discussed.

  8. Fabrication and characterization of hexagonally patterned quasi-1D ZnO nanowire arrays

    NASA Astrophysics Data System (ADS)

    Kuo, Shou-Yi; Lin, Hsin-I.

    2014-02-01

    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.

  9. Fabrication and characterization of hexagonally patterned quasi-1D ZnO nanowire arrays.

    PubMed

    Kuo, Shou-Yi; Lin, Hsin-I

    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

  10. Effect of the morphology on the optical properties of ZnO nanostructures

    NASA Astrophysics Data System (ADS)

    Yang, Zao; Ye, Zhizhen; Xu, Zheng; zhao, Binghui

    2009-12-01

    ZnO nanostructures are fabricated by citric acid-assisted annealing process. The samples are characterized by X-ray diffraction, field-emission scanning electron microscopy (FE-SEM), FTIR spectrophotometer, ultraviolet-visible-near IR spectroscopy and photoluminescence (PL) spectroscopy. The X-ray diffraction pattern of these samples shows that ZnO nanostructures are single crystalline and pure. The effect of morphology of ZnO nanostructures on the optical properties of ZnO nanostructures is analyzed on the basis of these results. Our results clearly demonstrate that tunable optical properties of ZnO nanostructures can be attained by changing the morphology of ZnO nanostructures.

  11. Effect of Intrinsic Point Defect on the Magnetic Properties of ZnO Nanowire

    PubMed Central

    Yun, Jiangni; Zhang, Zhiyong; Yin, Tieen

    2013-01-01

    The effect of intrinsic point defect on the magnetic properties of ZnO nanowire is investigated by the first-principles calculation based on the density functional theory (DFT). The calculated results reveal that the pure ZnO nanowire without intrinsic point defect is nonmagnetic and ZnO nanowire with VO, Zni, Oi, OZn, or ZnO point defect also is nonmagnetic. However, a strong spin splitting phenomenon is observed in ZnO nanowire with VZn defect sitting on the surface site. The Mulliken population analysis reveals that the oxygen atoms which are close to the VZn defect do major contribution to the magnetic moment. Partial density states calculation further suggests that the appearance of the half-metallic ferromagnetism in ZnO nanorod with VZn originates from the hybridization of the O2p states with Zn 3d states. PMID:24396300

  12. Rapid synthesis of Co, Ni co-doped ZnO nanoparticles: Optical and electrochemical properties

    NASA Astrophysics Data System (ADS)

    Romeiro, Fernanda C.; Marinho, Juliane Z.; Lemos, Samantha C. S.; de Moura, Ana P.; Freire, Poliana G.; da Silva, Luis F.; Longo, Elson; Munoz, Rodrigo A. A.; Lima, Renata C.

    2015-10-01

    We report for the first time a rapid preparation of Zn1-2xCoxNixO nanoparticles via a versatile and environmentally friendly route, microwave-assisted hydrothermal (MAH) method. The Co, Ni co-doped ZnO nanoparticles present an effect on photoluminescence and electrochemical properties, exhibiting excellent electrocatalytic performance compared to undoped ZnO sample. Photoluminescence spectroscopy measurements indicated the reduction of the green-orange-red visible emission region after adding Co and Ni ions, revealing the formation of alternative pathways for the generated recombination. The presence of these metallic ions into ZnO creates different defects, contributing to a local structural disorder, as revealed by Raman spectra. Electrochemical experiments revealed that the electrocatalytic oxidation of dopamine on ZnO attached to multi-walled carbon nanotubes improved significantly in the Co, Ni co-doped ZnO samples when compared to pure ZnO.

  13. Application of ZnO nanopillars and nanoflowers to field-emission luminescent tubes

    NASA Astrophysics Data System (ADS)

    Yun, Ye; Tailiang, Guo; Yadong, Jiang

    2012-04-01

    Zinc oxide (ZnO) nanopillars on a ZnO seed layer and ZnO nanoflowers were synthesized by electrochemical deposition on linear wires. The morphologies and crystal orientation of the ZnO nanostructures were investigated by a scanning electron microscopy and an X-ray diffraction pattern, respectively. Detailed study on the field-emission properties of ZnO nanostructures indicates that nanopillars with a high aspect ratio show good performance with a low turn-on field of 0.16 V/μm and a high field enhancement factor of 2.86 × 104. A luminescent tube with ZnO nanopillars on a linear wire cathode and a transparent anode could reach a luminance of about 1.5 × 104 cd/m2 under an applied voltage of 4 kV.

  14. Effect of intrinsic point defect on the magnetic properties of ZnO nanowire.

    PubMed

    Yun, Jiangni; Zhang, Zhiyong; Yin, Tieen

    2013-01-01

    The effect of intrinsic point defect on the magnetic properties of ZnO nanowire is investigated by the first-principles calculation based on the density functional theory (DFT). The calculated results reveal that the pure ZnO nanowire without intrinsic point defect is nonmagnetic and ZnO nanowire with V(O), Zn(i), O(i), O(Zn), or Zn(O) point defect also is nonmagnetic. However, a strong spin splitting phenomenon is observed in ZnO nanowire with V(Zn) defect sitting on the surface site. The Mulliken population analysis reveals that the oxygen atoms which are close to the V(Zn) defect do major contribution to the magnetic moment. Partial density states calculation further suggests that the appearance of the half-metallic ferromagnetism in ZnO nanorod with V(Zn) originates from the hybridization of the O2p states with Zn 3d states. PMID:24396300

  15. Theoretical prediction of low-density hexagonal ZnO hollow structures

    NASA Astrophysics Data System (ADS)

    Tuoc, Vu Ngoc; Huan, Tran Doan; Thao, Nguyen Thi; Tuan, Le Manh

    2016-10-01

    Along with wurtzite and zinc blende, zinc oxide (ZnO) has been found in a large number of polymorphs with substantially different properties and, hence, applications. Therefore, predicting and synthesizing new classes of ZnO polymorphs are of great significance and have been gaining considerable interest. Herein, we perform a density functional theory based tight-binding study, predicting several new series of ZnO hollow structures using the bottom-up approach. The geometry of the building blocks allows for obtaining a variety of hexagonal, low-density nanoporous, and flexible ZnO hollow structures. Their stability is discussed by means of the free energy computed within the lattice-dynamics approach. Our calculations also indicate that all the reported hollow structures are wide band gap semiconductors in the same fashion with bulk ZnO. The electronic band structures of the ZnO hollow structures are finally examined in detail.

  16. Temperature dependence of the growth of ZnO nanorod arrays by electrochemical deposition

    NASA Astrophysics Data System (ADS)

    Kim, Hyunghoon; Moon, Jin Young; Lee, Ho Seong

    2011-03-01

    ZnO nanorod arrays were prepared by the electrochemical deposition route on conductive Au/Si substrates. The effect of the bath temperature on the growth of the ZnO nanorod arrays was investigated. With an increase in bath temperature from 30°C to 80°C, the deposited ZnO changed from an amorphous structure to a hexagonal crystal structure. The ZnO nanorod arrays grown above 50°C were dense and vertically well-aligned. Scanning and transmission electron microscopy results showed that the diameter of the hexagon-shaped ZnO nanorod arrays ranged from 100 nm to 180 nm and the length was about 500 nm. On the basis of the characteristics of the ZnO crystal structure and the effect of the bath temperature, the growth mechanism is described.

  17. Application of Eu2O3/ZnO nanoparticles in dye sensitized solar cell

    NASA Astrophysics Data System (ADS)

    Kaur, Manveen; Verma, N. K.

    2013-06-01

    The synthesis of ZnO, Eu2O3 coated ZnO nanoparticles and their application in dye sensitized solar cells (DSSCs) has been reported. The synthesized samples have been characterized by XRD and the diffraction of crystal plane (222) of Eu2O3 was detected, demonstrating the existence of Eu2O3 on the surface of ZnO3, which has also been verified through EDAX. Compared to ZnO electrodes, Eu2O3 coated ZnO electrodes adsorbed more dye. Eu2O3 coating on ZnO forms an energy barrier, which suppresses the charge recombination. Consequently, the photoelectrochemical properties of the modified electrodes improved and the overall energy conversion efficiency η increased from 0.21% to 0.61% under the illumination of simulated light of 100mW/cm2.

  18. Recycling of an electric arc furnace flue dust to obtain high grade ZnO.

    PubMed

    Ruiz, Oscar; Clemente, Carmen; Alonso, Manuel; Alguacil, Francisco Jose

    2007-03-01

    The production of steel in electric arc furnace (EAF) generates a by-product called EAF dusts. These steelmaking flue dusts are classified in most industrialized countries as hazardous residues because the heavy metals contained in them, tend to leach under slightly acidic rainfall conditions. However, and at the same time they contain zinc species which can be used as a source to obtain valuable by-products. The present investigation shows results on the processing of an EAF flue dust using ammonium carbonate solutions. Once zinc is dissolved: ZnO + 4NH3 + H2O --> Zn(NH3)4(2+) + 2OH- with other impurities (i.e. cadmium and copper), these are eliminated from the zinc solution via cementation with metallic zinc. The purified zinc solution was evaporated (distilled) until precipitation of a zinc carbonate species, which then was calcined to yield a zinc oxide of a high grade. For the unattacked dust residue from the leaching operation, mainly composed of zinc ferrite, several options can be considered: back-recycling to the furnace, further treatment by sodium hydroxide processing or a more safely dumping due to its relatively inertness.

  19. 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.

  20. Modeling of nanoscale morphology of regioregular poly(3-hexylthiophene) on a ZnO (1010) surface.

    PubMed

    Dag, S; Wang, Lin-Wang

    2008-12-01

    We report detailed ab initio calculations of poly(3-hexylthiophene) (P3HT) on top of a ZnO (1010) surface. We studied different absorption sites and orientations. We found that the P3HT chain prefers to lay along the dimer row direction of the ZnO surface. We also found strong coupling between the P3HT molecule and the ZnO substrate in the conduction band states, while minimum coupling in the valence band states.

  1. Growth and characterization of Cl-doped ZnO hexagonal nanodisks

    SciTech Connect

    Yousefi, Ramin; Zak, A.K.; Mahmoudian, M.R.

    2011-10-15

    Cl-doped ZnO nanodisks were grown on a Si(111) substrate using a thermal evaporation method. The prepared nanodisks exhibited a hexagonal shape with an average thickness of 50 nm and average diagonal of 270 nm. In addition, undoped ZnO disks with hexagonal shape were grown under the same conditions, but the sizes of these undoped ZnO disks were on the micrometer order. A possible mechanism was proposed for the growth of the Cl-doped ZnO nanodisks, and it was shown that the Cl{sup 1-} anions play a crucial role in controlling the size. X-ray diffraction and Raman spectroscopy clearly showed an extension in the crystal lattice of ZnO because of the presence of chlorine. In addition, these nanodisks produced a strong photoluminescence emission peak in the ultraviolet (UV) region and a weak peak in the green region of the electromagnetic spectrum. Furthermore, the UV peak of the Cl-doped ZnO nanodisks was blueshifted with respect to that of the undoped ZnO disks. - Graphical abstract: Cl-doped ZnO nanodisks and undoped ZnO microdisks have been grown using a thermal evaporation method. Highlights: > Cl-doped ZnO nanodisks with hexagonal shape are grown using a thermal evaporation method. > It is shown that the Cl{sup 1-} anions play a crucial role in controlling the size of the nanodisks. > XRD and Raman results showed that the Cl-doped ZnO nanodisks structure is under a biaxial stress. > UV peak of the PL spectrum is blueshifted for the Cl-doped ZnO nanodisks.

  2. The effect of ZnO nanoparticles on liver function in rats.

    PubMed

    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

  3. Enhanced photocatalytic activity of Cu-doped ZnO nanorods

    NASA Astrophysics Data System (ADS)

    Mohan, Rajneesh; Krishnamoorthy, Karthikeyan; Kim, Sang-Jae

    2012-03-01

    Cu-doped ZnO nanorods with different Cu concentrations were synthesized through the vapor transport method. The synthesized nanorods were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and UV-vis spectroscopy. The XRD results revealed that Cu was successfully doped into ZnO lattice. The FE-SEM images showed that the undoped ZnO has needle like morphology whereas Cu-doped ZnO samples have rod like morphology with an average diameter and length of 60-90 nm and 1.5-3 μm respectively. The red shift in band edge absorption peak in UV-vis absorbance spectrum with increasing Cu content also confirm the doping of Cu in ZnO nanorods. The photocatalytic activity of pure and Cu-doped ZnO samples was studied by the photodegradation of resazurin (Rz) dye. Both pure ZnO and the Cu-doped ZnO nanorods effectively removed the Rz in a short time. This photodegradation of Rz followed the pseudo-first-order reaction kinetics. ZnO nanorods with increasing Cu doping exhibit enhanced photocatalytic activity. The pseudo-first-order reaction rate constant for 15 % Cu-doped ZnO is equal to 10.17×10-2min-1 about double of that with pure ZnO. The increased photocatalytic activity of Cu-doped ZnO is attributed to intrinsic oxygen vacancies due to high surface to volume ratio in nanorods and extrinsic defect due to Cu doping.

  4. 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.

  5. Synthesis, characterization, UV and dielectric properties of hexagonal disklike ZnO particles embedded in polyimides

    SciTech Connect

    Vural, Sema; Koeytepe, Sueleyman; Seckin, Turgay; Adiguezel, Ibrahim

    2011-10-15

    Graphical abstract: The hexagonal disklike ZnO particles with a diameter of 300-500 nm were synthesized from zinc acetate and NaOH in water with citric acid. ZnO/polyimide composite films with different ZnO contents was prepared. The prepared zinc oxide-polyimide composites were characterized for their structure, morphology and thermal behavior. Composites with ZnO particle contents from 1 to 5 wt% show good transparency in the visible region and luminescent properties. Highlights: {yields} A series of novel ZnO/polyimide composite films with different ZnO contents was prepared. {yields} The ZnO was homogeneously dispersed in the PI matrix. {yields} The composites showed the low dielectric constant of 50 at 10{sup 6} Hz. {yields} Homogenous dispersion and the amount of ZnO particles contributed to the dielectric properties of composites. -- Abstract: A series of novel ZnO/polyimide composite films with different ZnO contents was prepared through incorporation hexagonal disklike ZnO particles into poly(amic acid) of the pre polymer of the polyimide. The hexagonal disklike ZnO particles with a diameter of 300-500 nm were synthesized from zinc acetate and NaOH in water with citric acid. The prepared zinc oxide-polyimide composites were characterized for their structure, morphology, and thermal behavior employing Fourier transform infrared spectroscopy, scanning electron micrograph, X-ray diffraction and thermal analysis techniques. Thermal analyses show that the ZnO particles were successfully incorporated into the polymer matrix and these ZnO/polymer composites have a good thermal stability. Scanning electron microscopy studies indicate the ZnO particles were uniformly dispersed in the polymer and they remained at the original size (300-500 nm) before immobilization. All composite films with ZnO particle contents from 1 to 5 wt% show good transparency in the visible region and luminescent properties.

  6. Crystallographically oriented Zn nanocrystals formed in ZnO by Mn{sup +}-implantation

    SciTech Connect

    Li, Y. J.; Zhang, B.; Lu, W.; Wang, Y.; Zou, J.

    2008-09-29

    The nanostructural characteristics of ZnO implanted with Mn{sup +} to doses ranging from 1x10{sup 15} to 1x10{sup 17} cm{sup -2} are systematically studied for both as-implanted and postannealed cases. The detailed structural characterizations confirmed that the Mn{sup +} implantation and postannealing result in (1) the formation of crystallographically orientated Zn nanocrystals in the ZnO matrix and (2) Mn atoms occupy the Zn sites in ZnO.

  7. 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

  8. Effect of ZnO nanoparticles on structural and mechanical properties of HPMC polymer films

    NASA Astrophysics Data System (ADS)

    Rao, B. Lakshmeesha; Mahadeviah, Asha, S.; Somashekar, R.; Sangappa

    2013-02-01

    The Zinc Oxide (ZnO) nano-particles were synthesized by electrochemical method. The HPMC films were prepared by solution casting method and ZnO concentration was varied from 0.01 to 0.04%. The films were examined for structural and mechanical properties verifying how the addition of ZnO nano-particles affected the properties using X-ray diffraction (XRD) and Universal Testing Machine (UTM).

  9. Shape controlled Sn doped ZnO nanostructures for tunable optical emission and transport properties

    SciTech Connect

    Rakshit, T.; Manna, I.; Ray, S. K.

    2013-11-15

    Pure and Sn doped ZnO nanostructures have been grown on SiO{sub 2}/Si substrates by vapor-solid technique without using any catalysts. It has been found that the morphology of the nanostructures depend strongly on the growth temperature and doping concentration. By proper tuning of the growth temperature, morphology of pure ZnO can be changed from tetrapods to multipods. On the other hand, by varying the doping concentration of Sn in ZnO, the morphology can be tuned from tetrapods to flower-like multipods to nanowires. X-ray diffraction pattern reveals that the nanostructures have a preferred (0002) growth orientation, and they are tensile strained with the increase of Sn doping in ZnO. Temperature-dependent photoluminescence characteristics of these nanostructures have been investigated in the range from 10 to 300 K. Pure ZnO tetrapods exhibited less defect state emissions than that of pure ZnO multipods. The defect emission is reduced with low concentration of Sn doping, but again increases at higher concentration of doping because of increased defects. Transport properties of pure and Sn doped ZnO tetrapods have been studied using complex-plane impedance spectroscopy. The contribution from the arms and junctions of a tetrapod could be distinguished. Sn doped ZnO samples showed lower conductivity but higher relaxation time than that of pure ZnO tetrapods.

  10. Improving the ethanol gas-sensing properties of porous ZnO microspheres by Co doping

    SciTech Connect

    Xiao, Qi Wang, Tao

    2013-08-01

    Graphical abstract: - Highlights: • Co-doped porous ZnO microspheres were synthesized. • 3 mol% Co-doped ZnO sensor showed the highest response to ethanol. • 3 mol% Co-doped ZnO sensor exhibited fast recovery property. • 3 mol% Co-doped ZnO sensor exhibited good selectivity and long-term stability. - Abstract: Porous Co-doped ZnO microspheres were prepared by a simple hydrothermal method combined with post-annealing. Co species existed as a form of divalent state in the sample and substituted Zn{sup 2+} sites in ZnO crystal lattice, which was affirmed by X-ray diffraction, UV–vis diffuse reflectance spectroscopy and X-ray photoelectron spectroscopy. The gas-sensing measurements demonstrated that the 3 mol% Co-doped ZnO sample showed the highest response value to 100 ppm ethanol at 350 °C, which were 5 folds higher than that of the pure ZnO sample. In addition, the 3 mol% Co-doped ZnO sensor exhibited fast recovery property, good quantitative determination, good selectivity and long-term stability. The superior sensing properties were contributed to high specific surface area combined with the large amount of oxygen vacancies originating from Co doping.

  11. Selective growth of ZnO thin film nanostructures: Structure, morphology and tunable optical properties

    NASA Astrophysics Data System (ADS)

    Krishnakanth, Katturi Naga; Rajesh, Desapogu; Sunandana, C. S.

    2016-05-01

    The ZnO nanostructures (spherical, rod shape) have been successfully fabricated via a thermal evaporation followed by dip coating method. The pure, doped ZnO thin films were characterized by X-ray powder diffraction (XRD) and field emission scanning electron microscopy (FESEM) and UV-Vis spectroscopy, respectively. A possible growth mechanism of the spherical, rod shape ZnO nanostructures are discussed. XRD patterns revealed that all films consist of pure ZnO phase and were well crystallized with preferential orientation towards (002) direction. Doping by PVA, PVA+Cu has effective role in the enhancement of the crystalline quality and increases in the band gap.

  12. Improved conversion efficiency of amorphous Si solar cells using a mesoporous ZnO pattern

    NASA Astrophysics Data System (ADS)

    Go, Bit-Na; Kim, Yang Doo; suk Oh, Kyoung; Kim, Chaehyun; Choi, Hak-Jong; Lee, Heon

    2014-09-01

    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.

  13. 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.

  14. Growth of Single- and Bilayer ZnO on Au(111) and Interaction with Copper

    SciTech Connect

    Deng, Xingyi; Yao, Kun; Sun, Keju; Li, Wei-Xue; Lee, Junseok; Matranga, Christopher

    2013-05-02

    The stoichiometric single- and bi-layer ZnO(0001) have been prepared by reactive deposition of Zn on Au(111) and studied in detail with X-ray photoelectron spectroscopy, scanning tunneling microscopy, and density functional theory calculations. Both single- and bi-layer ZnO(0001) adopt a planar, graphite-like structure similar to freestanding ZnO(0001) due to the weak van der Waals interactions dominating their adhesion with the Au(111) substrate. At higher temperature, the single-layer ZnO(0001) converts gradually to bi-layer ZnO(0001) due to the twice stronger interaction between two ZnO layers than the interfacial adhesion of ZnO with Au substrate. It is found that Cu atoms on the surface of bi-layer ZnO(0001) are mobile with a diffusion barrier of 0.31 eV, and likely to agglomerate and form nanosized particles at low coverages; while Cu atoms tend to penetrate a single layer of ZnO(0001) with a barrier of 0.10 eV, resulting in a Cu free surface.

  15. Au-coated ZnO nanostructures for surface enhanced Raman spectroscopy applications

    SciTech Connect

    Dikovska, A O; Nedyalkov, N N; Imamova, S E; Atanasova, G B; Atanasov, P A

    2012-03-31

    Thin ZnO nanostructured films were produced by pulsed laser deposition (PLD) for surface enhanced Raman spectroscopy (SERS) studies. The experimental conditions used for preparation of the samples were chosen to obtain different types of ZnO nanostructures. The Raman spectra of rhodamine 6G (R6G) were measured at an excitation wavelength of 785 nm after coating the ZnO nanostructures with a thin Au layer. The influence of the surface morphology on the Raman signal obtained from the samples was investigated. High SERS signal enhancement was observed from all Au-coated ZnO nanostructures.

  16. Ag-doped ZnO nanorods synthesized by two-step method

    NASA Astrophysics Data System (ADS)

    Chen, Xian-Mei; Ji, Yong; Gao, Xiao-Yong; Zhao, Xian-Wei

    2012-11-01

    A two-step method is adopted to synthesize Ag-doped ZnO nanorods. A ZnO seed layer is first prepared on a glass substrate by thermal decomposition of zinc acetate. Ag-doped ZnO nanorods are then assembled on the ZnO seed layer using the hydrothermal method. The influences of the molar percentage of Ag ions to Zn ions (RAg/Zn) on the structural and optical properties of the ZnO nanorods obtained are carefully studied using X-ray diffractometry, scanning electron microscopy and spectrophotometry. Results indicate that Ag ions enter into the crystal lattice through the substitution of Zn ions. The (002) c-axis-preferred orientation of the ZnO nanorods decreases as RAg/Zn increases. At RAg/Zn > 1.0%, ZnO nanorods lose their c-axis-preferred orientation and generate Ag precipitates from the ZnO crystal lattice. The average transmissivity in the visible region first increases and then decreases as RAg/Zn increases. The absorption edge is first blue shifted and then red shifted. The influence of Ag doping on the average head face, and axial dimensions of the ZnO nanorods may be optimized to improve the average transmissivity at RAg/Zn < 1.0%.

  17. Fabrication of nanopore YSZ from YSZ and ZnO mixture.

    PubMed

    Hwang, Moon Jin; Han, Chong Soo

    2008-10-01

    Porous Yttria Stabilized Zirconia (YSZ) with macropore and nanopore was fabricated from sintering and leaching the mixture of YSZ and different types of ZnO. When we used nano-sized crystalline particle, porous YSZ with submicron pores was obtained. In the case of the spherical 30 nm to 100 nm ZnO particles obtained from hydrolysis of zinc acetate in methanol, 2 approximately 10 nm sized pores was observed in the YSZ. From the results, it was suggested that crystalline ZnO particles grew up while the spherical noncrystalline ZnO particles were enclosed in YSZ matrix in the sintering process.

  18. Electrical property studies on chemically processed polypyrolle/aluminum doped ZnO based hybrid heterostructures

    NASA Astrophysics Data System (ADS)

    Mohan Kumar, G.; Ilanchezhiyan, P.; Madhan Kumar, A.; Yuldashev, Sh. U.; Kang, T. W.

    2016-04-01

    A hybrid structure based on p-type polypyrolle (PPy) and n-type aluminum (Al) doped ZnO nanorods was successfully constructed. The effect of Al doping on material properties of wurtzite structured ZnO were studied using several analytical techniques. To establish the desired hybrid structure, pyrrole monomers were polymerized on hydrothermally grown Al doped ZnO nanorods by chemical polymerization. The current-voltage characteristics on the fabricated PPy/Al doped ZnO heterostructures were found to exhibit excellent rectifying characteristics under dark and illumination conditions. The obtained results augment the prescribed architecture to be highly suitable for high-sensitivity optoelectronic applications.

  19. Toxicity evaluation of ZnO nanostructures on L929 fibroblast cell line using MTS assay

    SciTech Connect

    Bakhori, Siti Khadijah Mohd; Mahmud, Shahrom; Ann, Ling Chuo; Mohamed, Azman Seeni; Saifuddin, Siti Nazmin; Masudi, Sam’an Malik; Mohamad, Dasmawati

    2015-04-24

    ZnO has wide applications in medical and dentistry apart from being used as optoelectronic devices such as solar cells, photodetectors, sensors and light emitting diodes (LEDs). Therefore, the toxicity evaluation is important to know the toxicity level on normal cell line. The toxicity of two grades ZnO nanostructures, ZnO-4 and ZnO-8 have been carried out using cytotoxicity test of MTS assay on L929 rat fibroblast cell line. Prior to that, ZnO-4 and ZnO-8 were characterized for its morphology, structure and optical properties using FESEM, X-ray diffraction, and Photoluminescence respectively. The two groups revealed difference in morphology and exhibit slightly shifted of near band edge emission of Photoluminescence other than having a similar calculated crystallite size of nanostructures. The viability of cells after 72h were obtained and the statistical significance value was calculated using SPSS v20. The p value is more than 0.05 between untreated and treated cell with ZnO. This insignificant value of p>0.05 can be summarized as a non-toxic level of ZnO-4 and ZnO-8 on the L929 cell line.

  20. Organic photovoltaic solar cells with cathode modified by ZnO.

    PubMed

    Kim, Hyeong Pil; Yusoff, Abd Rashid Bin Mohd; Jang, Jin

    2013-07-01

    Solution processed cathode organic photovoltaic cells (OPVs) utilizing thin layer of ZnO with 27% increase in power conversion efficiency (PCE) to control devices have been demonstrated. Devices without the presence of ZnO layer have much lower PCE than the ones with ZnO layer. Cathode modification layer can be used to reduce photogenerated excitions and finally improve the performance of the OPVs. The successful demonstrations of OPVs with an introduction of ZnO cathode layer give promise of further device progresses.

  1. Controllable growth of ZnO nanorods via electrodeposition technique: towards UV photo-detection

    NASA Astrophysics Data System (ADS)

    Sarangi, S. N.

    2016-09-01

    An electro-chemical approach for controlled growth of seedless ZnO nanorods was investigated. Field emission scanning electron microscopy confirms ZnO nanorod morphology can be controlled by varying the electrodeposition duration. Increased growth time enhances the crystallinity of ZnO nanorods and releases the strain on ZnO nanorods, as revealed by x-ray diffraction analysis. A significant change in the near band gap and the defect level luminescence were observed for different growth time ZnO nanorods. The variation in zone-centre E 2 (high) optical phonon mode of ZnO nanorods was studied using micro-Raman measurements. The I–V characteristics of the ZnO nanorods potentially enable applications in UV photodetection even at very low voltage range. Photodetectors based on ZnO nanorods have a faster response time (~29 s) and exhibited high photosensitivity, approximately 28 at 1 V forward bias, as compared to recent reported values. The results obtained are exciting in view of using a low cost electrodeposition technique at low temperature for achieving high-quality electrodeposited ZnO nanorods and its possible use in optoelectronic devices.

  2. Photoluminescence characteristics of ZnO clusters confined in the micropores of zeolite L

    SciTech Connect

    Wang Fang; Song Hongwei Pan Guohui; Fan Libo; Dai Qilin; Dong Biao; Liu Huihui; Yu Jihong; Wang Xi; Li Li

    2009-03-05

    Sub-nanometric ZnO clusters were prepared in the micropores of zeolite L by the incipient wetness impregnation method. The X-ray patterns (XRD), transmission electron microscope (TEM), N{sub 2} adsorption-desorption isotherms, UV-vis absorption spectra (UV-vis) and photoluminescence spectra (PL) were used to characterize the composite materials. The results indicate that a small amount of sub-nanometric ZnO clusters can be introduced into the channel of zeolite L, however, when the amount of ZnO loading exceeds 20 wt%, macrocrystalline ZnO appears on the external surface of zeolite L. Different from bulk ZnO materials, these sub-nanometric ZnO clusters exhibit their absorption onset below 255 nm and a blue luminescence band in the range of 404-422 nm. The temperature-dependent luminescence demonstrates that the amount of the ZnO loading significantly affects the exciton-phonon interaction between the ZnO clusters and the zeolite host. The ZnO clusters exhibit a picosecond scale emission lifetime at room temperature.

