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Sample records for co-doped zno powders

  1. Enhanced dielectric constant of Co-doped ZnO nanoparticulate powders

    Science.gov (United States)

    Franco, A.; Pessoni, H. V. S.

    2015-11-01

    In this work we studied the optical band-gap and dielectric properties of nanoparticulate powders of Co-doped ZnO with x=0.0, 0.5, 1.0, 3.0, 5, 7 and 9.0 at %Co synthesized by the combustion reaction method. X-ray diffraction patterns (XRD) of each sample showed broad peaks consistent with the ZnO wurtzite structure. The absence of extra reflections in the diffraction patterns ensures the phase purity. The average crystallite size determined from the most prominent (101) peak of the diffraction using Scherrer's equation was in good agreement with those determined by transmission electron microscopy (TEM), being ∼16 nm for undoped-ZnO sample and ∼21 nm for all Co-doped samples. Diffuse reflectance spectrum of each sample was obtained by using a UV/VIS/Near spectrometer and the optical band-gap Eg decreased with Co doping amount. The dielectric constant ε was determined using the Brus model (L.E. Brus, J. Chem. Phys. 80 (1984) 4403 [38]) increased with Co doping amount, reaching the maximum value of ∼10 for x=1.0 at %Co. These results were discussed in terms of the defects such as oxygen vacancies VO¨ or/and interstitial oxygen Oι¨ ″ present in Co-doped ZnO nanoparticles, which may be introduced during sample preparation.

  2. Photoluminescence properties of Co-doped ZnO nanocrystals

    DEFF Research Database (Denmark)

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

    2006-01-01

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

  3. Cr-N co-doped ZnO nanoparticles: synthesis, characterization and ...

    African Journals Online (AJOL)

    Modified photocatalysts were synthesized by the incipient wetness impregnation method (chromium-doped ZnO) and by solid state reactions using ZnO and urea as precursors (nitrogen-doped ZnO). Chromium-nitrogen co-doped ZnO nanomaterials were prepared from the already prepared N-doped ZnO nanomaterials via ...

  4. Influence of Co doping on combined photocatalytic and antibacterial activity of ZnO nanoparticles

    Science.gov (United States)

    Anandan, M.; Dinesh, S.; Krishnakumar, N.; Balamurugan, K.

    2016-11-01

    The present work aims to investigate the structural, optical, photocatalyst and antibacterial properties of bare and cobalt doped ZnO nanoparticles (NPs) with different concentrations Zn1-x Co x O (x = 0, 0.03, 0.06 and 0.09) synthesized by co-precipitation method. The XRD patterns confirmed that all samples of cobalt doped ZnO nanostructures revealed the formation of single phase having hexagonal wurtzite structure with crystallite size in the range of 31-41 nm. Further, the decreasing trend in lattice parameters and grain sizes were also seen with increasing doping concentrations which confirms the incorporation of Co ions into the ZnO lattice. This result was further supported by the FT-IR data. HR-TEM images demonstrated the distinct hexagonal like morphology with small agglomeration. The UV-visible absorption spectra exhibits red shift with increase in Co doping concentration in ZnO while corresponding bandgap energy of cobalt doped ZnO NPs decreased with increased Co doping concentration. PL spectra showed a weak UV and visible emission band which may be ascribed to the reduction in oxygen vacancy and defects by cobalt doping. XPS and EDX spectral results confirm the composition and the purity of Co doped ZnO NPs. Furthermore, the Co doped ZnO NPs were found to exhibit lesser photocatalytic activity for the degradation of methyl green dye under UV light illumination in comparison with the bare ZnO NPs. Moreover, anti-bacterial studies reveals that the Co doped ZnO NPs possess more antibacterial effect against gram positive Basillus subtills and gram negative Klebsiella pneumoniae bacterial strains than the bare ZnO NPs.

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

    Science.gov (United States)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Romeiro, Fernanda C.; Marinho, Juliane Z.; Lemos, Samantha C.S. [Instituto de Química, Universidade Federal de Uberlândia, 38400-902 Uberlândia, MG (Brazil); Moura, Ana P. de [LIEC, Instituto de Química, Universidade Estadual Paulista, 14800-900 Araraquara, SP (Brazil); Freire, Poliana G. [Instituto de Química, Universidade Federal de Uberlândia, 38400-902 Uberlândia, MG (Brazil); Silva, Luis F. da; Longo, Elson [LIEC, Instituto de Química, Universidade Estadual Paulista, 14800-900 Araraquara, SP (Brazil); Munoz, Rodrigo A.A. [Instituto de Química, Universidade Federal de Uberlândia, 38400-902 Uberlândia, MG (Brazil); Lima, Renata C., E-mail: rclima@iqufu.ufu.br [Instituto de Química, Universidade Federal de Uberlândia, 38400-902 Uberlândia, MG (Brazil)

    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.

  7. Structural, chemical and magnetic properties of secondary phases in Co-doped ZnO

    DEFF Research Database (Denmark)

    Ney, A; Kovács, András; Ney, V

    2011-01-01

    , chemical and magnetic properties of Co-doped ZnO samples. It can be established on a quantitative basis that the superparamagnetic (SPM) behavior observed by integral superconducting quantum interference device magnetometry is not an intrinsic property of the material but stems from precipitations...

  8. Cr-N CO-DOPED ZnO NANOPARTICLES: SYNTHESIS ...

    African Journals Online (AJOL)

    BCSE

    nanoparticles were synthesized by direct precipitation method via the reaction between zinc nitrate [Zn(NO3)2 .6H2O] and ... Thymol blue. (TB) is used in the textile, leather goods, industrial paints, food, plastics, cosmetics, and ... reported on the effect of ZnO nanoparticles modified with Cr and N co-doping for degradation.

  9. An effective low-temperature solution synthesis of Co-doped [0001]-oriented ZnO nanorods

    OpenAIRE

    Alnoor, Hatim; Savoyant, Adrien; Liu, Xianjie; Pozina, Galia; Willander, Magnus; Nur, Omer

    2017-01-01

    We demonstrate an efficient possibility to synthesize vertically aligned pure zinc oxide (ZnO) and Co-doped ZnO nanorods (NRs) using the low-temperature aqueous chemical synthesis (90 degrees C). Two different mixing methods of the synthesis solutions were investigated for the Co-doped samples. The synthesized samples were compared to pure ZnO NRs regarding the Co incorporation and crystal quality. Electron paramagnetic resonance (EPR) measurements confirmed the substitution of Co2+ inside th...

  10. Analysis of oxygen vacancy in Co-doped ZnO using the electron density distribution obtained using MEM

    National Research Council Canada - National Science Library

    Park, Ji Hun; Lee, Yeong Ju; Bae, Jong-Seong; Kim, Bum-Su; Cho, Yong Chan; Moriyoshi, Chikako; Kuroiwa, Yoshihiro; Lee, Seunghun; Jeong, Se-Young

    2015-01-01

    ...) to study changes in the VO concentration as a function of the Co-doping level of ZnO. Rietveld refinement yielded a different result from that determined via X-ray photoelectron spectroscopy (XPS...

  11. Magnetic Studies of Co-Doped ZnO Nanoparticles

    Science.gov (United States)

    Bandyopadhyay, S. K.; Singh, N. Surajkumar; Himanshu, A. K.; Chakraborty, Keka R.; Das, D.; Mukhopadhyay, P. K.; Mondal, Nagendra

    2011-07-01

    ZnO doped with Co has been synthesised at various concentrations from 1 to 20 atom % in bulk polycrystalline form by wet chemical method. Particle size was ranging from 40-50 nm. There was a signature of ferromagnetism at 7 atom % and higher with S-type curves in M-H plots. Remanent magnetization was quite appreciable. But, there is anomaly with decrease in moment at higher atomic concentrations. No sign of superparamagnetism due to nanoparticles was there. Magnetism is thought to be due to interaction between nearest neighbor Co(II) ions along with clusters of Co(II) in isolation, which may be due to precipitation.

  12. Fabrication of ZnO Bi-crystals with twist boundaries using Co doped ZnO single crystals

    CERN Document Server

    Ohashi, N; Ohgaki, T; Tsurumi, T; Fukunaga, O; Haneda, H; Tanaka, J

    1999-01-01

    Zn O single crystals doped with Co were grown by using a flux method and their electrical properties were investigated by Hall effect. Then, these crystals were polished with diamond paste and bonded to form bi-crystal by hot pressing under a pressure of 10 MPa at 1000 .deg. C. The bi-crystals showed nonlinear I-V curves, and the curvature of I-V relation agreed with that for Co-doped polycrystalline ZnO.

  13. Enhanced photoconductivity of ZnO films Co-doped with nitrogen and tellurium

    Science.gov (United States)

    Porter, H. L.; Cai, A. L.; Muth, J. F.; Narayan, J.

    2005-05-01

    Zinc oxide films are typically found to be n type, and conductive under most growth conditions and growth methods. Co-doping with multiple elements is one strategy for improving the electrical and optical properties of zinc oxide materials for optoelectronic device applications. Using pulsed-laser deposition, thin ZnO films were grown on c-axis oriented sapphire. The films were co-doped with nitrogen and tellurium. Depending on the relative concentrations of the dopants, the resistivity of the films was observed to increase by several orders of magnitude, significantly improving the photoconductive response. The enhancement of the photosensitivity reached a maximum at a tellurium concentration of around 1020cm-3.

  14. Cr-N co-doped ZnO nanoparticles: synthesis, characterization and photocatalytic activity for degradation of thymol blue

    Directory of Open Access Journals (Sweden)

    A. Nibret

    2015-07-01

    Full Text Available Here we report the synthesis of CrN co-doped ZnO for the first time. Zinc oxide (ZnO nanoparticles were synthesized by direct precipitation method via the reaction between zinc nitrate [Zn(NO32 .6H2O] and ammonium carbonate [(NH42CO3] in aqueous solutions with proper concentration. Modified photocatalysts were synthesized by the incipient wetness impregnation method (chromium-doped ZnO and by solid state reactions using ZnO and urea as precursors (nitrogen-doped ZnO. Chromium-nitrogen co-doped ZnO nanomaterials were prepared from the already prepared N-doped ZnO nanomaterials via one step impregnation method. The as-synthesized photocatalysts were investigated by XRD, BET, SEM-EDX, FTIR, and UV–Vis techniques. Photocatalytic degradation of thymol blue using as-synthesized photocatalysts was studied under visible as well as UV irradiations. Highest photocatalytic degradation efficiency of chromium-nitrogen co-doped zinc oxide could be attributed to the lower rate of recombination of the photo-generated electrons and holes as well as to its lower band gap energy as the result of the co-doping. Photocatalytic degradation is found to follow pseudo first order kinetics.

  15. Role of cobalt in room-temperature ferromagnetic Co-doped ZnO thin films

    Directory of Open Access Journals (Sweden)

    C. C. Wang

    2012-03-01

    Full Text Available A series of Co-doped ZnO thin films were prepared under various deposition conditions using the pulsed laser deposition method. X-ray photoelectron spectroscopy (XPS and XPS depth profiling were used to detect the elemental valence states of Zn, Co and O. It was found that the films deposited under low temperature and high oxygen pressure exhibited intrinsic ferromagnetic properties due to oxidation of Co (Co2+ from the material. However, when the films were deposited under high temperature and low oxygen pressure, metallic cobalt (Co0 appeared and the ferromagnetism was greatly enhanced.

  16. Color tunable ZnO nanorods by Eu and Tb co-doping for optoelectronic applications

    Science.gov (United States)

    Pal, Partha P.; Manam, J.

    2014-07-01

    Eu/Tb co-doped ZnO nanorods were prepared by co-precipitation method and the effect of Eu-Tb co-doping was studied by X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy, Fourier transform infrared spectroscopy (FTIR), UV-Vis-NIR diffuse reflectance (DR) and photoluminescence (PL) spectroscopy. The XRD pattern shows typical peak pattern for pure hexagonal wurtzite structure to match with the JCPDS data. The samples are found to be consisting of nanorods of diameter 20-30 nm as revealed by the TEM image. The FTIR pattern confirms the formation of the compounds. The DR study was carried to show the variation of absorption edge and the variation in band gap values, which showed the crystal size effect in the co-doped sample of different rare-earth ratios. The room temperature PL study shows bright emission spectra for the samples with different rare-earth ratios. It shows a very good energy transfer from Tb to Eu ions. The energy transfer mechanism and color tunability were discussed thoroughly.

  17. Structural, optical and magnetic properties of pulsed laser deposited Co-doped ZnO films

    Energy Technology Data Exchange (ETDEWEB)

    Karzazi, O., E-mail: ouiame_karzazi@hotmail.fr [Centre of Physics, University of Minho, Campus de Gualtar, 4710-057 Braga (Portugal); LPS, Physics Department, Faculty of Sciences, BP 1796, Fes (Morocco); Sekhar, K.C. [Centre of Physics, University of Minho, Campus de Gualtar, 4710-057 Braga (Portugal); El Amiri, A. [LPTA, Université Hassan II-Casablanca, Faculté des Sciences, B.P. 5366, Maârif (Morocco); Hlil, E.K. [Institut Néel, CNRS, Université J. Fourier, BP 166, 38042 Grenoble (France); Conde, O. [Departamento de Física, Faculdade de Ciências, Universidade de Lisboa and CeFEMA, Campo Grande, 1749-016 Lisboa (Portugal); Levichev, S. [Research Institute for Chemistry, Nizhni Novgorod State University, 603950 Nizhni Novgorod (Russian Federation); Agostinho Moreira, J. [IFIMUP and IN-Institute of Nanoscience and Nanotechnology, Departamento de Física e Astronomia, Faculdade de Ciências da Universidade do Porto, Rua do Campo Alegre 687, 4169-007, Porto (Portugal); Chahboun, A. [Centre of Physics, University of Minho, Campus de Gualtar, 4710-057 Braga (Portugal); FST Tanger, Physics Department, BP 416, Tangier (Morocco); Almeida, A. [IFIMUP and IN-Institute of Nanoscience and Nanotechnology, Departamento de Física e Astronomia, Faculdade de Ciências da Universidade do Porto, Rua do Campo Alegre 687, 4169-007, Porto (Portugal); Gomes, M.J.M. [Centre of Physics, University of Minho, Campus de Gualtar, 4710-057 Braga (Portugal)

    2015-12-01

    Zn{sub 1−x}Co{sub x}O films with different Co concentrations (with x=0.00, 0.10, 0.15, and 0.30) were grown by pulsed laser deposition (PLD) technique. The structural and optical properties of the films were investigated by grazing incidence X-ray diffraction (GIXRD), Raman spectroscopy and photoluminescence (PL). The magnetic properties were measured by conventional magnetometry using a SQUID and simulated by ab-initio calculations using Korring–Khon–Rostoker (KKR) method combined with coherent potential approximation (CPA). The effect of Co-doping on the GIXRD and Raman peaks positions, shape and intensity is discussed. PL studies demonstrate that Co-doping induces a decrease of the bandgap energy and quenching of the UV emission. They also suggest the presence of Zn interstitials when x≥0.15. The 10% Co-doped ZnO film shows ferromagnetism at 390 K with a spontaneous magnetic moment ≈4×10{sup −5} emu and coercive field ≈0.17 kOe. The origin of ferromagnetism is explained based on the calculations using KKR method. - Highlights: • Zn{sub 1−x}Co{sub x}O films (x=0.00, 0.10, 0.15, and 0.30) were grown by (PLD) technique. • Zn{sub 0.9}Co{sub 0.1}O film shows ferromagnetism above room temperature. • The origin of ferromagnetism behavior is attributed to the p-d hybridization. • Co-doping induces a decrease of the bandgap energy of the films.

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

    Science.gov (United States)

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

    2012-10-24

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

  19. Effect of Co doping on the structural and dielectric properties of ZnO nanoparticles

    Science.gov (United States)

    Ram, Mast; Bala, Kanchan; Sharma, Hakikat; Negi, N. S.