  3. Enhanced photocatalytic performance of Ga{sup 3+}-doped ZnO

    SciTech Connect

    Zhong, Jun Bo; Li, Jian Zhang; Zeng, Jun; He, Xi Yang; Hu, Wei; Shen, Yue Cheng

    2012-11-15

    Graphical abstract: In general, the strong SPS response corresponds to the high separation rate of photoinduced charge carriers on the basis of the SPS principle. The photovoltage of Ga{sup 3+}-doped ZnO is higher than that of ZnO, thus it can be confirmed that the Ga{sup 3+}-doped ZnO has a higher charge separation rate than the ZnO sample. Among these samples, 1%Ga has highest charge separation rate. Display Omitted Highlights: ► Ga{sup 3+} has been employed to dope ZnO photocatalyst. ► Ga{sup 3+} increases the BET surface area and changes the morphology of ZnO. ► The photoinduced charge separation rate has been enhanced. ► The photocatalytic activity has been greatly promoted. -- Abstract: ZnO and Ga{sup 3+}-doped ZnO with different molar ratio of Ga/Zn (1%, 2% and 3%) were prepared by a parallel flow precipitation method. The photocatalysts prepared were characterized by BET surface area, X-ray diffraction (XRD), UV/vis diffuse reflectance spectroscopy (DRS), scanning electron microscope (SEM) and surface photovoltage spectroscopy (SPS), respectively. The results show that doping Ga{sup 3+} into ZnO increases the BET surface area. The XRD spectra of the photocatalysts calcined at 573 K show only the characteristic peaks of wurtzite-type. Ga{sup 3+}-doped ZnO absorbs much more light than ZnO in the visible light region. Doping Ga{sup 3+} into ZnO greatly changes the morphology of ZnO and enhances the photoinduced charge separation rate. The photocatalytic activity of ZnO and Ga{sup 3+}-doped ZnO for decolorization of methyl orange (MO) solution was evaluated, of all the photocatalysts prepared, the Ga{sup 3+}-doped ZnO with 1% possesses the best photocatalytic activity and the possible reason was discussed.

  4. 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.

  5. Controllable growth of ZnO nanorods via electrodeposition technique: towards UV photo-detection

    NASA Astrophysics Data System (ADS)

    Sarangi, S. N.

    2016-09-01

    An electro-chemical approach for controlled growth of seedless ZnO nanorods was investigated. Field emission scanning electron microscopy confirms ZnO nanorod morphology can be controlled by varying the electrodeposition duration. Increased growth time enhances the crystallinity of ZnO nanorods and releases the strain on ZnO nanorods, as revealed by x-ray diffraction analysis. A significant change in the near band gap and the defect level luminescence were observed for different growth time ZnO nanorods. The variation in zone-centre E 2 (high) optical phonon mode of ZnO nanorods was studied using micro-Raman measurements. The I-V characteristics of the ZnO nanorods potentially enable applications in UV photodetection even at very low voltage range. Photodetectors based on ZnO nanorods have a faster response time (~29 s) and exhibited high photosensitivity, approximately 28 at 1 V forward bias, as compared to recent reported values. The results obtained are exciting in view of using a low cost electrodeposition technique at low temperature for achieving high-quality electrodeposited ZnO nanorods and its possible use in optoelectronic devices.

  6. Stable fluorescence conjugation of ZnO nanoparticles and their size dependent cellular uptake.

    PubMed

    Kim, Kyoung-Min; Kim, Min-Kyu; Paek, Hee-Jeong; Choi, Soo-Jin; Oh, Jae-Min

    2016-09-01

    We evaluated size dependent cellular uptake of ZnO nanoparticles utilizing stably introduced Cy5.5, which emits long-wavelength fluorescence. Through (3-aminopropyl)triethoxysilane modification, ZnO nanoparticles of different sizes (20 and 70nm) were functionalized with amine moiety, which was further reacted with Cy5.5-N-hydroxylsuccinimide ester to make covalently conjugated Cy5.5 dye on ZnO nanoparticles. Field emission-scanning electron microscopic images revealed that average particle size as well as particle morphology of ZnO nanoparticles were not altered by Cy5.5 conjugation. Zeta potential measurement confirmed that the positive surface charge of ZnO nanoparticles was well preserved after successive conjugation reactions. Based on infrared, ultraviolet-visible light and photoluminescence spectroscopies, we verify that the Cy5.5 was stably introduced to ZnO nanoparticles without serious aggregation. Surface conjugated Cy5.5 showed high stability in deionized water, phosphate buffered saline and cell culture medium, showing less than 2% of release during 85h. Confocal microscopy and fluorescence-activated cell sorting analysis demonstrated that smaller ZnO nanoparticles were more taken up in greater quantities by HaCaT cells. Moreover, systematic study on cellular uptake pathway showed that smaller ZnO nanoparticles were internalized into cells mainly by clathrin-mediated endocytosis, while larger ZnO nanoparticles entered cells via several pathways. PMID:27323344

  7. LED-controlled tuning of ZnO nanowires’ wettability for biosensing applications

    PubMed Central

    Bhavsar, Kaushalkumar; Ross, Duncan; Prabhu, Radhakrishna; Pollard, Pat

    2015-01-01

    Background Wettability is an important property of solid materials which can be controlled by surface energy. Dynamic control over the surface wettability is of great importance for biosensing applications. Zinc oxide (ZnO) is a biocompatible material suitable for biosensors and microfluidic devices. Nanowires of ZnO tend to show a hydrophobic nature which decelerates the adhesion or adsorption of biomolecules on the surface and, therefore, limits their application. Methods Surface wettability of the ZnO nanowires can be tuned using light irradiation. However, the control over wettability using light-emitting diodes (LEDs) and the role of wavelength in controlling the wettability of ZnO nanowires are unclear. This is the first report on LED-based wettability control of nanowires, and it includes investigations on tuning the desired wettability of ZnO nanowires using LEDs as a controlling tool. Results The investigations on spectral properties of the LED emission on ZnO nanowires’ wettability have shown strong dependency on the spectral overlap of LED emission on ZnO absorption spectra. Results indicate that LEDs offer an advanced control on dynamically tuning the wettability of ZnO nanowires. Conclusion The spectral investigations have provided significant insight into the role of irradiating wavelength of light and irradiation time on the surface wettability of ZnO nanowires. This process is suitable to realize on chip based integrated sensors and has huge potential for eco-friendly biosensing and environmental sensing applications. PMID:25855065

  8. Noble metal nanodisks epitaxially formed on ZnO nanorods and their effect on photoluminescence

    NASA Astrophysics Data System (ADS)

    Chu, Sheng; Ren, Jingjian; Yan, Dong; Huang, Jian; Liu, Jianlin

    2012-07-01

    Triangular and hexagonal shaped noble metal (Au, Ag, Pt, Pd) nanodisks were synthesized on the top facets of ZnO nanorods via simple deposition-annealing method. Other metals (Ni, Cu, Cr, Pb, Al) only formed irregular shaped nanostructures on ZnO nanorods. The morphology, elemental composition, as well as growth mechanism of the metal nanodisks/ZnO nanorod composite materials were studied. The localized surface plasmon resonant effects from different metal nanodisks on the photoluminescence of ZnO nanorods were investigated. It was demonstrated that the carriers transfer between the metal nanodisks and ZnO can efficiently manipulate the photoluminescence intensities from the nanorods.

  9. 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

    2013-08-01

    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.

  10. Synthesis and properties of novel liquid-medicine-filter shaped ZnO nanostructures.

    PubMed

    Zhuang, Huizhao; Xu, Peng; Li, Junlin

    2013-06-01

    Liquid-medicine-filter shaped ZnO nanostructures have been synthesized on Al2O3-coated Si (111) substrates by chemical vapor deposition method (CVD) at 1050 °C. Every liquid-medicine-filter shaped ZnO nanostructure is made up of one nanorod and two nanowires at the ends. The liquid-medicine-filter shaped ZnO nanostructures are characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), energy dispersive spectrometer (EDS) photoluminescence (PL). The results indicate that the liquid-medicine-filter shaped ZnO nanostructures are wurtzite hexagonal structure and the growth direction is [0001]. The liquid-medicine-filter shaped ZnO nanostructures became the new member of ZnO nanostructures for the novel configuration. PL reveals ultraviolet (UV) emission at 384 nm and a broad emission peak at 540 nm. These novel liquid-medicine-filter shaped ZnO nanostructures will provide an improvement for electronic and optical devices. The pre-prepared Al2O3 film on the Si (111) substrate solves the troublesome lattice mismatch problem between the Si substrate and ZnO, and makes the growth of liquid-medicine-filter shaped ZnO nanostructures more effective. In addition, the effect of screw dislocation and polar surfaces in understanding crystal growth mechanisms in nanometer scale were also provided.

  11. Atomic force microscopy using ZnO whisker tip

    NASA Astrophysics Data System (ADS)

    Kado, H.; Yokoyama, K.; Tohda, T.

    1992-06-01

    We have developed an atomic force microscope (AFM) using a zinc oxide (ZnO) whisker crystal as a probing tip. The ZnO whisker crystal is tetrapodal in shape, with each leg having a length of 5-30 μm, a radius of curvature less than 10 nm, and a cone half angle of 1°-2°. Polyimide thin films rubbed with cloths as liquid-crystal aligning films were employed for AFM imaging. Due to the needle shape of the probing tip, the AFM was able to resolve the tiny grooves (3-5 nm deep, 60-80 nm apart) on these films more clearly than that using a conventional pyramidal tip. The new AFM will be available for precise evaluation of surfaces on which fine structures are microfabricated in nanometer scale.

  12. Enhanced electromechanical behaviors of cellulose ZnO hybrid nanocomposites

    NASA Astrophysics Data System (ADS)

    Mun, Seongchoel; Min, Seung-Ki; Kim, Hyun Chan; Im, Jongbeom; Geddis, Demetris L.; Kim, Jaehwan

    2015-04-01

    Inorganic-organic hybrid composite has attracted as its combined synergistic properties. Cellulose based inorganicorganic hybrid composite was fabricated with semiconductive nanomaterials which has functionality of nanomaterial and biocompatibility piezoelectricity, high transparency and flexibility of cellulose electro active paper namely EAPap. ZnO is providing semiconductive functionality to EAPap for hybrid nanocomposite by simple chemical reaction. Cellulose- ZnO hybrid nanocomposite (CEZOHN) demonstrates novel electrical, photoelectrical and electromechanical behaviors. This paper deals with methods to improve electromechanical property of CEZOHN. The fabrication process is introduced briefly, charging mechanism and evaluation is studied with measured piezoelectric constant. And its candidate application will be discussed such as artificial muscle, energy harvester, strain sensor, flexible electrical device.

  13. Evidence for photogenerated intermediate hole polarons in ZnO

    NASA Astrophysics Data System (ADS)

    Sezen, Hikmet; Shang, Honghui; Bebensee, Fabian; Yang, Chengwu; Buchholz, Maria; Nefedov, Alexei; Heissler, Stefan; Carbogno, Christian; Scheffler, Matthias; Rinke, Patrick; Wöll, Christof

    2015-04-01

    Despite their pronounced importance for oxide-based photochemistry, optoelectronics and photovoltaics, only fairly little is known about the polaron lifetimes and binding energies. Polarons represent a crucial intermediate step populated immediately after dissociation of the excitons formed in the primary photoabsorption process. Here we present a novel approach to studying photoexcited polarons in an important photoactive oxide, ZnO, using infrared (IR) reflection-absorption spectroscopy (IRRAS) with a time resolution of 100 ms. For well-defined (10-10) oriented ZnO single-crystal substrates, we observe intense IR absorption bands at around 200 meV exhibiting a pronounced temperature dependence. On the basis of first-principles-based electronic structure calculations, we assign these features to hole polarons of intermediate coupling strength.

  14. Evidence for photogenerated intermediate hole polarons in ZnO.

    PubMed

    Sezen, Hikmet; Shang, Honghui; Bebensee, Fabian; Yang, Chengwu; Buchholz, Maria; Nefedov, Alexei; Heissler, Stefan; Carbogno, Christian; Scheffler, Matthias; Rinke, Patrick; Wöll, Christof

    2015-04-22

    Despite their pronounced importance for oxide-based photochemistry, optoelectronics and photovoltaics, only fairly little is known about the polaron lifetimes and binding energies. Polarons represent a crucial intermediate step populated immediately after dissociation of the excitons formed in the primary photoabsorption process. Here we present a novel approach to studying photoexcited polarons in an important photoactive oxide, ZnO, using infrared (IR) reflection-absorption spectroscopy (IRRAS) with a time resolution of 100 ms. For well-defined (10-10) oriented ZnO single-crystal substrates, we observe intense IR absorption bands at around 200 meV exhibiting a pronounced temperature dependence. On the basis of first-principles-based electronic structure calculations, we assign these features to hole polarons of intermediate coupling strength.

  15. Electrochemical deposition of ZnO nanostructures. mechanism of growth.

    PubMed

    Rayón, E; Ferrer, C

    2010-02-01

    The growth kinetics of ZnO nanorods were studied by means of an electrochemical deposition process on ITO electrodes submerged in an aqueous solution of 5 mM ZCl+0.1 M KCl at 80 degrees C. The stages of the growth kinetics showed a mechanism of formation of nano-spheres which with time were transformed into hexagonal crystals of ZnO. Cathodic current densities of 0.1 to 1 mAcm2 formed hexagonal columns of 800 nm thickness while stronger currents formed a high-density layer of cylindrical nanorods 80 nm in diameter. An amorphous barrier layer was found between the surface of the electrode and the base of the nano-columns. The conditions assayed showed the possibility of adjusting the morphological characteristics of the layer in order to obtain different properties in different applications.

  16. Lattice sites of Na dopants in ZnO

    NASA Astrophysics Data System (ADS)

    Wahl, U.; Correia, J. G.; Amorim, L.; Decoster, S.; da Silva, M. R.; Pereira, L. M. C.

    2016-09-01

    The angular distribution of β ‑ particles emitted by the radioactive isotope 24Na was monitored following implantation into ZnO single crystals at fluences above 5 × 1012 cm‑2 at CERN’s ISOLDE facility. We identified sodium on two distinct sites: on substitutional Zn sites and on interstitial sites that are close to the so-called octahedral site. The interstitial Na was to a large extent already converted to substitutional Na for annealing at 200 °C, from which an activation energy of 0.8–1.3 eV, most likely around 1.2 eV, is estimated for the migration of interstitial Na in ZnO.

  17. Dilute Magnetic Semiconductors from Electrodeposited ZnO Nanowires

    SciTech Connect

    Athavan, Nadarajah; Konenkamp, R.

    2011-02-02

    We present experimental results on the magnetic properties of doped ZnO nanowires grown at 80 8C in electrodeposition. We show that impurities such as Al, Mn, Co, and Cu can be incorporated in the nanowires by adding the corresponding metal salts to the electrolyte solution. At concentration levels of a few atomic percent we find the impurity concentration in the solid to be approximately proportional to the precursor concentration in solution. ZnO nanowrires doped with Cu, Co, and Mn show superparamagnetic response at room temperature, while undoped and Al-doped wires show no discernible magnetic response. The results indicate that with Cu, Mn, and Co doping dilute magnetic semiconductors can be prepared.

  18. ZnO nanoparticles based fiber optic gas sensor

    NASA Astrophysics Data System (ADS)

    Narasimman, S.; Balakrishnan, L.; Meher, S. R.; Sivacoumar, R.; Alex, Z. C.

    2016-05-01

    In this work, ZnO nanoparticles were synthesized by simple aqueous chemical route method. The synthesized ZnO nanoparticles were characterized by X-ray diffraction andscanning electron microscope. The sensitivity of the nanoparticles was studied for different gases like acetone, ammonia andethanol 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 low ppm level and acetone in high ppm level.

  19. ZnO Transistor Interfaces Sensitized with Photo Donor Molecules

    NASA Astrophysics Data System (ADS)

    Spalenka, Josef; Zhang, Lushuai; Gopalan, Padma; Evans, Paul

    2013-03-01

    A better understanding of the physics at interfaces between semiconducting oxides and monolayers of covalently bonded organic molecules is relevant to important applications such as inexpensive chemical sensors and improved dye-sensitized solar cells. We use field-effect transistor (FET) structures in which electrical measurements are made before and after functionalizing the surface of ZnO nanocrystalline films, which form the channel of the FET, with organic dye molecules based on rhenium-bipyridine complexes that act as electron donors during illumination with monochromatic light. Measurements of the charge transfer as a function of light intensity and dye coverage give the ratio between the rates of charge transfer and recombination between the dyes and the ZnO, an important parameter to maximize to further improve the efficiency of solar cells based on donor functionalized oxides. This work supported by the National Science Foundation through the University of Wisconsin Materials Research Science and Engineering Center under Grant No. DMR-1121288

  20. 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

  1. Vertically Aligned ZnO Nanorods: Effect of Synthesis Parameters.

    PubMed

    Rehman, Zeeshan Ur; Heo, Si-Nae; Cho, Hyeon Ji; Koo, Bon Heun

    2016-06-01

    This report is devoted to the synthesis of high quality nanorods using spin coating technique for seed layer growth. Effect of different parameter i.e., spins coating counts, spin coating speed, and the effect of temperature during the drying process was analyzed. Hot plate and furnace technique was used for heating purpose and the difference in the morphology was carefully observed. It is worthy to mention here that there is a substantial effect of all the above mentioned parameters on the growth and morphology of the ZnO nanostructure. The ZnO nanorods were finally synthesized using wet chemical method. The morphological properties of the obtained nanostructures were analyzed by using FESEM technique. PMID:27427752

  2. Lattice sites of Na dopants in ZnO

    NASA Astrophysics Data System (ADS)

    Wahl, U.; Correia, J. G.; Amorim, L.; Decoster, S.; da Silva, M. R.; Pereira, L. M. C.

    2016-09-01

    The angular distribution of β - particles emitted by the radioactive isotope 24Na was monitored following implantation into ZnO single crystals at fluences above 5 × 1012 cm-2 at CERN’s ISOLDE facility. We identified sodium on two distinct sites: on substitutional Zn sites and on interstitial sites that are close to the so-called octahedral site. The interstitial Na was to a large extent already converted to substitutional Na for annealing at 200 °C, from which an activation energy of 0.8-1.3 eV, most likely around 1.2 eV, is estimated for the migration of interstitial Na in ZnO.

  3. Neurotoxic potential of ingested ZnO nanomaterials on bees.

    PubMed

    Milivojević, Tamara; Glavan, Gordana; Božič, Janko; Sepčić, Kristina; Mesarič, Tina; Drobne, Damjana

    2015-02-01

    The honey bee is among most important pollinators threatened by environmental pollution, pest control and potentially, by products of nanotechnologies. The aim of the current study was an analysis of the neurotoxic potential of ingested zinc oxide nanomaterials (ZnO NMs) or zinc ions (Zn(2+)) on honey bees. We analysed a variety of biomarkers, including metabolic impairment, feeding rate, and survival, as well as the activities of a stress-related enzyme glutathione S-transferase, and the neurotoxicity biomarker acetylcholinesterase. Acetylcholinesterase activity was found to be elevated in bees exposed to either of the tested substances. In addition, we observed increased feeding rate in the group treated with Zn(2+) but not with ZnO NMs or control group. The observed effects we relate primarily to Zn(2+) ions. Here we provide evidence that zinc ions either originating from Zn salt or Zn-based NPs have a neurotoxic potential and thus might contribute to colony survival.

  4. ZnO Coated Nanospring-Based Gas Sensors

    NASA Astrophysics Data System (ADS)

    Bakharev, Pavel Viktorovich

    The current research demonstrates new techniques for characterization of electrical transport properties of the metal oxide polycrystalline structures, gas and vapor phase kinetics, surface processes such as gas-surface, vapor-surface interactions and redox processes by applying novel gas sensing devices. Real-time sensor electrical response characteristics obtained under highly controlled laboratory conditions have been used to characterize corresponding surface interactions and electrical properties of the gas sensitive structures. Novel redox chemical sensors (chemiresistors) have been fabricated with 3-D and 1-D ZnO coated nanospring (NS) structures. Silica NSs served as insulating scaffolding for a ZnO gas sensitive layer and has been grown via a vapor-liquid-solid (VLS) mechanism by using a chemical vapor deposition (CVD) technique. The NSs have been coated with polycrystalline ZnO by atomic layer deposition (ALD). The chemiresistor devices have been thoroughly characterized in terms of their crystal structures (by XRD, FESEM, TEM, and ellipsometry) and their electrical response properties. A 3-D gas sensor has been constructed from a xenon light bulb by coating it with a 3-D zinc oxide coated silica nanospring mat, where the xenon light bulb served as a sensor heater. This inexpensive sensor platform has been used to characterize gas-solid, vapor-solid, and redox processes. The optimal temperature of the gas sensitive ZnO layer, the temperature of the vapor-gas mixture and the crystal structure of the gas sensitive layer have been determined to reach the highest sensitivity of the gas sensors. The activation energy of toluene oxidation (Ed) on the ZnO surface and the activation energy of oxidation (Ea) of the depleted ZnO surface have been determined and analyzed. A 1-D chemiresistor has been fabricated with a single ZnO coated silica nanospring by photolithography. The question of sensor sensitivity of MOS nanomaterials and MOS thin films has been addressed

  5. Natural dye -sensitized mesoporous ZnO solar cell

    NASA Astrophysics Data System (ADS)

    Wu, Qishuang; Shen, Yue; Wu, Guizhi; Li, Linyu; Cao, Meng; Gu, Feng

    2011-02-01

    Natural dye-sensitized solar cells (N-DSSCs) were assembled using chlorophyll sensitized mesoporous ZnO (based on FTO) as the photoanode and platinum plate as the cathode. The natural dyes (chlorophyll) were extracted from spinach by simple procedure. The absorption spectrum and fluorescence spectrum of chlorophyll were studied. Mesoporous ZnO (m-ZnO) applied to the N-DSSCs was synthesized through hydrothermal method. The structures and morphologies were characterized by X-ray Diffraction (XRD) and diffuse reflection. The results indicated that the samples had an average pore size of 17 nm and the m-ZnO was hexagonal wurtzite structure. The performances of the N-DSSCs were investigated under AM 1.5G illumination. The Voc of the N-DSSCs was about 480mv, and the Isc was about 470μA. The performance of the N-DSSCs could be further improved by adjusting its structure.

  6. Natural dye -sensitized mesoporous ZnO solar cell

    NASA Astrophysics Data System (ADS)

    Wu, Qishuang; Shen, Yue; Wu, Guizhi; Li, Linyu; Cao, Meng; Gu, Feng

    2010-10-01

    Natural dye-sensitized solar cells (N-DSSCs) were assembled using chlorophyll sensitized mesoporous ZnO (based on FTO) as the photoanode and platinum plate as the cathode. The natural dyes (chlorophyll) were extracted from spinach by simple procedure. The absorption spectrum and fluorescence spectrum of chlorophyll were studied. Mesoporous ZnO (m-ZnO) applied to the N-DSSCs was synthesized through hydrothermal method. The structures and morphologies were characterized by X-ray Diffraction (XRD) and diffuse reflection. The results indicated that the samples had an average pore size of 17 nm and the m-ZnO was hexagonal wurtzite structure. The performances of the N-DSSCs were investigated under AM 1.5G illumination. The Voc of the N-DSSCs was about 480mv, and the Isc was about 470μA. The performance of the N-DSSCs could be further improved by adjusting its structure.

  7. Evidence for photogenerated intermediate hole polarons in ZnO.

    PubMed

    Sezen, Hikmet; Shang, Honghui; Bebensee, Fabian; Yang, Chengwu; Buchholz, Maria; Nefedov, Alexei; Heissler, Stefan; Carbogno, Christian; Scheffler, Matthias; Rinke, Patrick; Wöll, Christof

    2015-01-01

    Despite their pronounced importance for oxide-based photochemistry, optoelectronics and photovoltaics, only fairly little is known about the polaron lifetimes and binding energies. Polarons represent a crucial intermediate step populated immediately after dissociation of the excitons formed in the primary photoabsorption process. Here we present a novel approach to studying photoexcited polarons in an important photoactive oxide, ZnO, using infrared (IR) reflection-absorption spectroscopy (IRRAS) with a time resolution of 100 ms. For well-defined (10-10) oriented ZnO single-crystal substrates, we observe intense IR absorption bands at around 200 meV exhibiting a pronounced temperature dependence. On the basis of first-principles-based electronic structure calculations, we assign these features to hole polarons of intermediate coupling strength. PMID:25902307

  8. Structural, morphological and electroluminescence studies of Zno:Co nanophosphor

    NASA Astrophysics Data System (ADS)

    Singh, Anju; Vishwakarma, H. L.

    2016-09-01

    The nanoparticles of zinc oxide (ZnO) doped with various concentrations of cobalt (Co) were synthesized by chemical precipitation method in the presence of capping agent polyvinylpyrrolidone (PVP). The effect of doping concentration on structural and morphological properties has been studied by X-ray diffraction (XRD) and scanning electron microscope (SEM). Cell volume, bond length, texture coefficient, lattice constants and dislocation density are also studied. Here, we also compared the interplaner spacing and relative peak intensities from their standard values with different angles. Crystallite sizes have been calculated by Debye-Scherrer's formula whose values are decreasing with increase in cobalt content up to 3 %. It has been seen that the growth orientation of the prepared ZnO nanorods was (101). The XRD analysis also ensures that ZnO has a hexagonal (wurtzite) crystal structure. The electroluminescence (EL) cells were prepared by placing pure and cobalt-doped ZnO nanoparticles between ITO-coated conducting glass plate and aluminium foil. Alternating voltage of various frequencies was applied, and EL brightness at different voltages was measured and corresponding current was also recorded. The voltage dependence of electroluminescence (EL) brightness of the ZnO:Co shows exponential increase. The linear voltage-current characteristic indicates ohmic nature. The EL brightness at a particular voltage is found to increase by increasing Co doping, but for higher percentage of Co the EL brightness is reduced. It is also seen that Co does not influence the threshold voltage. The brightness is also affected by increasing the frequency of AC signal.

  9. Structure of grain boundaries in nanostructured ZnO

    NASA Astrophysics Data System (ADS)

    Wu, Zhihao; Zhou, Yingxue; Zhang, Xinyi; Wei, Shiqiang; Chen, Dongliang

    2004-05-01

    The grain boundary (GB) of nanocrystalline ZnO films is investigated using the x-ray absorption fine structure technique. With the advantage of the dominant GB volume fraction in our samples, the GB structure is found to be neither simply "gas-like" nor "similar to that of coarse-grained phase," but experiences a transition from the modestly ordered innermost coordination shell around centered atoms to partly disordered second coordination shell and then to completely disordered higher coordination shells.

  10. Heavy ion collisions

    SciTech Connect

    Jacak, B.V.

    1994-11-01

    Heavy ion collisions at very high energies provide an opportunity to recreate in the laboratory the conditions which existed very early in the universe, just after the big bang. We prepare matter at very high energy density and search for evidence that the quarks and gluons are deconfined. I describe the kinds of observables that are experimentally accessible to characterize the system and to search for evidence of new physics. A wealth of information is now available from CERN and BNL heavy ion experiments. I discuss recent results on two particle correlations, strangeness production, and dilepton and direct photon distributions.

  11. Synthesis and characterization of ZnO and Ni doped ZnO nanorods by thermal decomposition method for spintronics application

    SciTech Connect

    Saravanan, R.; Santhi, Kalavathy; Sivakumar, N.; Narayanan, V.; Stephen, A.

    2012-05-15

    Zinc oxide nanorods and diluted magnetic semiconducting Ni doped ZnO nanorods were prepared by thermal decomposition method. This method is simple and cost effective. The decomposition temperature of acetate and formation of oxide were determined by TGA before the actual synthesis process. The X-ray diffraction result indicates the single phase hexagonal structure of zinc oxide. The transmission electron microscopy and scanning electron microscopy images show rod like structure of ZnO and Ni doped ZnO samples with the diameter {approx} 35 nm and the length in few micrometers. The surface analysis was performed using X-ray photoelectron spectroscopic studies. The Ni doped ZnO exhibits room temperature ferromagnetism. This diluted magnetic semiconducting Ni doped ZnO nanorods finds its application in spintronics. - Highlights: Black-Right-Pointing-Pointer The method used is very simple and cost effective compared to all other methods for the preparation DMS materials. Black-Right-Pointing-Pointer ZnO and Ni doped ZnO nanorods Black-Right-Pointing-Pointer Ferromagnetism at room temperature.

  12. Well-integrated ZnO nanorod arrays on conductive textiles by electrochemical synthesis and their physical properties

    NASA Astrophysics Data System (ADS)

    Ko, Yeong Hwan; Kim, Myung Sub; Park, Wook; Yu, Jae Su

    2013-01-01

    We reported well-integrated zinc oxide (ZnO) nanorod arrays (NRAs) on conductive textiles (CTs) and their structural and optical properties. The integrated ZnO NRAs were synthesized by cathodic electrochemical deposition on the ZnO seed layer-coated CT substrate in ultrasonic bath. The ZnO NRAs were regularly and densely grown as well as vertically aligned on the overall surface of CT substrate, in comparison with the grown ZnO NRAs without ZnO seed layer or ultrasonication. Additionally, their morphologies and sizes can be efficiently controlled by changing the external cathodic voltage between the ZnO seed-coated CT substrate and the counter electrode. At an external cathodic voltage of -2 V, the photoluminescence property of ZnO NRAs was optimized with good crystallinity and high density.

  13. Spatially controlled growth of highly crystalline ZnO nanowires by an inkjet-printing catalyst-free method

    NASA Astrophysics Data System (ADS)

    Güell, Frank; Martínez-Alanis, Paulina R.; Khachadorian, Sevak; Zamani, Reza R.; Franke, Alexander; Hoffmann, Axel; Wagner, Markus R.; Santana, Guillermo

    2016-02-01

    High-density arrays of uniform ZnO nanowires with a high-crystal quality have been synthesized by a catalyst-free vapor-transport method. First, a thin ZnO film was deposited on a Si substrate as nucleation layer for the ZnO nanowires. Second, spatially selective and mask-less growth of ZnO nanowires was achieved using inkjet-printed patterned islands as the nucleation sites on a SiO2/Si substrate. Raman scattering and low temperature photoluminescence measurements were applied to characterize the structural and optical properties of the ZnO nanowires. The results reveal negligible amounts of strain and defects in the mask-less ZnO nanowires as compared to the ones grown on the ZnO thin film, which underlines the potential of the inkjet-printing approach for the growth of high-crystal quality ZnO nanowires.