    2016-05-01

    This paper reports on the synthesis of Co doped Zn1-xCoxO (x= 0.0, 0.01, 0.02, 0.03 and 0.05) nanoparticles by solution combustion method using urea as a fuel. The Structural and dielectric properties of the samples were studied. Crystallite sizes were obtained from X-ray diffraction (XRD) patterns whose values decreased with increase in Co concentration. The XRD study reveals that Co2+ ions substitute the Zn2+ ion without changing the wurtzite structure of pristine ZnO up to Co concentrations of 5%. The dielectric constants, dielectric loss (tanδ) and ac conductivity (σac) were studied as the function of frequency and composition, which have been explained by Maxwell-Wagner type interfacial polarization and discussed Koops phenomenological theory.

  20. Effect of Co doping on the structural and dielectric properties of ZnO nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Ram, Mast, E-mail: Mastram1999@yahoo.com; Bala, Kanchan; Sharma, Hakikat; Negi, N. S. [Himachal Pradesh University Summehill Shimla (India)

    2016-05-23

    This paper reports on the synthesis of Co doped Zn{sub 1-x}Co{sub x}O (x= 0.0, 0.01, 0.02, 0.03 and 0.05) nanoparticles by solution combustion method using urea as a fuel. The Structural and dielectric properties of the samples were studied. Crystallite sizes were obtained from X-ray diffraction (XRD) patterns whose values decreased with increase in Co concentration. The XRD study reveals that Co{sup 2+} ions substitute the Zn{sup 2+} ion without changing the wurtzite structure of pristine ZnO up to Co concentrations of 5%. The dielectric constants, dielectric loss (tanδ) and ac conductivity (σ{sub ac}) were studied as the function of frequency and composition, which have been explained by Maxwell-Wagner type interfacial polarization and discussed Koops phenomenological theory.

  1. Local fields in Co and Mn Co-doped ZnO

    Energy Technology Data Exchange (ETDEWEB)

    Sato, W., E-mail: wsato@se.kanazawa-u.ac.jp [Kanazawa University, Institute of Science and Engineering (Japan); Kano, Y.; Suzuki, T.; Nakagawa, M. [Kanazawa University, Graduate School of Natural Science and Technology (Japan); Kobayashi, Y. [The University of Electro-Communications, Department of Engineering Science (Japan)

    2016-12-15

    The magnetic properties of ZnO co-doped with 5 at. % Co and 5 at. % Mn(Zn{sub 0.90}Co{sub 0.05}Mn{sub 0.05}O) synthesized by a solid-state reaction were investigated by means of {sup 57}Co emission Mössbauer spectroscopy. The majority of the probe ions (80 %) residing in defect-free substitutional Zn sites take the oxidation state of {sup 57}Fe {sup 2+}, and the others presumably form local defects taking the state of {sup 57}Fe {sup 3+} at room temperature. Both components show doublets, and RT ferromagnetism was thus absent in the sample. For the measurement at 10 K, spectral broadening was observed, implying a possible presence of a weak magnetic component.

  2. Analysis of oxygen vacancy in Co-doped ZnO using the electron density distribution obtained using MEM

    Science.gov (United States)

    Park, Ji Hun; Lee, Yeong Ju; Bae, Jong-Seong; Kim, Bum-Su; Cho, Yong Chan; Moriyoshi, Chikako; Kuroiwa, Yoshihiro; Lee, Seunghun; Jeong, Se-Young

    2015-04-01

    Oxygen vacancy (VO) strongly affects the properties of oxides. In this study, we used X-ray diffraction (XRD) to study changes in the VO concentration as a function of the Co-doping level of ZnO. Rietveld refinement yielded a different result from that determined via X-ray photoelectron spectroscopy (XPS), but additional maximum entropy method (MEM) analysis led it to compensate for the difference. VO tended to gradually decrease with increased Co doping, and ferromagnetic behavior was not observed regardless of the Co-doping concentration. MEM analysis demonstrated that reliable information related to the defects in the ZnO-based system can be obtained using X-ray diffraction alone.

  3. Influences of Co doping on the structural and optical properties of ZnO nanostructured

    Science.gov (United States)

    Majeed Khan, M. A.; Wasi Khan, M.; Alhoshan, Mansour; Alsalhi, M. S.; Aldwayyan, A. S.

    2010-07-01

    Pure and Co-doped ZnO nanostructured samples have been synthesized by a chemical route. We have studied the structural and optical properties of the samples by using X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), field-emission transmission electron microscope (FETEM), energy-dispersive X-ray (EDX) analysis and UV-VIS spectroscopy. The XRD patterns show that all the samples are hexagonal wurtzite structures. Changes in crystallite size due to mechanical activation were also determined from X-ray measurements. These results were correlated with changes in particle size followed by SEM and TEM. The average crystallite sizes obtained from XRD were between 20 to 25 nm. The TEM images showed the average particle size of undoped ZnO nanostructure was about 20 nm whereas the smallest average grain size at 3% Co was about 15 nm. Optical parameters such as absorption coefficient ( α), energy band gap ( E g ), the refractive index ( n), and dielectric constants ( σ) have been determined using different methods.

  4. Influences of Co doping on the structural and optical properties of ZnO nanostructured

    Energy Technology Data Exchange (ETDEWEB)

    Majeed Khan, M.A.; Wasi Khan, M. [King Saud University, King Abdullah Institute for Nanotechnology, Riyadh (Saudi Arabia); Alhoshan, Mansour [King Saud University, King Abdullah Institute for Nanotechnology, Riyadh (Saudi Arabia); King Saud University, Chemical Engineering Department, Riyadh (Saudi Arabia); AlSalhi, M.S.; Aldwayyan, A.S. [King Saud University, King Abdullah Institute for Nanotechnology, Riyadh (Saudi Arabia); King Saud University, Department of Physics and Astronomy, Riyadh (Saudi Arabia)

    2010-07-15

    Pure and Co-doped ZnO nanostructured samples have been synthesized by a chemical route. We have studied the structural and optical properties of the samples by using X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), field-emission transmission electron microscope (FETEM), energy-dispersive X-ray (EDX) analysis and UV-VIS spectroscopy. The XRD patterns show that all the samples are hexagonal wurtzite structures. Changes in crystallite size due to mechanical activation were also determined from X-ray measurements. These results were correlated with changes in particle size followed by SEM and TEM. The average crystallite sizes obtained from XRD were between 20 to 25 nm. The TEM images showed the average particle size of undoped ZnO nanostructure was about 20 nm whereas the smallest average grain size at 3% Co was about 15 nm. Optical parameters such as absorption coefficient ({alpha}), energy band gap (E{sub g}), the refractive index (n), and dielectric constants ({sigma}) have been determined using different methods. (orig.)

  5. Local structure analysis of diluted magnetic semiconductor Co and Al co-doped ZnO nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Hyodo, K.; Morimoto, S.; Yamazaki, T.; Ishikawa, T.; Ichiyanagi, Y. [Department of Physics, Graduate School of Engineering, Yokohama National University, 79-5 Tokiwadai, Hodogaya, Yokohama, Kanagawa 240-8501 (Japan); Utsumi, J. [Engineering Department Machine Tool Division, Machinery, Equipment & Infrastructure, Mitsubishi Heavy Industries, Ltd., Ritto, Shiga 520-3080 (Japan)

    2016-02-01

    In this study, Co and Al ions co-doped ZnO nanoparticles (Zn(Al, Co)O NPs) were prepared by our original chemical preparation method. The obtained samples prepared by this method, were encapsulated in amorphous SiO{sub 2}. X-ray diffraction (XRD) results showed Zn(Al, Co)O NPs had a single-phase nature with hexagonal wurtzite structure. These particle sizes could be controlled to be approximately 30 nm. We investigate the effect that the increase in the carrier has on the magnetization by doping Al to Co-doped ZnO NPs. The local structures were qualitatively analyzed using X-ray absorption fine structure (XAFS) measurements.

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

    Energy Technology Data Exchange (ETDEWEB)

    Serrao, Felcy Jyothi, E-mail: jyothiserrao@gmail.com [Department of studies in Physics, Mangalore University, Mangalagangothri 574199 (India); Department of Physics, Karnataka Government Research centre SCEM, Mangalore, 575007 (India); Sandeep, K. M.; Bhat, Shreesha; Dharmaprakash, S. M. [Department of studies in Physics, Mangalore University, Mangalagangothri 574199 (India)

    2016-05-23

    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{sup −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.

  7. Ferromagnetism and Conductivity in Hydrogen Irradiated Co-Doped ZnO Thin Films.

    Science.gov (United States)

    Di Trolio, A; Alippi, P; Bauer, E M; Ciatto, G; Chu, M H; Varvaro, G; Polimeni, A; Capizzi, M; Valentini, M; Bobba, F; Di Giorgio, C; Amore Bonapasta, A

    2016-05-25

    Impressive changes in the transport and ferromagnetic properties of Co-doped ZnO thin films have been obtained by postgrowth hydrogen irradiation at temperatures of 400 °C. Hydrogen incorporation increases the saturation magnetization by one order of magnitude (up to ∼1.50 μB/Co) and increases the carrier density and mobility by about a factor of two. In addition to the magnetic characterization, the transport and structural properties of hydrogenated ZnO:Co have been investigated by Hall effect, local probe conductivity measurements, micro-Raman, and X-ray absorption spectroscopy. Particular care has been given to the detection of Co oxides and metal Co nanophases, whose influence on the increase in the transport and ferromagnetic properties can be excluded on the ground of the achieved results. The enhancement in ferromagnetism is directly related to the dose of H introduced in the samples. On the contrary, despite the shallow donor character of H atoms, the increase in carrier density n is not related to the H dose. These apparently contradictory effects of H are fully accounted for by a mechanism based on a theoretical model involving Co-VO (Co-O vacancy) pairs.

  8. (Er, Yb)-co-doped multifunctional ZnO transparent hybrid materials: fabrication, luminescent and magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Yang Lixin; Liu Peng; Liu Fangmin; Ge Shuibing [Department of Physics, Soochow University, Suzhou 215006 (China); Wang Xuefeng; Liu Bin; Shi Yi; Zhang Rong [Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, School of Electronic Science and Engineering, Nanjing University, Nanjing 210093 (China); Li Zhaoguo; Song Fengqi, E-mail: xfwang@nju.edu.cn [Nanjing National Laboratory of Microstructures, Nanjing University, Nanjing 210093 (China)

    2011-04-20

    We report the successful fabrication of (Er{sup 3+}, Yb{sup 3+})-co-doped ZnO transparent hybrid materials by controlling compositions and crystallization. The singly precipitated ZnO nanocrystals were preferentially oriented along the c-axis on the glass surface, leading to an intense luminescence at the bandgap energy of ZnO. The Er{sup 3+} and Yb{sup 3+} ions assembled around the low-phonon-energy ZnO nanocrystals, achieving an enhanced two-photon upconversion emission in the visible region. In addition, the glass ceramic exhibited typical paramagnetism with antiferromagnetic interactions. The multifunctional combination in such a low-cost, easily shapable and environmentally friendly bulk material may find a wide range of device applications.

  9. An effective low-temperature solution synthesis of Co-doped [0001]-oriented ZnO nanorods

    Science.gov (United States)

    Alnoor, Hatim; Savoyant, Adrien; Liu, Xianjie; Pozina, Galia; Willander, Magnus; Nur, Omer

    2017-06-01

    We demonstrate an efficient possibility to synthesize vertically aligned pure zinc oxide (ZnO) and Co-doped ZnO nanorods (NRs) using the low-temperature aqueous chemical synthesis (90 °C). Two different mixing methods of the synthesis solutions were investigated for the Co-doped samples. The synthesized samples were compared to pure ZnO NRs regarding the Co incorporation and crystal quality. Electron paramagnetic resonance (EPR) measurements confirmed the substitution of Co2+ inside the ZnO NRs, giving a highly anisotropic magnetic Co2+ signal. The substitution of Zn2+ by Co2+ was observed to be combined with a drastic reduction in the core-defect (CD) signal (g ˜ 1.956) which is seen in pure ZnO NRs. As revealed by the cathodoluminescence (CL), the incorporation of Co causes a slight red-shift of the UV peak position combined with an enhancement in the intensity of the defect-related yellow-orange emission compared to pure ZnO NRs. Furthermore, the EPR and the CL measurements allow a possible model of the defect configuration in the samples. It is proposed that the as-synthesized pure ZnO NRs likely contain Zn interstitial (Zni+) as CDs and oxygen vacancy (VO) or oxygen interstitial (Oi) as surface defects. As a result, Co was found to likely occupy the Zni+, leading to the observed CDs reduction and hence enhancing the crystal quality. These results open the possibility of synthesis of highly crystalline quality ZnO NRs-based diluted magnetic semiconductors using the low-temperature aqueous chemical method.

  10. Efficient photocatalytic performance enhancement in Co-doped ZnO nanowires coupled with CuS nanoparticles

    Science.gov (United States)

    Li, Wei; Wang, Guojing; Feng, Yimeng; Li, Zhengcao

    2018-01-01

    In this research, a kind of highly efficient semiconductor photocatalyst was fabricated by depositing CuS nanoparticles uniformly on the surface of Co-doped ZnO nanowires. ZnO nanowires were synthesized by hydrothermal method and CuS nanoparticles were modified by successive ionic layer adsorption and reaction (SILAR). By conducting methyl orange (MO) degradation experiments under the illumination of visible light, the photocatalytic activity of Co-doped ZnO nanowires modified with CuS nanoparticles was found to be nearly three times active when compared to bare ZnO nanowires. Its superior photocatalytic performance has two main reasons. The doped Co2+ ions can inhibit the recombination of photo-generated electron-hole pairs and decrease the optical bandgap, while the p-n heterostructure can enhance the visible light absorption ability and promote the separation of photo-excited charge carriers. Furthermore, the effect of the amount of deposited CuS nanoparticles on the photocatalysis was also investigated. The photocatalytic efficiency firstly raised along with the increment of SILAR cycle times and reached a maximum at 10 cycles but then decreased as the cycle times continue to increase. This originates from that an excessive amount of CuS would not only cover the active reacting sites, but also serve as recombination centers. Overall, this new nanostructure is expected to work as an efficient photocatalyst.

  11. Structural, Optical, and Magnetic Properties of Co Doped CdTe Alloy Powders Prepared by Solid-State Reaction Method

    Directory of Open Access Journals (Sweden)

    M. Rigana Begam

    2013-01-01

    Full Text Available Co doped CdTe powder samples were prepared by solid-state reaction method. In the present work effect of Co doping on structural, optical, and magnetic properties has been studied. X-ray diffraction studies confirm zinc blend structure for all the samples. The lattice parameter showed linear increase with the increase in Co content. The elemental constituents were characterized by EDAX. Optical studies showed the increase in band gap with increase in Co level. The samples were diluted magnetic semiconductors and exhibited clear hysteresis loop showing room temperature ferromagnetism as confirmed by vibrating sample magnetometer.

  12. Synergistic effect of Indium and Gallium co-doping on growth behavior and physical properties of hydrothermally grown ZnO nanorods

    OpenAIRE

    Jun Hyung Lim; Seung Muk Lee; Hyun-Suk Kim; Hyun You Kim; Jozeph Park; Seung-Boo Jung; Geun Chul Park; Jungho Kim; Jinho Joo

    2017-01-01

    We synthesized ZnO nanorods (NRs) using simple hydrothermal method, with the simultaneous incorporation of gallium (Ga) and indium (In), in addition, investigated the co-doping effect on the morphology, microstructure, electronic structure, and electrical/optical properties. The growth behavior of the doped NRs was affected by the nuclei density and polarity of the (001) plane. The c-axis parameter of the co-doped NRs was similar to that of undoped NRs due to the compensated lattice distortio...

  13. Intense up-conversion luminescence in Er3+/Yb3+ co-doped CeO2 powders

    Science.gov (United States)

    Singh, Vijay; Rathaiah, M.; Venkatramu, V.; Haase, Markus; Kim, S. H.

    2014-03-01

    The Er3+ and Er3+/Yb3+ co-doped CeO2 powders have been prepared by a urea combustion route. The structural, morphological, compositional and vibrational analysis of the Er3+:CeO2 and Er3+/Yb3+:CeO2 powders have been studied by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray and Fourier transform infrared spectroscopy. The optical and luminescence properties of Er3+:CeO2 and Er3+/Yb3+:CeO2 powders have been studied by using laser excited spectroscopy. The effects of Yb3+ doping on up-conversion luminescence of Er3+ co-doped CeO2 powders were studied. The ratio of red to green intensity is decreased in Er3+:CeO2 whereas the ratio is increased in Er3+/Yb3+:CeO2 powders with increase of power. The effect of co-doping with the Yb3+ ions on the visible luminescence of Er3+ and the energy transfer mechanism responsible for the variation in the green and red intensity are discussed. The results indicate that these materials may be suitable for display and light emitting devices.

  14. Synthesis, structural and optical characterization of undoped, N-doped ZnO and co-doped ZnO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Pathak, Trilok Kumar, E-mail: tpathak01@gmail.com; Kumar, R.; Purohit, L. P., E-mail: proflppurohitphys@gmail.com [Semiconductor Research Lab., Department of Physics, Gurukula Kangri University, Haridwar (India)

    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.

  15. First-principles study of p-type ZnO by S-Na co-doping

    Science.gov (United States)

    Tan, Xingyi; Li, Qiang; Zhu, Yongdan

    2017-08-01

    Using the first-principles method based on the density functional theory, the formation energy, electronic structures of S-Na co-doping in ZnO were calculated. The calculated results show that NaZn-SO have smaller formation energy than Nain-SO in energy ranges from -3.10 to 0 eV of {μ }{{O}}, indicating that it opens up a new opportunity for growth the p-type ZnO. The band structure shows that the NaZn system is a p-type direct-band-gap semiconductor material and the calculated band gap (0.84 eV) is larger than pure ZnO (0.74 eV). The NaZn-SO system is also a p-type semiconductor material with a direct band gap (0.80 eV). The influence of S-Na co-doping in ZnO on p-type conductivity is also discussed. The effective masses of NaZn-SO are larger than effective masses of NaZn and the NaZn-SO have more hole carriers than NaZn, meaning the hole in the NaZn-SO system may have a better carrier transfer character. So we inferred that NaZn-SO should be a candidate of p-type conduction. Project supported by the Natural Science Foundation of Hubei Province, China (Nos. 2014CFB342, 2014CFB619) and the Doctoral Foundation for Scientific Research of Hubei University for Nationalities (No. MY2013B020).

  16. First-principles study on electronic and magnetic properties of N mono-doped and (N, Co) co-doped ZnO

    Energy Technology Data Exchange (ETDEWEB)

    Abbad, A., E-mail: am.ben@voila.fr [Laboratory of Material Valorisation, Faculty of Sciences and Technology, BP 227, Abdelhamid Ibn Badis University, Mostaganem 27000 (Algeria); Bentounes, H.A. [Signals and Systems Laboratory (LSS), Faculty of Sciences and Technology, BP 227, Abdelhamid Ibn Badis University, Mostaganem 27000 (Algeria); Benstaali, W. [Laboratory of Material Valorisation, Faculty of Sciences and Technology, BP 227, Abdelhamid Ibn Badis University, Mostaganem 27000 (Algeria); Belaidi, A. [Automatic and Systems Analysis Laboratory (LAAS), ENSET, Oran 31000 (Algeria)

    2013-01-15

    Using first principles calculations based on the density functional theory and local spin density approximation, we predict magnetic and electronic properties of N mono-doped and (N-Co) co-doped ZnO for different dopants concentration. The results show that ZnO doped with N concentration of 12.5% is p-type, semi-metallic and ferromagnetic due to the strong hybridization effect between N 2p and O 2p states, with a total magnetic moment of 1 {mu}{sub B} mainly arises from N 2p orbitals. Nevertheless we find a deep and narrow acceptor level, resulting in large acceptor ionization energy of ZnO (N). With increasing N concentration to 25% we find that the impurity energy level is shallow and shifts downward to the direction of low energy, consequentially, the acceptor binding energy is reduced. (N-Co) co-doped ZnO with a concentration of 12.5% for the two dopants is p-type and half-metallic with an important magnetic moment of 3.98 {mu}{sub B}, due to Co 3d and N 2p states. - Highlights: Black-Right-Pointing-Pointer The electronic and magnetic properties of N mono-doped and (N-Co) co-doped ZnO have been investigated. Black-Right-Pointing-Pointer ZnO doped with 12.5% of Nitrogen is p-type and semi-metallic. Black-Right-Pointing-Pointer N-doping can enhance electronic conductivity of N-doped ZnO. Black-Right-Pointing-Pointer We find narrow N-impurity band for N-doped ZnO. Black-Right-Pointing-Pointer The co-doping of Co donors with N-acceptors causes an important change from semi-metallic material to half-metallic one.

  17. Room temperature ferromagnetism and structural characterization of Fe,Ni co-doped ZnO nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Dhiman, Pooja, E-mail: pdhimanhpu@yahoo.in [Department of Physics, Himachal Pradesh University, Shimla 5 (India); Batoo, Khalid Mujasam [King Abdullah Institute for Nanotechnology, King Saud University, PO Box 2455, Riyadh 11451 (Saudi Arabia); Kotnala, R.K. [National Physical Laboratory, Pusa Road, New Delhi 110012 (India); Chand, Jagdish; Singh, M. [Department of Physics, Himachal Pradesh University, Shimla 5 (India)

    2013-12-15

    A systematic investigation on the structural and magnetic properties of Fe{sub x}Ni{sub 0.01}Zn{sub 1−x}O (x = 0.01, 0.03, 0.05) nanoparticles synthesized by easy and inexpensive solution combustion technique is presented. X-ray diffraction (XRD), HRTEM and selected area electron diffraction (SAED) results show single phase nature with hexagonal wurtzite structure, and reveal the incorporation of Fe and Ni ions into lattice positions of Zn ions in ZnO lattice. Micro-Raman analysis suggests the suppression of surface defects with increasing Fe content. The magnetization measurements results into ferromagnetic state for all co-doped samples. Saturation magnetization increases with Fe doping indicating the role of interaction between Fe and Ni ions. Ferromagnetic interaction enhances at low temperature and remains non-zero above room temperature as suggested by magnetization vs. temperature measurements.

  18. Comparative study of quaternary Mg and Group III element co-doped ZnO thin films with transparent conductive characteristics

    Energy Technology Data Exchange (ETDEWEB)

    Kim, In Young [Department of Materials Science and Engineering, Chonnam National University, 300 Yongbong-Dong, Puk-Gu, Gwangju 500-757 (Korea, Republic of); Shin, Seung Wook [Department of Materials Science and Engineering, KAIST, IBS 291 Daehak-ro Yuseong-gu, Daejeon 305-701 (Korea, Republic of); Center for Nanomaterials and Chemical Reactions, Institute for Basic Science, Daejeon 305-701 (Korea, Republic of); Gang, Myeng Gil; Lee, Seung Hyoun; Gurav, K.V. [Department of Materials Science and Engineering, Chonnam National University, 300 Yongbong-Dong, Puk-Gu, Gwangju 500-757 (Korea, Republic of); Patil, P.S. [Thin Film Materials Laboratory, Department of Physics, Shivaji University, Kolhapur 416004 (India); Yun, Jae Ho [Photovoltaic Research Group, Korea Institute of Energy Research, 71-2 Jang-Dong Yuseong-Gu, Daejeon 305-343 (Korea, Republic of); Lee, Jeong Yong [Department of Materials Science and Engineering, KAIST, IBS 291 Daehak-ro Yuseong-gu, Daejeon 305-701 (Korea, Republic of); Center for Nanomaterials and Chemical Reactions, Institute for Basic Science, Daejeon 305-701 (Korea, Republic of); Kim, Jin Hyeok, E-mail: jinhyeok@chonnam.ac.kr [Department of Materials Science and Engineering, Chonnam National University, 300 Yongbong-Dong, Puk-Gu, Gwangju 500-757 (Korea, Republic of)

    2014-11-03

    Mg and Ga co-doped ZnO (Mg{sub x}Ga{sub y}Zn{sub z}O, x + y + z = 1, x = 0.05, y = 0.02 and z = 0.93, MGZO), Mg and Al co-doped ZnO (Mg{sub x}Al{sub y}Zn{sub z}O, x + y + z = 1, x = 0.05, y = 0.02 and z = 0.93, MAZO), Mg and In co-doped ZnO (Mg{sub x}In{sub y}Zn{sub z}O, x + y + z = 1, x = 0.05, y = 0.02 and z = 0.93, MIZO), Mg doped ZnO (Mg{sub x}Zn{sub y}O, x + y = 1, x = 0.05 and y = 0.95, MZO) and pure ZnO thin films have been prepared on the glass substrates by RF magnetron sputtering. Their structural, morphological, compositional, electrical, and optical properties were characterized. The X-ray diffraction patterns showed that all the thin films were grown as a hexagonal wurtzite phase with c-axis preferred orientation without secondary phase. The (0002) peak positions of MGZO, MAZO and MIZO thin films were not significantly changed. The cross-section field emission scanning electron microscopy images of MGZO, MAZO and MIZO thin films showed that all the thin films have a columnar structure with dense morphology. The MGZO thin film showed the best electrical characteristics in terms of the carrier concentration (3.7 × 10{sup 20}/cm{sup 3}), charge carrier mobility (8.39 cm{sup 2}/Vs), and a lower resistivity (1.85 × 10{sup −3} Ω cm). UV–visible spectroscopy studies showed that the MGZO, MAZO and MIZO thin films exhibit high transmittance over 85% in the visible region. The MGZO thin films showed wider optical band gap energy of 3.75 eV. - Highlights: • Mg and Group III Co-doped ZnO thin films were prepared by RF sputtering technique. • The Co-doped ZnO thin films showed better properties than those of un-doped. • The Mg and Ga Co-doped ZnO (MGZO) thin film showed the best properties. • The MGZO thin films showed the band gap of 3.75 eV and resistivity of 1.83 × 10{sup −3} Ω cm.

  19. Morphological evolution and electronic alteration of ZnO nanomaterials induced by Ni/Fe co-doping

    Science.gov (United States)

    Fletcher, Cameron; Jiang, Yijiao; Sun, Chenghua; Amal, Rose

    2014-06-01

    Zinc oxide (ZnO) nanocrystals mono- and co-doped with nickel/iron were prepared using a facile solvothermal procedure. A significant change in the surface morphology from nanorods to plate-like nanoparticles was observed with an increase in the dopant concentration. The variations of their optical and electronic properties induced by metal dopants were investigated using a combination of characterization techniques and ab initio calculations. It is found that both nickel and iron atoms have been successfully incorporated into the crystal lattice rather than forming a secondary phase, suggesting good dispersion of dopants within the ZnO matrix. Doping with iron has red-shifted the absorption edges of ZnO towards the visible portion resulting in lower band gap energies with increasing dopant concentration. Evidenced by Raman and EPR spectroscopy, the addition of iron has been shown to promote the formation of more oxygen vacancy and crystal defects within the host lattice as well as increasing the free-electron density of the nanomaterial. The DFT plus Hubbard model calculations confirm that low concentration Ni-doping does not induce band gap narrowing but results in localized states. The calculations show that Fe-doping has the potential to greatly improve the optical absorption characteristics and lead to structural deformation, corroborating the UV-Vis, Raman, and EPR spectra.Zinc oxide (ZnO) nanocrystals mono- and co-doped with nickel/iron were prepared using a facile solvothermal procedure. A significant change in the surface morphology from nanorods to plate-like nanoparticles was observed with an increase in the dopant concentration. The variations of their optical and electronic properties induced by metal dopants were investigated using a combination of characterization techniques and ab initio calculations. It is found that both nickel and iron atoms have been successfully incorporated into the crystal lattice rather than forming a secondary phase

  20. Effect of (Li, Mn) co-doping on structural, optical and magnetic properties of chunk-shaped nano ZnO

    Energy Technology Data Exchange (ETDEWEB)

    Rajamanickam, N., E-mail: nrajamku@gmail.com; Mariammal, R.N.; Rajashabala, S.; Ramachandran, K.

    2014-11-25

    Highlights: • Chunk-shaped nano ZnO synthesized by varying Li and Mn doping concentrations. • The growth mechanism was discussed for chunk-shaped morphologies. • Undoped and Li doped CSNS ZnO exhibit weak ferromagnetic behavior with diamagnetism. • Room temperature ferromagnetism observed for Mn doped and Li/Mn co-doped CSNS ZnO. • Verdet constants and magneto-optic properties were measured from Faraday Effect method. - Abstract: Chunk shaped ZnO nanostructures (CSNS) simultaneously doped with Li and Mn for varying Li/Mn concentrations have been synthesized using wet-chemical method. Their crystal structural, optical and magnetic properties at room temperature (RT) were then investigated, which revealed that all the samples have a single phase with the wurtzite structure. Undoped and co-doped ZnO chunk-shape structures has been demonstrated by transmission electron microscope (TEM). The Mn/Li incorporation also creates more lattice defects and disorders, which influence directly characteristic photoluminescence (PL), FTIR and UV–vis spectra of Zn{sub 1−x−y}Mn{sub y}Li{sub x}O CSNS. Where green emission due to concentration of defects is seen. Magnetic measurements by VSM and the ferro fluid of synthesized nano ZnO by Faraday optical rotation for various concentration of Mn and Li in nano ZnO are done. Change of magnetic and magneto-optic (MO) properties due to Mn and Li ions are discussed in detail.

  1. Systematic approach on the fabrication of Co doped ZnO semiconducting nanoparticles by mixture of fuel approach for Antibacterial applications

    Science.gov (United States)

    Rajendar, V.; Dayakar, T.; Shobhan, K.; Srikanth, I.; Venkateswara Rao, K.

    2014-11-01

    Zinc oxide (ZnO) is a wide band gap semiconductor (3.2 eV) with a high exciton binding energy (60 meV), where it has wide applications in advanced spintronic devices. The theoretical prediction of room temperature ferromagnetism and also antibacterial activity will be possible through the investigation of diluted magnetic semiconductors (DMS), such as transition metal doped ZnO, especially Cobalt doped ZnO. The aim of the work is the synthesis of Cobalt (Co) doped ZnO nanopowders were prepared Zn1-xCoxO (0 ⩽ x ⩾ 0.09) nanopowders from Sol-Gel auto combustion method have been synthesized with precursors such as Zinc and Cobalt nitrates with the assistance Ammonium acetate & Urea as fuel by increasing the cobalt concentration in zinc oxide and their structural, morphological, optical, Thermal, magnetic and antibacterial properties were studied by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), Transmission Electron microscope (TEM), UV-visible spectroscopy, thermo gravimetric/differential thermal analysis (TG/DTA) and vibrating sample magneto meter (VSM). From the antibacterial studies, against gram positive Bacillus subtilis bacteria is most abundant bacteria in soil and indoor atmosphere, which affects the stored spintronic devices so that the devices should be made with antibacterial activity of DMS like Co doped ZnO. In this article is found that ZnO:Co nanopowders with higher Co doping level (0.07 and 0.09 wt%) exhibit good antibacterial efficiency. The magnetization curves obtained using vibrating sample magnetometer (VSM) show a sign of strong room temperature ferromagnetic behavior when the Co doping level is 0.05 wt% and a weak room temperature ferromagnetic behavior Co doping level is below 0.07 wt%, and also they found to exhibit antiferromagnetic and paramagnetic properties, when the Co doping levels are 0.07 and 0.09 wt%, respectively, to enhance and increase the special magnetic and antibacterial property for

  2. Development of transparent conductive indium and fluorine co-doped ZnO thin films: Effect of F concentration and post-annealing temperature

    Energy Technology Data Exchange (ETDEWEB)

    Hadri, A. [University Mohammed V, Faculty of Sciences, Physics Department, LPM, B.P. 1014, Rabat (Morocco); Taibi, M. [University of Mohammed V, LPCMIN, Ecole Normale Superieure, Rabat (Morocco); Loghmarti, M.; Nassiri, C.; Slimani Tlemçani, T. [University Mohammed V, Faculty of Sciences, Physics Department, LPM, B.P. 1014, Rabat (Morocco); Mzerd, A., E-mail: mzerd@yahoo.fr [University Mohammed V, Faculty of Sciences, Physics Department, LPM, B.P. 1014, Rabat (Morocco)

    2016-02-29

    In the present work ZnO, In doped ZnO and In-F co-doped ZnO (IFZO) films were synthesized on heated glass substrates (350 °C) by the chemical spray technique. The effect of fluorine concentration on the structural, morphological, optical and electrical properties was studied. It was observed from X-ray diffraction (XRD) that the films have a polycrystalline structure and the intensity of the peaks depend on the doping and co-doping concentration. No diffraction peak related to dopants in XRD patterns along with shift in peaks angles to ZnO proved that In and F ions were doped into ZnO thin films. The Raman spectra confirm the hexagonal structure of the as-deposited films, and demonstrated an enhancement of the surface phonon mode of doped and co-doped films as compared to undoped films. The as-deposited films showed an average transmittance above 70%, in the wavelength range of 400–800 nm. A minimum electrical resistivity, in the order of 5.2 × 10{sup −} {sup 2} Ω cm was obtained for the IFZO thin film with 5 at.% F doping. Moreover, the electrical properties of doped and co-doped films were enhanced after post-deposition annealing. It was found that post-annealed thin films at 350 °C showed a decrease of one order of magnitude of the resistivity values. Such a transparent and conducting thin film can be suitable for optical and electrical applications owing to their low resistivity combined with high transmittance in the visible range. - Highlights: • Conductive transparent ZnO, IZO, IFZO thin films were deposited by spray pyrolysis. • Doping and co-doping affect morphology and optoelectrical properties. • As deposited film with high fluorine content exhibited high carrier mobility (55 cm{sup 2} V{sup −} {sup 1} s{sup −} {sup 1}). • Correlation between intrinsic defects and carrier mobility was observed. • Post-annealing in Ar atmosphere improves conductivity.