  14. Effect of various shapes of ZnO nanoparticles on cotton fabric via electrospinning for UV-blocking.

    PubMed

    Neamjan, Natthawut; Sricharussin, Wimonrat; Threepopnatkul, Poonsub

    2012-01-01

    Various shapes of ZnO; multi-petals, rod and spherical were prepared and then applied on cotton fabric for UV-blocking. The ZnO particles were investigated by XRD and SEM. The mixture solution of ZnO with polyvinyl alcohol was applied onto cotton fabrics via electrospinning. The characteristics of the fabric coating were investigated by SEM, XRD, Tensile testing and Atomic absorption spectroscopy (AAS). UV-blocking property was determined by UV-vis spectrophotometer. The results of XRD and SEM on the ZnO powders show that we can produce various shape of ZnO. The investigation by SEM and AAS clearly revealed that ZnO in polyvinyl alcohol nanofibers was effectively deposited on the cotton surface. The sphericals-shaped ZnO coated fabrics show excellent UV-blocking properties. The shape of ZnO shows no considerable effect on the tensile strength of the samples.

  15. Conductivity fluctuations in proton-implanted ZnO microwires.

    PubMed

    Dolgin, B; Lorite, I; Kumar, Y; Esquinazi, P; Jung, G; Straube, B; Heluani, S Perez de

    2016-07-29

    Electric noise can be an important limitation for applications of conducting elements in the nanometer size range. The intrinsic electrical noise of prospective materials for opto-spintronics applications like ZnO has not yet been characterized. In this study, we have investigated the conductivity fluctuations in 10 nm thick current paths produced by proton implantation of ZnO microwires at room temperature. The voltage noise under a constant dc current bias in undoped, as well as in Li-doped microwires, is characterized by [Formula: see text] power spectra with [Formula: see text]. The noise intensity scales with the square of the bias current pointing to bias-independent resistivity fluctuations as a source of the observed noise. The normalized power spectral density appears inversely proportional to the number of carriers in the probed sample volume, in agreement with the phenomenological Hooge law. For the proton-implanted ZnO microwire and at 1 Hz we obtain a normalized power spectral density as low as [Formula: see text] Hz(-1). PMID:27306486

  16. Conductivity fluctuations in proton-implanted ZnO microwires

    NASA Astrophysics Data System (ADS)

    Dolgin, B.; Lorite, I.; Kumar, Y.; Esquinazi, P.; Jung, G.; Straube, B.; Perez de Heluani, S.

    2016-07-01

    Electric noise can be an important limitation for applications of conducting elements in the nanometer size range. The intrinsic electrical noise of prospective materials for opto-spintronics applications like ZnO has not yet been characterized. In this study, we have investigated the conductivity fluctuations in 10 nm thick current paths produced by proton implantation of ZnO microwires at room temperature. The voltage noise under a constant dc current bias in undoped, as well as in Li-doped microwires, is characterized by 1/{f}a power spectra with a∼ 1. The noise intensity scales with the square of the bias current pointing to bias-independent resistivity fluctuations as a source of the observed noise. The normalized power spectral density appears inversely proportional to the number of carriers in the probed sample volume, in agreement with the phenomenological Hooge law. For the proton-implanted ZnO microwire and at 1 Hz we obtain a normalized power spectral density as low as ∼ {10}-11 Hz‑1.

  17. 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.

  18. Earthworm coelomocytes as nanoscavenger of ZnO NPs

    PubMed Central

    2014-01-01

    Earthworms can ‘biotransform’ or ‘biodegrade’ chemical contaminants, rendering them harmless in their bodies, and can bioaccumulate them in their tissues. They ‘absorb’ the dissolved chemicals through their moist ‘body wall’ due to the interstitial water and also ingest by ‘mouth’ while soil passes through the gut. Since the advent of the nanotechnology era, the environmental sink has been continuously receiving engineered nanomaterials as well as their derivatives. Our current understanding of the potential impact of nanomaterials and their natural scavenger is limited. In the present investigation, we studied the cellular uptake of ZnO nanoparticles (NPs) by coelomocytes especially by chloragocytes of Eisenia fetida and their role as nanoscavenger. Results from exposure to 100- and 50-nm ZnO NPs indicate that coelomocytes of the earthworm E. fetida show no significant DNA damage at a dose lower than 3 mg/l and have the potential ability to uptake ZnO NPs from the soil ecosystem and transform them into microparticles. PMID:24959107

  19. Optical properties of ZnO doped with Cobalt ions

    NASA Astrophysics Data System (ADS)

    Ivanov, V. Yu; Zakrzewski, A. J.; Witkowski, B. S.; Godlewski, M.

    2016-09-01

    While doping with rare earth ions is used for emission activation, doping with transition metal ions is often used to get specific magnetic properties of a given host material. Recently investigations of transition metal doped materials focused on chances of achieving a room temperature ferromagnetic response. This is because carrier mediated room temperature ferromagnetic order was theoretically predicted for ZnO doped with Mn or Co ions. Such order is required for some of spintronics applications. To realize RT FM both Mn and Co should stay in 2+ charge state, expected when Mn/Co substitute zinc in ZnO. Both ZnMnO and ZnCoO alloys show a strong absorption band, which appears below ZnO band gap transitions. The origin of this absorption in ZnCoO is discussed in the present work. We show based on the results of photoluminescence and photo-ESR investigations that the broad absorption band is related to Co photo-ionization.

  20. Field emission properties of ZnO nanosheet arrays

    SciTech Connect

    Naik, Kusha Kumar; Rout, Chandra Sekhar E-mail: dj.late@ncl.res.in E-mail: csrout@iitbbs.ac.in; Khare, Ruchita; More, Mahendra A.; Chakravarty, Disha; Late, Dattatray J. E-mail: dj.late@ncl.res.in E-mail: csrout@iitbbs.ac.in; Thapa, Ranjit E-mail: dj.late@ncl.res.in E-mail: csrout@iitbbs.ac.in

    2014-12-08

    Electron emission properties of electrodeposited ZnO nanosheet arrays grown on Indium tin oxide coated glass substrates have been studied. Influence of oxygen vacancies on electronic structures and field emission properties of ZnO nanosheets are investigated using density functional theory. The oxygen vacancies produce unshared d electrons which form an impurity energy state; this causes shifting of Fermi level towards the vacuum, and so the barrier energy for electron extraction reduces. The ZnO nanosheet arrays exhibit a low turn-on field of 2.4 V/μm at 0.1 μA/cm{sup 2} and current density of 50.1 μA/cm{sup 2} at an applied field of 6.4 V/μm with field enhancement factor, β = 5812 and good field emission current stability. The nanosheet arrays grown by a facile electrodeposition process have great potential as robust high performance vertical structure electron emitters for future flat panel displays and vacuum electronic device applications.

  1. Optical behavior of native defects in ZnO

    NASA Astrophysics Data System (ADS)

    Lyons, John L.; Steiauf, Daniel; Alkauskas, Audrius; Janotti, Anderson; van de Walle, Chris G.

    2013-03-01

    The behavior of native defects in ZnO has been fiercely debated for years, yet questions still remain regarding their fundamental properties. Once blamed for causing unintentional n-type conductivity, it is now well-established that native donors are highly unlikely to act as shallow donors in as-grown material. Still, both native donors and acceptors may be present in some samples, acting as either compensating acceptors or deep donors that may inhibit attempts to obtain high-conductivity n-type ZnO. In this work, we re-examine the properties of native donors and acceptors in ZnO using hybrid density functional calculations, which allow for the quantitative prediction of defect transition levels and formation energies. We focus on the optical and electrical properties of these defects, and calculate both their optical and thermodynamic transition levels. Most of the defects give rise to deep, broad luminescence signals that can serve as a means of experimentally verifying the nature of the center. We also examine how interactions with hydrogen interstitials affect the properties of these defects. This work was supported by the NSF.

  2. Study of the wettability of ZnO nanofilms

    NASA Astrophysics Data System (ADS)

    Subedi, Deepak Prasad; Madhup, Dinesh Kumar; Sharma, Ashish; Joshi, Ujjwal Man; Huczko, Andrzej

    2012-04-01

    Al-doped and un-doped ZnO thin films deposited on quartz substrates by the nebulized spray pyrolysis method were studied to investigate the wettability of the surface. The main objective of the present study was to investigate the wettability of ZnO thin film by changing the concentration of Al doping. Microstructure and water contact angles of the films were measured by scanning electron microscopy (SEM) and using a contact angle goniometer. SEM studies revealed that the grain size within the film increases with the doping concentration. The contact angles were studied to see the effect of aluminum doping on the hydrophilicity of the film. ZnO films were found to be hydrophobic in nature. A good correlation was observed between the SEM micrographs and contact angle results. The nature of the film was found to change from being hydrophobic to hydrophilic after the treatment in low-pressure DC glow discharge plasma, which, however, was reversible with the storage time.

  3. Nanophotoactivity of Porphyrin Functionalized Polycrystalline ZnO Films.

    PubMed

    Rogero, Celia; Pickup, David F; Colchero, Jaime; Azaceta, Eneko; Tena-Zaera, Ramón; Palacios-Lidón, Elisa

    2016-07-01

    Kelvin probe force microscopy in darkness and under illumination is reported to provide nanoscale-resolved surface photovoltage maps of hybrid materials. In particular, nanoscale charge injection and charge recombination mechanisms occurring in ZnO polycrystalline surfaces functionalized with Protoporphyrin IX (H2PPIX) are analyzed. Local surface potential and surface photovoltage maps not only reveal that upon molecular adsorption the bare ZnO work function increases, but also they allow study of its local dependence. Nanometer-sized regions not correlated with apparent topographic features were identified, presenting values significantly different from the average work function. Depending on the region, the response to the light excitation is different, distinguishing two relaxation processes, one faster than the other. This behavior can be explained in terms of electrons trapped closed to the molecule-semiconductor interface or electrons pushed into the ZnO bulk, respectively. Moreover, the origin of these differences is correlated with the H2PPIX-ZnO bonding and molecules configuration and aggregation. The chenodeoxycholic acid (CDCA) coadsorption leads to a more homogeneous surface potential distribution, confirming the antiaggregate effect of this additive, while the surface photovoltage is mostly dominated by the slow relaxation component. This work reveals the complexity of real device architectures with ill-defined surfaces even in a relatively simple system with only one type of dye molecule and hightlights the importance of nanoscale characterization with appropriate tools. PMID:27303943

  4. Electrodeposited ZnO films with high UV emission properties

    SciTech Connect

    Matei, Elena; Enculescu, Ionut

    2011-11-15

    Highlights: {yields} Electrodeposition of ZnO from nitrate baths is investigated. {yields} The influence of process parameters on morphological and optical properties is studied. {yields} Experimental conditions to fabricate ZnO films with high UV emission were found. -- Abstract: We report here our results in the preparation of ZnO films with high UV band to band characteristic luminescence emission by potentiostatic electrodeposition. Zinc nitrate aqueous baths with different concentration and additives were employed for the preparation of the films on platinum substrates. We focused our research in determining how the electrodeposition bath composition, i.e. zinc nitrate concentration and addition of KCl or polyvinyl pyrolidone and applied overpotential influence the morphological and optical properties of the oxide films. Scanning electron microscopy was employed for characterizing the films in terms of morphology. Optical reflection, photoluminescence spectroscopy and cathodoluminescence were used for determining the optical characteristics of the samples. The morphology of the deposit varies from hexagonal prisms to platelets as a function of the deposition rate. This experimental parameter also influences the luminescence properties. We found that at low deposition rates high UV luminescent material is obtained.

  5. Earthworm coelomocytes as nanoscavenger of ZnO NPs

    NASA Astrophysics Data System (ADS)

    Gupta, Shruti; Kushwah, Tanuja; Yadav, Shweta

    2014-05-01

    Earthworms can `biotransform' or `biodegrade' chemical contaminants, rendering them harmless in their bodies, and can bioaccumulate them in their tissues. They `absorb' the dissolved chemicals through their moist `body wall' due to the interstitial water and also ingest by `mouth' while soil passes through the gut. Since the advent of the nanotechnology era, the environmental sink has been continuously receiving engineered nanomaterials as well as their derivatives. Our current understanding of the potential impact of nanomaterials and their natural scavenger is limited. In the present investigation, we studied the cellular uptake of ZnO nanoparticles (NPs) by coelomocytes especially by chloragocytes of Eisenia fetida and their role as nanoscavenger. Results from exposure to 100- and 50-nm ZnO NPs indicate that coelomocytes of the earthworm E. fetida show no significant DNA damage at a dose lower than 3 mg/l and have the potential ability to uptake ZnO NPs from the soil ecosystem and transform them into microparticles.

  6. Transparent conductive Nd-doped ZnO thin films

    NASA Astrophysics Data System (ADS)

    Nistor, M.; Millon, E.; Cachoncinlle, C.; Seiler, W.; Jedrecy, N.; Hebert, C.; Perrière, J.

    2015-03-01

    Transparent Nd-doped ZnO films with thickness in the range of 70 to 250 nm were grown by pulsed-laser deposition (PLD) on c-cut sapphire substrates at various oxygen pressures and substrate temperatures. A wide range of optical and electrical properties of the films were obtained and correlated to the composition and crystalline structure. The Nd-doped ZnO films are smooth, dense, and display the wurtzite phase. Different epitaxial relationships between films and substrate as a function of growth pressure and substrate temperature were evidenced by asymmetric x-ray diffraction measurements. By varying PLD growth conditions, the films can be tuned to have either metallic or semiconductor characteristics, with good optical transmittance in the visible range. Moreover, a low-temperature metal-insulator transition may be observed in Nd-doped ZnO films grown under low oxygen pressure. Resistivities as low as 6 × 10-4 Ω cm and 90% optical transmittance in the visible range and different near-infrared transmittance are obtained with approximately 1.0-1.5 at.% Nd doping and growth temperature of approximately 500 °C.

  7. Conductivity fluctuations in proton-implanted ZnO microwires

    NASA Astrophysics Data System (ADS)

    Dolgin, B.; Lorite, I.; Kumar, Y.; Esquinazi, P.; Jung, G.; Straube, B.; Perez de Heluani, S.

    2016-07-01

    Electric noise can be an important limitation for applications of conducting elements in the nanometer size range. The intrinsic electrical noise of prospective materials for opto-spintronics applications like ZnO has not yet been characterized. In this study, we have investigated the conductivity fluctuations in 10 nm thick current paths produced by proton implantation of ZnO microwires at room temperature. The voltage noise under a constant dc current bias in undoped, as well as in Li-doped microwires, is characterized by 1/{f}a power spectra with a˜ 1. The noise intensity scales with the square of the bias current pointing to bias-independent resistivity fluctuations as a source of the observed noise. The normalized power spectral density appears inversely proportional to the number of carriers in the probed sample volume, in agreement with the phenomenological Hooge law. For the proton-implanted ZnO microwire and at 1 Hz we obtain a normalized power spectral density as low as ˜ {10}-11 Hz-1.

  8. Structural and Morphology of ZnO Nanorods Synthesized Using ZnO Seeded Growth Hydrothermal Method and Its Properties as UV Sensing

    PubMed Central

    Ridhuan, Nur Syafinaz; Abdul Razak, Khairunisak; Lockman, Zainovia; Abdul Aziz, Azlan

    2012-01-01

    In this study, zinc oxide (ZnO) nanorod arrays were synthesized using a simple hydrothermal reaction on ZnO seeds/n-silicon substrate. Several parameters were studied, including the heat-treatment temperature to produce ZnO seeds, zinc nitrate concentration, pH of hydrothermal reaction solution, and hydrothermal reaction time. The optimum heat-treatment temperature to produce uniform nanosized ZnO seeds was 400°C. The nanorod dimensions depended on the hydrothermal reaction parameters. The optimum hydrothermal reaction parameters to produce blunt tip-like nanorods (770 nm long and 80 nm in top diameter) were 0.1 M zinc nitrate, pH 7, and 4 h of growth duration. Phase analysis studies showed that all ZnO nanorods exhibited a strong (002) peak. Thus, the ZnO nanorods grew in a c-axis preferred orientation. A strong ultraviolet (UV) emission peak was observed for ZnO nanorods grown under optimized parameters with a low, deep-level emission peak, which indicated high optical property and crystallinity of the nanorods. The produced ZnO nanorods were also tested for their UV-sensing properties. All samples responded to UV light but with different sensing characteristics. Such different responses could be attributed to the high surface-to-volume ratio of the nanorods that correlated with the final ZnO nanorods morphology formed at different synthesis parameters. The sample grown using optimum synthesis parameters showed the highest responsivity of 0.024 A/W for UV light at 375 nm under a 3 V bias. PMID:23189199

  9. Synthesis of high surface area ZnO powder by continuous precipitation

    SciTech Connect

    Boz, Ismail; Kaluza, Stefan; Boroglu, Mehtap Safak; Muhler, Martin

    2012-05-15

    Graphical abstract: High surface area ZnO powders are synthesized by a low temperature continuous precipitation under ultrasonication. Urea is used as precipitating agent so that no contamination of ZnO powder emanating from precipitating agent, such as, alkalis, is observed. pH and type of precursor greatly affects the surface area and other properties. In this manuscript, we report a very simple and effective continuous precipitation to synthesize high surface area ZnO powder. Highlights: Black-Right-Pointing-Pointer The synthesis of high surface area ZnO powder was achieved at 90 Degree-Sign C in a continuous precipitation unit. Black-Right-Pointing-Pointer Continuous precipitation unit was ultrasonicated to improve final product homogeneity. Black-Right-Pointing-Pointer Precipitation intermediate, hydrozincite, was led to high surface area ZnO powder. Black-Right-Pointing-Pointer The synthesized ZnO nanoparticles had a rather uniform mesoporous structure. -- Abstract: Synthesis of high surface area ZnO powder was achieved by continuous precipitation using zinc ions and urea at low temperature of 90 Degree-Sign C. The powder precipitated resulted in high-purity single-phase ZnO powder when calcined at 280 Degree-Sign C for 3 h in air. The solution pH and the precipitation duration strongly affected the surface area of the calcined ZnO powder. Detailed structural characterizations demonstrated that the synthesized ZnO powder were single crystalline with wurtzite hexagonal phase. The powdered samples precipitated by homogeneous precipitation crystallized directly to hydrozincite without any intermediate phase formation. The phase structures, morphologies and properties of the final ZnO powders were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), dynamic light scattering particle size analysis (DLS), and nitrogen physisorption in order to determine the specific surface area (BET) and the pore size distribution (BJH).

  10. 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.

  11. UV and humidity sensing properties of ZnO nanorods prepared by the arc discharge method.

    PubMed

    Fang, F; Futter, J; Markwitz, A; Kennedy, J

    2009-06-17

    The UV and humidity sensing properties of ZnO nanorods prepared by arc discharge have been studied. Scanning electron microscopy and photoluminescence spectroscopy were carried out to analyze the morphology and optical properties of the as-synthesized ZnO nanorods. Proton induced x-ray emission was used to probe the impurities in the ZnO nanorods. A large quantity of high purity ZnO nanorod structures were obtained with lengths of 0.5-1 microm. The diameters of the as-synthesized ZnO nanorods were found to be between 40 and 400 nm. The nanorods interlace with each other, forming 3D networks which make them suitable for sensing application. The addition of a polymeric film-forming agent (BASF LUVISKOL VA 64) improved the conductivity, as it facilitates the construction of conducting networks. Ultrasonication helped to separate the ZnO nanorods and disperse them evenly through the polymeric agent. Improved photoconductivity was measured for a ZnO nanorod sensor annealed in air at 200 degrees C for 30 min. The ZnO nanorod sensors showed a UV-sensitive photoconduction, where the photocurrent increased by nearly four orders of magnitude from 2.7 x 10(-10) to 1.0 x 10(-6) A at 18 V under 340 nm UV illumination. High humidity sensitivity and good stability were also measured. The resistance of the ZnO nanorod sensor decreased almost linearly with increasing relative humidity (RH). The resistance of the ZnO nanorods changed by approximately five orders of magnitude from 4.35 x 10(11) Omega in dry air (7% RH) to about 4.95 x 10(6) Omega in 95% RH air. It is experimentally demonstrated that ZnO nanorods obtained by the arc discharge method show excellent performance and promise for applications in both UV and humidity sensors. PMID:19468159

  12. 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.

  13. 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. PMID:26039692

  14. 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

  15. Fabrication and Characterization of ZnO Nanorods on Multiple Substrates.

    PubMed

    Rana, Abu ul Hassan Sarwar; Ko, Kyul; Hong, Sejun; Kang, Mingi; Kim, Hyun-Seok

    2015-11-01

    In this study, we present the fabrication and characterization of ZnO nanorods (NRs) grown on p-Si, gold (Au) and nickel (Ni) coated on Si wafer, indium tin oxide (ITO), and quartz substrates. The aqueous chemical growth method is used for the vertical growth of ZnO NRs on multiple substrates. The samples are characterized with scanning electron microscope and energy dispersive X-ray spectroscopy to probe into the growth, alignment, density, diameter, and length of ZnO NRs on multiple substrates. It is found that under same conditions, like growth temperature, growth time, and solution concentration, ZnO NRs on ITO and quartz have same length but comparatively larger diameter than on other samples. The effects of growth time on the diameter and length of ZnO NRs are also explored. All the samples are characterized with probe station to look at the current-voltage (I-V) behavior of ZnO NRs on multiple substrates. It is found that ZnO NRs on p-Si show a simple p-n heterojunction diode like behavior. ZnO NRs grown on Au- and Ni-coated Si wafers show Schottky I-V characteristic behaviors while ZnO NRs on ITO show a simple ohmic I-V response with comparatively higher level of current. Finally, the I-V response of ZnO NRs on p-Si is also studied under ultraviolet illumination. Because of the photo-generated carriers in ZnO, the sample shows higher level of current upon illumination. PMID:26726520

  16. pH-dependent phosphatization of ZnO nanoparticles and its influence on subsequent lead sorption.

    PubMed

    Xu, Huacheng; Li, Lina; Lv, Hua; Liu, Xin; Jiang, Helong

    2016-01-01

    Phosphatization of ZnO nanoparticles (ZNPs) at various pHs and its influence on subsequent lead sorption were investigated. Results showed that, in presence of phosphate, both the chemical speciation and crystalline phase of ZNPs were pH dependent that most of them were converted to crystalline Zn3(PO4)2 at acidic pHs, but only little amorphous hopeites can be formed under alkaline condition. Phosphatization process significantly enhanced subsequent lead sorption with the order of acidic process > alkaline > pristine ZNPs. Spectroscopic analysis including ATR-FTIR and XPS revealed main mechanisms of lead phosphate precipitation and inner-sphere complexes for lead sorption on acidic and alkaline treatment products, respectively. The potential toxicity of ZNPs and heavy metals in eutrophic aquatic ecosystems would thus be reduced due to the ubiquitous phosphatization process. This study highlights the importance of environmental variables in exploring the environmental behavior and fate of heavy metals as well as nanoparticles in natural waters. PMID:26561448

  17. pH-dependent phosphatization of ZnO nanoparticles and its influence on subsequent lead sorption.

    PubMed

    Xu, Huacheng; Li, Lina; Lv, Hua; Liu, Xin; Jiang, Helong

    2016-01-01

    Phosphatization of ZnO nanoparticles (ZNPs) at various pHs and its influence on subsequent lead sorption were investigated. Results showed that, in presence of phosphate, both the chemical speciation and crystalline phase of ZNPs were pH dependent that most of them were converted to crystalline Zn3(PO4)2 at acidic pHs, but only little amorphous hopeites can be formed under alkaline condition. Phosphatization process significantly enhanced subsequent lead sorption with the order of acidic process > alkaline > pristine ZNPs. Spectroscopic analysis including ATR-FTIR and XPS revealed main mechanisms of lead phosphate precipitation and inner-sphere complexes for lead sorption on acidic and alkaline treatment products, respectively. The potential toxicity of ZNPs and heavy metals in eutrophic aquatic ecosystems would thus be reduced due to the ubiquitous phosphatization process. This study highlights the importance of environmental variables in exploring the environmental behavior and fate of heavy metals as well as nanoparticles in natural waters.

  18. Heavy Vehicle Systems

    SciTech Connect

    Sid Diamond; Richard Wares; Jules Routbort

    2000-04-11

    Heavy Vehicle (HV) systems are a necessary component of achieving OHVT goals. Elements are in place for a far-ranging program: short, intermediate, and long-term. Solicitation will bring industrial input and support. Future funding trend is positive, outlook for HV systems is good.

  19. Heavy Quark Fluorescence

    SciTech Connect

    Torres-Rincon, Juan M.; Llanes-Estrada, Felipe J.

    2010-07-09

    Heavy hadrons containing heavy quarks (for example, {Upsilon} mesons) feature a scale separation between the heavy-quark mass and the QCD scale that controls the effective masses of lighter constituents. As in ordinary molecules, the deexcitation of the lighter, faster degrees of freedom leaves the velocity distribution of the heavy quarks unchanged, populating the available decay channels in qualitatively predictable ways. Automatically an application of the Franck-Condon principle of molecular physics explains several puzzling results of {Upsilon}(5S) decays as measured by the Belle Collaboration, such as the high rate of B{sub s}*B{sub s}* versus B{sub s}*B{sub s} production, the strength of three-body B{sup *}B{pi} decays, or the dip in B momentum shown in these decays. We argue that the data show the first Sturm-Liouville zero of the {Upsilon}(5S) quantum-mechanical squared wave function and provide evidence for a largely bb composition of this meson.

  20. STAR heavy flavor tracker

    NASA Astrophysics Data System (ADS)

    Qiu, Hao

    2014-11-01

    Hadrons containing heavy quarks are a clean probe of the early dynamic evolution of the dense and hot medium created in high-energy nuclear collisions. To explore heavy quark production at RHIC, the Heavy Flavor Tracker (HFT) for the STAR experiment was built and installed in time for RHIC Run 14. The HFT consists of four layers of silicon detectors. The two outermost layers are silicon strip detectors and the two innermost layers are made from state-of-the-art ultra-thin CMOS Monolithic Active Pixel Sensors (MAPS). This is the first application of a CMOS MAPS detector in a collider experiment. The use of thin pixel sensors plus the use of carbon fiber supporting material limits the material budget to be only 0.4% radiation length per pixel detector layer, enabling the reconstruction of low pT heavy flavor hadrons. The status and performance of the HFT in the RHIC 200 GeV Au + Au run in 2014 are reported. Very good detector efficiency, hit residuals and track resolution (DCAs) were observed in the cosmic ray data and in the Au + Au data.

  1. Heavy Chain Diseases

    MedlinePlus

    ... cells often prevents proper absorption of nutrients from food (malabsorption), resulting in severe diarrhea and weight loss. A rare form that affects the respiratory tract also exists. Blood tests are done when alpha heavy chain disease is suspected. Serum protein electrophoresis, measurement of ...

  2. Dolly For Heavy Towbar

    NASA Technical Reports Server (NTRS)

    Soper, Terry A.

    1992-01-01

    Proposed lightweight dolly enables operator to cart heavy towbar to remote site over unpaved roads or rough terrain. Acts as simple, lightweight towed vehicle to support rear of towbar. Removed quickly at point of use. Saves labor, and eliminates need for truck and forklift.

  3. Heavy quark physics in CMS

    NASA Astrophysics Data System (ADS)

    Fedi, G.; CMS Collaboration

    2016-07-01

    The most recent results which concern the heavy quark hadrons done in the CMS experiment are reported. The searching area spans over the heavy quark spectroscopy, production cross sections, beauty meson decay properties, rare decays, and CP violation.

  4. Heavy quarks and lattice QCD

    SciTech Connect

    Andreas S. Kronfeld

    2003-11-05

    This paper is a review of heavy quarks in lattice gauge theory, focusing on methodology. It includes a status report on some of the calculations that are relevant to heavy-quark spectroscopy and to flavor physics.

  5. Angle-dependent photodegradation over ZnO nanowire arrays on flexible paper substrates

    PubMed Central

    2014-01-01

    In this study, we grew zinc oxide (ZnO) nanowire arrays on paper substrates using a two-step growth strategy. In the first step, we formed single-crystalline ZnO nanoparticles of uniform size distribution (ca. 4 nm) as seeds for the hydrothermal growth of the ZnO nanowire arrays. After spin-coating of these seeds onto paper, we grew ZnO nanowire arrays conformally on these substrates. The crystal structure of a ZnO nanowire revealed that the nanowires were single-crystalline and had grown along the c axis. Further visualization through annular bright field scanning transmission electron microscopy revealed that the hydrothermally grown ZnO nanowires possessed Zn polarity. From photocatalytic activity measurements of the ZnO nanowire (NW) arrays on paper substrate, we extracted rate constants of 0.415, 0.244, 0.195, and 0.08 s-1 for the degradation of methylene blue at incident angles of 0°, 30°, 60°, and 75°, respectively; that is, the photocatalytic activity of these ZnO nanowire arrays was related to the cosine of the incident angle of the UV light. Accordingly, these materials have promising applications in the design of sterilization systems and light-harvesting devices. PMID:25593556

  6. 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. PMID:27245962

  7. 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.

  8. 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. PMID:26367556

  9. Structural and optical characterizations of ZnO aerogel nanopowder synthesized from zinc acetate ethanolic solution

    NASA Astrophysics Data System (ADS)

    Djouadi, D.; Meddouri, M.; Chelouche, A.