  3. CL from ZnO nanowires and microneedles Co-doped with N and Mn

    Science.gov (United States)

    Herrera, M.; Morales, A.; Díaz, J. A.

    2014-05-01

    Cathodoluminescence (CL) was used to study the luminescence emission of ZnO : N, Mn nanowires and microneedles grown by thermal evaporation. CL spectra acquired at room temperature showed the presence of near band edge and defect-related emissions. The defect related emission comprised two bands centered at 2.28 and 2.5 eV. The first component was attributed to the formation of spinel ZnMn2O4 and the second to the well-known ZnO green emission. CL spectra acquired at 100 K showed two emissions centered at 3.22 and 3.25 eV that were attributed to donor-acceptor pair (DAP) and FA transitions, respectively. It was proposed that substitutional nitrogen (NO) and zinc interstitial (Zni) were acceptor and shallow-donor centers in the DAP transition.

  4. Optical properties of p-type Al and N co-doped ZnO films

    Science.gov (United States)

    Zhang, Li; Yu, Wei; Zhang, Zicai; Zhang, Jinchuan; Fu, Guangsheng

    2008-11-01

    Effect of Al-N codoping ratio on the conducting and optical properties of ZnO films deposited by helicon wave plasma assisted radio frequency magnetron sputtering under various N2 gas flow is investigated. Hall measurements show that p-type ZnO thin films have been achieved with proper N2 flow rate. X-ray diffraction patterns indicate that all the films are highly c-axis oriented. Room temperature photoluminescence spectra show a strong near-band-edge emission. With increasing N doping, the intensity of the emission behaves an increased and then decreased trend while the full width at half maximum is narrowed and then widened. In addition, photoluminescence spectrum at 77 K in the p-type ZnO film with the highest hole concentration show a much stronger peak near 3.32 eV (due to N related neutral acceptor bound excitons), than at 3.36 eV (neutral donor bound excitons), and the acceptor energy level is estimated to be 186 meV.

  5. Sulfur and Nitrogen co-doped graphene quantum dot decorated ZnO nanorod/polymer hybrid flexible device for photosensing applications

    Energy Technology Data Exchange (ETDEWEB)

    Hmar, Jehova Jire L.; Majumder, Tanmoy; Dhar, Saurab; Mondal, Suvra Prakash, E-mail: suvraphy@gmail.com

    2016-08-01

    S and N co-doped graphene quantum dots (S,N-GQDs) have been synthesized by a hydrothermal process. S,N-GQDs are made up of 1–5 monolayer of graphene with average diameter 13.3 nm. The absorption peaks at 336 and 621 nm, are attributed to n → Π{sup ⁎} transitions of electrons in C=O and S=O bonds, respectively. S,N-GQDs are highly luminescent and showed excitation dependent emission behaviors. Hybrid photosensing device has been fabricated with S,N-GQD sensitized ZnO nanorods and a conjugated polymer poly(3-hexylthiophene) (P3HT). S,N-GQD decorated ZnO nanorod demonstrated higher photoresponse compared to pristine ZnO nanorod based device. S,N-GQD/ZnO nanorod hybrid device showed superior incident photon to electron conversion efficiency (IPCE), photoresponsivity and detectivity compared to the control samples. The flexibility study of the samples has been monitored by measuring current-voltage characteristics at different bending angles. - Highlights: • S and N co-doped graphene quantum dots (S,N-GQDs) were synthesized. • ZnO nanorods were grown on ITO coated flexible PET substrates. • S,N-GQDs were attached with ZnO nanorods and used as a green sensitizer. • Photosensing properties of S,N-GQD/ZnO and P3HT polymer hybrid device was studied.

  6. Local study of the magnetism of Co-doped ZnO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Moreno, M S [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ (United Kingdom); Centro Atomico Bariloche and Instituto Balseiro, 8400 San Carlos de Bariloche (Argentina); Kasama, T [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ (United Kingdom); Frontier Research System, Institute of Physical and Chemical Research, Hatoyama, Saitama 350-0395 (Japan); Dunin-Borkowski, R E [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ (United Kingdom); Frontier Research System, Institute of Physical and Chemical Research, Hatoyama, Saitama 350-0395 (Japan); Cooper, D [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ (United Kingdom); Midgley, P A [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ (United Kingdom); Steren, L B [Centro Atomico Bariloche and Instituto Balseiro, 8400 San Carlos de Bariloche (Argentina); Duhalde, S [Laboratorio de Ablacion Laser, Facultad de IngenierIa, Universidad de Buenos Aires, Paseo Colon 850, 1063 Buenos Aires (Argentina); Vignolo, M F [Laboratorio de Ablacion Laser, Facultad de IngenierIa, Universidad de Buenos Aires, Paseo Colon 850, 1063 Buenos Aires (Argentina)

    2006-05-07

    Complementary electron microscopy techniques that provide local information about structural, electronic and magnetic properties have been used to study thin films of Zn{sub 0.85}Co{sub 0.15}O grown on Si{sub 3}N{sub 4} buffered (100) Si substrates at 673 K. No evidence of secondary phases at interfaces was found. For this growth temperature, Co is incorporated into the ZnO lattice by substituting for Zn, and its oxidation state is 2{sup +}. Off-axis electron holography reveals no measurable magnetic signal, either at domains or at interfaces, in agreement with macroscopic measurements that indicate a non-ferromagnetic behaviour.

  7. Synergistic effect of Indium and Gallium co-doping on growth behavior and physical properties of hydrothermally grown ZnO nanorods

    Science.gov (United States)

    Lim, Jun Hyung; Lee, Seung Muk; Kim, Hyun-Suk; Kim, Hyun You; Park, Jozeph; Jung, Seung-Boo; Park, Geun Chul; Kim, Jungho; Joo, Jinho

    2017-02-01

    We synthesized ZnO nanorods (NRs) using simple hydrothermal method, with the simultaneous incorporation of gallium (Ga) and indium (In), in addition, investigated the co-doping effect on the morphology, microstructure, electronic structure, and electrical/optical properties. The growth behavior of the doped NRs was affected by the nuclei density and polarity of the (001) plane. The c-axis parameter of the co-doped NRs was similar to that of undoped NRs due to the compensated lattice distortion caused by the presence of dopants that are both larger (In3+) and smaller (Ga3+) than the host Zn2+ cations. Red shifts in the ultraviolet emission peaks were observed in all doped NRs, owing to the combined effects of NR size, band gap renormalization, and the presence of stacking faults created by the dopant-induced lattice distortions. In addition, the NR/p-GaN diodes using co-doped NRs exhibited superior electrical conductivity compared to the other specimens due to the increase in the charge carrier density of NRs and the relatively large effective contact area of (001) planes. The simultaneous doping of In and Ga is therefore anticipated to provide a broader range of optical, physical, and electrical properties of ZnO NRs for a variety of opto-electronic applications.

  8. Comparative investigation on cation-cation (Al-Sn) and cation-anion (Al-F) co-doping in RF sputtered ZnO thin films: Mechanistic insight

    Energy Technology Data Exchange (ETDEWEB)

    Mallick, Arindam; Basak, Durga, E-mail: sspdb@iacs.res.in

    2017-07-15

    Highlights: • Comparative study on Al, Al-Sn and Al-F doped ZnO films has been carried out. • High transparent Al-F co-doped film shows three times enhanced carrier density. • Al-F co-doped film shows larger carrier relaxation time. • Al-Sn co-doped films shows carrier transport dominated by impurity scattering. • Al-F co-doped ZnO film can be applied as transparent electrode. - Abstract: Herein, we report a comparative mechanistic study on cation-cation (Al-Sn) and cation-anion (Al-F) co-doped nanocrystalline ZnO thin films grown on glass substrate by RF sputtering technique. Through detailed analyses of crystal structure, surface morphology, microstructure, UV-VIS-NIR transmission-reflection and electrical transport property, the inherent characteristics of the co-doped films were revealed and compared. All the nanocrystalline films retain the hexagonal wurtzite structure of ZnO and show transparency above 90% in the visible and NIR region. As opposed to expectation, Al-Sn (ATZO) co-doped film show no enhanced carrier concentration consistent with the probable formation of SnO{sub 2} clusters supported by the X-ray photoelectron spectroscopy study. Most interestingly, it has been found that Al-F (AFZO) co-doped film shows three times enhanced carrier concentration as compared to Al doped and Al-Sn co-doped films attaining a value of ∼9 × 10{sup 20} cm{sup −3} due to the respective cation and anion substitution. The carrier relaxation time increases in AFZO while it decreases significantly for ATZO film consistent with the concurrence of the impurity scattering in the latter.

  9. Investigation of structural and optical properties in Cobalt–Chromium co-doped ZnO thin films within the Lattice Compatibility Theory scope

    Energy Technology Data Exchange (ETDEWEB)

    Mimouni, R.; Boubaker, K., E-mail: mmbb11112000@yahoo.fr; Amlouk, M.

    2015-03-05

    Highlights: • Co/Cr co-doped ZnO thin films were synthesized by a low-cost spray technique. • Optical and morphological properties of the Co/Cr co-doped ZnO system were described. • Lattice Compatibility Theory explains Co preferential incorporation in ZnO lattice. - Abstract: (Co,Cr)-codoped zinc oxide thin films (ZnO:Cr:Co) at different percentages (0%, 1–1%, 1–2%, 2–1%) were deposited on glass substrates using a chemical low-cost spray technique. The effect of Cr and Co concentration on the structural, morphological and optical properties of the ZnO:Cr:Co thin films were investigated by means of X-ray diffraction, optical measurement, contact Atomic Force Microscopy (AFM), and Photoluminescence spectroscopy. The results revealed that all films consist of single phase ZnO and were well crystallized in würtzite phase with the crystallites preferentially oriented towards (0 0 2) direction parallel to c-axis. Also, the co-doping has effective role in the enhancement of the crystallinity and leads to an improvement of roughness of the ZnO films. Doping by chrome and cobalt resulted in a slight decrease in the optical band gap energy of the films. The optical band gap of these films is calculated. The optical absorption spectra show that the absorption mechanism is a direct transition. The UV peak positions for ZnO:Cr:Co samples slightly red shift to the longer wavelength in comparison with the pure ZnO which can be attributed to the change in the acceptor level induced by the substitutional Co{sup 2+} and Cr{sup 3+} and the band-gap narrowing of ZnO with the Cr and Co dopants. The Lattice Compatibility Theory analyses have been applied in order to give original, plausible and founded explanation to the recorded preferential incorporation of cobalt ions within ZnO lattice over chromium.

  10. Investigation on intra-3d-shell transitions in Co-doped ZnO

    Science.gov (United States)

    Guo, Shuxia; Li, Jiwu; Du, Zuliang

    2015-11-01

    Two kinds of Zn0.97Co0.03O powders were prepared under different conditions. One grown at low temperature shows no surface photovoltage at the intra-3d-shell absorption range, while the other grown at high temperature exhibits an opposite result. The band gap energies of two samples are almost invariable, about 3.3 eV. It is proposed that the d- d* transition of Co2+ inducing electron-hole separation could not occur spontaneously, and needs oxygen vacancies (VO) assistance.

  11. Resistive switching characteristics and conduction mechanisms of nonvolatile memory devices based on Ga and Sn co-doped ZnO films

    Energy Technology Data Exchange (ETDEWEB)

    Oh, Dohyun; Yun, Dong Yeol; Lee, Nam Hyun; Kim, Tae Whan, E-mail: twk@hanyang.ac.kr

    2015-07-31

    Nonvolatile memory devices were fabricated utilizing Ga and Sn co-doped ZnO (GZTO) films formed by using a solution process method. X-ray diffraction patterns showed that the crystallinity of the annealed GZTO films was an amorphous phase. X-ray photoelectron spectroscopy spectra of the GZTO films depicted Zn−O, Ga−O, and Sn−O bonds. Current–voltage measurements on the Al/GZTO/indium-tin-oxide (ITO) devices at 300 K showed bipolar resistive switching behaviors. The resistances at both the low resistance state (LRS) and high resistance state (HRS) measured at 0.5 V for the devices maintain almost constant without any damage and breakdown above 130 s, indicative of the memory stability of the devices. A difference in the resistance between the HRS and the LRS was more than 1 order of the magnitude. The conduction mechanisms of the HRS in the set process for the Al/GZTO/ITO devices were dominated by a space-charge-limited current model. - Highlights: • Nonvolatile memory devices were fabricated utilizing Ga and Sn co-doped ZnO (GZTO) films. • X-ray diffraction patterns showed that the annealed GZTO films were an amorphous phase. • Current–voltage measurements on the devices showed bipolar resistive switching behaviors. • One order magnitude difference in resistance between low and high resistance states (HRS) • Space charge limited conduction is the dominant conduction mechanisms of the HRS.