    2014-11-01

    ZnO aerogel powder has been synthesized by a modified sol-gel process using zinc acetate ethanolic solution. XRD, SEM, EDAX, FTIR, UV-visible absorption and photoluminescence (PL) techniques have been used to characterize the as-prepared and the annealed ZnO aerogel powders. The as-prepared ZnO powder has a well-defined polycrystalline hexagonal wurtzite structure. This measurement has demonstrated that the lattice parameters are lower than the standard ones indicating that drying in supercritical conditions of ethanol does not affect the crystallinity but acts as a compressive agent. EDAX measurements show that the obtained aerogel contains only O and Zn elements. Annealing improves the crystallinity in the low DRX angles and decreases the crystalline quality in the high diffraction angles. Also, annealing acts as a tensile agent and increases the lattice parameters. FTIR spectra confirm the annealing effect by the apparition of the strong Zn-O vibration band. The ZnO absorption band shifts to lower wave numbers after annealing indicating an increase in the Zn-O bond length and confirms the XRD results. UV-visible results show a decrease of the ZnO aerogel optical band gap after annealing and confirm the thermal decompression effect on the lattice parameters. The photoluminescence measurements show that the annealing of ZnO aerogel favors the thermal generation of zinc interstitials and oxygen vacancies defects existing in the as-prepared zinc oxide aerogel and shifts the emission toward lower energies.

  10. Antifungal activity of ZnO nanoparticles—the role of ROS mediated cell injury

    NASA Astrophysics Data System (ADS)

    Lipovsky, Anat; Nitzan, Yeshayahu; Gedanken, Aharon; Lubart, Rachel

    2011-03-01

    Metal oxide nanoparticles have marked antibacterial activity. The toxic effect of these nanoparticles, such as those comprised of ZnO, has been found to occur due to an interaction of the nanoparticle surface with water, and to increase with a decrease in particle size. In the present study, we tested the ability of ZnO nanoparticles to affect the viability of the pathogenic yeast, Candida albicans (C. albicans). A concentration-dependent effect of ZnO on the viability of C. albicans was observed. The minimal fungicidal concentration of ZnO was found to be 0.1 mg ml - 1 ZnO; this concentration caused an inhibition of over 95% in the growth of C. albicans. ZnO nanoparticles also inhibited the growth of C. albicans when it was added at the logarithmic phase of growth. Addition of histidine (a quencher of hydroxyl radicals and singlet oxygen) caused reduction in the effect of ZnO on C. albicans depending on its concentration. An almost complete elimination of the antimycotic effect was achieved following addition of 5 mM of histidine. Exciting the ZnO by visible light increased the yeast cell death. The effects of histidine suggest the involvement of reactive oxygen species, including hydroxyl radicals and singlet oxygen, in cell death. In light of the above results it appears that metal oxide nanoparticles may provide a novel family of fungicidal compounds.

  11. Antifungal activity of ZnO nanoparticles--the role of ROS mediated cell injury.

    PubMed

    Lipovsky, Anat; Nitzan, Yeshayahu; Gedanken, Aharon; Lubart, Rachel

    2011-03-11

    Metal oxide nanoparticles have marked antibacterial activity. The toxic effect of these nanoparticles, such as those comprised of ZnO, has been found to occur due to an interaction of the nanoparticle surface with water, and to increase with a decrease in particle size. In the present study, we tested the ability of ZnO nanoparticles to affect the viability of the pathogenic yeast, Candida albicans (C. albicans). A concentration-dependent effect of ZnO on the viability of C. albicans was observed. The minimal fungicidal concentration of ZnO was found to be 0.1 mg ml(-1) ZnO; this concentration caused an inhibition of over 95% in the growth of C. albicans. ZnO nanoparticles also inhibited the growth of C. albicans when it was added at the logarithmic phase of growth. Addition of histidine (a quencher of hydroxyl radicals and singlet oxygen) caused reduction in the effect of ZnO on C. albicans depending on its concentration. An almost complete elimination of the antimycotic effect was achieved following addition of 5 mM of histidine. Exciting the ZnO by visible light increased the yeast cell death. The effects of histidine suggest the involvement of reactive oxygen species, including hydroxyl radicals and singlet oxygen, in cell death. In light of the above results it appears that metal oxide nanoparticles may provide a novel family of fungicidal compounds. PMID:21289395

  12. Assessment of phytotoxicity of ZnO NPs on a medicinal plant, Fagopyrum esculentum.

    PubMed

    Lee, Sooyeon; Kim, Sunghyun; Kim, Saeyeon; Lee, Insook

    2013-02-01

    Fagopyrum esculentum commonly named as buckwheat plant is pseudocereal food crops and healthy herbs but is not known as a bioindicator of environmental condition. In the present study, the effects of ZnO nanoparticles (NPs) and microparticles (MPs) on plant growth, bioaccumulation, and antioxidative enzyme activity in buckwheat were estimated under hydroponic culture. The significant biomass reduction at concentrations of 10-2,000 mg/L was 7.7-26.4 % for the ZnO NP and 11.4-23.5 % for the ZnO MP treatment, (p < 0.05). ZnO NPs were observed in root cells and root cell surface by scanning electron microscopy and transmission electron microscopy analysis. Zn bioaccumulation in plant increased with increasing treatment concentrations. The upward translocation (translocation factor <0.2) of Zn in plant was higher with the ZnO NP treatment than that with the ZnO MP treatment. Additionally, reactive oxygen species generation by ZnO NPs was estimated as the reduced glutathione level and catalase activity, which would be a predictive biomarker of nanotoxicity. The results are the first study to evaluate the phytotoxicity of ZnO NPs to medicinal plant. F. esculentum can be as a good indicator of plant species in NP-polluted environment.

  13. [Optical Properties of ZnO Films Fabricated by Atomic Layer Deposition].

    PubMed

    Zhang, Chun-mei; Wang, Dong-dong; Fang, Ming; Zhang, Ao; Wang, Xiao-yu; Chen, Qiang; Meng, Tao

    2016-01-01

    The ZnO films were deposited by atomic layer deposition method using water and diethylzinc as precursors at different temperatures (110 and 190 degrees C). X-ray photoelectron spectroscopy, spectroscopic ellipsometry and photoluminescence spectra (PL) were used to investigate the elemental composition and optical properties of ZnO films. Our results showed that with the increasing of the growth temperature, the amount of -OH groups in the ZnO film decreased, which indicated that the reactions went to completion at high processing temperatures. The PL spectra of the ZnO film deposited at 110 degrees C exhibited two emission bands, one in the UV region and the other in the visible region. When the deposition temperature increased to 190 degrees C, the emission bands in the visible region disappeared, which indicated that the deep level defect in ZnO became less. The carrier mobility improved from 25 to 32 cm2 x (V x S)(-1) with the reduction of the defects in the ZnO film. The refractive index of the ZnO films decreased from 2.33 to 1.9 in the 375-800 nm region. The optical absorption edge (E(g)) values of the ZnO films deposited at different temperature were about 3.27 eV.

  14. Visible WGM emissions from rare earth ion doped ZnO microspheres

    NASA Astrophysics Data System (ADS)

    K, Fabitha; Rao, M. S. Ramachandra

    ZnO is known to be an ideal candidate for short wavelength range opto-electronic device applications due to its wide and direct bandgap (3.37 eV) and high excitonic binding energy (60 meV). Apart from the UV emission at ~380 nm (free exciton emission) ZnO also possesses a broad emission band centered at ~530 nm which is expected to be originated from the oxygen vacancy (Vo) defects. In rare earth (RE) ion doped ZnO, emissions originate from the 4f levels of RE ions will be obtained in addition to the characteristic emissions of ZnO. Small micro/nanostructures made of ZnO with high crystalline quality show unique characteristics in light emission, especially in lasing applications. A micro/ nanostructured ZnO crystal generally has a wurtzite structure with a natural hexagonal cross section, which serves as a WGM lasing micro cavity owing to its high reflective index (~2). However, there exists a potential optical loss at corners of hexagons; therefore, an isotropic structure like spheres may be a better candidate to achieve efficient light confinement. In our work, highly smooth micro spheres with different diameters were grown. Raman spectroscopy measurements confirm the hexagonal wurtzite structure of ZnO, SEM and AFM studies shows the smooth surfaced spheres. WGM lasing characteristics of ZnO spheres have been investigated using optical pumping with 488 nm laser in a micro-PL system. Details of the results will be presented.

  15. Hydrothermal synthesis of various hierarchical ZnO nanostructures and their methane sensing properties.

    PubMed

    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

  16. Solvents induced ZnO nanoparticles aggregation associated with their interfacial effect on organic solar cells.

    PubMed

    Li, Pandeng; Jiu, Tonggang; Tang, Gang; Wang, Guojie; Li, Jun; Li, Xiaofang; Fang, Junfeng

    2014-10-22

    ZnO nanofilm as a cathode buffer layer has surface defects due to the aggregations of ZnO nanoparticles, leading to poor device performance of organic solar cells. In this paper, we report the ZnO nanoparticles aggregations in solution can be controlled by adjusting the solvents ratios (chloroform vs methanol). These aggregations could influence the morphology of ZnO film. Therefore, compact and homogeneous ZnO film can be obtained to help achieve a preferable power conversion efficiency of 8.54% in inverted organic solar cells. This improvement is attributed to the decreased leakage current and the increased electron-collecting efficiency as well as the improved interface contact with the active layer. In addition, we find the enhanced maximum exciton generation rate and exciton dissociation probability lead to the improvement of device performance due to the preferable ZnO dispersion. Compared to other methods of ZnO nanofilm fabrication, it is the more convenient, moderate, and effective to get a preferable ZnO buffer layer for high-efficiency organic solar cells.

  17. Photocatalytic activity of 6.5 MeV electron-irradiated ZnO nanorods

    NASA Astrophysics Data System (ADS)

    Sapnar, K. B.; Ghule, L. A.; Bhoraskar, S. V.; Garadkar, K. M.; Dhole, S. D.; Bhoraskar, V. N.

    2012-04-01

    The microwave-synthesized zinc-oxide (ZnO) nanonorods of average length of ∼ 1500 nm and diameter ∼ 100 nm were irradiated with 6.5 meV electrons. From sample to sample, the electron fluence was varied over the range 5×1014 to 2.5×1015 e-cm-2. The pre- and post-electron-irradiated ZnO nanorods were characterized by X-ray diffraction, UV-VIS, EDAX, scanning electron microscopy, transmission electron microscopy, and BET methods. The results show that after electron irradiation, the ZnO nanorods could retain the hexagonal phase with the wurtzite structure; however, the average length of the ZnO nanorods reduced to ∼ 800 nm. Moreover, the oxygen atoms from a fraction of ZnO molecules were dislodged, and the process contributed to the formation of Zn-ZnO mixed phase, with increased zinc to oxygen ratio. In the photo-degradation of Rhodamine-B, a significant enhancement in the photocatalytic activity of the electron-irradiated ZnO nanorods was observed. This could be attributed to the induced defects, reduced dimensions, and increased surface area of the ZnO nanorods, in addition to the formation of the Zn-ZnO phase. All these could collectively contribute to the effective separation of the photogenerated electrons from the holes on the ZnO nanorods, and therefore enhance the photocatalytic activity under UV exposure.

  18. Luminescence dynamics of bound exciton of hydrogen doped ZnO nanowires

    DOE PAGESBeta

    Yoo, Jinkyoung; Yi, Gyu -Chul; Chon, Bonghwan; Joo, Taiha; Wang, Zhehui

    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

  19. 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.

  20. Optical characteristics of ZnO single crystal grown by the hydrothermal method

    SciTech Connect

    Chen, G. Z.; Yin, J. G. E-mail: yjg@siom.ac.cn; Zhang, L. H.; Zhang, P. X.; Wang, X. Y.; Liu, Y. C.; Zhang, C. L.; Gu, S. L.; Hang, Y.

    2015-12-15

    ZnO single crystals have been grown by the hydrothermal method. Raman scattering and Photoluminescence spectroscopy (PL) have been used to study samples of ZnO that were unannealed or annealed in different ambient gases. It is suggested that the green emission may originate from defects related to copper in our samples.

  1. Modulation of antibiotic resistance in Pseudomonas aeruginosa by ZnO nanoparticles

    PubMed Central

    Bayroodi, Elnaz; Jalal, Razieh

    2016-01-01

    Background and Objectives: Bacterial resistance to conventional antibiotics has become a widespread public health problem. The aim of this study was to investigate the influence of zinc oxide nanoparticles (ZnO NPs) on the antibacterial activity of several conventional antibiotics against Pseudomonas aeruginosa. Materials and Methods: ZnO NPs were prepared by solvothermal method and dispersed in glycerol with the help of ammonium citrate as a dispersant. The antibacterial effects of the resulting ZnO nanofluid, ceftazidime, tobramycin, and ciprofloxacin were investigated against two P. aeruginosa strains, including one clinical isolate and P. aeruginosa ATCC 9027 using microdilution method. For the evaluation of the combined effect of ZnO nanofluid and antibiotics, the fractional inhibitory concentration indices were calculated and isobolograms were plotted. Results: Clinical strain in comparison to standard strain of P. aeruginosa showed more resistance to ZnO nanofluid and the antibiotics. ZnO nanofluid acted synergistically with ceftazidime and tobramycin against both strains. Combination of ZnO nanofluid and ciprofloxacin displayed synergistic and partial synergistic activity against clinical and standard strains of P. aeruginosa, respectively. Conclusion: The results suggest that bacterial resistance to antimicrobials could be reduced by the synergistic action of ZnO NPs. PMID:27307973

  2. 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.

  3. Thermo-electrochemical selective growth of ZnO nanorods on any noble metal electrodes

    NASA Astrophysics Data System (ADS)

    You, Xueqiu; Park, Jungil; Choi, Jae-hoon; Pak, James Jungho

    2010-10-01

    Selective growth of ZnO nanorods has been successfully performed on the patterned Au/Ti metal electrode regions on a glass substrate by using a seeded thermo-electrochemical method in an acidic growth solution. The selective growth mechanism of the thermo-electrochemical method was proposed by using a series of chemical reactions for the first time. The thermo-electrochemical selective ZnO growth was performed on the cathode electrode at a temperature below 90 °C. A ZnO seed layer was precoated and selectively etched away from the non-metal regions in order to create the patterned selective nucleation sites on which the precursors are transferred and crystallized into ZnO nanorods. Both the dimensions and the placements of the ZnO nanorods have been simultaneously controlled. Energy dispersive X-ray spectrometry showed that the selectively grown ZnO nanorods consist of only Zn and O, indicating that the selectively grown ZnO nanorods are pure and contamination free. XRD and electron diffraction patterns revealed that the obtained ZnO nanorods have a wurtzite single-crystal structure.

  4. Heavy Stars Thrive among Heavy Elements

    NASA Astrophysics Data System (ADS)

    2002-08-01

    VLT Observes Wolf-Rayet Stars in Virgo Cluster Galaxies [1] Summary Do very massive stars form in metal-rich regions of the Universe and in the nuclei of galaxies ? Or does "heavy element poisoning" stop stellar growth at an early stage, before young stars reach the "heavyweight class"? What may at the first glance appear as a question for specialists actually has profound implications for our understanding of the evolution of galaxies, those systems of billions of stars - the main building blocks of the Universe. With an enormous output of electromagnetic radiation and energetic elementary particles, massive stars exert a decisive influence on the surrounding (interstellar) gas and dust clouds . They also eject large amounts of processed elements, thereby participating in the gradual build-up of the many elements we see today. Thus the presence or absence of such stars at the centres of galaxies can significantly change the overall development of those regions and hence, presumably, that of the entire galaxy. A team of European astronomers [2] has now directly observed the presence of so-called Wolf-Rayet stars (born with masses of 60 - 90 times that of the Sun or more) within metal-rich regions in some galaxies in the Virgo cluster, some 50 million light-years away. This is the first unambiguous detection of such massive stellar objects in metal-rich regions . PR Photo 20a/02 : H II regions in the Virgo cluster galaxy NGC 4254 . PR Photo 20b/02 : Multi-object-slit observation of galaxy NGC 4303 . PR Photo 20c/02 : Spectrum of H II region in NGC 4254 with Wolf-Rayet signatures. Production of heavy elements in the Universe Most scientists agree that the Universe in which we live underwent a dramatic event, known as the Big Bang , approximately 15,000 million years ago. During the early moments, elementary particles were formed which after some time united into more complex nuclei and in turn resulted in the production of hydrogen and helium atoms and their isotopes

  5. Synthesis of multi-shelled ZnO hollow microspheres and their improved photocatalytic activity

    PubMed Central

    2014-01-01

    Herein, we report an effective, facile, and low-cost route for preparing ZnO hollow microspheres with a controlled number of shells composed of small ZnO nanoparticles. The formation mechanism of multiple-shelled structures was investigated in detail. The number of shells is manipulated by using different diameters of carbonaceous microspheres. The products were characterized by X-ray powder diffraction, scanning electron microscopy, and transmission electron microscopy. The as-prepared ZnO hollow microspheres and ZnO nanoparticles were then used to study the degradation of methyl orange (MO) dye under ultraviolet (UV) light irradiation, and the triple-shelled ZnO hollow microspheres exhibit the best photocatalytic activity. This work is helpful to develop ZnO-based photocatalysts with high photocatalytic performance in addressing environmental protection issues, and it is also anticipated to other multiple-shelled metal oxide hollow microsphere structures. PMID:25328500

  6. Data on the growth of ZnO nanorods on Nylon 6 and photocatalytic activity.

    PubMed

    Ummartyotin, S; Tangnorawich, B

    2016-09-01

    ZnO was successfully synthesized by a conventional synthetic route using zinc nitrate as a source for ZnO formation. X-ray diffraction and thermogravimetric analysis revealed a crystal size of 66 nm of ZnO and a thermal stability of 500 °C. A small amount of ZnO particles was employed as the source for ZnO-rod growth on nylon 6 surfaces. Scanning electron microscope images were taken to evaluate the morphological properties of ZnO, which presented as a hexagonal needle-like shape. Preliminary evaluation of photocatalytic activity was performed through measurement of the degradation of methylene blue solution over 4 h. PMID:27437437

  7. Nd-doped ZnO monolayer: High Curie temperature and large magnetic moment

    NASA Astrophysics Data System (ADS)

    Tan, Changlong; Sun, Dan; Zhou, Long; Tian, Xiaohua; Huang, Yuewu

    2016-10-01

    We performed first-principles calculations within density-functional theory to study the structural, electronic, and magnetic properties of Nd-doped ZnO monolayer. The calculated results reveal that Nd-doped ZnO monolayer exhibits stable room temperature ferromagnetism with a large saturation magnetic moment of 3.99 μB per unit in ZnO monolayer. The magnetic property is contributed to the localized f sates of Nd atoms. When two Zn atoms are substituted by two Nd dopants, they tend to form ferromagnetic (FM) coupling and the estimated Curie temperature is higher than room temperature. More interesting, the impurity bands appear within the band gap of ZnO monolayer due to the introduction of Nd dopant. Our results may provide a reference for modifying the material property of ZnO monolayer and are promising as nanoscale building block in spintronic devices.

  8. Synthesis and characterization of flowerlike ZnO nanostructures via an ethylenediamine-meditated solution route

    SciTech Connect

    Gao Xiangdong . E-mail: xdgao@mail.sic.ac.cn; Li Xiaomin; Yu Weidong

    2005-04-15

    Flowerlike ZnO nanostructures were deposited on Si substrate by choosing hexamethylenetetramine as the nucleation control reagent and ethylenediamine as the chelating and capping reagent. Structural and optical measurements reveal that obtained ZnO exhibits well-defined flowerlike morphology, hexagonal wurtzite structure, uniform distribution on substrate, and strong photoluminescence in ultraviolet band. The well-arrayed pedals of each ZnO flower possess the typical tapering feature, and are built up by many well-aligned ZnO nanorods. Moreover, each single nanorod building up the pedal exhibits the single crystal nature and the growth direction along c-axis. Effects of the precursor composition on the morphology of ZnO were discussed.

  9. Emission Properties from ZnO Quantum Dots Dispersed in SiO{sub 2} Matrix

    SciTech Connect

    Panigrahi, Shrabani; Basak, Durga

    2011-07-15

    Dispersion of ZnO quantum dots in SiO{sub 2} matrix has been achieved in two techniques based on StOeber method to form ZnO QDs-SiO{sub 2} nanocomposites. Sample A is formed with random dispersion by adding tetraethyl orthosilicate (TEOS) to an ethanolic solution of ZnO nanoparticles and sample B is formed with a chain-like ordered dispersion by adding ZnO nanoparticles to an already hydrolyzed ethanolic TEOS solution. The photoluminescence spectra of the as-grown nanocomposites show strong emission in the ultraviolet region. When annealed at higher temperature, depending on the sample type, these show strong red or white emission. Interestingly, when the excitation is removed, the orderly dispersed ZnO QDs-SiO{sub 2} composite shows a very bright blue fluorescence visible by naked eyes for few seconds indicating their promise for display applications.

  10. Fabrication of tunable hydrophobic surface of ZnO nanorods with Cu doping

    SciTech Connect

    Chakraborty, Mohua; Thangavel, R.

    2015-08-28

    In this work, tunable wettability of the Zinc Oxide (ZnO) nanorod surface with Cu doping prepared by a hydrothermal method. These grown samples were characterized by XRD, FESEM, AFM and water contact angle measurements. The wettability of the ZnO nanorods surface area was controlled and tuned by different concentration of copper doping. It was found that the hydrophobic surface of doped ZnO Nanorods shows a maximum and minimum contact angle of about 156.60° and 136.36° was achieved with doping concentration of 10 and 20 M % respectively. Further, the surface properties such as surface energy and work of adhesion were calculated for undoped and Cu doped ZnO nanostructure surfaces. These nanosructures can be potentially applicable to enlarge time honoured application of ZnO based electronic devices.

  11. Electrochemically grown ZnO nanorods for hybrid solar cell applications

    SciTech Connect

    Hames, Yakup; Alpaslan, Zuehal; Koesemen, Arif; San, Sait Eren; Yerli, Yusuf

    2010-03-15

    A hybrid solar cell is designed and proposed as a feasible and reasonable alternative, according to acquired efficiency with the employment of zinc oxide (ZnO) nanorods and ZnO thin films at the same time. Both of these ZnO structures were grown electrochemically and poly(3-hexylthiophene):phenyl-C61-butyric acid methyl ester; (P3HT:PCBM) was used as an active polymer blend, which was found to be compatible to prepared indium-tin-oxide (ITO) substrate base. This ITO base was introduced with mentioned ZnO structure in such a way that, the most efficient configuration was optimized to be ITO/ZnO film/ZnO nanorod/P3HT: PCBM/Ag. Efficiency of this optimized device is found to be 2.44%. All ZnO works were carried out electrochemically, that is indeed for the first time and at relatively lower temperatures. (author)

  12. Nano ZnO structures synthesized in presence of anionic and cationic surfactant under hydrothermal process

    NASA Astrophysics Data System (ADS)

    Thilagavathi, T.; Geetha, D.

    2012-12-01

    Uniform ZnO nano structures are synthesized in the presence of anionic surfactant, sodium dodecyl benzene sulfonate (SDBS) and cationic surfactant, cetyl tri methyl ammonium bromide (CTAB) at 100 °C using NaOH as the reactant. The particle size, morphology and structure of the nano ZnO particles are collected by X-ray diffraction, scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) spectra. Rod and cone shaped ZnO nano structure is observed. It may vary in morphology from pure ZnO structure due to the presence of surfactants. The results show that there is an extrinsic relation between the morphology of the samples. Based on the relation, we proposed that there might be two kinds of interactions between SDBS and CTAB with ZnO particles, i.e., inter- and intra-interactions.

  13. Fabrication of tunable hydrophobic surface of ZnO nanorods with Cu doping

    NASA Astrophysics Data System (ADS)

    Chakraborty, Mohua; Thangavel, R.

    2015-08-01

    In this work, tunable wettability of the Zinc Oxide (ZnO) nanorod surface with Cu doping prepared by a hydrothermal method. These grown samples were characterized by XRD, FESEM, AFM and water contact angle measurements. The wettability of the ZnO nanorods surface area was controlled and tuned by different concentration of copper doping. It was found that the hydrophobic surface of doped ZnO Nanorods shows a maximum and minimum contact angle of about 156.60° and 136.36° was achieved with doping concentration of 10 and 20 M % respectively. Further, the surface properties such as surface energy and work of adhesion were calculated for undoped and Cu doped ZnO nanostructure surfaces. These nanosructures can be potentially applicable to enlarge time honoured application of ZnO based electronic devices.

  14. ZnO nanorods/plates on Si substrate grown by low-temperature hydrothermal reaction

    NASA Astrophysics Data System (ADS)

    Gao, S. Y.; Li, H. D.; Yuan, J. J.; Li, Y. A.; Yang, X. X.; Liu, J. W.

    2010-02-01

    The zinc oxide (ZnO) nanorods/plates are obtained via hydrothermal method assisted by etched porous Al film on Si substrate. The products consist of nanorods with average diameter of 100 nm and nanoplates with thickness of 200-300 nm, which are uniformly distributed widely and grown perpendicularly to the substrate. The ZnO nanoplates with thickness of 150-300 nm were grown on Si substrate coated with a thin continuous Al film (without etching) in the same aqueous solution. The growth mechanism and room temperature photoluminescence (PL) properties of ZnO nanorods/plates and nanoplates were investigated. It is found that the introduction of the etched Al film plays a key role in the formation of ZnO nanorods/plates. The annealing process is favorable to enhance the UV PL emissions of the ZnO nanorods/plates.

  15. Electric Characteristics of the Carbon Nanotube Network Transistor with Directly Grown ZnO Nanoparticles.

    PubMed

    Kim, Un Jeong; Bae, Gi Yoon; Suh, Dong Ik; Park, Wanjun

    2016-03-01

    We report on the electrical characteristics of field effect transistors fabricated with random networks of single-walled carbon nanotubes with surfaces modified by ZnO nanoparticles. ZnO nanoparticles are directly grown on single-walled carbon nanotubes by atomic layer deposition using diethylzinc (DEZ) and water. Electrical observations show that ZnO nanoparticles act as charge transfer sources that provide electrons to the nanotube channel. The valley position in ambipolar transport of nanotube transistors is negatively shifted for 3V due to the electronic n-typed property of ZnO nanoparticles. However, the Raman resonance remains invariant despite the charge transfer effect produced by ZnO nanoparticles.

  16. Hydrothermal growth of flower-like ZnO nanostructures on porous silicon substrate

    NASA Astrophysics Data System (ADS)

    Eswar, K. A.; Rouhi, Jalal; Husairi, F. S.; Dalvand, Ramazanali; Alrokayan, Salman A. H.; Khan, Haseeb A.; Rusop Mahmood, M.; Abdullah, S.

    2014-09-01

    Flower-like zinc oxide (ZnO) nanostructures were successfully synthesized on porous silicon substrates using a simple hydrothermal method. The characteristics of the ZnO nanostructures were investigated through field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and photoluminescence (PL). FESEM images revealed shape transitions from nanoflowers comprising nanoparticles to well-faceted hexagonal ZnO nanostructures when the precursor molarity increased from 0.01 to 0.20 M. The strong intensity and narrow width of XRD peaks indicate that ZnO nanostructures with high molarities have good crystallinity. The PL spectra indicate that ultraviolet emissions shift slightly toward lower wavelengths with increasing precursor solution molarity and that the intensity increases with improvement in ZnO crystallization.

  17. Au sensitized ZnO nanorods for enhanced liquefied petroleum gas sensing properties

    NASA Astrophysics Data System (ADS)

    Nakate, U. T.; Bulakhe, R. N.; Lokhande, C. D.; Kale, S. N.

    2016-05-01

    The zinc oxide (ZnO) nanorods have grown on glass substrate by spray pyrolysis deposition (SPD) method using zinc acetate solution. The phase formation, surface morphology and elemental composition of ZnO films have been investigated using X-ray diffraction, field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM) and energy dispersive X-ray (EDX) techniques. The liquefied petroleum gas (LPG) sensing response was remarkably improved by sensitization of gold (Au) surface noble metal on ZnO nanorods film. Maximum LPG response of 21% was observed for 1040 ppm of LPG, for pure ZnO nanorods sample. After Au sensitization on ZnO nanorods film sample, the LPG response greatly improved up to 48% at operating temperature 623 K. The improved LPG response is attributed Au sensitization with spill-over mechanism. Proposed model for LPG sensing mechanism discussed.

  18. The effect of laser environment on the characteristics of ZnO nanoparticles by laser ablation

    NASA Astrophysics Data System (ADS)

    Farahani, Sahar Varvani; Mahmoodi, Azam; Goranneviss, Mahmood

    2016-11-01

    In this paper, zinc oxide (ZnO) nanoparticles were prepared by laser ablation of Zinc (purity of 99/99 %) target. The effect of solvents, methanol and distilled water on the characterization of ZnO has been investigated. The beam of a Q-switched Nd: Yag laser with the length wave of 1064 nm and pulse duration of 6 ns was used. ZnO nanoparticles which were produced in distilled water and methanol were characterized by transmission electron microscopy, X-ray diffraction (XRD) and the optical absorption spectroscopy-ultraviolet (UV-VIS-IR). The XRD results showed that the ZnO nanoparticles have a hexagonal crystal structure. Different size of ZnO nanoparticles were formed because of different environment of laser pulse generated.