  12. Effect of substrate temperature on transparent conducting Al and F co-doped ZnO thin films prepared by rf magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Fang-Hsing, E-mail: fansen@dragon.nchu.edu.tw; Chang, Chiao-Lu

    2016-05-01

    Highlights: • Al and F co-doped ZnO (AFZO) thin films were prepared by rf magnetron sputtering. • Effects of substrate temperature on properties of AFZO films were investigated. • The AFZO films show a typical hexagonal wurtzite structure and are (0 0 2) oriented. • The AFZO thin film prepared at 200 °C exhibits a low resistivity of 2.88 × 10{sup −4} Ω-cm. • The average visible transmittances of all the AFZO thin films exceed 92%. - Abstract: ZnO is a wide bandgap semiconductor that has many potential applications such as solar cells, thin film transistors, light emitting diodes, and gas/biological sensors. In this study, a composite ceramic ZnO target containing 1 wt% Al{sub 2}O{sub 3} and 1.5 wt% ZnF{sub 2} was prepared and used to deposit transparent conducting Al and F co-doped zinc oxide (AFZO) thin films on glass substrates by radio frequency magnetron sputtering. The effect of substrate temperatures ranging from room temperature (RT) to 200 °C on structural, morphological, electrical, chemical, and optical properties of the deposited thin films were investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), Hall effect measurement, X-ray photoelectron spectroscopy, secondary ion mass spectrometry, and UV–vis spectrophotometer. The XRD results showed that all the AFZO thin films had a (0 0 2) diffraction peak, indicating a typical wurtzite structure with a preferential orientation of the c-axis perpendicular to the substrate. The FE-SEM and AFM analyses indicated that the crystallinity and grain size of the films were enhanced while the surface roughness decreased as the substrate temperature increased. Results of Hall effect measurement showed that Al and F co-doping decreased the resistivity more effectively than single-doping (either Al or F doping) in ZnO thin films. The resistivity of the AFZO thin films decreased from 5.48 × 10{sup −4} to 2.88 × 10{sup −4}

  13. Low resistivity of Ni–Al co-doped ZnO thin films deposited by DC magnetron sputtering at low sputtering power

    Energy Technology Data Exchange (ETDEWEB)

    Lee, JongWoo [Department of Materials Science and Engineering, Pusan National University, San 30 Jangjeon-dong, Geumjeong-gu, Busan 609-735 (Korea, Republic of); Hui, K.N. [Department of Mechanical Engineering, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul 133-791 (Korea, Republic of); Hui, K.S., E-mail: kshui@hanyang.ac.kr [Department of Mechanical Engineering, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul 133-791 (Korea, Republic of); Cho, Y.R., E-mail: yescho@pusan.ac.kr [Department of Materials Science and Engineering, Pusan National University, San 30 Jangjeon-dong, Geumjeong-gu, Busan 609-735 (Korea, Republic of); Chun, Ho-Hwan [Global Core Research Center for Ships and Offshore Plants (GCRC-SOP), Pusan National University, San 30 Jangjeon-dong, Geumjeong-gu, Busan 609-735 (Korea, Republic of)

    2014-02-28

    Ni–Al co-doped ZnO (NiAl:ZnO) thin films were deposited on glass substrates by DC magnetron sputtering in Ar using a single ceramic, spark-plasma-sintered target with 2 wt% Al and 5 wt% Ni. The effects of the sputtering power and gas pressure on the NiAl:ZnO films were studied. The structural, electrical, and optical properties of the films were characterized by X-ray diffraction, field emission scanning electron microscopy, Hall effect measurements and UV–vis transmission spectroscopy. As the sputtering power and gas pressure increased, the crystallinity, electrical properties and optical band gap of the films were improved. The NiAl:ZnO film deposited at 40 W at 6.0 mTorr had the strongest (0 0 2) XRD peak and the lowest resistivity of approximately 2.19 × 10{sup −3} Ω cm with an optical transmittance of 90%.

  14. Direct observation of hopping induced spin polarization current in oxygen deficient Co-doped ZnO by Andreev reflection technique

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Kung-Shang; Huang, Tzu-Yu; Dwivedi, G.D. [Department of Physics, National Sun Yat-sen University, Kaohsiung, Taiwan (China); Lin, Lu-Kuei; Lee, Shang-Fan [Taiwan Institute of Physics, Academia Sinica, Taipei, Taiwan (China); Sun, Shih-Jye [Department of Applied Physics, National Kaohsiung University, Kaohsiung, Taiwan (China); Chou, Hsiung, E-mail: hchou@mail.nsysu.edu.tw [Department of Physics, National Sun Yat-sen University, Kaohsiung, Taiwan (China)

    2017-07-01

    Highlights: • Co-doped ZnO thin-films were grown with varying V{sub O} concentartion. • PCAR measurements were done to study the SPC. • High spin polarization was observed above a certain V{sub O} concentartion. • High V{sub O} samples provide a high density of completed percolation path. • This complete percolation path gives rise to high SPC. - Abstract: Oxygen vacancy induced ferromagnetic coupling in diluted magnetic oxide (DMO) semiconductors have been reported in several studies, but technologically more crucial spin-polarized current (SPC) is still under-developed in DMOs. Few studies have claimed that VRH mechanism can originate the SPC, but, how VRH mechanism associated with percolation path, is not clearly understood. We used Point-contact Andreev reflection (PCAR) technique to probe the SPC in Co-doped ZnO (CZO) films. Since the high resistance samples cause broadening in conductance(G)-voltage(V) curves, which may result in an unreliable evaluation of spin polarization, we include two extra parameters, (i) effective temperature and (ii) spreading resistance, for the simulation to avoid the uncertainty in extracting spin polarization. The effective G-V curves and higher spin polarization can be obtained above a certain oxygen vacancy concentration. The number of completed and fragmentary percolation paths is proportional to the concentration of oxygen vacancies. For low oxygen vacancy samples, the Pb-tip has a higher probability of covering fragmentary percolation paths than the complete ones, due to its small contact size. The completed paths may remain independent of one another and get polarized in different directions, resulting in lower spin-polarization value. High oxygen vacancy samples provide a high density of completed path, most of them link to one another by crossing over, and gives rise to high spin-polarization value.

  15. Effect of Co and O defects on ferromagnetism in Co-doped ZnO: An X-ray absorption spectroscopic investigation

    Science.gov (United States)

    Singhal, Rishi K.; Jakhar, Narendra; Samariya, A.; Dolia, S. N.; Kumar, Sudhish

    2018-02-01

    Understanding of origin of ferromagnetism in dilute magnetic oxides (DMO's) has become one of the most challenging research problems in condensed matter physics. Here we are reporting a detailed study of magnetic properties and electronic structure of two 5% Co-doped ZnO samples (the as-prepared sample Zn0.95Co0.05O and the hydrogenated sample Zn0.95Co0.05O:H). The as-prepared sample is found to be paramagnetic while through hydrogenation, we observed inducement of remarkable ferromagnetism in it. The H-mediated magnetic transition is accompanied by electronic structure modifications with no structural deviations. To get in-depth information into electronic structure correlations of the observed ferromagnetism, we have investigated their electronic properties in detail. For this purpose, we have employed the site-selective and element-sensitive X-ray-absorption spectroscopy (XAS) in the vicinity of the Cobalt L2,3 edge, the oxygen K edge, and the Zinc L3 edge using synchrotron radiation. The Co L2,3 edge spectra clearly show that Co dopants reside at the Zn sites for both these samples and that they are tetrahedrally coordinated with the ligand O atoms. Very minor changes are observed in the Zn L3 edge spectra. However, the O 1s edge spectra display dominant additional components in the ferromagnetic hydrogenated sample Zn0.95Co0.05O:H, not observed in the as-prepared non-magnetic sample Zn0.95Co0.05O. We conclude that the observed spectral features can be attributed to the presence of O vacancies and the hybridization of Co 3d states with O 2p vacancy states. These two factors together are likely to play important role in inducement of ferromagnetic ordering in this Co-doped ZnO system. However, which of these two weighs more in this mechanism, cannot be pinpointed and more studies are required in this regard.

  16. Wide-spectrum Mg and Ga co-doped ZnO TCO thin films for solar cells grown via magnetron sputtering with H{sub 2} introduction

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Xin-liang, E-mail: cxlruzhou@163.com [Institute of Photo-electronic Thin Film Devices and Technology, Nankai University, Tianjin 300071 (China); Tianjin Key Laboratory of Photo-electronic Thin Film Devices and Technology, Nankai University, Tianjin 300071 (China); Key Laboratory of Opto-electronic Information Science and Technology for Ministry of Education, Nankai University, Tianjin 300071 (China); Liu, Jie-ming; Ni, Jian; Zhao, Ying; Zhang, Xiao-dan [Institute of Photo-electronic Thin Film Devices and Technology, Nankai University, Tianjin 300071 (China); Tianjin Key Laboratory of Photo-electronic Thin Film Devices and Technology, Nankai University, Tianjin 300071 (China); Key Laboratory of Opto-electronic Information Science and Technology for Ministry of Education, Nankai University, Tianjin 300071 (China)

    2015-02-15

    Highlights: • Hydrogenated Mg and Ga co-doped ZnO thin films are obtained. • Low resistivity and high optical transmittances in wide spectrum range are achieved. • Solar cells with HMGZO layer present higher quantum efficiency. - Abstract: Wide-spectrum Mg and Ga co-doped ZnO transparent conductive oxide (TCO) thin films are deposited via magnetron sputtering at various H{sub 2} flow rates on glass substrates. The structural, electrical, and optical properties of MGZO thin films are investigated with different H{sub 2} flow rates. The experiment results show that the MGZO thin films are polycrystalline with a hexagonal wurtzite structure exhibiting a preferred (0 0 2) crystal plane orientation. The carrier concentration remarkably increases from 5.15 × 10{sup 19} cm{sup −3} to 2.12 × 10{sup 20} cm{sup −3} with increasing the H{sub 2} flow rate from 0 sccm to 4.0 sccm and then decreases when further increasing the H{sub 2} flow rate. The glass/MGZO thin film deposited at the H{sub 2} flow rate of 4.0 sccm exhibits the lowest resistivity of 1.96 × 10{sup −3} Ω cm (film thickness d ∼ 548 nm) and an average transmittance (Ta) of 80.5% in the wavelength range from 340 nm to 1100 nm. Optical measurements indicate that the optical band gap (E{sub g}) of MGZO thin films varies from 3.45 eV to 3.78 eV with adjusting H{sub 2} flow rate from 0 sccm to 12.0 sccm. The obtained MGZO thin films with an appropriate thickness are preliminarily applied in p–i–n type hydrogenated amorphous silicon (a-Si:H) thin film solar cells. The a-Si:H solar cell with MGZO layer presents higher quantum efficiency in the short wavelength region than that with GZO layer, resulting from widened optical band gap.

  17. Direct observation of hopping induced spin polarization current in oxygen deficient Co-doped ZnO by Andreev reflection technique

    Science.gov (United States)

    Yang, Kung-Shang; Huang, Tzu-Yu; Dwivedi, G. D.; Lin, Lu-Kuei; Lee, Shang-Fan; Sun, Shih-Jye; Chou, Hsiung

    2017-07-01

    Oxygen vacancy induced ferromagnetic coupling in diluted magnetic oxide (DMO) semiconductors have been reported in several studies, but technologically more crucial spin-polarized current (SPC) is still under-developed in DMOs. Few studies have claimed that VRH mechanism can originate the SPC, but, how VRH mechanism associated with percolation path, is not clearly understood. We used Point-contact Andreev reflection (PCAR) technique to probe the SPC in Co-doped ZnO (CZO) films. Since the high resistance samples cause broadening in conductance(G)-voltage(V) curves, which may result in an unreliable evaluation of spin polarization, we include two extra parameters, (i) effective temperature and (ii) spreading resistance, for the simulation to avoid the uncertainty in extracting spin polarization. The effective G-V curves and higher spin polarization can be obtained above a certain oxygen vacancy concentration. The number of completed and fragmentary percolation paths is proportional to the concentration of oxygen vacancies. For low oxygen vacancy samples, the Pb-tip has a higher probability of covering fragmentary percolation paths than the complete ones, due to its small contact size. The completed paths may remain independent of one another and get polarized in different directions, resulting in lower spin-polarization value. High oxygen vacancy samples provide a high density of completed path, most of them link to one another by crossing over, and gives rise to high spin-polarization value.

  18. Microstructure, optical and FTIR studies of Ni, Cu co-doped ZnO nanoparticles by co-precipitation method

    Science.gov (United States)

    Ashokkumar, M.; Muthukumaran, S.

    2014-11-01

    Zn0.96-xCu0.04NixO (0 ⩽ x ⩽ 0.04) nanoparticles were synthesized by co-precipitation method. The X-ray diffraction pattern showed the crystalline nature of prepared nanoparticles with hexagonal wurtzite structure. The average crystal size is decreased from 27 to 22.7 nm when Ni concentration is increased from 0% to 2% due to the suppression of nucleation and subsequent growth of ZnO by Ni-doping. The increased crystal size from 22.7 to 25.8 nm (ΔD ∼ 3.1 nm) by Ni-doping from 2% to 4% is due to the creation of distortion centers and Zn/Ni interstitials. The cell parameters and volume of the lattice showed solubility limit at 2% of Ni doping. The energy dispersive X-ray spectra confirmed the presence of Cu and Ni in Zn-O. The optical absorption spectra showed that the absorption was increased up to Ni = 2% due to the creation of carrier concentration by Ni-doping and decreased beyond 2% due to the presence of more defects and interstitials in the Zn-Ni-Cu-O lattice. The observed red shift of energy gap from 3.65 eV (Ni = 0%) to 3.59 eV (Ni = 2%, ΔEg ≈ 0.06 eV) is explained by sp-d exchange interactions between the band electrons and the localized d-electrons of the Ni2+ ions. The blue shift of energy gap from 3.59 eV (Ni = 2%) to 3.67 eV (Ni = 4%, ΔEg ≈ 0.08 eV) is explained by Burstein-Moss effect. Presence of chemical bonding was confirmed by FTIR spectra.

  19. Surface defect mediated magnetic interactions and ferromagnetism in Cr/Co Co-doped ZnO nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Aljawfi, Rezq Naji, E-mail: rizqnaji@yahoo.com [Department of Physics, Aligarh Muslim University, Aligarh 202002 (India); Rahman, F. [Department of Physics, Aligarh Muslim University, Aligarh 202002 (India); Batoo, Khalid Mujasam [King Abdullah Institute for Nanotechnology, King Saud University (Saudi Arabia)

    2013-04-15

    We report the structural and ferromagnetic properties of Zn{sub 0.97−x}Cr{sub x}Co{sub 0.03}O (x=0.0, 0.03, 0.06 and 0.09) nanoparticles (NPs) synthesized through citric–gel route. X-ray diffraction (XRD) and selected area electron diffraction (SAED) results show the single phase nature with hexagonal wurtzite structure, and reveal the incorporation of Cr{sup 3+} and Co{sup 2+} ions into lattice positions of Zn{sup 2+} ions in ZnO lattice. The average size of NPs decreases from ∼24 to 9 nm with increasing Cr dopant concentrations (x). Micro-Raman and X-ray photoelectron spectroscopy (XPS) studies show the presence of oxygen vacancies (V{sub O}) defects. The XPS study shows interaction between Cr–Co dopant and transfer of electrons from Cr (3d) state to unfilled (3d) state of Co. The observed ferromagnetism is intrinsic in nature, and not due to any metallic segregation or impurity phase. The oxygen vacancies mediated the dopant ions interaction, and the ferromagnetism can be elucidated by bound magnetic polaron (BMP) mechanism. - Highlights: ► Nanoparticles Zn{sub 0.97−x}Cr{sub x}Co{sub 0.03}O (x=0.0, 0.03, 0.06 and 0.09) are synthesized through sol–gel route. ► Crystalline structure and single phase character are confirmed by XRD, SEM, TEM, SAED and EDAX techniques. ► Raman and UV–vis spectra reveal the incorporation of Cr and Co into the ZnO lattice structure. ► The oxygen vacancies are observed from XPS and Raman spectra but there is no evidence of Co metallic cluster or CoO. ► The observed ferromagnetism is intrinsic in nature and not due to any metallic Co segregation or cobalt oxide which can be explained by bound magnetic polaron (BMP) theory.

  20. Surface defect mediated magnetic interactions and ferromagnetism in Cr/Co Co-doped ZnO nanoparticles

    Science.gov (United States)

    Aljawfi, Rezq Naji; Rahman, F.; Batoo, Khalid Mujasam

    2013-04-01

    We report the structural and ferromagnetic properties of Zn0.97-xCrxCo0.03O (x=0.0, 0.03, 0.06 and 0.09) nanoparticles (NPs) synthesized through citric-gel route. X-ray diffraction (XRD) and selected area electron diffraction (SAED) results show the single phase nature with hexagonal wurtzite structure, and reveal the incorporation of Cr3+ and Co2+ ions into lattice positions of Zn2+ ions in ZnO lattice. The average size of NPs decreases from ˜24 to 9 nm with increasing Cr dopant concentrations (x). Micro-Raman and X-ray photoelectron spectroscopy (XPS) studies show the presence of oxygen vacancies (VO) defects. The XPS study shows interaction between Cr-Co dopant and transfer of electrons from Cr (3d) state to unfilled (3d) state of Co. The observed ferromagnetism is intrinsic in nature, and not due to any metallic segregation or impurity phase. The oxygen vacancies mediated the dopant ions interaction, and the ferromagnetism can be elucidated by bound magnetic polaron (BMP) mechanism.

  1. Carrier recombination in sonochemically synthesized ZnO powders

    Directory of Open Access Journals (Sweden)

    Zakirov M.I.

    2017-04-01

    Full Text Available ZnO powders with particle size in the nm to μm range have been fabricated by sonochemical method, utilizing zinc acetate and sodium hydroxide as starting materials. Carrier recombination processes in the powders have been investigated using the photoluminescence, FT-IR and surface photovoltage techniques. It has been shown that the photoluminescence spectra exhibit a number of defect-related emission bands which are typically observed in ZnO lattice and which depend on the sonication time. It has been found that the increase of the stirring time results in a faster decay of the photovoltage transients for times shorter than approximately 5 ms. From the obtained data it has been concluded that the sonication modifies the complicated trapping dynamics from volume to surface defects, whereas the fabrication method itself offers a remarkably convenient means of modifying the relative content of the surface-to-volume defect ratio in powder grains and altering the dynamics of photoexcited carriers.

  2. Preparation and Study of morphological properties of ZnO nano Powder

    Directory of Open Access Journals (Sweden)

    Mohammed Salab Hamza

    2016-04-01

    Full Text Available In this work, ZnO nanostructures for powder ZnO were synthesized by Hydrothermal Method. Size and shape of ZnO nanostructureas can be controlled by change ammonia concentration. In the preparation of ZnO nanostructure, zinc nitrate hexahydrate [Zn(NO32·6H2O] was used as a precursor. The structure and morphology of ZnO nanostructure have been characterized by scanning electron microscopy (SEM, atomic force microscopy (AFM, X-ray diffraction (XRD. The synthesized ZnO nanostructures have a hexagonal wurtzite structure. Also using Zeta potential and Particle Size Analyzers and size distribution of the ZnO powder

  3. Low-temperature growth and physical investigations of undoped and (In, Co) doped ZnO thin films sprayed on PEI flexible substrate

    Science.gov (United States)

    Ben Ameur, S.; Barhoumi, A.; Mimouni, R.; Amlouk, M.; Guermazi, H.

    2015-08-01

    ZnO thin films were deposited on polymer substrate Polyethyerimide (PEI) at 250 °C by spray pyrolysis technique. The effects of different doping elements (Co and In) on physical properties of ZnO thin films were investigated. Thin film characterizations were carried out using X-ray diffraction technique, UV-Vis-NIR spectroscopy, Photoluminescence (PL) spectroscopy and the contact angle measurement method. XRD measurement showed a successful growth of crystalline films on polymer substrate at low temperature by the spray pyrolysis process. XRD patterns revealed that all films consist of single ZnO phase and were well crystallized with preferential orientation towards (1 0 1) direction. Doping by cobalt has effective role in the enhancement of the crystalline quality, increases in the band gap according to Burstein Moss effect. Doping with indium leads rather to the decrease of both crystallinity and optical band gap energy value. Photoluminescence of the films showed UV emission (NBE) and visible emission related to defects. The contact angles were measured to study the effect of various doping elements on the hydrophobicity of the film depending on surface roughness. Results showed strong dependence on the doping element. In fact, doping with cobalt element increases the roughness of ZnO films and reinforces the surface from hydrophilic to hydrophobic (θ > 90°).

  4. Enhanced green upconversion luminescence in ZnO:Er3+, Yb3+ on Mo6+ co-doping for temperature sensor application

    Science.gov (United States)

    Anjana, Radhakrishnan; Subha, Perumpallikkattil P.; Kurias, Markose K.; Jayaraj, Madambi K.

    2018-01-01

    Erbium (Er) doped zinc oxide (ZnO) powder was prepared using co-precipitation method. Effect of ytterbium (Yb) and molybdenum (Mo) co-doping on upconversion emission was studied. The emission intensity has been enhanced on Yb co-doping due to energy transfer from Yb to Er. Co-doping Mo in ZnO:Er, Yb has brought a significant enhancement in green upconversion emission, when excited with 980 nm laser. The enhancement in green emission on Mo doping is because of the formation of {{{Yb}}}3+{--}{{{{MoO}}}4}2- dimer. Since ZnO is a material having high thermal stability, the enhanced green emission in Mo, Er, Yb doped ZnO can be used for temperature sensor applications. The variation in relative intensity ratio of 2H11/2 → 4I15/2, 4S3/2 → 4I15/2 transition can be used to sense the sample temperature.

  5. Effect of temperature and discharge voltage on the properties of Co-doped ZnO thin films deposited by pulsed electron beam ablation

    Science.gov (United States)

    Ali, Asghar; Henda, Redhouane; Fagerberg, Ragnar

    2017-11-01

    Cobalt-doped ZnO (CZO) thin films have been deposited from CoxZn1-xO (x = 0.20) target on Si (100) substrate by pulsed electron beam ablation (PEBA). The effects of process temperature (350 °C-800 °C) and electron beam acceleration voltage (15 kV, 16 kV) on the deposited films have been assessed. The films have been prepared at constant beam pulse frequency (2 Hz) and Argon background pressure (∼3 mTorr). The structure and surface morphology of CZO films have been investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM). As per SEM data, the results show that the films consist of Co rich nano-sized globules (∼20 nm-300 nm). Energy dispersive x-ray (EDX) measurements reveal that Co content in the films seems to be unaffected by accelerating voltage while it increases with temperature in the range 350 °C-450 °C. At higher deposition temperatures (600 °C & 800 °C), the films exhibit faceted particles and are relatively rough. The films deposited at 800 °C consist of a predominantly Co phase. X-ray photoelectron spectroscopy (XPS) data confirm the presence of metallic cobalt in the films, whose content increases with temperature but is practically unaffected by beam voltage. X-ray diffraction (XRD) analysis confirms the presence of herxagonal close-packed (hcp) metallic cobalt in the films.

  6. Enhanced 2 μm broad-band emission and NIR to visible frequency up-conversion from Ho3+/Yb3+ co-doped Bi2O3-GeO2-ZnO glasses.

    Science.gov (United States)

    Biswas, Kaushik; Sontakke, Atul D; Sen, R; Annapurna, K

    2013-08-01

    In this work, a new and non-conventional oxide glass composition based on Bi2O3-GeO2-ZnO system has been formulated with an aim to realize low phonon oxide glass and elucidate its performance when co-doped with Ho(3+)/Yb(3+) for the energy transfer based NIR emission at 2 μm from Ho(3+) ions under Yb(3+) excitation. The glass with 1.0 mol% Ho2O3 and 0.5 mol% Yb2O3 has exhibited maximum energy transfer rate (3602 s(-1)) and energy transfer efficiency (65.92%). Important radiative properties have been predicted for emission transitions of Ho(3+) ions using intensity parameters derived from measured absorption spectra using standard Judd-Ofelt theory. At lower acceptor ion concentration (0.1 mol%), an efficient NIR to visible up-conversion emission has been observed based on two photon absorption process which has found to be reduced significantly at higher Ho(3+) concentrations with simultaneous enhancement in 2 μm emission. Hence, this newly developed glass codoped with Yb(3+)/Ho(3+) is promising glass for sensitized 2 μm emission applications as broad band tunable lasers because of the combination of low phonon energy (707 cm(-1)), high energy transfer efficiency, moderately high emission cross-section (5.33×10(-21) cm(2)) and larger effective half-width of the emission band value of 169 nm. Copyright © 2013 Elsevier B.V. All rights reserved.

  7. Modification of the structural and optical properties of commercial ZnO powder by mechanical activation

    Directory of Open Access Journals (Sweden)

    Šćepanović M.

    2006-01-01

    Full Text Available Mechanical activation was used as a method for modification of the structural and optical properties of commercial ZnO powder. For this purpose zinc oxide powder was mechanically treated by grinding in a high-energy vibro-mill in a continual regime in air up to 300 minutes. Starting and modified ZnO samples were characterized using XRD, BET and TEM measurements. Optical properties of these samples were investigated by Raman and photoluminescence (PL spectroscopy. The color of commercial ZnO powder was white while mechanically activated ZnO powder was dark yellow, indicating the presence of nonstoichiometry. In the Raman spectra of non-activated sample Raman modes of bulk ZnO were observed, while the spectra of modified samples point out structural and stoichiometric changes. The PL spectra of modified samples excited by 325 and 442 nm lines of a He-Cd laser show great difference with respect to the spectra of the original sample. This study confirms that change in the defect structure of the ZnO crystal lattice introduced by mechanical activation affects the optical properties of this material.

  8. Tunable color emission via energy transfer in co-doped Ce3+/Dy3+: Li2O-LiF-B2O3-ZnO glasses for photonic applications

    Science.gov (United States)

    Vijayalakshmi, L.; Naveen Kumar, K.; Srinivasa Rao, K.; Hwang, Pyung

    2017-10-01

    A set of co-doped (Ce3+/Dy3+): LBZ glasses were prepared by standard melt quenching technique. The pertinent absorption bands were observed in the optical absorption spectrum of co-doped Ce3+/Dy3+: LBZ glasses. We have been observed a prominent blue and yellow emission pertaining to Dy3+ ions at 0.5 mol % under the excitation of 385 nm doped glasses. However, the photoluminescence intensities were remarkably enhanced by co-doping with Ce3+ ions to Dy3+: LBZ glasses due to energy transfer from Ce3+ to Dy3+. The emission spectra of co-doped (Ce3+/Dy3+): LBZ glass exhibits three strong emissions at 440 nm, 480 nm and 574 nm which are assigned with corresponding electronic transitions of 4I15/2 → 6H15/2, 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 respectively. The Commission International de E'clairage coordinates were calculated from their emission spectra of single doped Dy3+ and co-doped (Ce3+/Dy3+): LBZ glasses. The obtained CIE chromaticity coordinates for optimized co-doped glass are found to be very close to the standard white region. Based on the concentration of Ce3+, the emitting color of the co-doped glass can be changed from blue to white color. The transformation of the color from blue to white region due to energy transfer from Ce3+ to Dy3+. The energy transfer mechanism was substantiated by various fluorescence dynamics such as overlapped spectral profiles, photoluminescence, lifetime decay and CIE color coordinate analysis. These results could be suggested that the obtained co-doped (Ce3+/Dy3+): LBZ glasses are promising candidates for commercial white light applications.

  9. C, N co-doped TiO{sub 2}/TiC{sub 0.7}N{sub 0.3} composite coatings prepared from TiC{sub 0.7}N{sub 0.3} powder using ball milling followed by oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Hao, Liang, E-mail: haoliang@tust.edu.cn [Tianjin Key Lab of Integrated Design and On-line Monitoring for Light Industry & Food Machinery and Equipment, Tianjin (China); College of Mechanical Engineering, Tianjin University of Science & Technology, No. 1038 Dagu Nanlu, Hexi District, Tianjin 300222 (China); Wang, Zhenwei, E-mail: 1004329228@qq.com [School of Naval Architecture and Ocean Engineering, Harbin Institute of Technology, Weihai, No. 2, Wenhua West Road, Weihai 264209 (China); Zheng, Yaoqing, E-mail: 13612177268@163.com [College of Mechanical Engineering, Tianjin University of Science & Technology, No. 1038 Dagu Nanlu, Hexi District, Tianjin 300222 (China); Li, Qianqian, E-mail: 1482471595@qq.com [College of Mechanical Engineering, Tianjin University of Science & Technology, No. 1038 Dagu Nanlu, Hexi District, Tianjin 300222 (China); Guan, Sujun, E-mail: sujunguan1221@gmail.com [College of Mechanical Engineering & Graduate School, Chiba University, 1-33, Yayoi-cho, Inage-ku, Chiba 263-8522 (Japan); Zhao, Qian, E-mail: zhaoqian@tust.edu.cn [Tianjin Key Lab of Integrated Design and On-line Monitoring for Light Industry & Food Machinery and Equipment, Tianjin (China); College of Mechanical Engineering, Tianjin University of Science & Technology, No. 1038 Dagu Nanlu, Hexi District, Tianjin 300222 (China); Cheng, Lijun, E-mail: chenglijun@tust.edu.cn [Tianjin Key Lab of Integrated Design and On-line Monitoring for Light Industry & Food Machinery and Equipment, Tianjin (China); College of Mechanical Engineering, Tianjin University of Science & Technology, No. 1038 Dagu Nanlu, Hexi District, Tianjin 300222 (China); Lu, Yun, E-mail: luyun@faculty.chiba-u.jp [College of Mechanical Engineering & Graduate School, Chiba University, 1-33, Yayoi-cho, Inage-ku, Chiba 263-8522 (Japan); Liu, Jizi, E-mail: jzliu@njust.edu.cn [Herbert Gleiter Institute of Nanoscience, Nanjing University of Science and Technology, No. 200, Xiaolingwei Street, Nanjing 210094 (China)

    2017-01-01

    Highlights: • TiO{sub 2}/TiC{sub 0.7}N{sub 0.3} coatings were prepared by ball milling followed by oxidation. • In situ co-doping of C and N with simultaneous TiO{sub 2} formation was observed. • Improved photocatalytic activity under UV/visible light was noticed. • Synergism in co-doping and heterojunction formation promoted carrier separation. - Abstract: Ball milling followed by heat oxidation was used to prepared C, N co-doped TiO{sub 2} coatings on the surfaces of Al{sub 2}O{sub 3} balls from TiC{sub 0.7}N{sub 0.3} powder. The as-prepared coatings were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and ultraviolet-visible spectrophotometer (UV–vis). The results show that continuous TiC{sub 0.7}N{sub 0.3} coatings were formed after ball milling. C, N co-doped TiO{sub 2}/TiC{sub 0.7}N{sub 0.3} composite coatings were prepared after the direct oxidization of TiC{sub 0.7}N{sub 0.3} coatings in the atmosphere. However, TiO{sub 2} was hardly formed in the surface layer of TiC{sub 0.7}N{sub 0.3} coatings within a depth less than 10 nm during the heat oxidation of TiC{sub 0.7}N{sub 0.3} coatings in carbon powder. Meanwhile, the photocatalytic activity evaluation of these coatings was conducted under the irradiation of UV and visible light. All the coatings showed photocatalytic activity in the degradation of MB no matter under the irradiation of UV or visible light. The C, N co-doped TiO{sub 2}/TiC{sub 0.7}N{sub 0.3} composite coatings showed the most excellent performance. The enhancement under visible light irradiation should attribute to the co-doping of carbon and nitrogen, which enhances the absorption of visible light. The improvement of photocatalytic activity under UV irradiation should attribute to the synergistic effect of C, N co-doping, the formation of rutile-anatase mixed phases and the TiO{sub 2}/TiC{sub 0.7}N{sub 0.3} composite microstructure.

  10. First-principle study on the effect of high Ag–2N co-doping on the ...

    Indian Academy of Sciences (India)

    acceptor co-doped ZnO, further theoretical studies are required ... atoms per unit cell. The 2 × 2 × 2 supercell of pure ZnO employed contained 32 atoms. The calculated lattice parame- ters for ZnO are a = 3.249 Å and c/a = 1.602, in good agree-.

  11. Photocatalytic and antibacterial activity of ZnO powders prepared via sol-gel method

    Directory of Open Access Journals (Sweden)

    Weerachai Sangchay

    2016-02-01

    Full Text Available We report on synthesis of ZnO powders via sol-gel method. The prepared powders were calcined at the temperature of 300, 500 and 700°C for 1 h with the heating rate of 10°C/min. The microstructures of the fabricated powders were characterized by SEM and XRD techniques, and the results show that all samples were the agglomeration and spherical shape and reveal only the wurtzite phase. The photocatalytic activities of the powders were also tested via the degradation of methylene blue (MB solution under UV irradiation. Finally, antibacterial activity efficiency was evaluated by the inactivation of E. coli. It was observed that higher calcined at the temperature gives better photocatalytic and antibacterial activity. With the highest calcined at the temperature investigated in this experiment (T700 condition the powders show photocatalytic and antibacterial activities of 80.06 and 99.00%, respectively.