  19. Electric Characteristics of the Carbon Nanotube Network Transistor with Directly Grown ZnO Nanoparticles.

    PubMed

    Kim, Un Jeong; Bae, Gi Yoon; Suh, Dong Ik; Park, Wanjun

    2016-03-01

    We report on the electrical characteristics of field effect transistors fabricated with random networks of single-walled carbon nanotubes with surfaces modified by ZnO nanoparticles. ZnO nanoparticles are directly grown on single-walled carbon nanotubes by atomic layer deposition using diethylzinc (DEZ) and water. Electrical observations show that ZnO nanoparticles act as charge transfer sources that provide electrons to the nanotube channel. The valley position in ambipolar transport of nanotube transistors is negatively shifted for 3V due to the electronic n-typed property of ZnO nanoparticles. However, the Raman resonance remains invariant despite the charge transfer effect produced by ZnO nanoparticles. PMID:27455727

  20. Manipulation of exciton and photon lasing in a membrane-type ZnO microcavity

    SciTech Connect

    Lai, Ying-Yu; Chen, Jee-Wei; Chang, Tsu-Chi; Lu, Tien-Chang; Chou, Yu-Hsun

    2015-03-30

    We report on the fabrication and characterization of a membrane-type ZnO microcavity (MC). The ZnO membrane was cut from a single crystalline ZnO substrate by using focused ion beam milling, and was then placed onto a SiO{sub 2} substrate by using glass microtweezers. Through changing the pumping regime, manipulation of P-band exciton lasing and whispering-gallery mode (WGM) photon lasing could be easily achieved. P-band exciton lasing was observed only when the pumping laser was focused at the center of the ZnO MC with a small pumping size because of the innate ring-shaped WGM distribution. Furthermore, the lasing threshold of the ZnO MC could be reduced to an order lower by using a larger pumping spot because of the more favorable spatial overlap between the optical gain and WGM.

  1. Fabrication of ZnO photonic amorphous diamond nanostructure from parrot feathers for modulated photoluminescence properties

    NASA Astrophysics Data System (ADS)

    Zhang, Zhengli; Yu, Ke; Liao, Na; Yin, Haihong; Lou, Lei; Yu, Qian; Liao, Yuanyuan; Zhu, Ziqiang

    2011-12-01

    A ZnO photonic amorphous diamond nanostructure was successfully synthesised using a feather barb of the Rosy-Faced Lovebird as supporting template via a facile sol-gel process. Different from ordered structures, an isotropic PBG around 500 nm was evidenced from reflectance spectra and an optical metallurgical microscopy image, which overlaps with the visible emission peak of ZnO. As a result, the inhibition of visible emission inside the PBG and the enhancement of UV emission at the PBG edges have both been observed, which is independent from the incident angle. Moreover, the rapid thermal annealing can also help improve the crystallinity of ZnO and raise the UV/visible emission ratio without affecting the structure. These results can be very useful for the study of the modification of the optical emission properties of ZnO and other semiconductor materials as well as research on ZnO random lasing.

  2. Lead sulfide nanocrystal quantum dot solar cells with trenched ZnO fabricated via nanoimprinting.

    PubMed

    Kim, Sarah; Kim, Jun Kwan; Gao, Jianbo; Song, Jung Hoon; An, Hey Jin; You, Tae-Soo; Lee, Tae-Soo; Jeong, Jong-Ryul; Lee, Eung-Sug; Jeong, Jun-Ho; Beard, Matthew C; Jeong, Sohee

    2013-05-01

    The improvement of power conversion efficiency, especially current density (Jsc), for nanocrystal quantum dot based heterojunction solar cells was realized by employing a trenched ZnO film fabricated using nanoimprint techniques. For an optimization of ZnO patterns, various patterned ZnO films were investigated using electrical and optical analysis methods by varying the line width, interpattern distance, pattern height, and residual layer. Analyzing the features of patterned ZnO films allowed us to simultaneously optimize both the pronounced electrical effects as well as optical properties. Consequently, we achieved an enhancement in Jsc from 7.82 to 12.5 mA cm(-2) by adopting the patterned ZnO with optimized trenched shape.

  3. Influence of electromechanical coupling and electron irradiation on the conductivity of individual ZnO nanowire

    NASA Astrophysics Data System (ADS)

    Li, Huifeng; Huang, Yunhua; Zhang, Qi; Liu, Jing; Zhang, Yue

    2011-03-01

    We reported the electrical properties of individual ZnO nanowire (NW) with length 20 μm and diameter 100 nm, which prepared by thermal evaporation process. The individual ZnO NW was connected to the tungsten tips with typical metal-semiconductor-metal model, and the current-voltage curves were measured in a nano-manipulation and measurement system. The results indicated that the conductivity of the individual ZnO NW was decreased for inflicting an additional force on ZnO NW from tungsten tip. Moreover, the rectifier characteristics of ZnO NW were affected with the electron beam turning on or off in the chamber of scanning electron microscope.

  4. Surface Morphological and Nanomechanical Properties of PLD-Derived ZnO Thin Films

    PubMed Central

    2008-01-01

    This study reports the surface roughness and nanomechanical characteristics of ZnO thin films deposited on the various substrates, obtained by means of atomic force microscopy (AFM), nanoindentation and nanoscratch techniques. ZnO thin films are deposited on (a- and c-axis) sapphires and (0001) 6H-SiC substrates by using the pulsed-laser depositions (PLD) system. Continuous stiffness measurements (CSM) technique is used in the nanoindentation tests to determine the hardness and Young’s modulus of ZnO thin films. The importance of the ratio (H/Efilm) of elastic to plastic deformation during nanoindentation of ZnO thin films on their behaviors in contact-induced damage during fabrication of ZnO-based devices is considered. In addition, the friction coefficient of ZnO thin films is also presented here.

  5. Linear and nonlinear optical properties of luminescent ZnO nanoparticles embedded in PMMA matrix

    NASA Astrophysics Data System (ADS)

    Sreeja, R.; John, Jobina; Aneesh, P. M.; Jayaraj, M. K.

    2010-07-01

    ZnO nanoparticles embedded in the PMMA matrix were prepared by wet chemical synthesis. The optical band gap of the ZnO nanoparticles decreases with increase in NaOH concentration. The photoluminescence spectra of the ZnO colloids show strong UV, green and blue emissions. The optical absorptive nonlinearity of the ZnO:PMMA composites was analyzed using an open aperture Z-scan technique which shows optical limiting type nonlinearity due to the two photon absorption in ZnO. The efficiency of limiting is found to increase with decrease in the band gap. ZnO:PMMA shows a negative value for nonlinear refractive index n2 and the magnitude of n2 increases with decrease of band gap. Stability as well as the mechanical properties of the nanoparticles embedded in the PMMA matrix makes it more suitable for device fabrication as compared to the ZnO nanoparticles dispersed in solution.

  6. The effect of pH on ZnO hydrothermal growth on PES flexible substrates

    NASA Astrophysics Data System (ADS)

    Shin, C. M.; Heo, J. H.; Park, J. H.; Lee, T. M.; Ryu, H.; Shin, B. C.; Lee, W. J.; Kim, H.-K.

    2010-11-01

    The effect of pH value and a ZnO buffer layer on structural properties and morphology of ZnO nanostructures was investigated in this work. The nanostructures were fabricated on polyethersulfone (PES) flexible substrates with and without a ZnO buffer layer using a hydrothermal synthesis process, and the pH value was varied from 6.65 to 8.5. The ZnO buffer layer was deposited onto the substrates using atomic layer deposition (ALD). X-ray diffraction and scanning electron microscopy were used to characterize the samples. Hydrothermally grown ZnO deposited onto a buffer-ZnO/PES substrate at a pH of 7.5 was found to exhibit the optimal structural properties.

  7. Wafer-scale high-throughput ordered growth of vertically aligned ZnO nanowire arrays.

    PubMed

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

    2010-09-01

    This article presents an effective approach for patterned growth of vertically aligned ZnO nanowire (NW) arrays with high throughput and low cost at wafer scale without using cleanroom technology. Periodic hole patterns are generated using laser interference lithography on substrates coated with the photoresist SU-8. ZnO NWs are selectively grown through the holes via a low-temperature hydrothermal method without using a catalyst and with a superior control over orientation, location/density, and as-synthesized morphology. The development of textured ZnO seed layers for replacing single crystalline GaN and ZnO substrates extends the large-scale fabrication of vertically aligned ZnO NW arrays on substrates of other materials, such as polymers, Si, and glass. This combined approach demonstrates a novel method of manufacturing large-scale patterned one-dimensional nanostructures on various substrates for applications in energy harvesting, sensing, optoelectronics, and electronic devices.

  8. Synthesis, characterization and photoluminescence property of La-doped ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Lang, Jihui; Fang, Yue; Zhang, Qi; Wang, Jiaying; Li, Tianshun; Li, Xiuyan; Han, Qiang; Wang, Dandan; Wei, Maobin; Yang, Jinghai

    2016-10-01

    La-doped ZnO nanoparticles were synthesized via a facile and surfactant-free chemical precipitation route, and the effects of lanthanum doping concentration on the structures, morphologies and photoluminescence properties were investigated by XRD, TEM, EDX, PL and UV-Vis absorption spectra. The results showed that the La3+ ions were successfully incorporated into the ZnO host, and the products were well-crystalline. The average size and band gap of La-doped ZnO nanoparticles were varied with the lanthanum doping concentration. The average size of doped nanoparticles was much smaller as compared to that of undoped ZnO. The increasing of lanthanum doping concentration increased the defects in ZnO and resulted in a red shift of UV emission, indicating the narrow band gap in doped nanoparticles. This was probably attributed to the impurity energy levels in band gap introduced by substitutional La3+ ions.

  9. Direct Kinetic Correlation of Carriers and Ferromagnetism in Co[superscript 2+]:ZnO

    SciTech Connect

    Kittilstved, Kevin R.; Schwartz, Dana A.; Tuan, Allan C.; Heald, Steve M.; Chambers, Scott A.; Gamelin, Daniel R.

    2008-06-09

    The hypothesis that high-Curie-temperature ferromagnetism in cobalt-doped ZnO (Co{sup 2+}:ZnO) is mediated by charge carriers was tested by controlled introduction and removal of the shallow donor interstitial zinc. Using oriented epitaxial Co{sup 2+}:ZnO films grown by chemical vapor deposition, kinetics measurements demonstrate a direct correlation between the oxidative quenching of ferromagnetism and the diffusion and oxidation of interstitial zinc. These results demonstrate controlled systematic variation of a key parameter involved in the ferromagnetism of Co{sup 2+}:ZnO and, in the process, unambiguously reveal this ferromagnetism to be dependent upon charge carriers. The distinction between defect-bound and free carriers in Co{sup 2+}:ZnO is discussed.

  10. Direct kinetic correlation of carriers and ferromagnetism in Co2+ : ZnO

    SciTech Connect

    Kittilstved, Kevin R.; Schwartz, Dana A.; Tuan, Allan C.; Heald, Steve M.; Chambers, Scott A.; Gamelin, Daniel R.

    2006-07-21

    We report the use of controlled introduction and removal of Zni to test the hypothesis that high-Curie-temperature ferromagnetism in cobalt-doped ZnO (Co2+:ZnO) is mediated by carriers. Using oriented epitaxial Co2+:ZnO films grown by chemical vapor deposition, kinetics measurements were used to correlate the oxidative quenching of ferromagnetism with the diffusion and oxidation of interstitial zinc. These results demonstrate controlled systematic variation of a key parameter involved in the ferromagnetism of Co2+:ZnO, namely interstitial zinc, and in the process unambiguously reveal this ferromagnetism to be dependent upon carriers. The distinction between defect-bound and free carriers in Co2+:ZnO is discussed

  11. Photochemical performance of ZnO nanostructures in dye sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Das, Partha Pratim; Mukhopadhyay, Soumita; Agarkar, Shruti A.; Jana, Arpita; Devi, P. Sujatha

    2015-10-01

    In this work, the photoconversion efficiencies of ZnO having diverse microstructures and structural defects have been investigated. A conversion efficiency of 1.38% was achieved for the DSSCs fabricated with as prepared ZnO nanorods having minimum vacancy defects and a favourable one dimensional directional pathway for electron conduction. The DSSCs fabricated with ZnO nanoparticles exhibited relatively low conversion efficiency of 1.004% probably due to multiple trapping/detrapping phenomena within the grain boundaries and ZnO flowers though exhibited a high dye adsorption capability exhibited the lowest conversion efficiency of 0.59% due to a high concentration of structural defects. Based on the experimental evidences, we believe that the type of defects and their concentrations are more important than shape in controlling the overall performance of ZnO based DSSCs.

  12. Atomic layer deposition of epitaxial ZnO on GaN and YSZ

    NASA Astrophysics Data System (ADS)

    Lin, Chih-Wei; Ke, Dong-Jie; Chao, Yen-Cheng; Chang, Li; Liang, Mei-Hui; Ho, Yen-Teng

    2007-01-01

    ZnO thin films were epitaxially grown by atomic layer deposition on both of GaN/c-sapphire and yttria-stabilized zirconia (YSZ) substrates for comparison. X-ray diffraction, cross-sectional transmission electron microscopy (TEM) and photoluminescence (PL) measurements show that epitaxial ZnO films have better structural qualities and optical properties on GaN than on YSZ, whereas atomic force microscopy (AFM) shows that the surface of ZnO films on YSZ is smoother than on GaN. From the ZnO thickness measured by TEM, the growth rate of ZnO on GaN is about one (0 0 0 2) monolayer per cycle, which is roughly four times of that on YSZ.

  13. Synthesis of ZnO nanosheet arrays with exposed (100) facets for gas sensing applications.

    PubMed

    Xiao, Chuanhai; Yang, Tianye; Chuai, Mingyan; Xiao, Bingxin; Zhang, Mingzhe

    2016-01-01

    ZnO nanosheet (NS) arrays have been synthesized by a facile ultrathin liquid layer electrodeposition method. The ion concentration and electrode potential play important roles in the formation of ZnO NS arrays. Studies on the structural information indicate that the NSs are exposed with (100) facets. The results of Raman and PL spectra indicate that there existed a large amount of oxygen vacancies in the NSs. The gas sensing performances of the ZnO NS arrays are investigated: the ZnO NS arrays exhibited high gas selectivity and quick response/recovery for detecting NO2 at a low working temperature. High binding energies between NO2 molecules and exposed ZnO(100) facets lead to large surface reconstructions, which is responsible for the intrinsic NO2 sensing properties. In addition, the highly exposed surface and a large amount of oxygen vacancies existing in the NSs also make a great contribution to the gas sensing performance.

  14. UV light sensing properties of Sm doped vertically aligned ZnO nanorod arrays

    SciTech Connect

    Kumar, D. Ranjith; Ranjith, K. S.; Rajendrakumar, R. T.

    2015-06-24

    Samarium doped ZnO nanorods were grown on silicon substrate by using vapor phase transport method (VPT) with the growth temperature of 950°C. The synthesized nanorods were characterized by XRD, field emission scanning electron microscopy, Raman spectra, and photocurrent measurements. The XRD result revealed that Sm was successfully doped into lattice plane of hexagonal ZnO nanorods. The FESEM result confirms the pure ZnO has nanorod like morphology with an average diameter and length of 130nm and 10µm respectively. The above observation is supported by the Micro-Raman spectroscopy result. The photocurrent in the visible region has been significantly enhanced due to deposition of Sm on the surface of the ZnO nanorods. Sm acts as a visible sensitizer because of its lower band gap compared to ZnO.

  15. Investigation of thin ZnO layers in view of laser desorption-ionization

    NASA Astrophysics Data System (ADS)

    Grechnikov, A. A.; Georgieva, V. B.; Alimpiev, S. S.; Borodkov, A. S.; Nikiforov, S. M.; Simanovsky, Ya O.; Dimova-Malinovska, D.; Angelov, O. I.

    2010-04-01

    Thin zinc oxide films (ZnO) were developed as a matrix-free platform for surface assisted laser desorption-ionization (SALDI) time-of-flight mass spectrometry. The ZnO films were deposited by RF magnetron sputtering of ZnO ceramic targets in Ar atmospheres on monocrystalline silicon. The generation under UV (355 nm) laser irradiation of positive ions of atenolol, reserpine and gramicidin S from the ZnO layers deposited was studied. All analytes tested were detected as protonated molecules with no or very structure-specific fragmentation. The mass spectra obtained showed low levels of chemical background noise. All ZnO films studied exhibited high stability and good reproducibility. The detection limits for test analytes are in the 10 femtomol range.

  16. Luminescence of colloidal ZnO nanoparticles synthesized in alcohols and biological application of ZnO passivated by MgO.

    PubMed

    Sikora, Bożena; Fronc, Krzysztof; Kamińska, Izabela; Koper, Kamil; Stępień, Piotr; Elbaum, Danek

    2013-05-15

    This report presents the results of spectroscopic measurements of colloidal ZnO nanoparticles synthesized in various alcohols. Luminescence of colloidal ZnO was monitored under different reaction conditions to elucidate the mechanism of the visible emission. We performed the process in different alcohols, temperatures and reaction times for two different reactants: water and NaOH. Based on the presented and previously published results it is apparent that the luminescence of the nanoparticles is influenced by several competing phenomena: the formation of new nucleation centers, the growth of the nanoparticles and surface passivation. Superimposed on the above effects is a size dependent luminescence alteration resulting from the quantum confinement. The study contributes to our understanding of the origin of ZnO nanoparticles' green emission which is important in a rational design of fluorescent probes for nontoxic biological applications. The ZnO nanoparticles were coated with a magnesium oxide layer and introduced into a HeLa cancer cell.

  17. Synthesis, structural and optical characterization of undoped, N-doped ZnO and co-doped ZnO thin films

    SciTech Connect

    Pathak, Trilok Kumar Kumar, R.; Purohit, L. P.

    2015-05-15

    ZnO, N-doped ZnO and Al-N co-doped ZnO thin films were deposited on ITO coated corning glass by spin coater using sol-gel method. The films were annealed in air at 450°C for one hour. The crystallographic structure and morphology of the films were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM) respectively. The X-ray diffraction results confirm that the thin films are of wurtzite hexagonal with a very small distortion. The optical properties were investigated by transmission spectra of different films using spectrophotometer (Shimadzu UV-VIS-NIR 3600). The results indicate that the N doped ZnO thin films have obviously enhanced transmittance in visible region. Moreover, the thickness of the films has strong influences on the optical constants.

  18. Modulation of field emission properties of znO nanorods during arc discharge.

    PubMed

    Fang, F; Kennedy, J; Carder, D A; Futter, J; Murmu, P; Markwitz, A

    2010-12-01

    Zinc oxide (ZnO) nanorods have been synthesized via the arc discharge method. Different oxygen partial pressures were applied in the arc discharge chamber to modulate the field emission properties of the as-synthesized ZnO nanorods. Scanning electron microscopy (SEM) was carried out to analyze the morphology of the ZnO nanorods. The ion beam analysis technique of proton induced X-ray emission (PIXE) was performed to probe the impurities in ZnO nanorods. SEM images clearly revealed the formation of randomly oriented ZnO nanorods with diameters between 10-50 nm. It was found that the morphology and the electrical properties of the ZnO nanorods were dependent on the oxygen partial pressure during arc discharge. In addition enhanced UV-sensitive photoconductivity was found for ZnO nanorods synthesized at high oxygen partial pressure during arc discharge. The field emission properties of the nanorods were studied. The turn-on field, which is defined at a current density of 10 microA cm(-2), was about 3 V microm(-1) for ZnO nanorods synthesized at 99% oxygen partial pressure during arc discharge. The turn-on field for ZnO nanorods increased with the decrease of oxygen partial pressure during arc discharge. The simplicity of the synthesis route coupled with the modulation of field emission properties due to the arc discharge method make the ZnO nanorods a promising candidate for a low cost and compact cold cathode material. PMID:21121322

  19. Synthesis, characterization and optical properties of sheet-like ZnO

    SciTech Connect

    Liu, Changzhen; Meng, Dawei; Wu, Xiuling; Wang, Yongqian; Yu, Xiaohong; Zhang, Zhengjie; Liu, Xiaoyang

    2011-09-15

    Highlights: {yields} Sheet-like ZnO with regular hexagon shape was synthesized with a two-step method. {yields} Sheet-like ZnO predecessor was synthesized at low temperature in open system. {yields} The diameter and thickness of ZnO sheet can be controlled conveniently. {yields} This low-cost and environmentally benign approach is controllable and reproducible. {yields} Sheet-like ZnO may have potential application in optical and electrical devices. -- Abstract: Sheet-like ZnO with regular hexagon shape and uniform diameter has been successfully synthesized through a two-step method without any metal catalyst. First, the sheet-like ZnO precursor was synthesized in a weak alkaline carbamide environment with stirring in a constant temperature water-bath by the homogeneous precipitation method, then sheet-like ZnO was obtained by calcining at 600 {sup o}C for 2 h. The structures and optical properties of sheet-like ZnO have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), photoluminescence (PL) and UV-vis-NIR spectrophotometer. The results reveal that the product is highly crystalline with hexagonal wurtzite phase and has appearance of hexagon at (0 0 0 1) plane. The HRTEM images confirm that the individual sheet-like ZnO is single crystal. The PL spectrum exhibits a narrow ultraviolet emission at 397 nm and a broad visible emission centering at 502 nm. The band gap of sheet-like ZnO is about 3.15 eV.

  20. Facilitating ZnO nanostructure growths by making seeds for self-catalytic reactions

    SciTech Connect

    Yin Liang; Yu, Choongho

    2012-03-15

    Long and straight single-crystalline ZnO nanowires were successfully synthesized on ZnCl{sub 2}-coated Zn foils in oxygen environment by using simple thermal annealing processes. With relatively low reaction temperatures (410 and 700 Degree-Sign C), nanowires whose lengths and diameters are up to {approx}50 {mu}m and 10-100 nm were obtained. We found that ZnO seeds created from ZnCl{sub 2} played an important role in facilitating the ZnO nanowire growth via self-catalytic reactions. Systematic studies by altering critical synthesis factors that determine shape, length, diameter, and density of the nanowires were performed in order to unveil the growth mechanisms. We also compared the nanowires synthesized from Zn foils with tetrapod ZnO nanostructures synthesized from Zn powders at various temperatures. - Graphical abstract: (Left panel) ZnO seeds from ZnCl{sub 2} after thermal annealing at 500 Degree-Sign C for 5 min, (right panel) dense ZnO nanowires grown from Zn foils with ZnCl{sub 2} coating after thermal annealing at 700 Degree-Sign C for 60 min. Highlights: Black-Right-Pointing-Pointer ZnCl{sub 2} facilitated ZnO nanowire growth by creating ZnO seeds. Black-Right-Pointing-Pointer ZnO nanowires were synthesized via self-catalytic reactions. Black-Right-Pointing-Pointer Long and straight single-crystalline ZnO nanowires were synthesized. Black-Right-Pointing-Pointer Key parameters in thermal annealing processes were identified.

  1. Rapid synthesis of Co, Ni co-doped ZnO nanoparticles: Optical and electrochemical properties

    SciTech Connect

    Romeiro, Fernanda C.; Marinho, Juliane Z.; Lemos, Samantha C.S.; Moura, Ana P. de; Freire, Poliana G.; Silva, Luis F. da; Longo, Elson; Munoz, Rodrigo A.A.; Lima, Renata C.

    2015-10-15

    We report for the first time a rapid preparation of Zn{sub 1−2x}Co{sub x}Ni{sub x}O nanoparticles via a versatile and environmentally friendly route, microwave-assisted hydrothermal (MAH) method. The Co, Ni co-doped ZnO nanoparticles present an effect on photoluminescence and electrochemical properties, exhibiting excellent electrocatalytic performance compared to undoped ZnO sample. Photoluminescence spectroscopy measurements indicated the reduction of the green–orange–red visible emission region after adding Co and Ni ions, revealing the formation of alternative pathways for the generated recombination. The presence of these metallic ions into ZnO creates different defects, contributing to a local structural disorder, as revealed by Raman spectra. Electrochemical experiments revealed that the electrocatalytic oxidation of dopamine on ZnO attached to multi-walled carbon nanotubes improved significantly in the Co, Ni co-doped ZnO samples when compared to pure ZnO. - Graphical abstract: Rapid synthesis of Co, Ni co-doped ZnO nanoparticles: optical and electrochemical properties. Co, Ni co-doped ZnO hexagonal nanoparticles with optical and electrocatalytic properties were successfully prepared for the first time using a microwave hydrothermal method at mild conditions. - Highlights: • Co{sup 2+} and Ni{sup 2+} into ZnO lattice obtained a mild and environmentally friendly process. • The heating method strongly influences in the growth and shape of the particles. • Short-range defects generated by the ions insertion affects the photoluminescence. • Doped ZnO nanoparticles improve the electrocatalytic properties of pure oxide.

  2. Biotinylation of ZnO nanoparticles and thin films: a two-step surface functionalization study.

    PubMed

    SelegArd, Linnéa; Khranovskyy, Volodymyr; Söderlind, Fredrik; Vahlberg, Cecilia; Ahrén, Maria; Käll, Per-Olov; Yakimova, Rositza; Uvdal, Kajsa

    2010-07-01

    This study reports ZnO nanoparticles and thin film surface modification using a two-step functionalization strategy. A small silane molecule was used to build up a stabilizing layer and for conjugation of biotin (vitamin B7), as a specific tag. Biotin was chosen because it is a well-studied bioactive molecule with high affinity for avidin. ZnO nanoparticles were synthesized by electrochemical deposition under oxidizing condition, and ZnO films were prepared by plasma-enhanced metal-organic chemical vapor deposition. Both ZnO nanoparticles and ZnO thin films were surface modified by forming a (3-mercaptopropyl)trimethoxysilane (MPTS) layer followed by attachment of a biotin derivate. Iodoacetyl-PEG2-biotin molecule was coupled to the thiol unit in MPTS through a substitution reaction. Powder X-ray diffraction, transmission electron microscopy, X-ray photoemission electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, and near-edge X-ray absorption fine structure spectroscopy were used to investigate the as-synthesized and functionalized ZnO materials. The measurements showed highly crystalline materials in both cases with a ZnO nanoparticle diameter of about 5 nm and a grain size of about 45 nm for the as-grown ZnO thin films. The surface modification process resulted in coupling of silanes and biotin to both the ZnO nanoparticles and ZnO thin films. The two-step functionalization strategy has a high potential for specific targeting in bioimaging probes and for recognition studies in biosensing applications.

  3. Plasma versus thermal annealing for the Au-catalyst growth of ZnO nanocones and nanowires on Al-doped ZnO buffer layers

    NASA Astrophysics Data System (ADS)

    Güell, Frank; Martínez-Alanis, Paulina R.; Roso, Sergio; Salas-Pérez, Carlos I.; García-Sánchez, Mario F.; Santana, Guillermo; Marel Monroy, B.

    2016-06-01

    We successfully synthesized ZnO nanocones and nanowires over polycrystalline Al-doped ZnO (AZO) buffer layers on fused silica substrates by a vapor-transport process using Au-catalyst thin films. Different Au film thicknesses were thermal or plasma annealed in order to analyze their influence on the ZnO nanostructure growth morphology. Striking differences have been observed. Thermal annealing generates a distribution of Au nanoclusters and plasma annealing induces a fragmentation of the Au thin films. While ZnO nanowires are found in the thermal-annealed samples, ZnO nanocones and nanowires have been obtained on the plasma-annealed samples. Enhancement of the preferred c-axis (0001) growth orientation was demonstrated by x-ray diffraction when the ZnO nanocones and nanowires have been grown over the AZO buffer layer. The transmittance spectra of the ZnO nanocones and nanowires show a gradual increase from 375 to 900 nm, and photoluminescence characterization pointed out high concentration of defects leading to observation of a broad emission band in the visible range from 420 to 800 nm. The maximum emission intensity peak position of the broad visible band is related to the thickness of the Au-catalyst for the thermal-annealed samples and to the plasma power for the plasma-annealed samples. Finally, we proposed a model for the plasma versus thermal annealing of the Au-catalyst for the growth of the ZnO nanocones and nanowires. These results are promising for renewable energy applications, in particular for its potential application in solar cells.

  4. Heavy Vehicle Propulsion Materials

    SciTech Connect

    Ray Johnson

    2000-01-31

    The objectives are to Provide Key Enabling Materials Technologies to Increase Energy Efficiency and Reduce Exhaust Emissions. The following goals are listed: Goal 1: By 3rd quarter 2002, complete development of materials enabling the maintenance or improvement of fuel efficiency {ge} 45% of class 7-8 truck engines while meeting the EPA/Justice Department ''Consent Decree'' for emissions reduction. Goal 2: By 4th quarter 2004, complete development of enabling materials for light-duty (class 1-2) diesel truck engines with efficiency over 40%, over a wide range of loads and speeds, while meeting EPA Tier 2 emission regulations. Goal 3: By 4th quarter 2006, complete development of materials solutions to enable heavy-duty diesel engine efficiency of 50% while meeting the emission reduction goals identified in the EPA proposed rule for heavy-duty highway engines.''

  5. Detecting heavy quarks

    SciTech Connect

    Benenson, G.; Chau, L.L.; Ludlam, T.; Paige, F.E.; Platner, E.D.; Protopopescu, S.D.; Rehak, P.

    1983-01-01

    In this exercise we examine the performance of a detector specifically configured to tag heavy quark (HQ) jets through direct observations of D-meson decays with a high resolution vertex detector. To optimize the performance of such a detector, we assume the small diamond beam crossing configuration as described in the 1978 ISABELLE proposal, giving a luminosity of 10/sup 32/ cm/sup -2/ sec/sup -1/. Because of the very large backgrounds from light quark (LQ) jets, most triggering schemes at this luminosity require high P/sub perpendicular to/ leptons and inevitably give missing neutrinos. If alternative triggering schemes could be found, then one can hope to find and calculate the mass of objects decaying to heavy quarks. A scheme using the high resolution detector will also be discussed in detail. The study was carried out with events generated by the ISAJET Monte Carlo and a computer simulation of the described detector system. (WHK)

  6. Synergistic effect of dual interfacial modifications with room-temperature-grown epitaxial ZnO and adsorbed indoline dye for ZnO nanorod array/P3HT hybrid solar cell.