  12. Changing interfaces: Photoluminescent ZnO nanoparticle powders in different aqueous environments

    Science.gov (United States)

    Kocsis, Krisztina; Niedermaier, Matthias; Bernardi, Johannes; Berger, Thomas; Diwald, Oliver

    2016-10-01

    We transformed vapor phase grown ZnO nanoparticle powders into aqueous ZnO nanoparticle dispersions and studied the impact of associated microstructure and interface property changes on their spectroscopic properties. With photoluminescence (PL) spectroscopy, we probed oxygen interstitials Oi2 - in the near surface region and tracked their specific PL emission response at hvEM = 2.1 eV during the controlled conversion of the solid-vacuum into the solid-liquid interface. While oxygen adsorption via the gas phase does affect the intensity of the PL emission bands, the O2 contact with ZnO nanoparticles across the solid-liquid interface does not. Moreover, we found that the near band edge emission feature at hvEM = 3.2 eV gains relative intensity with regard to the PL emission features in the visible light region. Searching for potential PL indicators that are specific to early stages of particle dissolution, we addressed for aqueous ZnO nanoparticle dispersions the effect of formic acid adsorption. In the absence of related spectroscopic features, we were able to consistently track ZnO nanoparticle dissolution and the concomitant formation of solvated Zinc formate species by means of PL and FT-IR spectroscopy, dynamic light scattering, and zeta potential measurements. For a more consistent and robust assessment of nanoparticle properties in different continuous phases, we discuss characterization challenges and potential pitfalls that arise upon replacing the solid-gas with the solid-liquid interface.

  13. Effects of Cu and Zn co-doping on the electrical properties of Ni0.5Mn2.5O4 NTC ceramics

    NARCIS (Netherlands)

    Zhao, Chunhua; Wang, Biyun; Winnubst, Aloysius J.A.; Yang, Pinghua; Chen, Chusheng

    2008-01-01

    The effects of Cu and Zn co-doping on Ni–Mn–O spinel-structured NTC ceramics were investigated. Dense Cu and Zn co-doped Ni0.5Mn2.5O4 spinel-structured ceramics were prepared from mixed oxalate-derived powders. XPS analysis revealed that in the co-doped material CuxZn1.0Ni0.5Mn1.5−xO4, the majority

  14. co-doped zinc oxide

    Indian Academy of Sciences (India)

    and TEM analyses indicated the presence of nanocrystal- lites aggregated in different shape particles. The band gap decreases in the case of the doped ZnO samples. Regarding the doped samples, the highest average visible transmittance of 89% and the lowest resistivity of 6.7 × 10−3 cm. PL spectra of the nanopowder ...

  15. Nano-sized ZnO powders prepared by co-precipitation method with various pH

    Science.gov (United States)

    Purwaningsih, S. Y.; Pratapa, S.; Triwikantoro, Darminto

    2016-04-01

    In this work, nano-sized ZnO powders have been synthesized by the co-precipitation method with Zn(CH3COOH)2.2H2O, HCl, and NH3.H2O as raw materials in various pH ranging from 8 to 10. The purity, microstructure, chemical group analysis, morphology of the prepared ZnO powders were studied by X-ray diffraction (XRD), Fourier transform infrared spectrometer (FTIR), energy dispersive X-ray spectrometry (EDX), and scanning electron microscope (SEM), respectively. Rietveld refinement of XRD data showed that ZnO crystallizes in the wurtzite structure with high purity. The obtained powders were nano-sized particles with the average crystallite size about 17.9 ± 2.1 nm synthesized with pH of 9.5, at 85°C, and stirring time of 6 h. The SEM results have visualied the morphology of ZnO nanoparticles with spherical-like shape. The effect of processing conditions on morphology of ZnO was also discussed.

  16. Clean Synthesis of Pyrano[2,3- D]Pyrimidines Using ZnO Nano-Powders

    Directory of Open Access Journals (Sweden)

    Maleki Nariman

    2016-07-01

    Full Text Available ZnO nano-powders were used for the one-pot synthesis of pyrano[2,3- d]pyrimidines via the solvent-free multi-component reaction of aromatic aldehydes, 1,3-dimethylbarbituric acid and malononitrile, in good to excellent yields of products.

  17. Sintering behavior of doped ZnO powders for high field varistors

    Energy Technology Data Exchange (ETDEWEB)

    Ghirlanda, M.

    1990-08-01

    The sintering of ZnO varistor precursor powders, doped with Co, Mn and different concentrations of Bi and Al, is investigated and discussed in relation with sintering models. One purpose of the present study is to provide information valuable for the fabrication of high field varistors. As the fundamental parameter of these electronic components is the breakdown voltage per unit of thickness, which is determined by the number of grain boundaries per linear dimension, the grain size and the sintered density are crucial variables, and the sintering is a central step in the manufacturing of such varistors. Sintering experiments performed at constant heating rate in a loading dilatometer provide data on the densification and creep of the compacted powders. Another goal of the present study is to provide an experimental basis for the interpretation of the evolution of the ratio between densification rate and creep rate in terms of competition between densification and microstructure coarsening. This is accomplished by taking advantage of the variety of sintering behaviors that takes place in the system ZnO-Bi-Al: the comparison of these behaviors allows us to correlate the macroscopic sintering parameters to the evolution of the microstructure. It results that, while in non-doped powders densification and coarsening develop in a balanced way, resulting in the constancy of the ratio between densification rate and creep rate, the effect of the dopants on the sintering kinetics alters such a balance, leading this ratio to vary. 17 figs.

  18. Preparation, Infrared Emissivity, and Dielectric and Microwave Absorption Properties of Fe-Doped ZnO Powder

    Science.gov (United States)

    Su, Xiaolei; Jia, Yan; Liu, Xiaoqin; Wang, Junbo; Xu, Jie; He, Xinhai; Fu, Chong; Liu, Songtao

    2014-11-01

    Fe-doped ZnO powders have been synthesized by the coprecipitation method using zinc nitrate [Zn(NO3)2·6H2O] as starting material, urea [CO(NH2)2] as precipitator, and ferric nitrate [Fe(NO3)3·9H2O] as doping source. The microstructure of the prepared powders has been characterized by x-ray diffraction and scanning electron microscopy. Results show that, when the molar ratio of Fe to (Zn + Fe) was less than 0.09, the prepared powder was ZnO(Fe) solid solution, and the ZnFe2O4 impurity phase appeared when the Fe doping content was further increased. The electric permittivity in the frequency range of 8.2 GHz to 12.4 GHz and the average infrared emissivity in the wavelength range of 8 μm to 14 μm have been determined for the prepared powders. The average infrared emissivity decreased with increasing Fe doping content. The real ( ɛ') and imaginary part ( ɛ″) of the permittivity of the prepared powders showed opposite trends. When the molar ratio of Fe to (Zn + Fe) was 0.03, the prepared Fe-doped ZnO powder demonstrated the best microwave absorption in the frequency range of 8.2 GHz to 12.4 GHz.

  19. Sea-urchin-like ZnO nanostructures on Si by oxidation of Zn metal powders: Structural and optical properties

    Science.gov (United States)

    Umar, A.; Kim, S. H.; Hahn, Y. B.

    2006-01-01

    High-density sea-urchin-like ZnO nanostructures were grown on Si(100) substrates by the oxidation of metallic Zn powders at a low growth temperature without the use of any catalyst or additives. The morphological studies indicated that the grown structures are uniformly dispersed on the substrate and exhibited a sea-urchin-like shape consisting of several thousands of nanorods in one array, each ZnO nanorod of these structures having the diameter of 20-50 nm with the length of 2-4 μm. The high-resolution transmission electron microscopy and selected area electron diffraction patterns showed that the prepared sea-urchin-like ZnO nanostructures were single crystalline with wurtzite hexagonal structure and preferably grown along the [0001] direction. Room temperature Raman scattering and photoluminescence studies found that the as-grown nanostructures have good crystal quality with the hexagonal wurtzite phase.

  20. Room temperature ferromagnetism in Eu-doped ZnO nanoparticulate powders prepared by combustion reaction method

    Science.gov (United States)

    Franco, A.; Pessoni, H. V. S.; Soares, M. P.

    2014-04-01

    Nanoparticulate powders of Eu-doped ZnO with 1.0, 1.5, 2.0 and 3.0 at% Eu were synthesized by combustion reaction method using zinc nitrate, europium nitrate and urea as fuel without subsequent heat treatments. X-ray diffraction patterns (XRD) of all samples showed broad peaks consistent with the ZnO wurtzite structure. The absence of extra reflections in the diffraction patterns ensures the phase purity, except for x=0.03 that exhibits small reflection corresponding to Eu2O3 phase. The average crystallite size determined from the most prominent (1 0 1) peak of the diffraction using Scherrer's equation was in good agreement with those determined by transmission electron microscopy (TEM); being ~26 nm. The magnetic properties measurements were performed using a vibrating sample magnetometer (VSM) in magnetic fields up to 2.0 kOe at room temperature. The hysteresis loops, typical of magnetic behaviors, indicating that the presence of an ordered magnetic structure can exist in the Eu-doped ZnO wurtzite structure at room temperature. The room temperature ferromagnetism behavior increases with the Eu3+ doping concentration. All samples exhibited the same Curie temperature (TC) around ~726 K, except for x=0.01; TC~643 K. High resolution transmission electron microscopy (HRTEM) images revealed defects/strain in the lattice and grain boundaries of Eu-doped ZnO nanoparticulate powders. The origin of room temperature ferromagnetism in Eu-doped ZnO nanoparticulate powders was discussed in terms of these defects, which increase with the Eu3+ doping concentration.

  1. A Mössbauer and magnetic study of ball milled Fe-doped ZnO Powders

    Energy Technology Data Exchange (ETDEWEB)

    Zamora, Ligia E., E-mail: ligia.zamora@correounivalle.edu.co; Paz, J. C.; Piamba, J. F.; Tabares, J. A.; Alcázar, G. A. Pérez [Universidad del Valle, Departamento de física (Colombia)

    2015-06-15

    The structural and magnetic properties of Fe-doped ZnO are reported in this study, as obtained by mechanical alloying from elemental powders of ZnO and Fe. The properties of Zn{sub 0.90}Fe{sub 0.10}O samples alloying while varying the milling time (6, 12, 24 and 36 h) are also reported. The Rietveld refinement of X-ray Diffraction (XRD) patterns revealed that the system presents two structures: the würtzite structure of ZnO and the bcc structure of α-Fe. The Mössbauer spectra show that the samples present three components: a ferromagnetic component, associated with the Fe phase and two paramagnetic components, associated with the Fe atoms, which penetrate inside the ZnO matrix behaving as Fe{sup 3+} and Fe{sup 2+}. The milling time contributes to an increase in the paramagnetic sites, and a solubility limit of the Fe atoms in the ZnO lattice was detected. The VSM measurements at room temperature detected ferromagnetic behavior with a saturation magnetization of 11 emu/g and a coercive field of 330 Oe for the sample alloyed over 24 h. A similar behavior was shown by the other samples.

  2. Effect of Li+ co-doping on the luminescence properties of ZnO:Tb 3+ nanophosphors

    OpenAIRE

    PARTHA P. PAL; MANAM J.

    2013-01-01

    Li + co-doped ZnO:Tb 3+ nanocrystals were synthesized via the chemical co-precipitation method in order to study the effect of Li + co-doping. The samples were characterized by means of SEM, XRD, FTIR, Reflectance, PL and TL studies. SEM images showed that the samples were composed of nanorods with diameters of 50 to 90 nm and lengths of approximately 600 nm to 1.3 μm. XRD analysis revealed pure phase of ZnO with hexagonal wurtzite structure. XRD study also showed no change in the peak patter...

  3. Polymer-assisted deposition of co-doped zinc oxide thin films for the detection of aromatic organic compounds.

    Science.gov (United States)

    Li, Wei; Kim, Dojin

    2011-12-01

    Co-doped Zinc oxide thin films are deposited onto SiO2/Si substrate by polymer-assisted deposition method. The surface morphology, structures and chemical states of the thin films are examined by scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The gas-sensing properties of the thin films upon exposure to aromatic organic compound vapors are also investigated. Co-doping is shown to be very effective in enhancing the response of ZnO thin film to aromatic organic compound.

  4. Gallium and indium co-doping of epitaxial zinc oxide thin films grown in water at 90 °C

    Science.gov (United States)

    Quang Le, Hong; Chua, Soo Jin

    2011-03-01

    Zinc oxide (ZnO) thin films were intentionally co-doped with group III elements (gallium) in order to investigate and understand the effects of co-doping on the morphological, electrical and optical properties of gallium-doped ZnO (GZO) films. The co-doped films were grown on MgAl2O4 spinel substrates using a low-temperature solution-phase method known as hydrothermal synthesis. Gallium with indium co-doped ZnO (GIZO) films displayed a dramatic improvement in surface morphology as compared with the Ga-doped ZnO (GZO) films due to the compensation effect of gallium and indium doping which reduced the lattice strain. The 0.0033M gallium with 3.3 × 10-4M indium co-doped film exhibited an electron concentration of 3.14 × 1020 cm-3 and resistivity of 7.4 × 10-4 Ω cm which were both enhancements of 1.5 times over the GZO film. These films were comparable to the films fabricated by more expensive and complicated vapour-phase methods. The figure of merit for this film was determined to be 1.63 × 10-2 sq/Ω which was very close to the indium tin oxide conducting films currently used commercially. Finally, the GIZO film was hydrothermally grown on a p-GaN film to form an n-ZnO/p-GaN heterojunction light-emitting diode (LED). This LED showed diode I-V characteristics and exhibited strong cool-white light emission which signified the prospect of using GIZO as an effective and low-cost n-type layer in LEDs.

  5. Morphological and Humidity Sensing Studies of WO3 Mixed with ZnO and TiO2 Powders

    Directory of Open Access Journals (Sweden)

    N. K. Pandey

    2008-09-01

    Full Text Available This paper reports resistive type humidity sensing properties of composite powder of WO3, ZnO and TiO2 taken in the ratio of 8:2:1. Tungsten oxide powder has been obtained by oxidizing Tungsten powder (Lobachemie, 99 % pure at 600 0C. 250 mg of ZnO (qualigens, 99% pure and 125 mg of TiO2 (qualigens, 98% pure have been mixed with 1 gram of WO3. Pellet of this powder mixture has been made at pressure of 3 tones for half an hour. The pellet has been annealed at temperatures of 300 0C, 400 0C and 500 0C. Humidity sensing application of pellet has been studied in a specially designed chamber. Standard solution of potassium sulphate has been used as humidifier and potassium hydroxide as de-humidifier. Variation in resistances has been noted using Sinometre (MΩ range,VC 9808. Relative humidity is measured using standard hygrometer (Huger, Germany. It has been observed that as relative humidity increases, there is decrease in the resistance of the pellet. After annealing of sample at each temperature, it has been exposed to humidity in the chamber. The mean sensitivity of the pellet is calculated for each annealing temperature. It has been observed that as annealing temperature increases from 300 0C to 500 0C, mean sensitivity increases. This composite material carries a good scope for the development of resistive type humidity sensor.

  6. Adsorption of Remazol Brilliant Blue R using ZnO fine powder: equilibrium, kinetic and thermodynamic modeling studies.