    PubMed

    Chen, Dian-Wei; Wang, Ting-Chung; Liao, Wen-Pin; Wu, Jih-Jen

    2013-09-11

    ZnO nanorod (NR)/poly(3-hexylthiophene) (P3HT) hybrid solar cells with interfacial modifications are investigated in this work. The ZnO NR arrays are modified with room-temperature (RT)-grown epitaxial ZnO shells or/and D149 dye molecules prior to the P3HT infiltration. A synergistic effect of the dual modifications on the efficiency of the ZnO NR/P3HT solar cell is observed. The open-circuit voltage and fill factor are considerable improved through the RT-grown ZnO and D149 modifications in sequence on the ZnO NR array, which brings about a 2-fold enhancement of the efficiency of the ZnO NR/P3HT solar cell. We suggested that the more suitable surface of RT-grown ZnO for D149 adsorption, the chemical compatibility of D149 and P3HT, and the elevated conduction band edge of the RT-grown ZnO/D149-modified ZnO NR array construct the superior interfacial morphology and energetics in the RT-grown ZnO/D149-modified ZnO NR/P3HT hybrid solar cell, resulting in the synergistic effect on the cell efficiency. An efficiency of 1.16% is obtained in the RT-grown ZnO/D149-modified ZnO NR/P3HT solar cell. PMID:23937447

  7. First principles investigations on the electronic structure of anchor groups on ZnO nanowires and surfaces

    SciTech Connect

    Dominguez, A.; Lorke, M.; Rosa, A. L.; Frauenheim, Th.; Schoenhalz, A. L.; Dalpian, G. M.; Rocha, A. R.

    2014-05-28

    We report on density functional theory investigations of the electronic properties of monofunctional ligands adsorbed on ZnO-(1010) surfaces and ZnO nanowires using semi-local and hybrid exchange-correlation functionals. We consider three anchor groups, namely thiol, amino, and carboxyl groups. Our results indicate that neither the carboxyl nor the amino group modify the transport and conductivity properties of ZnO. In contrast, the modification of the ZnO surface and nanostructure with thiol leads to insertion of molecular states in the band gap, thus suggesting that functionalization with this moiety may customize the optical properties of ZnO nanomaterials.

  8. Growth of periodic ZnO nano-crystals on buffer layer patterned by interference laser irradiation

    NASA Astrophysics Data System (ADS)

    Nakamura, D.; Shimogaki, T.; Okazaki, K.; Higashihata, M.; Nakata, Y.; Okada, T.

    2013-03-01

    Zinc oxide (ZnO) nano-crystal is great interest for optoelectronic applications in particular ultraviolet (UV) region such as UV-LEDs, UV-lasers, etc. For the practical optoelectronic applications based on the ZnO nanocrystals, control of nanowire growth direction, shape, density, and position are essentially required. In our study, we introduced a ZnO buffer layer and interference laser irradiation to control the growth position of ZnO nanocrystals. In this presentation, structural and morphological characteristics of periodic ZnO nano-crystals synthesized by the nanoparticle-assisted pulsed laser deposition will be discussed.

  9. Utah Heavy Oil Program

    SciTech Connect

    J. Bauman; S. Burian; M. Deo; E. Eddings; R. Gani; R. Goel; C.K. Huang; M. Hogue; R. Keiter; L. Li; J. Ruple; T. Ring; P. Rose; M. Skliar; P.J. Smith; J.P. Spinti; P. Tiwari; J. Wilkey; K. Uchitel

    2009-10-20

    The Utah Heavy Oil Program (UHOP) was established in June 2006 to provide multidisciplinary research support to federal and state constituents for addressing the wide-ranging issues surrounding the creation of an industry for unconventional oil production in the United States. Additionally, UHOP was to serve as an on-going source of unbiased information to the nation surrounding technical, economic, legal and environmental aspects of developing heavy oil, oil sands, and oil shale resources. UHOP fulGilled its role by completing three tasks. First, in response to the Energy Policy Act of 2005 Section 369(p), UHOP published an update report to the 1987 technical and economic assessment of domestic heavy oil resources that was prepared by the Interstate Oil and Gas Compact Commission. The UHOP report, entitled 'A Technical, Economic, and Legal Assessment of North American Heavy Oil, Oil Sands, and Oil Shale Resources' was published in electronic and hard copy form in October 2007. Second, UHOP developed of a comprehensive, publicly accessible online repository of unconventional oil resources in North America based on the DSpace software platform. An interactive map was also developed as a source of geospatial information and as a means to interact with the repository from a geospatial setting. All documents uploaded to the repository are fully searchable by author, title, and keywords. Third, UHOP sponsored Give research projects related to unconventional fuels development. Two projects looked at issues associated with oil shale production, including oil shale pyrolysis kinetics, resource heterogeneity, and reservoir simulation. One project evaluated in situ production from Utah oil sands. Another project focused on water availability and produced water treatments. The last project considered commercial oil shale leasing from a policy, environmental, and economic perspective.

  10. Improved UV photoresponse properties of high-quality ZnO thin films through the use of a ZnO buffer layer on flexible polyimide substrates

    NASA Astrophysics Data System (ADS)

    Kim, Mincheol; Leem, Jae-Young; Son, Jeong-Sik

    2016-03-01

    An oxidized ZnO buffer layer was prepared by using thermal oxidation of a Zn buffer layer on a polyimide (PI) substrate; then, ZnO thin films with (sample 1) and without (sample 2) an oxidized ZnO buffer layer were grown by using the sol-gel spin-coating method. The intensities of the ZnO (002) diffraction peaks observed in sample 1 were stronger than those observed in sample 2, implying that the crystal quality was enhanced by the oxidized ZnO buffer layer. Moreover, the residual stress of sample 1 was reduced compared to that of sample 2 due to the decreased number of defects. Sample 2 exhibited defect-related deep-level orange-yellow emissions, which almost disappeared with the introduction of the ZnO buffer layer (sample 1). The values of the responsivity were 0.733 (sample 1) and 0.066 (sample 2) mA/W; therefore, the proposed method could provide a pathway to the easy fabrication of fast-response UV sensors.

  11. Fabrication and characterization of silicon wire solar cells having ZnO nanorod antireflection coating on Al-doped ZnO seed layer

    PubMed Central

    2012-01-01

    In this study, we have fabricated and characterized the silicon [Si] wire solar cells with conformal ZnO nanorod antireflection coating [ARC] grown on a Al-doped ZnO [AZO] seed layer. Vertically aligned Si wire arrays were fabricated by electrochemical etching and, the p-n junction was prepared by spin-on dopant diffusion method. Hydrothermal growth of the ZnO nanorods was followed by AZO film deposition on high aspect ratio Si microwire arrays by atomic layer deposition [ALD]. The introduction of an ALD-deposited AZO film on Si wire arrays not only helps to create the ZnO nanorod arrays, but also has a strong impact on the reduction of surface recombination. The reflectance spectra show that ZnO nanorods were used as an efficient ARC to enhance light absorption by multiple scattering. Also, from the current-voltage results, we found that the combination of the AZO film and ZnO nanorods on Si wire solar cells leads to an increased power conversion efficiency by more than 27% compared to the cells without it. PMID:22222067

  12. Fabrication and characterization of silicon wire solar cells having ZnO nanorod antireflection coating on Al-doped ZnO seed layer.

    PubMed

    Baek, Seong-Ho; Noh, Bum-Young; Park, Il-Kyu; Kim, Jae Hyun

    2012-01-05

    In this study, we have fabricated and characterized the silicon [Si] wire solar cells with conformal ZnO nanorod antireflection coating [ARC] grown on a Al-doped ZnO [AZO] seed layer. Vertically aligned Si wire arrays were fabricated by electrochemical etching and, the p-n junction was prepared by spin-on dopant diffusion method. Hydrothermal growth of the ZnO nanorods was followed by AZO film deposition on high aspect ratio Si microwire arrays by atomic layer deposition [ALD]. The introduction of an ALD-deposited AZO film on Si wire arrays not only helps to create the ZnO nanorod arrays, but also has a strong impact on the reduction of surface recombination. The reflectance spectra show that ZnO nanorods were used as an efficient ARC to enhance light absorption by multiple scattering. Also, from the current-voltage results, we found that the combination of the AZO film and ZnO nanorods on Si wire solar cells leads to an increased power conversion efficiency by more than 27% compared to the cells without it.

  13. Self-assembled 3D ZnO porous structures with exposed reactive {0001} facets and their enhanced gas sensitivity.

    PubMed

    Chang, Jin; Ahmad, Muhammad Z; Wlodarski, Wojtek; Waclawik, Eric R

    2013-07-02

    Complex three-dimensional structures comprised of porous ZnO plates were synthesized in a controlled fashion by hydrothermal methods. Through subtle changes to reaction conditions, the ZnO structures could be self-assembled from 20 nm thick nanosheets into grass-like and flower-like structures which led to the exposure of high proportions of ZnO {0001} crystal facets for both these materials. The measured surface area of the flower-like and the grass, or platelet-like ZnO samples were 72.8 and 52.4 m2∙g-1, respectively. Gas sensing results demonstrated that the porous, flower-like ZnO structures exhibited enhanced sensing performance towards NO2 gas compared with either grass-like ZnO or commercially sourced ZnO nanoparticle samples. The porous, flower-like ZnO structures provided a high surface area which enhanced the ZnO gas sensor response. X-ray photoelectron spectroscopy characterization revealed that flower-like ZnO samples possessed a higher percentage of oxygen vacancies than the other ZnO sample-types, which also contributed to their excellent gas sensing performance.

  14. Defect induced ferromagnetism in undoped ZnO nanoparticles

    SciTech Connect

    Rainey, K.; Chess, J.; Eixenberger, J.; Tenne, D. A.; Hanna, C. B.; Punnoose, A.

    2014-05-07

    Undoped ZnO nanoparticles (NPs) with size ∼12 nm were produced using forced hydrolysis methods using diethylene glycol (DEG) [called ZnO-I] or denatured ethanol [called ZnO-II] as the reaction solvent; both using Zn acetate dehydrate as precursor. Both samples showed weak ferromagnetic behavior at 300 K with saturation magnetization M{sub s} = 0.077 ± 0.002 memu/g and 0.088 ± 0.013 memu/g for ZnO-I and ZnO-II samples, respectively. Fourier transform infrared (FTIR) spectra showed that ZnO-I nanocrystals had DEG fragments linked to their surface. Photoluminescence (PL) data showed a broad emission near 500 nm for ZnO-II which is absent in the ZnO-I samples, presumably due to the blocking of surface traps by the capping molecules. Intentional oxygen vacancies created in the ZnO-I NPs by annealing at 450 °C in flowing Ar gas gradually increased M{sub s} up to 90 min and x-ray photoelectron spectra (XPS) suggested that oxygen vacancies may have a key role in the observed changes in M{sub s}. Finally, PL spectra of ZnO showed the appearance of a blue/violet emission, attributed to Zn interstitials, whose intensity changes with annealing time, similar to the trend seen for M{sub s}. The observed variation in the magnetization of ZnO NP with increasing Ar annealing time seems to depend on the changes in the number of Zn interstitials and oxygen vacancies.

  15. First-principles study on the physical properties of a layered ZnO with hexagonal α-BN structure

    NASA Astrophysics Data System (ADS)

    Su, Y. L.; Zhang, Q. Y.; Zhao, J. J.

    2016-05-01

    A layered ZnO with α-BN structure has been studied using first-principles calculations based on density functional theory. The physical properties of the layered ZnO are calculated in terms of dielectric function, infrared reflectance, elastic coefficients, modulus, hardness, and heat capacity. The layered ZnO exhibits a good infrared reflectance with a broad reststrahlen band covering the infrared band below 600 cm-1. The layered ZnO is predicted to be a material behaving in a brittle manner, with a microhardness ~3.6 times higher than that of the wurtzite ZnO. The temperature-dependent thermodynamic functions suggest that the layered ZnO has the thermal properties similar to those of wurtzite ZnO, but having a little higher Debye temperature above room temperature.

  16. Enhanced photocatalytic activity of ultra-high aspect ratio ZnO nanowires due to Cu induced defects

    NASA Astrophysics Data System (ADS)

    Pasupathi Sugavaneshwar, Ramu; Duy Dao, Thang; Nanda, Karuna Kar; Nagao, Tadaaki; Hishita, Shunichi; Sakaguchi, Isao

    2015-12-01

    We report the synthesis of ZnO nanowires in ambient air at 650°C by a single-step vapor transport method using two different sources Zn (ZnO nanowires-I) and Zn:Cu (ZnO nanowires-II). The Zn:Cu mixed source co-vaporize Zn with a small amount of Cu at temperatures where elemental Cu source does not vaporize. This method provides us a facile route for Cu doping into ZnO. The aspect ratio of the grown ZnO nanowires-II was found to be higher by more than five times compared ZnO nanowires-I. Photocatalytic activity was measured by using a solar simulator and its ultraviolet-filtered light. The ZnO nanowires-II shows higher catalytic activity due to increased aspect ratio and higher content of surface defects because of incorporation of Cu impurities.

  17. N-doped ZnO films grown from hybrid target by the pulsed laser deposition technique

    NASA Astrophysics Data System (ADS)

    Martín-Tovar, E. A.; Chan y Díaz, E.; Acosta, M.; Castro-Rodríguez, R.; Iribarren, A.

    2016-10-01

    ZnO thin films were grown by the pulsed laser deposition technique on glass substrate using a hybrid target composed of ZnO powder embedded into a poly(ethyl cyanoacrylate) matrix. The resulting thin film presented ZnO wurtzite structure with very low stress and diffractogram very similar to that of the powder pattern. From comparing with ZnO thin films grown from traditional sintered target, it is suggested that the use of this hybrid target with a soft matrix led to ejection of ZnO clusters that conveniently disposed and adhered to substrate and previous deposited layers. Chemical measurements showed the presence of Zn-N bonds, besides Zn-O ones. Optical absorption profile confirmed the presence of low-polymerized zinc oxynitride molecular subunits, besides ZnO.

  18. Electronic nose based on multipatterns of ZnO nanorods on a quartz resonator with remote electrodes.

    PubMed

    Ko, Wooree; Jung, Namchul; Lee, Moonchan; Yun, Minhyuk; Jeon, Sangmin

    2013-08-27

    An electrodeless monolithic multichannel quartz crystal microbalance (MQCM) sensor was developed via the direct growth of ZnO nanorod patterns of various sizes onto an electrodeless quartz crystal plate. The patterned ZnO nanorods acted as independent resonators with different frequencies upon exposure to an electric field. The added mass of ZnO nanostructures was found to significantly enhance the quality factor (QF) of the resonator in electrodeless QCM configuration. The QF increased with the length of the ZnO nanorods; ZnO nanorods 5 μm in length yielded a 7-fold higher QF compared to the QF of a quartz plate without ZnO nanorods. In addition, the ZnO nanorods offered enhanced sensitivity due to the enlarged sensing area. The developed sensor was used as an electronic nose for detection of vapor mixtures with impurities.

  19. ZnO thin film as MSG for sensitive biosensor

    NASA Astrophysics Data System (ADS)

    Iftimie, N.; Savin, A.; Steigmann, R.; Faktorova, D.; Salaoru, I.

    2016-08-01

    In this paper, we investigate the cholesterol sensors consisting of a mixture of cholesterol oxidase (ChOx) and zinc oxide (ZnO) nanoparticles were grown on ITO/glass substrates by vacuum thermal evaporation method and their sensing characteristics are examined in air. Also, the interest in surface waves appeared due to evanescent waves in the metallic strip grating in sub-wavelength regime. Before testing the transducer with metamaterials lens in the sub-wavelength regime, a simulation of the evanescent wave's formation has been performed at the edge of Ag strips, with thicknesses in the range of micrometers.

  20. Ultrafast exciton formation at the ZnO(1010) surface.

    PubMed

    Deinert, J-C; Wegkamp, D; Meyer, M; Richter, C; Wolf, M; Stähler, J

    2014-08-01

    We study the ultrafast quasiparticle dynamics in and below the ZnO conduction band using femtosecond time-resolved two-photon photoelectron spectroscopy. Above band gap excitation causes hot electron relaxation by electron-phonon scattering down to the Fermi level E_{F} followed by ultrafast (200 fs) formation of a surface exciton (SX). Transient screening of the Coulomb interaction reduces the SX formation probability at high excitation densities near the Mott limit. Located just below the surface, the SX are stable with regard to hydrogen-induced work function modifications and thus the ideal prerequisite for resonant energy transfer applications.

  1. Cu-Doping of ZnO by Nuclear Transmutation

    SciTech Connect

    Selim, F. A.; Tarun, M. C.; Wall, D. E.; Boatner, Lynn A; McCluskey, M. D.

    2011-01-01

    Zinc oxide single crystals were doped with copper acceptors by means of the nuclear transmutation doping (NTD) method, which gives highly uniform dopant distributions and has a much higher probability of controlling the dopant locations in the lattice. The Cu doping was confirmed by the infrared absorption signature of Cu2+ at 5780 cm-1. Hall-effect measurements were performed to study the effect of CuZn on the electrical properties of ZnO. These measurements indicated that the Cu acceptor level lies 0.126 eV below the conduction-band minimum.

  2. Incorporation of Cu Acceptors in ZnO Nanocrystals

    SciTech Connect

    Oo, W.M.H.; Mccluskey, Matthew D.; Huso, Jesse; Morrison, J.; Bergman, Leah; Engelhard, Mark H.; Saraf, Laxmikant V.

    2010-09-16

    Doping of semiconductor nanocrystals is an important problem in nanomaterials research. Using infrared (IR) and x-ray photoelectron spectroscopy (XPS), we have observed Cu acceptor dopants that were intentionally introduced into ZnO nanocrystals. The incorporation of Cu2+ dopants increased as the diameter of the nanocrystals was increased from ~3 to 5 nm. Etching the nanocrystals with acetic acid revealed a core-shell structure, where a 2-nm lightly doped core is surrounded by a heavily doped shell. These observations are consistent with the trapped dopant model, in which dopant atoms stick to the surface of the core and are overgrown by the nanocrystal material.

  3. Ferromagnetism in Tb doped ZnO nanocrystalline films

    NASA Astrophysics Data System (ADS)

    Zou, W. Q.; Ge, C. N.; Venkataiah, G.; Su, H. L.; Hsu, H. S.; Huang, J. C. A.; Liu, X. C.; Zhang, F. M.; Du, Y. W.

    2012-06-01

    Nanocrystalline Tb-doped ZnO films have been prepared by ion-beam sputtering technique. Magnetic characterization showed that the films are ferromagnetic with Curie temperature (TC) higher than room temperature. By further treated with a rapid thermal annealing process, both the grain size and the carrier concentration of the films increase, while the saturation magnetization of the films decreases. This magnetic behavior can be hardly explained by either bound magnetic polaron model or free carrier mediation model, thus suggests that the grain boundaries play a key role for the origin of ferromagnetism in these films.

  4. Nature of room-temperature photoluminescence in ZnO

    SciTech Connect

    Shan, W.; Walukiewicz, W.; Ager III, J.W.; Yu, K.M.; Yuan, H.B.; Xin, H.P.; Cantwell, G.; Song, J.J.

    2004-11-11

    The temperature dependence of the photoluminescence (PL) transitions associated with various excitons and their phonon replicas in high-purity bulk ZnO has been studied at temperatures from 12 K to above room temperature (320 K). Several strong PL emission lines associated with LO phonon replicas of free and bound excitons are clearly observed. The room temperature PL spectrum is dominated by the phonon replicas of the free exciton transition with the maximum at the first LO phonon replica. The results explain the discrepancy between the transition energy of free exciton determined by reflection measurement and the peak position obtained by the PL measurement.

  5. Exciton recombination dynamics in single ZnO tetrapods

    SciTech Connect

    Fernandes-Silva, Lígia C.; Martín, Maria D.; Meulen, Herko P. van der; Calleja, José M.; Viña, Luis; Klopotowski, Lukasz

    2013-12-04

    We present the optical properties of individual ZnO tetrapods as a function of excitation power and temperature by time-integrated and time-resolved spectroscopy. At 10K, we identify the different excitonic transitions by both their characteristic energy and their excitation power dependence. When we increase the tetrapod temperature we observe that the emission intensity decrease and occur a red shift of the emission energies. Our time-resolved studies confirm the predominance of the radiative recombination at low temperatures (< 45 K). Increasing the temperature opens up the non-radiative channels, which are evidenced by a much faster decay time.

  6. Piezospectroscopic study of substitutional Ni in ZnO

    SciTech Connect

    Lavrov, E. V.; Herklotz, F.; Kutin, Y. S.

    2014-02-21

    The effect of uniaxial stress on the electronic {sup 3}T{sub 1}(F)→{sup 3}T{sub 2}(F) transitions of Ni{sup 2+} in ZnO at 4216, 4240, and 4247 cm{sup −1} is investigated by means of Fourier transform IR absorption spectroscopy. A stress Hamiltonian is constructed which accounts for the behavior of these transitions under uniaxial stress. It is shown that the split pattern and polarization properties of these IR absorption lines are consistent with a dynamic Jahn-Teller effect in the {sup 3}T{sub 2}(F) state of Ni.

  7. Heavy Stars Thrive among Heavy Elements

    NASA Astrophysics Data System (ADS)

    2002-08-01

    VLT Observes Wolf-Rayet Stars in Virgo Cluster Galaxies [1] Summary Do very massive stars form in metal-rich regions of the Universe and in the nuclei of galaxies ? Or does "heavy element poisoning" stop stellar growth at an early stage, before young stars reach the "heavyweight class"? What may at the first glance appear as a question for specialists actually has profound implications for our understanding of the evolution of galaxies, those systems of billions of stars - the main building blocks of the Universe. With an enormous output of electromagnetic radiation and energetic elementary particles, massive stars exert a decisive influence on the surrounding (interstellar) gas and dust clouds . They also eject large amounts of processed elements, thereby participating in the gradual build-up of the many elements we see today. Thus the presence or absence of such stars at the centres of galaxies can significantly change the overall development of those regions and hence, presumably, that of the entire galaxy. A team of European astronomers [2] has now directly observed the presence of so-called Wolf-Rayet stars (born with masses of 60 - 90 times that of the Sun or more) within metal-rich regions in some galaxies in the Virgo cluster, some 50 million light-years away. This is the first unambiguous detection of such massive stellar objects in metal-rich regions . PR Photo 20a/02 : H II regions in the Virgo cluster galaxy NGC 4254 . PR Photo 20b/02 : Multi-object-slit observation of galaxy NGC 4303 . PR Photo 20c/02 : Spectrum of H II region in NGC 4254 with Wolf-Rayet signatures. Production of heavy elements in the Universe Most scientists agree that the Universe in which we live underwent a dramatic event, known as the Big Bang , approximately 15,000 million years ago. During the early moments, elementary particles were formed which after some time united into more complex nuclei and in turn resulted in the production of hydrogen and helium atoms and their isotopes

  8. Effect of implanted species on thermal evolution of ion-induced defects in ZnO

    SciTech Connect

    Azarov, A. Yu.; Rauwel, P.; Kuznetsov, A. Yu.; Svensson, B. G.; Hallén, A.; Du, X. L.

    2014-02-21

    Implanted atoms can affect the evolution of ion-induced defects in radiation hard materials exhibiting a high dynamic annealing and these processes are poorly understood. Here, we study the thermal evolution of structural defects in wurtzite ZnO samples implanted at room temperature with a wide range of ion species (from {sup 11}B to {sup 209}Bi) to ion doses up to 2 × 10{sup 16} cm{sup −2}. The structural disorder was characterized by a combination of Rutherford backscattering spectrometry, nuclear reaction analysis, and transmission electron microscopy, while secondary ion mass spectrometry was used to monitor the behavior of both the implanted elements and residual impurities, such as Li. The results show that the damage formation and its thermal evolution strongly depend on the ion species. In particular, for F implanted samples, a strong out-diffusion of the implanted ions results in an efficient crystal recovery already at 600 °C, while co-implantation with B (via BF{sub 2}) ions suppresses both the F out-diffusion and the lattice recovery at such low temperatures. The damage produced by heavy ions (such as Cd, Au, and Bi) exhibits a two-stage annealing behavior where efficient removal of point defects and small defect clusters occurs at temperatures ∼500 °C, while the second stage is characterized by a gradual and partial annealing of extended defects. These defects can persist even after treatment at 900 °C. In contrast, the defects produced by light and medium mass ions (O, B, and Zn) exhibit a more gradual annealing with increasing temperature without distinct stages. In addition, effects of the implanted species may lead to a nontrivial defect evolution during the annealing, with N, Ag, and Er as prime examples. In general, the obtained results are interpreted in terms of formation of different dopant-defect complexes and their thermal stability.

  9. Ethanol Steam Reforming on Co/CeO2: The Effect of ZnO Promoter

    SciTech Connect

    Davidson, Stephen; Sun, Junming; Wang, Yong

    2013-12-02

    A series of ZnO promoted Co/CeO2 catalysts were synthesized and characterized using XRD, TEM, H2-TPR, CO chemisorption, O2-TPO, IR-Py, and CO2-TPD. The effects of ZnO on the catalytic performances of Co/CeO2 were studied in ethanol steam reforming. It was found that the addition of ZnO facilitated the oxidation of Co0 via enhanced oxygen mobility of the CeO2 support which decreased the activity of Co/CeO2 in C–C bond cleavage of ethanol. 3 wt% ZnO promoted Co/CeO2 exhibited minimum CO and CH4 selectivity and maximum CO2 selectivity. This resulted from the combined effects of the following factors with increasing ZnO loading: (1) enhanced oxygen mobility of CeO2 facilitated the oxidation of CHx and CO to form CO2; (2) increased ZnO coverage on CeO2 surface reduced the interaction between CHx/CO and Co/CeO2; and (3) suppressed CO adsorption on Co0 reduced CO oxidation rate to form CO2. In addition, the addition of ZnO also modified the surface acidity and basicity of CeO2, which consequently affected the C2–C4 product distributions.

  10. Low-temperature growth and optical properties of Ce-doped ZnO nanorods

    NASA Astrophysics Data System (ADS)

    Yang, Jinghai; Gao, Ming; Yang, Lili; Zhang, Yongjun; Lang, Jihui; Wang, Dandan; Wang, Yaxin; Liu, Huilian; Fan, Hougang

    2008-12-01

    Ce-doped ZnO nanorods were prepared by sol-gel method with low annealing temperature of 500 °C. The effects of Ce doping on the structural and optical properties of ZnO nanorods were investigated in detail. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) and Raman-scattering spectroscopy measurements. The XRD results showed that Ce was doped into ZnO nanorods because of no diffraction peaks of Ce or cerium oxide in the pattern. The synthesis temperature of Ce-doped ZnO nanorods decreased from 900 to 500 °C compared to that of pure ZnO nanorods. Compared with pure ZnO, UV peaks shifted towards the blue color and the intensity of visible peaks decreased after Ce doping. The PL properties of Ce-doped ZnO nanorods depend on both the synthesis temperatures and the dopant. In Raman spectra of doped samples, some classical modes, such as A 1 and E 1 modes, disappear, and the E 2 modes blue shift.

  11. Thermoelectric properties of rocksalt ZnO from first-principles calculations

    SciTech Connect

    Alvarado, Andrew; Attapattu, Jeevake; Zhang, Yi; Chen, Changfeng

    2015-10-28

    Zinc oxide (ZnO) undergoes a pressure-induced structural transition from its normal ambient-pressure wurtzite (WZ) phase to a rocksalt (RS) phase around 10 GPa. A recent experiment shows that the high-pressure RS ZnO phase can be recovered and stabilized at ambient conditions, which raises exciting prospects of expanding the range of properties of ZnO. For a fundamental understanding of the RS ZnO phase, we have performed first-principles calculations to determine its electronic, phonon, and thermodynamic properties at high (20 GPa) and ambient (0 GPa) pressure. Furthermore, we have calculated its electrical and thermal transport properties, which allow an evaluation of its thermoelectric figure of merit ZT at different temperature and doping levels. Our calculations show that the ambient-pressure RS ZnO phase can reach ZT values of 0.25 to 0.3 under both n-type and p-type doping in a large temperature range of 400 K to 800 K, which is considerably lower than the temperature range of 1400 K to 1600 K where WZ ZnO reaches similar ZT values. These results establish RS ZnO as a promising material for thermoelectric devices designed to operate at temperatures desirable for many heat recovery applications.

  12. Highly active lanthanum doped ZnO nanorods for photodegradation of metasystox.

    PubMed

    Korake, P V; Dhabbe, R S; Kadam, A N; Gaikwad, Y B; Garadkar, K M

    2014-01-01

    La-doped ZnO nanorods with different La contents were synthesized by microwave assisted method and characterized by various sophisticated techniques such as XRD, UV-Vis., EDS, XPS, SEM and TEM. The XRD patterns of the La-doped ZnO indicate hexagonal crystal structure with an average crystallite size of 30nm. It was found that the crystallite size of La-doped ZnO is much smaller as compared to pure ZnO and decreases with increasing La content. The photocatalytic activity of 0.5mol% La-doped ZnO in the degradation of metasystox was studied. It was observed that degradation efficiency of metasystox over La-doped ZnO increases up to 0.5mol% doping then decreases for higher doping levels. Among the catalyst studied, the 0.5mol% La-doped ZnO was the most active, showing high photocatalytic activity for the degradation of metasystox. The maximum reduction of concentration of metasystox was observed under static condition at pH 8. Reduction in the Chemical Oxygen Demand (COD) of metasystox was observed after 150min. The cytotoxicological studies of meristematic root tip cells of Allium cepa were studied. The results obtained indicate that photocatalytically degraded products of metasystox were less toxic as compared to metasystox. PMID:24231392

  13. Impurity induced crystallinity and optical emissions in ZnO nanorod arrays

    NASA Astrophysics Data System (ADS)

    Panda, N. R.; Acharya, B. S.

    2015-01-01

    We report the growth of ZnO nanocrystallites doped with impurities such as B, N and S by green chemistry route using ultrasound. The effect of intrinsic defects and impurity doping on the structural and optical properties of ZnO nanostructures has been studied and discussed. Characterization studies carried out using x-ray diffraction (XRD) reveal the change in lattice parameters and crystallinity of ZnO in the presence of dopant. This has been explained on the basis of the dopant substitution at regular anion and interstitial sites. Study on surface morphology by field emission scanning electron microscopy (FESEM) shows a change from particle-like structure to aligned nanorods nucleated at definite sites. Elemental analysis such as x-ray photon electron spectroscopy (XPS) has been carried out to ascertain the dopant configuration in ZnO. This has been corroborated by the results obtained from FTIR and Raman studies. UV-vis light absorption and PL studies show an expansion of the band gap which has been explained on the basis of Moss-Burstein shift in the electronic band gap of ZnO by impurity incorporation. The optical emissions corresponding to excitonic transition and defect centres present in the band gap of ZnO is found to shift towards lower/higher wavelength sides. New PL bands observed have been assigned to the transitions related to the impurity states present in the band gap of ZnO along with intrinsic defects.

  14. 2-Aminoethanol-mediated wet chemical synthesis of ZnO nanostructures

    NASA Astrophysics Data System (ADS)

    Naz, Tehmina; Afzal, Adeel; Siddiqi, Humaira M.; Akhtar, Javeed; Habib, Amir; Banski, Mateusz; Podhorodecki, Artur

    2015-04-01

    The synthesis of ZnO nanostructures via co-precipitation of Zn(NO3)2·2H2O in 2-aminoethanol under different reaction conditions is presented. The effect of temperature and time on crystal structure, size, morphology, and optical properties of ZnO nanopowders is studied. XRD analyses demonstrate that single crystalline wurtzite ZnO nanostructures are instantaneously formed at higher temperature, or at low temperature with growth times equal to 2 h. However, the mean crystallite size increases as a function of reaction temperature and growth time. XRD and SEM results reveal that ZnO nuclei grow along favored crystallographic planes [wurtzite (101)] in 2-aminoethanol to form single crystalline nanorods. The optical band-gap energies of ZnO crystallites measured from their UV absorption spectra increase from 3.31 to 3.52 eV with decreasing particle size. ZnO nanopowders also exhibit good photoluminescent characteristics with strong UV and weak visible (violet, blue) light emissions corresponding to surface defects and oxygen vacancies in ZnO products.

  15. Effect of ZnO on the Thermal Degradation Behavior of Poly(Methyl Methacrylate) Nanocomposites.

    PubMed

    Japić, Dajana; Marinšek, Marjan; Crnjak Orel, Zorica

    2016-01-01

    The influence of ZnO nanoparticles on the thermal degradation behavior of poly(methyl methacrylate) (PMMA) was tested using thermoanalytical techniques. The studied materials were investigated using TG, DTA, EGA, XRD, SEM and TEM. The ZnO nanoparticles were synthesized via precipitation by adding LiOH into Zn2+ water/ethylene glycol solutions. The ZnO-PMMA nanocomposites were prepared by adding the appropriate amount of ZnO into MMA and subsequent MMA radical polymerization. According to the experimental results and model-free isoconversional activation energy calculations, the addition of ZnO into PMMA played a double role. The ZnO concentrations up to 0.15% stabilized the composite by shifting the degradation interval toward higher temperatures and increasing the apparent activation energy relative to pure PMMA. At higher concentrations, the catalytic effect of ZnO started to prevail and was reflected in the lower temperature intervals of intense PMMA degradation and lower apparent activation energy. The addition of ZnO generally did not change the nature of the PMMA decomposition process. PMID:27640380

  16. Formation of ST12 phase Ge nanoparticles in ZnO thin films

    NASA Astrophysics Data System (ADS)

    Ceylan, Abdullah; Gumrukcu, Emre; Ozcan, Sadan

    2015-03-01

    In this work, we investigate the effects of reactive and nonreactive growth of ZnO on the rapid thermal annealing (RTA) induced formation of Ge nanoparticles (Ge-np) in ZnO: Ge nanocomposite thin films. The samples were deposited by sequential sputtering of ZnO and Ge thin film layers with a total thickness of about 600 nm on Si substrates followed by an ex-situ (RTA) at 600°C for 30, 60, 90, 120, 150, 180, and 210 s under forming gas atmosphere. In order for the reactive sputtering of ZnO layer, 5 mTorr Oxygen was introduced to the growth chamber. XRD and Raman analyses were utilized to investigate the effect of RTA time on the structural evolution of the samples. It has been realized that crystal structure of Ge nanoparticles is significantly affected by the growth method of the embedding ZnO layer. While reactive deposition of ZnO layers results in a mixture of diamond cubic (DC) and simple tetragonal (ST12) Ge-np, nonreactive deposition of ZnO layers leads to the formation of pure DC Ge-np upon RTA process. Formation of these two phases has been discussed based on the existence of native point defects such as oxygen vacancies and Zn interstitials.

  17. ZnO nanowires as effective luminescent sensing materials for nitroaromatic derivatives.

    PubMed

    Aad, Roy; Simic, Vesna; Le Cunff, Loïc; Rocha, Licinio; Sallet, Vincent; Sartel, Corinne; Lusson, Alain; Couteau, Christophe; Lerondel, Gilles

    2013-10-01

    We report on the efficient room-temperature photoluminescence (PL) quenching of ZnO in the presence of 2,4-dinitrotoluene (DNT) vapor and for concentration as low as 180 ppb. Compared to ZnO thin films, ZnO nanowires exhibit a strong (95%) and fast (41 s) quenching of the PL intensity in the presence of DNT vapor. Assuming that the PL quenching is due to a trapping of the ZnO excitons by adsorbed DNT molecules, Monte-Carlo calculations show that the nanometric dimensions as well as the better crystallographic quality (longer mean free path) of the ZnO nanowires result in an enhanced trapping process at the origin of the improved sensing properties of the nanowires. The results demonstrate the importance of nanostructures in improving the sensitivity of ZnO. The study also reveals the sensing capability of ZnO nanowires and paves the path towards the potential realization of low-cost sub-ppb nitroaromatic derivative sensors.

  18. Enhanced ultraviolet photoresponse based on ZnO nanocrystals/Pt bilayer nanostructure

    NASA Astrophysics Data System (ADS)

    Tong, Xiao-Lin; Xia, Xiao-Zhi; Li, Qing-Xia

    2015-06-01

    The development of solution strategies for Zinc oxide (ZnO) quantum dots provides a pathway to utilizing ZnO nanocrystal thin films in optoelectronic devices. In this work, quasi-spherical ZnO quantum dots with a diameter of 5 nm are synthesized by using ethanol as a solvent. ZnO nanocrystal thin film is obtained by spin-coating ZnO quantum dots on a Au interdigital electrode (IDE)/Al2O3 substrate and annealing at different temperatures in order to yield the optimal photosensitive on/off ratio of ZnO. For further enhancing the responsivity, ion sputtering is utilized to deposit Pt nanoparticles on the surface of ZnO nanocrystal thin film, the responsivity of the ZnO/Pt bilayer nanostructure increases from 0.07 A/W to 54 A/W, showing that the metal/inorganic nanocrystal bilayer nanostructure can be used to improve the performance of optoelectronic devices. The excellent properties of ZnO/Pt bilayer nanostructure have important applications in future electronic and optoelectronic devices. Project supported by the National Natural Science Foundation of China (Grant No. 41176156).

  19. Hexagonal ZnO nanorods assembled flowers for photocatalytic dye degradation: Growth, structural and optical properties

    NASA Astrophysics Data System (ADS)

    Rahman, Qazi Inamur; Ahmad, Musheer; Misra, Sunil Kumar; Lohani, Minaxi B.

    2013-12-01

    A facile hydrothermal method was used to synthesize highly crystalline hexagonal ZnO nanorods assembled flowers by the reaction of zinc acetate and hexamethylenetetraamine (HMTA) at 105 °C. The morphological characterizations revealed that well defined ZnO nanorods were assembled into flowers morphology. X-rays diffraction patterns showed the highly crystalline nature of ZnO with hexagonal wurtzite structure. The structural and optical properties of hexagonal ZnO nanorods assembled flowers were measured by Fourier transform infra-red (FT-IR) and ultraviolet-visible (UV-Vis) measurements. The as-synthesized hexagonal ZnO nanorods assembled flowers were applied as an efficient photocatalyst for the photodegradation of organic dyes under UV-light irradiation. The methylene blue (MB) and rhodamine B (RhB) over the surface of hexagonal ZnO nanorods assembled flowers considerably degraded by ∼91% and ∼80% within 140 min respectively. The degradation rate constants were found to be kapp (0.01313 mint-1) and kapp(0.0104 mint-1) for MB and RhB dye respectively. The enhanced dye degradation might be attributed to the efficient charge separation and the large number of oxyradicals generation on the surface of the hexagonal ZnO nanorods assembled flowers.

  20. Branched ZnO nanostructures as building blocks of photoelectrodes for efficient solar energy conversion.

    PubMed

    Chen, Wei; Qiu, Yongcai; Yang, Shihe

    2012-08-21

    ZnO nanotetrapods are distinguished by their unique nanocrystalline geometric form with four tetrahedrally directed arms, which endows them the ability to handily assemble three-dimensional network structures. Such network structures, coupled with the intrinsically excellent electronic properties of the semiconducting ZnO, have proved advantageous for building photoelectrodes in energy conversion devices since they allow fast vectorial electron transport. In this review article, we summarize recent efforts, with partial emphasis on our own, in the development of ZnO nanotetrapod-based devices for solar energy conversion, including dye-sensitized solar cells and photoelectrochemical cells for water splitting. A pure ZnO nanotetrapod network was firstly demonstrated to have excellent charge collection properties even with just physical contacts. Composition design of ZnO nanotetrapods/SnO(2) nanoparticles yielded a high efficiency of 4.91% in flexible DSSCs. More significantly, by secondary branching and nitrogen doping, a record performance for water splitting has been achieved. A perspective on future research directions in ZnO nanotetrapod-based solar energy conversion devices is also discussed together with possible strategies of pursuit. It is hoped that the results obtained so far with the ZnO nanotetrapods could inspire and catalyze future developments of solar energy conversion systems based on branched nanostructural materials, contributing to solving global energy and environmental issues.

  1. Hydrothermal growth of ZnO nanowires on flexible fabric substrates

    NASA Astrophysics Data System (ADS)

    Hong, Gwang-Wook; Yun, Sang-Ho; Kim, Joo-Hyung

    2016-04-01

    ZnO nanowires (NWs) would provide significant enhancement in sensitivity due to high surface to volume ratio. We investigated the first methodical study on the quantitative relationship between the process parameters of solution concentration ratio, structure, and physical and properties of ZnO NWs grown on different flexible fabric surfaces. To develop a fundamental following concerning various substrates, we controlled the growth speed of ZnO NWs and nanowires on cotton surface with easy and moderate cost fabrication method. Using ammonium hydroxide as the reactant with zinc nitrate hexahydrate, ZnO NWs layer have been grown on metal layers, instead of seed layer. ZnO NWs fabrication was done on different fabric substrates such as wool, nylon and polypropylene (PP). After the ZnO NWs grown to each substrates, we coated insulating layer with polyurethane (PU) and ethyl cellulose for prevent external intervention. Detailed electrical characterization was subsequently performed to reveal the working characteristics of the hybrid fabric. For electrical verification of fabricated ZnO NWs, we implemented measurement impact test and material properties with FFT analyzer and LCR meter.

  2. ZnO nanowires as effective luminescent sensing materials for nitroaromatic derivatives

    NASA Astrophysics Data System (ADS)

    Aad, Roy; Simic, Vesna; Le Cunff, Loïc; Rocha, Licinio; Sallet, Vincent; Sartel, Corinne; Lusson, Alain; Couteau, Christophe; Lerondel, Gilles

    2013-09-01

    We report on the efficient room-temperature photoluminescence (PL) quenching of ZnO in the presence of 2,4-dinitrotoluene (DNT) vapor and for concentration as low as 180 ppb. Compared to ZnO thin films, ZnO nanowires exhibit a strong (95%) and fast (41 s) quenching of the PL intensity in the presence of DNT vapor. Assuming that the PL quenching is due to a trapping of the ZnO excitons by adsorbed DNT molecules, Monte-Carlo calculations show that the nanometric dimensions as well as the better crystallographic quality (longer mean free path) of the ZnO nanowires result in an enhanced trapping process at the origin of the improved sensing properties of the nanowires. The results demonstrate the importance of nanostructures in improving the sensitivity of ZnO. The study also reveals the sensing capability of ZnO nanowires and paves the path towards the potential realization of low-cost sub-ppb nitroaromatic derivative sensors.

  3. ZnO nanorod growth by plasma-enhanced vapor phase transport with different growth durations

    SciTech Connect

    Kim, Chang-Yong; Oh, Hee-bong; Ryu, Hyukhyun; Yun, Jondo; Lee, Won-Jae

    2014-09-01

    In this study, the structural properties of ZnO nanostructures grown by plasma-enhanced vapor phase transport (PEVPT) were investigated. Plasma-treated oxygen gas was used as the oxygen source for the ZnO growth. The structural properties of ZnO nanostructures grown for different durations were measured by scanning electron microscopy, x-ray diffraction, and transmission electron microscopy. The authors comprehensively analyzed the growth of the ZnO nanostructures with different growth durations both with and without the use of plasma-treated oxygen gas. It was found that PEVPT has a significant influence on the growth of the ZnO nanorods. PEVPT with plasma-treated oxygen gas facilitated the generation of nucleation sites, and the resulting ZnO nanorod structures were more vertical than those prepared by conventional VPT without plasma-treated oxygen gas. As a result, the ZnO nanostructures grown using PEVPT showed improved structural properties compared to those prepared by the conventional VPT method.

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

    SciTech Connect

    Wang, Canxing; Jiang, Haotian; Li, Yunpeng; Ma, Xiangyang; Yang, Deren

    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, the 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.

  5. ZnO nanoparticle tracking from uptake to genotoxic damage in human colon carcinoma cells.

    PubMed

    Condello, Maria; De Berardis, Barbara; Ammendolia, Maria Grazia; Barone, Flavia; Condello, Giancarlo; Degan, Paolo; Meschini, Stefania

    2016-09-01

    Zinc Oxide (ZnO) nanoparticles are widely used both in the industry and in biomedical applications for their chemical and physical nanomaterial properties. It is therefore essential to go in depth into the cytotoxicity mechanisms and interactions between nanomaterials and cells. The aim of this work was to evaluate the dissolution of ZnO nanoparticles and their uptake, from a few minutes after treatments up to 24h. ZnO nanoparticles routes of entry into the human colon carcinoma cells (LoVo) were followed at different times by a thorough ultrastructural investigation and semiquantitative analysis. The intracellular release of Zn(2+) ions by Zinquin fluorescent dye, and phosphorylated histone H2AX (γ-H2AX) expression were evaluated. The genotoxic potential of ZnO nanoparticles was also investigated by determining the levels of 8-hydroxyl-2'-deoxyguanosine (8-oxodG). The experimental data show that ZnO nanoparticles entered LoVo cells by either passive diffusion or endocytosis or both, depending on the agglomeration state of the nanomaterial. ZnO nanoparticles coming into contact with acid pH of lysosomes altered organelles structure, resulting in the release of Zn(2+) ions. The simultaneous presence of ZnO nanoparticles and Zn(2+) ions in the LoVo cells determined the formation of reactive oxygen species at the mitochondrial and nuclear level, inducing severe DNA damage. PMID:27317967

  6. Electrical and Optical Properties of ZnO Films Grown on GaAs Substrates

    NASA Astrophysics Data System (ADS)

    Yuldashev, Shavkat U.; Panin, Gennady N.; Choi, Sung Woo; Yalishev, Vadim Sh.; Nosova, Ludmila A.; Ryu, Min Ki; Lee, Sanghern; Jang, Min Su; Chung, Kwan Soo; Kang, Tae Won

    2003-06-01

    Undoped ZnO films were deposited on GaAs substrates by conventional rf magnetron sputtering technique. After thermal annealing at temperatures of 500°C and higher for 20 min, the Hall coefficient of ZnO films on GaAs substrate becomes positive. The long-time annealing of 550 min at a temperature of 400°C also converts the sign of the Hall coefficient to positive. X-ray microanalysis shows that the diffusion of Zn atoms into the GaAs substrate and Ga atoms from the GaAs substrate into the ZnO film during thermal annealing occurs. The results of Hall measurements were analyzed by using the two-layer model of conductivity. It was shown that the positive sign of the Hall coefficient for the annealed ZnO film on the GaAs substrate is due to p-type conductivity of the GaAs substrate as a result of the diffusion of the Zn atoms from ZnO film into the GaAs substrate. With increasing annealing temperature or annealing time the ZnO films become more n-type due to the diffusion of Ga atoms from the GaAs substrate into the ZnO film.

  7. Morphological, physical, antimicrobial and release properties of ZnO nanoparticles-loaded bacterial cellulose films.

    PubMed

    Shahmohammadi Jebel, Fereshteh; Almasi, Hadi

    2016-09-20

    Bacterial cellulose (BC) monolayer and multilayer films, incorporating 5wt.% ZnO nanoparticles (NPs) have been obtained. Ultrasound (US) irradiation (40kHz) was applied during ZnO-BC nanocomposites preparation. X-ray diffraction (XRD) patterns showed that ZnO NPs were crystallized in their pure phase. SEM scanning electron microscopy (SEM) results indicated that US treatment causes to decrease ZnO particle size, forming a stable hybrid nanostructure and evenly distributed ZnO NPs coated BC nanofibers. ZnO NPs enhanced the mechanical properties and diminished water vapor permeability and moisture absorption of BC films. Antibacterial activity of ZnO-BC films against Staphylococcus aureus was more than Escherichia coli. The antibacterial activity was enhanced with the utilization of US irradiation. The ZnO release was influenced by films composition; the multilayer and US treated films being promising in order to achieve controlled release of ZnO. Results suggest that ZnO-BC films may be used as controlled release antimicrobial food active packaging. PMID:27261725

  8. Low temperature atomic layer deposited ZnO photo thin film transistors

    SciTech Connect

    Oruc, Feyza B.; Aygun, Levent E.; Donmez, Inci; Biyikli, Necmi; Okyay, Ali K.; Yu, Hyun Yong

    2015-01-01

    ZnO thin film transistors (TFTs) are fabricated on Si substrates using atomic layer deposition technique. The growth temperature of ZnO channel layers are selected as 80, 100, 120, 130, and 250 °C. Material characteristics of ZnO films are examined using x-ray photoelectron spectroscopy and x-ray diffraction methods. Stoichiometry analyses showed that the amount of both oxygen vacancies and interstitial zinc decrease with decreasing growth temperature. Electrical characteristics improve with decreasing growth temperature. Best results are obtained with ZnO channels deposited at 80 °C; I{sub on}/I{sub off} ratio is extracted as 7.8 × 10{sup 9} and subthreshold slope is extracted as 0.116 V/dec. Flexible ZnO TFT devices are also fabricated using films grown at 80 °C. I{sub D}–V{sub GS} characterization results showed that devices fabricated on different substrates (Si and polyethylene terephthalate) show similar electrical characteristics. Sub-bandgap photo sensing properties of ZnO based TFTs are investigated; it is shown that visible light absorption of ZnO based TFTs can be actively controlled by external gate bias.

  9. Synthesis and field emission properties of different ZnO nanostructure arrays

    PubMed Central

    2012-01-01

    In this article, zinc oxide (ZnO) nanostructures of different shapes were fabricated on silicon substrate. Well-aligned and long ZnO nanowire (NW) arrays, as well as leaf-like ZnO nanostructures (which consist of modulated and single-phase structures), were fabricated by a chemical vapor deposition (CVD) method without the assistance of a catalyst. On the other hand, needle-like ZnO NW arrays were first fabricated with the CVD process followed by chemical etching of the NW arrays. The use of chemical etching provides a low-cost and convenient method of obtaining the needle-like arrays. In addition, the field emission properties of the different ZnO NW arrays were also investigated where some differences in the turn-on field and the field-enhancement factors were observed for the ZnO nanostructures of different lengths and shapes. It was experimentally observed that the leaf-like ZnO nanostructure is most suitable for field emission due to its lowest turn-on and threshold field as well as its high field-enhancement factor among the different synthesized nanostructures. PMID:22444723

  10. Nitrogen doped p-type ZnO films and p-n homojunction

    NASA Astrophysics Data System (ADS)

    Snigurenko, D.; Kopalko, K.; Krajewski, T. A.; Jakiela, R.; Guziewicz, E.

    2015-01-01

    We demonstrate the ZnO homojunction fully obtained by the atomic layer deposition technique at low temperature growth of 100-130 °C. For the n-type partner of the junction we used undoped ZnO film obtained at 130 °C, while nitrogen doped ZnO acted as the p-type partner of the junction. Nitrogen was introduced into the ZnO film during the ALD process by using ammonia water as an oxygen precursor and diethylzinc as a zinc precursor. The p-type conductivity of ZnO was activated by the subsequent annealing of the ZnO:N film in an oxygen or nitrogen atmosphere. The initial rectification ratio of 102 at ±2 V was raised to 4 · 104 by inserting an ultrathin Al2O3 layer between p- and n-type ZnO. The resulting rectification ratio is among the best parameters reported for a ZnO homojunction so far.

  11. Selective growth of hierarchical ZnO nanorod arrays on the graphene nanosheets

    NASA Astrophysics Data System (ADS)

    Yang, Hui; Li, Lan; Li, Jinliang; Mo, Zhaojun

    2016-01-01

    We report directly selective-area grown (SAG) high-quality hierarchical ZnO nanorod arrays on the graphene nanosheets without invoking damage or introducing a catalyst. The SAG behavior in the non-catalytic growth mechanism is attributed to dangling bonds on the boundary edges of graphene nanosheets, which serve as the preferential adsorption and nucleation sites of ZnO nanorod. High densities of hierarchical ZnO nanorods show single-crystalline hexagonal wurtzite structure and are vertically well-aligned on the graphene nanosheets, with the diameter and the density strongly dependent on the growth temperature. Furthermore, no carbon impurity can be seen in the tips of the ZnO nanorods and also no carbon-related defect peak in the 10 K PL spectrum of ZnO nanorods. Our approach using a graphene-nanosheet substrate provides an efficient route for the growth of high-quality ZnO with a one-dimensional (1D) hierarchical nanostructure, which is highly desirable for fabricating 1D ZnO hybrid optoelectronic devices, particularly for a fast-response UV photodetector and highly-sensitive gas sensor.

  12. Effects of interfacial layer structures on crystal structural properties of ZnO films

    SciTech Connect

    Park, J. S.; Minegishi, T.; Lee, S. H.; Im, I. H.; Park, S. H.; Hanada, T.; Goto, T.; Cho, M. W.; Yao, T.; Hong, S. K.; Chang, J. H.

    2008-01-15

    Single crystalline ZnO films were grown on Cr compound buffer layers on (0001) Al{sub 2}O{sub 3} substrates by plasma assisted molecular beam epitaxy. In terms of lattice misfit reduction between ZnO and substrate, the CrN and Cr{sub 2}O{sub 3}/CrN buffers are investigated. The structural and optical qualities of ZnO films suggest the feasibility of Cr compound buffers for high-quality ZnO films growth on (0001) Al{sub 2}O{sub 3} substrates. Moreover, the effects of interfacial structures on selective growth of different polar ZnO films are investigated. Zn-polar ZnO films are grown on the rocksalt CrN buffer and the formation of rhombohedral Cr{sub 2}O{sub 3} results in the growth of O-polar films. The possible mechanism of polarity conversion is proposed. By employing the simple patterning and regrowth procedures, a periodical polarity converted structure in lateral is fabricated. The periodical change of the polarity is clearly confirmed by the polarity sensitive piezo response microscope images and the opposite hysteretic characteristic of the piezo response curves, which are strict evidences for the validity of the polarity controlling method as well as the successful fabrication of the periodical polarity controlled ZnO structure.

  13. Fractal aggregation of ZnO nanoparticles under different aqueous solution chemistries

    NASA Astrophysics Data System (ADS)

    Zhou, D.; Keller, A. A.

    2009-12-01

    The aggregation of ZnO nanoparticles influences not only their environmental transport but also their toxicity. In natural aquatic systems, the ubiquitous presence of natural organic matter (NOM) can lead to interactions with released ZnO nanoparticles (NPs) and influence their transport. In this study, the aggregation kinetics of ZnO with and without NOM under different ionic strength and pH were examined by both time-resolved dynamic light scattering and sedimentation experiments. ZnO aggregates faster as the pH approaches its point of zero charge. The role of ionic strength role was examined by determining the reaction-limited cluster regime (RLCR) and diffusion-limited cluster regime (DLCR). The critical coagulation concentration (CCC) was determined as 25mM using NaCl as the electrolyte at pH 8. A higher initial ZnO concentration leads to faster aggregation. DLVO calculations agreed well with the experimental data. At high NOM concentration, ZnO aggregation was significantly slowed. However, at low NOM concentration, bridging effect was observed. Finally, the fractal dimensions of ZnO aggregates under different conditions were determined by static light scattering (SLS).

  14. Ionothermal precipitation of highly dispersive ZnO nanoparticles with improved photocatalytic performance

    NASA Astrophysics Data System (ADS)

    Cun, Tangxiang; Dong, Chengjun; Huang, Qiang

    2016-10-01

    ZnO nanoparticles (NPs) were prepared by an ionothermal precipitation method in a ChCl:DEG deep eutectic solvent using Zn(CH3COO)2·2H2O as a zinc source. A possible mechanism for the ZnO nucleation is discussed. The as-prepared ZnO samples were thoroughly examined by XRD, TEM, SEM, FTIR and XPS. The thermal and optical properties were further characterized by TGA/DTA, UV-vis and PL spectra, respectively. The results show that wurtzite ZnO mono-crystals with an average size of 30 ± 1 nm were achieved, and their morphology was expressed as a polyhedron with distorted hexagonal base faces. Furthermore, the DEG molecules were incorporated into the surfaces of the ZnO crystals and could only be removed by thermal annealing; the molecules persisted after washing with ordinary solvents. Dynamic light scattering (DLS) shows that the ZnO NPs modified via DEG molecules are stable in an aqueous suspension without additives. In addition, the inclusion of DEG promotes light absorption at a longer wavelength but reduces the intensity of emissions. XPS reveals that the removal of DEG induced exposed polar surfaces and defects and thus increased the intensity of photoluminescence, especially blue emission. The findings of this work not only provide a facile and environmentally friendly ionothermal method to prepare uniform ZnO NPs protected by DEG but also improve the aqueous suspension stability. Consequently, the photocatalytic performance is enhanced.

  15. Enhanced UV absorbance and photoluminescence properties of ultrasound assisted synthesized gold doped ZnO nanorods

    NASA Astrophysics Data System (ADS)

    Sahu, Dojalisa; Panda, N. R.; Acharya, B. S.; Panda, A. K.

    2014-06-01

    Au doped ZnO (ZnO:Au) nanostructures were synthesized by ultrasound assisted wet chemical method. The concentration of dopant was varied and both structural and optical properties of ZnO:Au were investigated. The crystal structure and morphology of the samples were examined by X-ray diffraction (XRD) and transmission electron microscopy (TEM). These results showed the formation of nanorods of ZnO:Au having wurtzite structure and c-axis orientation. Gradual increase in crystallite size and bond length was also observed with the increase in gold concentration in ZnO intending the expansion of lattice after gold doping. The optical absorption measurements showed high ultraviolet (UV) absorbance property of ZnO:Au with sharp and intense absorption band in this region as compared to pristine ZnO. Photoluminescence (PL) measurements showed excitonic emission band of ZnO around 390 nm for both undoped and Au doped ZnO nanoparticles. Further, a strong emission around 467 nm was observed in the PL spectra of ZnO/ZnO:Au which was attributed to the transitions related to excess of oxygen vacancies. Interestingly, a new band was observed at 582 nm for doped ZnO samples which grew in intensity with doping concentration. This band was ascribed to the gold nanoparticle adsorbed on the surface of ZnO.

  16. (Al, Er) co-doped ZnO nanoparticles for photodegradation of rhodamine blue

    NASA Astrophysics Data System (ADS)

    Ghomri, R.; Shaikh, M. Nasiruzzaman; Ahmed, M. I.; Bououdina, M.; Ghers, M.

    2016-10-01

    Pure and co-doped (Al, Er) ZnO nanoparticles (NPs) have been synthesized by hydrothermal method using (Zn, Er and Al) nitrates. X-ray diffraction patterns reveal the formation of single phase of ZnO würtzite-type structure. The crystallite size for pure ZnO is in the order of 26.5 nm which decreases up to the range 14.2-22.0 nm after (Al, Er) co-doping. SEM micrographs show that the specimen is composed of regular spherical particles in the nanoscale regime with homogeneous size distribution and high tendency to agglomeration. FTIR spectra exhibit absorption lines located at wavenumbers corresponding to vibration modes between the constituent atoms. Raman spectra recorded under excitation ( λ exc = 632.8 nm) reveal peaks related to modes of transverse and longitudinal optical phonons of the würtzite ZnO structure. The energy band gap E g of ZnO:(Al, Er) NPs ranges in 3.264-3.251 eV. The photocatalytic activity of pure and co-doped (Al, Er) ZnO NPs was evaluated by the photodegradation of rhodamine blue under an irradiation of wavelength 554 nm. It is found that a photodegradation rate above 90 % could be achieved for a period of time of 40 min for pure ZnO and 120 min for (Al, Er) co-doped ZnO. A photodegradation mechanism is proposed.

  17. Dye-sensitized solar cells based on ZnO nanorod arrays

    NASA Astrophysics Data System (ADS)

    Xie, Yu; Li, Shaoyan; Zhang, Ting; Joshi, Prakash; Fong, Hao; Ropp, Mike; Galipeau, David; Qiao, Qiquan

    2008-08-01

    A series of dye-sensitized solar cells (DSSCs) were fabricated using ZnO nanorod arrays as the anode electrode. The ZnO nanorod arrays were grown on the fluorine doped tin dioxide (FTO) substrates by a hydrothermal method. The scanning electron microscopy (SEM) images indicated that the ZnO nanorod arrays were highly oriented on FTO substrates with an average diameter of ~40 nm and an average length of ~1 μm. After sensitized by Z-907 dye via impregnation in solution, ZnO nanorod arrays changed the color from white to pink. This indicated that the dye had been successfully attached to ZnO nanorods. The high-aspect-ratio (~25) ZnO nanorod arrays are expected to improve charge transport through the formation of continuous channels along the nanorods. We fabricated photovoltaic cells based on these ZnO nanorod arrays and found the deposition time and effective area were two important factors affecting short circuit current densities and cell efficiencies. The device performance (Voc = 0.48 V, Jsc = 5.39 mA/cm2, η = 0.73 %) showed a great potential for solar energy conversion.

  18. Heavy Truck Engine Program

    SciTech Connect

    Nelson, Christopher

    2009-01-08

    The Heavy Duty Truck Engine Program at Cummins embodied three significant development phases. All phases of work strove to demonstrate a high level of diesel engine efficiency in the face of increasingly stringent emission requirements. Concurrently, aftertreatment system development and refinement was pursued in support of these efficiency demonstrations. The program's first phase focused on the demonstration in-vehicle of a high level of heavy duty diesel engine efficiency (45% Brake Thermal Efficiency) at a typical cruise condition while achieving composite emissions results which met the 2004 U.S. EPA legislated standards. With a combination of engine combustion calibration tuning and the development and application of Urea-based SCR and particulate aftertreatment, these demonstrations were successfully performed by Q4 of 2002. The second phase of the program directed efforts towards an in-vehicle demonstration of an engine system capable of meeting 2007 U.S. EPA legislated emissions requirements while achieving 45% Brake Thermal Efficiency at cruise conditions. Through further combustion optimization, the refinement of Cummins Cooled EGR architecture, the application of a high pressure common rail fuel system and the incorporation of optimized engine parasitics, Cummins Inc. successfully demonstrated these deliverables in Q2 of 2004. The program's final phase set a stretch goal of demonstrating 50% Brake Thermal Efficiency from a heavy duty diesel engine system capable of meeting 2010 U.S. EPA legislated emissions requirements. Cummins chose to pursue this goal through further combustion development and refinement of the Cooled EGR system architecture and also applied a Rankine cycle Waste Heat Recovery technique to convert otherwise wasted thermal energy to useful power. The engine and heat recovery system was demonstrated to achieve 50% Brake Thermal Efficiency while operating at a torque peak condition in second quarter, 2006. The 50% efficient engine

  19. Growth of hierarchical based ZnO micro/nanostructured films and their tunable wettability behavior

    NASA Astrophysics Data System (ADS)

    Suresh Kumar, P.; Dhayal Raj, A.; Mangalaraj, D.; Nataraj, D.; Ponpandian, N.; Li, Lin; Chabrol, G.

    2011-05-01

    Hierarchical zinc oxide (ZnO) micro/nanostructured thin films were grown onto as-prepared and different annealed ZnO seed layer films by a simple two step chemical process. A cost effective successive ionic layer adsorption and reaction (SILAR) method was employed to grow the seed layer films at optimal temperature (80 °C) and secondly, different hierarchical based ZnO structured thin films were deposited over the seed layered films by chemical bath deposition (CBD). The influence of seed layer on the structural, surface morphological, optical and wettability behavior of the ZnO thin films were systematically investigated. The XRD analysis confirms the high crystalline nature of both the seed layer and corresponding ZnO micro/nanostructured films with a perfect hexagonal structure oriented along (0 0 2) direction. The surface morphology revels a complex and orientated hierarchical based ZnO structured films with diverse shapes from plates to hexagonal rod-like crystal to tube-like structure and even much more complex needle-like shapes during secondary nucleation, by changing the seed layer conditions. The water contact angle (WCA) measurements on hierarchical ZnO structured films are completely examined to study its surface wettability behavior for its suitability in future self-cleaning application. Photoluminescence (PL) spectra of the ZnO structured film exhibit UV and visible emissions in the range of 420-500 nm. The present approach demonstrates its potential for low-temperature, large-scale, controlled synthesis of crystalline hierarchical ZnO nanostructures films.

  20. Novel Biomimatic Synthesis of ZnO Nanorods Using Egg White (Albumen) and Their Antibacterial Studies.

    PubMed

    Ahmed, Faheem; Arshi, Nishat; Jeong, Yeong Seung; Anwar, M S; Dwivedi, Saurabh; Alsharaeh, Edreese; Koo, B H

    2016-06-01

    Zinc oxide (ZnO) is well-recognized as a biocompatible multifunctional material with outstanding properties as well as low toxicity and biodegradability. In this work, a simple and versatile technique was developed to prepare highly crystalline ZnO nanorods by introducing egg white to a bio-inspired approach. X-ray diffraction (XRD) and selected area electron diffraction (SAED) pattern results indicated that the ZnO nanorods have single phase nature with the wurtzite structure. Field emission scanning electron microscopy (FESEM) and Transmission electron microscopy (TEM) results showed the nanometer dimension of the nanorods. Raman, FTIR, and TGA/DTA analyses revealed the formation of wurtzite ZnO. The antibacterial properties of ZnO nanorods were investigated using both Gram-positive and Gram-negative microorganisms. These studies demonstrate that ZnO nanorods have a wide range of antibacterial activities toward various microorganisms that are commonly found in environmental settings. Survival ratio of bacteria decreased with increasing powder concentration, i.e., increase in antibacterial activity. The antibacterial activity of the ZnO nanorods toward Pseudomonas aeruginosa was stronger than that of Escherichia coli and Staphylococcus aureus. Surprisingly, the antibacterial activity did not require specific UV activation using artificial lamps, rather activation was achieved under ambient lighting conditions. Overall, the experimental results suggest that ZnO nanorods could be developed as antibacterial agents against a wide range of microorganisms to control and prevent the spreading and persistence of bacterial infections. This research introduces a new concept to synthesize ZnO nanorods by using egg white as a biological template for various applications including food science, animal science, biochemistry, microbiology and medicine.

  1. Novel Biomimatic Synthesis of ZnO Nanorods Using Egg White (Albumen) and Their Antibacterial Studies.

    PubMed

    Ahmed, Faheem; Arshi, Nishat; Jeong, Yeong Seung; Anwar, M S; Dwivedi, Saurabh; Alsharaeh, Edreese; Koo, B H

    2016-06-01

    Zinc oxide (ZnO) is well-recognized as a biocompatible multifunctional material with outstanding properties as well as low toxicity and biodegradability. In this work, a simple and versatile technique was developed to prepare highly crystalline ZnO nanorods by introducing egg white to a bio-inspired approach. X-ray diffraction (XRD) and selected area electron diffraction (SAED) pattern results indicated that the ZnO nanorods have single phase nature with the wurtzite structure. Field emission scanning electron microscopy (FESEM) and Transmission electron microscopy (TEM) results showed the nanometer dimension of the nanorods. Raman, FTIR, and TGA/DTA analyses revealed the formation of wurtzite ZnO. The antibacterial properties of ZnO nanorods were investigated using both Gram-positive and Gram-negative microorganisms. These studies demonstrate that ZnO nanorods have a wide range of antibacterial activities toward various microorganisms that are commonly found in environmental settings. Survival ratio of bacteria decreased with increasing powder concentration, i.e., increase in antibacterial activity. The antibacterial activity of the ZnO nanorods toward Pseudomonas aeruginosa was stronger than that of Escherichia coli and Staphylococcus aureus. Surprisingly, the antibacterial activity did not require specific UV activation using artificial lamps, rather activation was achieved under ambient lighting conditions. Overall, the experimental results suggest that ZnO nanorods could be developed as antibacterial agents against a wide range of microorganisms to control and prevent the spreading and persistence of bacterial infections. This research introduces a new concept to synthesize ZnO nanorods by using egg white as a biological template for various applications including food science, animal science, biochemistry, microbiology and medicine. PMID:27427657

  2. Physicochemical properties and cellular toxicity of (poly)aminoalkoxysilanes-functionalized ZnO quantum dots

    NASA Astrophysics Data System (ADS)

    Aboulaich, Abdelhay; Tilmaciu, Carmen-Mihaela; Merlin, Christophe; Mercier, Cédric; Guilloteau, Hélène; Medjahdi, Ghouti; Schneider, Raphaël

    2012-08-01

    Luminescent ZnO nanocrystals were synthesized by basic hydrolysis of Zn(OAc)2 in the presence of oleic acid and then functionalized with (poly)aminotrimethoxysilanes in the presence of tetramethylammonium hydroxide to render the QDs water-dispersible. The highest photoluminescence quantum yield (17%) was achieved using N1-(2-aminoethyl)-N2-[3-(trimethoxysilyl)propyl]-1,2-ethanediamine as surface ligand. Transmission electron microscopy and powder x-ray diffraction showed highly crystalline materials with a ZnO nanoparticle diameter of about 4 nm. The cytotoxicity of the different siloxane-capped ZnO QDs towards growing Escherichia coli bacterial cells was evaluated in MOPS-minimal medium. Although concentrations of 5 mM in QDs caused a complete growth arrest in E. coli, siloxane-capped ZnO QDs appeared weakly toxic at lower doses (0.5 or 1 mM). The concentration of bioavailable Zn 2+ ions leaked from ZnO QDs was evaluated using the biosensor bacteria Cupriavidus metallidurans AE1433. The results obtained clearly demonstrate that concentrations of bioavailable Zn2+ are too low to explain the inhibitory effects of the ZnO QDs against bacteria cells at 1 mM and that the siloxane shell prevents ZnO QDs from dissolution contrary to uncapped ZnO nanoparticles. Because of their low cytotoxicity, good biocompatibility, low cost and large number of functional amine end groups, which makes them easy to tailor for end-user purposes, siloxane-capped ZnO QDs offer a high potential as fluorescent probes and as biosensors.

  3. Continuous and Localized Mn Implantation of ZnO

    PubMed Central

    2009-01-01

    We present results derived from continuous and localized 35 keV55Mn+ion implantations into ZnO. Localized implantations were carried out by using self-ordered alumina membranes as masks leading to ordered arrays of implanted volumes on the substrate surfaces. Defects and vacancies in the small implantation volumes of ZnO were generated due to the implantation processes besides the creation of new phases. Rapid thermal annealing was applied in the case of continuous implantation. The samples were characterized by HRSEM, GIXRD, Raman spectroscopy and RBS/C. Magnetic characterization of the samples pointed out appreciable differences among the samples obtained by the different implantation methods. This fact was mainly attributed to the different volume/surface ratios present in the implanted zones as well as to the increase of Mn atom concentrations along the grain frontiers in the nanostructured surfaces. The samples also showed a ferromagnetic transition phase at temperature value higher than room temperature. PMID:20596285

  4. Local structures of copper-doped ZnO films

    SciTech Connect

    Ma, Q.; Buchholz, D.B.; Chang, R.P.H.

    2009-01-05

    We report the local structures of a series of copper-doped zinc oxide films using polarization-dependent x-ray-absorption spectroscopy. The films were grown by pulsed-laser ablation under various conditions. The results show that films where copper exists solely as clusters are not ferromagnetic. The results also show that some of the copper-doped zinc oxide films are not ferromagnetic despite the fact that the copper substitution for zinc in the ZnO lattice is in the Cu{sup 2+} state, which provides the necessary unpaired spins for ferromagnetism. Therefore, Cu{sup 2+}/Zn{sup 2+} substitution is not the only imperative condition for ferromagnetism to occur. We present characteristics unique to the electronic and atomic structure of ferromagnetic films and argue that the increased covalence of the Cu{sub Zn}-O bond found in these films is a prerequisite for the spin alignments in a substitutionally copper-doped zinc oxide film.

  5. Unusual ferromagnetism in high purity ZnO sintered ceramics

    SciTech Connect

    Das, J.; Pradhan, S.K.; Mishra, D.K.; Sahu, D.R.; Nayak, B.B.; Huang, Jow-Lay; Roul, B.K.

    2011-01-15

    We report our novel result regarding the observation of unusual but clean ferromagnetic (FM) signature at room temperature (RT) in high pure (99.999%) ZnO bulk ceramics processed by slow step sintering schedule (SSSS). All the sintered samples showed ferromagnetic signature at room temperature. However, sample sintered at 850 {sup o}C showed more prominent M-H loop and saturation magnetization with respect to samples sintered at 500 {sup o}C and 1300 {sup o}C. Observation of FM behavior in sintered ceramics may be attributed to the presence of defects like cation (Zn)/anion (O) vacancies and interstitials created during the processing of sample. It is anticipated that SSSS promotes enhanced physical bulk as well as surface densification and at the same time confined the outgassing of free oxygen and Zn from the bulk which are acting as suitable defect sites inside the sintered grains and grain boundary junctions. Our micro-Raman and X-ray photoelectron studies revealed the existence of these defects which are believed to be the origin of the unconventional ferromagnetism (FM) of ZnO bulk ceramic at room temperature.

  6. A Novel Ionic Polymer Metal ZnO Composite (IPMZC)

    PubMed Central

    Kim, Sang-Mun; Tiwari, Rashi; Kim, Kwang J.

    2011-01-01

    The presented research introduces a new Ionic Polymer-Metal-ZnO Composite (IPMZC) demonstrating photoluminescence (PL)-quenching on mechanical bending or application of an electric field. The newly fabricated IPMZC integrates the optical properties of ZnO and the electroactive nature of Ionic Polymer Metal Composites (IPMC) to enable a non-contact read-out of IPMC response. The electro-mechano-optical response of the IPMZC was measured by observing the PL spectra under mechanical bending and electrical regimes. The working range was measured to be 375–475 nm. It was noted that the PL-quenching increased proportionally with the increase in curvature and applied field at 384 and 468 nm. The maximum quenching of 53.4% was achieved with the membrane curvature of 78.74/m and 3.01% when electric field (12.5 × 103 V/m) is applied. Coating IPMC with crystalline ZnO was observed to improve IPMC transduction. PMID:22163869

  7. Study of the antibacterial activity of ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Surti, Arjuman; Radha, S.; Garje, S. S.

    2013-02-01

    This study focuses on the antibacterial activity of the ZnO nanoparticles against organisms causing skin and wound infections. The nanoparticles were synthesized by a wet chemical route. The method was quick and nanoparticles were obtained in 3 days of incubation in dark. Characterization of the nanoparticles was done by X-Ray Diffraction and UV-Visible Spectrophotometry. It was observed that the UV-Visible spectrum peak was obtained at 357 nm corresponding to the Plasmon absorbance of Zinc oxide. X-Ray diffraction exhibited the 2θ values corresponding to Zinc oxide and the particle size was estimated to be 20 nm. The antibacterial effect of nanoparticles was observed against Staphylococcus spp and Bacillus spp. The significance of the bactericidal activity of the nanoparticles lies in the reduction of using antibiotics against nosocomial infections, especially in prolonged treatments. The bandage material used in wound dressing was coated with ZnO nanoparticles by adsorption method. The textile was found to be efficient in inhibiting the growth of these organisms. The effect of adverse storage conditions on the coated bandage material was also studied. On comparing the results obtained at extreme pH and temperature and those obtained at optimum conditions, it was seen that the nanoparticles were less effective at these extreme conditions.

  8. Highly Uniform Epitaxial ZnO Nanorod Arrays for Nanopiezotronics

    PubMed Central

    2009-01-01

    Highly uniform and c-axis-aligned ZnO nanorod arrays were fabricated in predefined patterns by a low temperature homoepitaxial aqueous chemical method. The nucleation seed patterns were realized in polymer and in metal thin films, resulting in, all-ZnO and bottom-contacted structures, respectively. Both of them show excellent geometrical uniformity: the cross-sectional uniformity according to the scanning electron micrographs across the array is lower than 2%. The diameter of the hexagonal prism-shaped nanorods can be set in the range of 90–170 nm while their typical length achievable is 0.5–2.3 μm. The effect of the surface polarity was also examined, however, no significant difference was found between the arrays grown on Zn-terminated and on O-terminated face of the ZnO single crystal. The transmission electron microscopy observation revealed the single crystalline nature of the nanorods. The current–voltage characteristics taken on an individual nanorod contacted by a Au-coated atomic force microscope tip reflected Schottky-type behavior. The geometrical uniformity, the designable pattern, and the electrical properties make the presented nanorod arrays ideal candidates to be used in ZnO-based DC nanogenerator and in next-generation integrated piezoelectric nano-electromechanical systems (NEMS). PMID:20596319

  9. Laser nanostructuring of ZnO thin films

    NASA Astrophysics Data System (ADS)

    Nedyalkov, N.; Koleva, M.; Nikov, R.; Atanasov, P.; Nakajima, Y.; Takami, A.; Shibata, A.; Terakawa, M.

    2016-06-01

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

  10. A novel ionic polymer metal ZnO composite (IPMZC).

    PubMed

    Kim, Sang-Mun; Tiwari, Rashi; Kim, Kwang J

    2011-01-01

    The presented research introduces a new Ionic Polymer-Metal-ZnO Composite (IPMZC) demonstrating photoluminescence (PL)-quenching on mechanical bending or application of an electric field. The newly fabricated IPMZC integrates the optical properties of ZnO and the electroactive nature of Ionic Polymer Metal Composites (IPMC) to enable a non-contact read-out of IPMC response. The electro-mechano-optical response of the IPMZC was measured by observing the PL spectra under mechanical bending and electrical regimes. The working range was measured to be 375-475 nm. It was noted that the PL-quenching increased proportionally with the increase in curvature and applied field at 384 and 468 nm. The maximum quenching of 53.4% was achieved with the membrane curvature of 78.74/m and 3.01% when electric field (12.5 × 10(3) V/m) is applied. Coating IPMC with crystalline ZnO was observed to improve IPMC transduction.

  11. Valency configuration of transition metal impurities in ZnO

    SciTech Connect

    Petit, Leon; Schulthess, Thomas C; Svane, Axel; Temmerman, Walter M; Szotek, Zdzislawa; Janotti, Anderson

    2006-01-01

    We use the self-interaction corrected local spin-density approximation to investigate the ground state valency configuration of transition metal (TM=Mn, Co) impurities in n- and p-type ZnO. We find that in pure Zn{sub 1-x}TM{sub x}O, the localized TM{sup 2+} configuration is energetically favored over the itinerant d-electron configuration of the local spin density (LSD) picture. Our calculations indicate furthermore that the (+/0) donor level is situated in the ZnO gap. Consequently, for n-type conditions, with the Fermi energy {epsilon}F close to the conduction band minimum, TM remains in the 2+ charge state, while for p-type conditions, with {epsilon}F close to the valence band maximum, the 3+ charge state is energetically preferred. In the latter scenario, modeled here by co-doping with N, the additional delocalized d-electron charge transfers into the entire states at the top of the valence band, and hole carriers will only exist, if the N concentration exceeds the TM impurity concentration.

  12. ZnO nanorod arrays for photoelectrochemical cells.

    PubMed

    Yu, Qiang; Cao, Chuanbao

    2012-05-01

    The splitting of water using photoelectrochemical (PEC) cells to produce hydrogen is one of the most sustainable forms of energy production and more and more 1-D nanostructrues semiconductors used as photoelectrodes have been studied extensively. However, it is not clear whether the photoconversion efficiencies of such nanostructure devices are limited by the architectures of the 1-D electrodes. Here, we explore the effect of the architecture like the length and width of ZnO nanorods on the PEC cells performance for the first time. The as-prepared nanorods have diameters of 40-50 nm and lengths of 400-800 nm. Preliminary measurements exhibit that the resulting electrodes have promising PEC properties. Mott-Schottky measurements give a flat-band potential of +0.10 V, a carrier density of 3.7 x 10(17) cm(-3), and a space-charge layer of 26 nm. The photocurrent of 800 nm-long nanorods shows 10 times higher than that of 400 nm-long ones, and an encouraging maximum photoconversion efficiency of 0.25% is obtained under illumination of 100 mW/cm2 (AM 1.5), which is among the highest reported for an undoped ZnO photoelectrode to date.

  13. Semiconducting properties of Al doped ZnO thin films.

    PubMed

    Al-Ghamdi, Ahmed A; Al-Hartomy, Omar A; El Okr, M; Nawar, A M; El-Gazzar, S; El-Tantawy, Farid; Yakuphanoglu, F

    2014-10-15

    Aluminum doped ZnO (AZO) thin films were successfully deposited via spin coating technique onto glass substrates. Structural properties of the films were analyzed by X-ray diffraction, atomic force microscopy (AFM) and energy dispersive X-ray spectroscopy. X-ray diffraction results reveal that all the films are polycrystalline with a hexagonal wurtzite structure with a preferential orientation according to the direction (002) plane. The crystallite size of ZnO and AZO films was determined from Scherrer's formula and Williamson-Hall analysis. The lattice parameters of the AZO films were found to decrease with increasing Al content. Energy dispersive spectroscopy (EDX) results indicate that Zn, Al and O elements are present in the AZO thin films. The electrical conductivity, mobility carriers and carrier concentration of the films are increased with increasing Al doping concentration. The optical band gap (Eg) of the films is increased with increasing Al concentration. The AZO thin films indicate a high transparency in the visible region with an average value of 86%. These transparent AZO films may be open a new avenue for optoelectronic and photonic devices applications in near future. PMID:24840493

  14. Nanoparticle Self-Assembled Grain Like Curcumin Conjugated ZnO: Curcumin Conjugation Enhances Removal of Perylene, Fluoranthene, and Chrysene by ZnO.

    PubMed

    Moussawi, Rasha N; Patra, Digambara

    2016-04-15

    Curcumin conjugated ZnO, referred as Zn(cur)O, nanostructures have been successfully synthesized, these sub-micro grain-like structures are actually self-assemblies of individual needle-shaped nanoparticles. The nanostructures as synthesized possess the wurtzite hexagonal crystal structure of ZnO and exhibit very good crystalline quality. FT-Raman and TGA analysis establish that Zn(cur)O is different from curcumin anchored ZnO (ZnO@cur), which is prepared by physically adsorbing curcumin on ZnO surfaces. Chemically Zn(cur)O is more stable than ZnO@cur. Diffuse reflectance spectroscopy indicates Zn(cur)O have more impurities compared to ZnO@cur. The solid-state photoluminescence of Zn(cur)O has been investigated, which demonstrates that increase of curcumin concentration in Zn(cur)O suppresses visible emission of ZnO prepared through the same method, this implies filling ZnO defects by curcumin. However, at excitation wavelength 425 nm the emission is dominated by fluorescence from curcumin. The study reveals that Zn(cur)O can remove to a far extent high concentrations of perylene, fluoranthene, and chrysene faster than ZnO. The removal depends on the extent of curcumin conjugation and is found to be faster for PAHs having smaller number of aromatic rings, particularly, it is exceptional for fluoranthene with 93% removal after 10 minutes in the present conditions. The high rate of removal is related to photo-degradation and a mechanism has been proposed.

  15. Nanoparticle Self-Assembled Grain Like Curcumin Conjugated ZnO: Curcumin Conjugation Enhances Removal of Perylene, Fluoranthene, and Chrysene by ZnO

    NASA Astrophysics Data System (ADS)

    Moussawi, Rasha N.; Patra, Digambara

    2016-04-01

    Curcumin conjugated ZnO, referred as Zn(cur)O, nanostructures have been successfully synthesized, these sub-micro grain-like structures are actually self-assemblies of individual needle-shaped nanoparticles. The nanostructures as synthesized possess the wurtzite hexagonal crystal structure of ZnO and exhibit very good crystalline quality. FT-Raman and TGA analysis establish that Zn(cur)O is different from curcumin anchored ZnO (ZnO@cur), which is prepared by physically adsorbing curcumin on ZnO surfaces. Chemically Zn(cur)O is more stable than ZnO@cur. Diffuse reflectance spectroscopy indicates Zn(cur)O have more impurities compared to ZnO@cur. The solid-state photoluminescence of Zn(cur)O has been investigated, which demonstrates that increase of curcumin concentration in Zn(cur)O suppresses visible emission of ZnO prepared through the same method, this implies filling ZnO defects by curcumin. However, at excitation wavelength 425 nm the emission is dominated by fluorescence from curcumin. The study reveals that Zn(cur)O can remove to a far extent high concentrations of perylene, fluoranthene, and chrysene faster than ZnO. The removal depends on the extent of curcumin conjugation and is found to be faster for PAHs having smaller number of aromatic rings, particularly, it is exceptional for fluoranthene with 93% removal after 10 minutes in the present conditions. The high rate of removal is related to photo-degradation and a mechanism has been proposed.

  16. Nanoparticle Self-Assembled Grain Like Curcumin Conjugated ZnO: Curcumin Conjugation Enhances Removal of Perylene, Fluoranthene, and Chrysene by ZnO

    PubMed Central

    Moussawi, Rasha N.; Patra, Digambara

    2016-01-01

    Curcumin conjugated ZnO, referred as Zn(cur)O, nanostructures have been successfully synthesized, these sub-micro grain-like structures are actually self-assemblies of individual needle-shaped nanoparticles. The nanostructures as synthesized possess the wurtzite hexagonal crystal structure of ZnO and exhibit very good crystalline quality. FT-Raman and TGA analysis establish that Zn(cur)O is different from curcumin anchored ZnO (ZnO@cur), which is prepared by physically adsorbing curcumin on ZnO surfaces. Chemically Zn(cur)O is more stable than ZnO@cur. Diffuse reflectance spectroscopy indicates Zn(cur)O have more impurities compared to ZnO@cur. The solid-state photoluminescence of Zn(cur)O has been investigated, which demonstrates that increase of curcumin concentration in Zn(cur)O suppresses visible emission of ZnO prepared through the same method, this implies filling ZnO defects by curcumin. However, at excitation wavelength 425 nm the emission is dominated by fluorescence from curcumin. The study reveals that Zn(cur)O can remove to a far extent high concentrations of perylene, fluoranthene, and chrysene faster than ZnO. The removal depends on the extent of curcumin conjugation and is found to be faster for PAHs having smaller number of aromatic rings, particularly, it is exceptional for fluoranthene with 93% removal after 10 minutes in the present conditions. The high rate of removal is related to photo-degradation and a mechanism has been proposed. PMID:27080002

  17. Nanoparticle Self-Assembled Grain Like Curcumin Conjugated ZnO: Curcumin Conjugation Enhances Removal of Perylene, Fluoranthene, and Chrysene by ZnO.

    PubMed

    Moussawi, Rasha N; Patra, Digambara

    2016-01-01

    Curcumin conjugated ZnO, referred as Zn(cur)O, nanostructures have been successfully synthesized, these sub-micro grain-like structures are actually self-assemblies of individual needle-shaped nanoparticles. The nanostructures as synthesized possess the wurtzite hexagonal crystal structure of ZnO and exhibit very good crystalline quality. FT-Raman and TGA analysis establish that Zn(cur)O is different from curcumin anchored ZnO (ZnO@cur), which is prepared by physically adsorbing curcumin on ZnO surfaces. Chemically Zn(cur)O is more stable than ZnO@cur. Diffuse reflectance spectroscopy indicates Zn(cur)O have more impurities compared to ZnO@cur. The solid-state photoluminescence of Zn(cur)O has been investigated, which demonstrates that increase of curcumin concentration in Zn(cur)O suppresses visible emission of ZnO prepared through the same method, this implies filling ZnO defects by curcumin. However, at excitation wavelength 425 nm the emission is dominated by fluorescence from curcumin. The study reveals that Zn(cur)O can remove to a far extent high concentrations of perylene, fluoranthene, and chrysene faster than ZnO. The removal depends on the extent of curcumin conjugation and is found to be faster for PAHs having smaller number of aromatic rings, particularly, it is exceptional for fluoranthene with 93% removal after 10 minutes in the present conditions. The high rate of removal is related to photo-degradation and a mechanism has been proposed. PMID:27080002

  18. Heavy ion therapy: Bevalac epoch

    SciTech Connect

    Castro, J.R.

    1993-10-01

    An overview of heavy ion therapy at the Bevelac complex (SuperHILac linear accelerator + Bevatron) is given. Treatment planning, clinical results with helium ions on the skull base and uveal melanoma, clinical results with high-LET charged particles, neon radiotherapy of prostate cancer, heavy charged particle irradiation for unfavorable soft tissue sarcoma, preliminary results in heavy charged particle irradiation of bone sarcoma, and irradiation of bile duct carcinoma with charged particles and-or photons are all covered. (GHH)

  19. Heavy quark production and spectroscopy

    SciTech Connect

    Appel, J.A.

    1993-11-01

    This review covers many new experimental results on heavy flavor production and spectroscopy. It also shows some of the increasingly improved theoretical understanding of results in light of basic perturbative QCD and heavy quark symmetry. At the same time, there are some remaining discrepancies among experiments as well as significant missing information on some of the anticipated lowest lying heavy quark states. Most interesting, perhaps, are some clearly measured production effects awaiting full explanation.

  20. Optical and morphological properties of graphene sheets decorated with ZnO nanowires via polyol enhancement

    SciTech Connect

    Sharma, Vinay Rajaura, Rajveer Singh; Sharma, Preetam K.; Srivastava, Subodh; Vijay, Y. K.; Sharma, S. S.

    2014-04-24

    Graphene-ZnO nanocomposites have proven to be very useful materials for photovoltaic and sensor applications. Here, we report a facile, one-step in situ polymerization method for synthesis of graphene sheets randomly decorated with zinc oxide nanowires using ethylene glycol as solvent. We have used hydrothermal treatment for growth of ZnO nanowires. UV-visible spectra peak shifting around 288nm and 307 nm shows the presence of ZnO on graphene structure. Photoluminiscence spectra (PL) in 400nm-500nm region exhibits the luminescence quenching effect. Scanning electron microscopy (SEM) image confirms the growth of ZnO nanowires on graphene sheets.