    Science.gov (United States)

    Ada, Kezban; Ergene, Aysun; Tan, Sema; Yalçin, Emine

    2009-06-15

    Zinc oxide powders with six-sided flake-like particles were prepared by homogeneous precipitation from boiling aqueous solutions that contained excess urea and 0.075 (Z075) and 0.300 (Z300)M Zn(2+). The average sizes of the particles are 37 and 46 microm, while the average sizes of the crystals are approximately 45 for Z075 and Z300 at 1000 degrees C. Equilibrium, kinetic and thermodynamic studies were carried out for the adsorption of RBBR dye from aqueous solution using both types of ZnO in the form of fine powders. The effects of pH, initial dye concentration, contact time and temperature of solution on the adsorption were studied. Langmuir, Temkin and Dubinin-Radushkevich (D-R) isotherm models were used to describe the adsorption of RBBR onto ZnO powders. The Langmuir and D-R isotherm models fit the equilibrium data better than the Temkin isotherm model. The monomolecular adsorption capacity of Z075 and Z300 was determined to be 190 and 345 mg g(-1) for RBBR, respectively. The Lagergren first-order, Ritchie second-order kinetic and intra-particle diffusion models were used for the adsorption of the dye onto ZnO powders. The Ritchie second-order model was suitable for describing the adsorption kinetics for the removal of RBBR from aqueous solution onto Z075 and Z300. Thermodynamic parameters, such as the Gibbs free energy (DeltaG(#)), enthalpy (DeltaH(#)), entropy (DeltaS(#)) and equilibrium constant of activation (K(#)) were calculated. These parameters showed that the adsorption process of RBBR onto Z075 and Z300 was an endothermic process of a chemical nature under the studied conditions.

  7. Adsorption of Remazol Brilliant Blue R using ZnO fine powder: Equilibrium, kinetic and thermodynamic modeling studies

    Energy Technology Data Exchange (ETDEWEB)

    Ada, Kezban [Department of Chemistry, Faculty of Arts and Sciences, Kirikkale University, 71450 Yahsihan-Kirikkale (Turkey); Ergene, Aysun, E-mail: ayergene@yahoo.com [Department of Biology, Faculty of Arts and Sciences, Kirikkale University, 71450 Yahsihan-Kirikkale (Turkey); Tan, Sema; Yalcin, Emine [Department of Biology, Faculty of Arts and Sciences, Kirikkale University, 71450 Yahsihan-Kirikkale (Turkey)

    2009-06-15

    Zinc oxide powders with six-sided flake-like particles were prepared by homogeneous precipitation from boiling aqueous solutions that contained excess urea and 0.075 (Z075) and 0.300 (Z300) M Zn{sup 2+}. The average sizes of the particles are 37 and 46 {mu}m, while the average sizes of the crystals are {approx}45 for Z075 and Z300 at 1000 deg. C. Equilibrium, kinetic and thermodynamic studies were carried out for the adsorption of RBBR dye from aqueous solution using both types of ZnO in the form of fine powders. The effects of pH, initial dye concentration, contact time and temperature of solution on the adsorption were studied. Langmuir, Temkin and Dubinin-Radushkevich (D-R) isotherm models were used to describe the adsorption of RBBR onto ZnO powders. The Langmuir and D-R isotherm models fit the equilibrium data better than the Temkin isotherm model. The monomolecular adsorption capacity of Z075 and Z300 was determined to be 190 and 345 mg g{sup -1} for RBBR, respectively. The Lagergren first-order, Ritchie second-order kinetic and intra-particle diffusion models were used for the adsorption of the dye onto ZnO powders. The Ritchie second-order model was suitable for describing the adsorption kinetics for the removal of RBBR from aqueous solution onto Z075 and Z300. Thermodynamic parameters, such as the Gibbs free energy ({Delta}G{sup numbersign}), enthalpy ({Delta}H{sup numbersign}), entropy ({Delta}S{sup numbersign}) and equilibrium constant of activation (K{sup numbersign}) were calculated. These parameters showed that the adsorption process of RBBR onto Z075 and Z300 was an endothermic process of a chemical nature under the studied conditions.

  8. Ferromagnetism at room temperature in Co-doped KNbO{sub 3} bulk samples

    Energy Technology Data Exchange (ETDEWEB)

    Astudillo, A., E-mail: jaastudillo@unicauca.edu.co [Low Temperature Laboratory, Department of Physics, University of Cauca, Calle 5 No. 4-70, Popayán (Colombia); Izquierdo, J.L. [Universidad Nacional de Colombia, Campus Medellín, Departamento de Física, Laboratorio de Materiales Cerámicos y Vítreos, A.A. 568, Medellín (Colombia); Gómez, A. [Universidad Nacional de Colombia, Campus Medellín, Facultad de Minas, Laboratorio de Caracterización de Materiales, A.A. 568, Medellín (Colombia); Bolaños, G. [Low Temperature Laboratory, Department of Physics, University of Cauca, Calle 5 No. 4-70, Popayán (Colombia); Morán, O. [Universidad Nacional de Colombia, Campus Medellín, Departamento de Física, Laboratorio de Materiales Cerámicos y Vítreos, A.A. 568, Medellín (Colombia)

    2015-01-01

    In this work, polycrystalline KNb{sub 1−x}Co{sub x}O{sub 3} (x=0, 0.05 and 0.1) samples were synthesized through standard solid-state reaction, and their structural and magnetic properties were carefully studied. The X-ray powder diffraction (XRD) patterns show reflections of a pure orthorhombic structure (space group Bmm2) with lattice parameters being very close to those reported in the literature. The most important point here is that all the samples ended up being single-phase with no affectation by impurities or segregates. The XRD peaks of Co-doped samples are broadened and shifted to the right side as compared to those of the pristine compound (x=0) suggesting effective substitution of Nb by Co ions. The Co-doped samples exhibit ferromagnetic properties at room temperature, which contrasts starkly with the paramagnetic behavior exhibited by the undoped sample. Interactions between bound magnetic polarons are considered as a possible scenario to explain the appearance of the ferromagnetic signal in the Co-doped samples. - Highlights: • Polycrystalline KNb{sub 1−x}Co{sub x}O{sub 3} (x=0, 0.05 and 0.1) is synthesized by physical route. • XRD patterns show reflections of a pure orthorhombic structure. • No affectation by impurities or segregates is verified by XRD analysis. • The Co-doped samples exhibit ferromagnetic properties at room temperature.

  9. Synthesis and characterization of nano ZnO and MgO powder by low temperature solution combustion method: studies concerning electrochemical and photocatalytic behavior

    OpenAIRE

    KUMARA K. N. SHRAVANA; NAGASWARUPA H.P.; MAHESH K. R. VISHNU; S.C. Prashantha; MYLARAPPA M.; SIDDESHWARA D.M.K.

    2016-01-01

    The objective of the research was mainly focused on the synthesis of ZnO and MgO nanoparticle by low temperature solution combustion method using Urea as fuel. The accurate size and morphology of the nanoparticles were studied from Transmission Electron Microscopy (TEM) to assess the structure of the ZnO and MgO particles. The phase composition of the Synthesized ZnO and MgO nanoparticles were confirmed from powder X-ray diffractometer (PXRD). The electrochemical impedance spectroscopy (EIS) ...

  10. Tuning the photoluminescence of graphene quantum dots by co-doping of nitrogen and sulfur

    Science.gov (United States)

    Luo, Yi; Li, Ming; Sun, Lang; Xu, Yongjie; Hu, Guanghui; Tang, Tao; Wen, Jianfeng; Li, Xinyu

    2017-11-01

    Nitrogen and sulfur co-doped graphene quantum dots (NS-GQDs) were successfully synthesized using a facile, inexpensive, and environmentally friendly hydrothermal reaction of aqueous ammonia, S powder, and graphene quantum dots. The NS-GQDs with oxygen-rich functional groups have a high quantum yield of 41% and a diameter of 1-5 nm. The photoluminescence (PL) properties of the nitrogen-doped graphene quantum dots (N-GQDs) and NS-GQD were investigated. The results showed that the PL emission of the NS-GQD exhibits a clear blue shift of 54 nm compared to that of the N-GQDs.

  11. Switch 'on' and 'off' ferromagnetic ordering through the induction and removal of oxygen vacancies and carriers in doped ZnO: A magnetization and electronic structure study

    Energy Technology Data Exchange (ETDEWEB)

    Singhal, R.K.; Samariya, A.; Dolia, S.N. [Department of Physics, University of Rajasthan, Jaipur 302004 (India); Kumar, S. [Department of Physics, ML Sukhadia University, Udaipur 313002 (India); Xing, Y.T.; Saitovitch, Elisa B. [CBPF, Rua Dr. Xavier Sigaud 150, Rio de Janeiro (Brazil); Deshpande, U.P.; Shripathi, T. [UGC-DAE CSR, University Campus, Indore 452001 (India)

    2010-10-15

    The electronic structure and magnetic properties of cobalt-doped (7.5%) and manganese co-doped (2.5%) ZnO polycrystalline samples have been investigated to understand the mechanism of room temperature ferromagnetism (RTFM) in dilute magnetic semiconductors. The samples in powder form were annealed in argon and hydrogen atmospheres followed by their repressing into pellets and reheating in air. Rietveld analysis of X-ray diffraction patterns confirmed the single-phase nature of the samples in the wurtzite type hexagonal (P6{sub 3}mc) ZnO structure. The X-ray photoelectron spectroscopy (XPS) results indicate that the Co and Mn atoms are in +2 oxidation states, which incorporate at the Zn{sup 2+} site, with no signature of metallic clusters. The Co-doped sample prepared in air displays a paramagnetic state while the sample annealed in Ar atmosphere shows a weak ferromagnetic ordering at 300 K. The co-doping of Mn further enhances the ferromagnetic ordering, indicating that Co and Mn ions play an additive role in inducing the ferromagnetic ordering in the ZnO matrix. Interestingly, the Co- and (Co+Mn)-doped ZnO samples annealed in hydrogen atmosphere show a huge increment in the magnetic moment, however, the Mn ions seem to stay passive towards the hydrogen induced magnetization. Notably, the samples reheated in air show suppression of the induced ferromagnetism (FM). The resistance measurements suggest that the additional carriers induced upon hydrogenation also play some role in mediating the exchange coupling. The O 1s XPS and the XRD results show clear evidence of oxygen depletion in the samples upon hydrogenation, followed by a recovery upon their reheating in air. The observed FM is explained in terms of composite effect of the oxygen vacancies and the carrier density. Our results point out that the ferromagnetic ordering could be switched between 'on' and 'off' by introducing (through hydrogenation) and by removing (through reheating in air

  12. Synthesis and Characterization of La, Sc, Yb and Nd co-doped Gadolinium doped Cerium (GDC) Composite Electrolyte for IT-SOFC

    Science.gov (United States)

    Damisih; Raharjo, Jarot; Masmui; Setya Aninda, Raffty; Ami Lestari, Novita

    2017-07-01

    Composite based on gadolinium doped cerium (GDC) co-doped Lanthanum (La), Scandium (Sc), Ytterbium (Yb) were investigated as electrolyte for solid oxide fuel cell (SOFC), namely GDC-La, GDC-Sc, GDC-Yb and GDC-Nd, respectively. The second co-doped La, Sc, Yb and Nd ensured the stability and high ionic conductivity of the GDC ceria-based electrolyte materials for SOFC. The GDC powder was synthesized via sol-gel technique. Then the La-GDC, Sc-GDC, Yb-GDC and GDC-Nd were subsequently prepared by mixing the GDC with La, Sc, Yb, and Nd respectively, through solid-state reaction in ballmill at 200rpm alumina balls. The composite electrolytes were then characterized in terms of its morphology, phase and thermal properties of the powders. Among the composite electrolytes investigated, GDC-Yb powder show higher purity and better dispersion than the others co-doped GDC. TGA analysis present that the addition of co-dopant led to improve thermal resistance and stability of solid electrolyte powders. The results confirm that GDC with co-dopant is promising alternative electrolyte for intermediate temperature solid oxide fuel cells (IT-SOFC).

  13. Lu3+/Yb3+ and Lu3+/Er3+ co-doped antimony selenide nanomaterials: synthesis, characterization, and electrical, thermoelectrical, and optical properties

    Science.gov (United States)

    Hanifehpour, Younes; Joo, Sang Woo; Min, Bong-Ki

    2013-03-01

    Lu3+/Yb3+ and Lu3+/Er3+ co-doped Sb2Se3 nanomaterials were synthesized by co-reduction method in hydrothermal condition. Powder X-ray diffraction patterns indicate that the Ln x Ln' x Sb2-2 x Se3 Ln: Lu3+/Yb3+ and Lu3+/Er3+ crystals ( x = 0.00 - 0.04) are isostructural with Sb2Se3. The cell parameters were increased for compounds upon increasing the dopant content ( x). Scanning electron microscopy and transmission electron microscopy images show that co-doping of Lu3+/Yb3+ ions in the lattice of Sb2Se3 produces nanorods, while that in Lu3+/Er3+ produces nanoparticles, respectively. The electrical conductivity of co-doped Sb2Se3 is higher than that of the pure Sb2Se3 and increases with temperature. By increasing the concentration of Ln3+ions, the absorption spectrum of Sb2Se3 shows red shifts and some intensity changes. In addition to the characteristic red emission peaks of Sb2Se3, emission spectra of co-doped materials show other emission bands originating from f- f transitions of the Yb3+ ions.

  14. Structure and characterization of Sn, Al co-doped zinc oxide thin films prepared by sol–gel dip-coating process

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Min-I [Institute of Materials Science and Engineering, National Central University, Taiwan (China); Laboratoire de Nanotechnologie et d' Instrumentation Optique, Institut Charles Delaunay, CNRS - UMR STMR 6279, Université de Technologie de Troyes (France); Huang, Mao-Chia [Institute of Materials Science and Engineering, National Central University, Taiwan (China); Legrand, David [Institute of Materials Science and Engineering, National Central University, Taiwan (China); Laboratoire de Nanotechnologie et d' Instrumentation Optique, Institut Charles Delaunay, CNRS - UMR STMR 6279, Université de Technologie de Troyes (France); Lerondel, Gilles [Laboratoire de Nanotechnologie et d' Instrumentation Optique, Institut Charles Delaunay, CNRS - UMR STMR 6279, Université de Technologie de Troyes (France); Lin, Jing-Chie, E-mail: jclin4046@gmail.com [Institute of Materials Science and Engineering, National Central University, Taiwan (China)

    2014-11-03

    Transparent conductive zinc oxide co-doped with tin and aluminum (TAZO) thin films were prepared via sol–gel dip-coating process. Non-toxic ethanol was used in this study instead of 2-methoxyethanol used in conventional work. Dip-coating was repeated several times to obtain relatively thick films consisting of six layers. The films were then annealed at 500 °C for 1 h in air or in vacuum and not subsequently as employed in other studies. The X-ray diffraction patterns indicated that all the samples revealed a single phase of hexagonal ZnO polycrystalline structure with a main peak of (002). The optical band gap and resistivity of the TAZO films were in the ranges of 3.28 to 3.32 eV and 0.52 to 575.25 Ω cm, respectively. The 1.0 at.% Sn, 1.0 at.% Al co-doped ZnO thin film annealed in vacuum was found to have a better photoelectrochemical performance with photocurrent density of about 0.28 mA/cm{sup 2} at a bias of 0.5 V vs. SCE under a 300 W Xe lamp illumination with the intensity of 100 mW/cm{sup 2}. Compared to the same dopant concentration but annealed in air (∼ 0.05 mA/cm{sup 2} bias 0.5 V vs. SCE), the photocurrent density of the film annealed in vacuum was 5 times higher than the film annealed in air. Through electrochemical measurements, we found that the dopant concentration of Sn plays an important role in TAZO that affected photocurrent density, stability of water splitting and anti-corrosion. - Highlights: • Al, Sn co-doped ZnO (TAZO) films was synthesized by sol–gel process. • The parameters of TAZO films were dopant concentration and annealed ambient. • The photoelectrochemical characteristics of TAZO films were investigated.

  15. Multifunctional lanthanide and silver ion co-doped nano-chlorapatites with combined spectroscopic and antimicrobial properties.

    Science.gov (United States)

    Wiglusz, R J; Drulis-Kawa, Z; Pazik, R; Zawisza, K; Dorotkiewicz-Jach, A; Roszkowiak, J; Nedelec, J M

    2015-04-21

    Nanocrystalline chlorapatites (Ca10(PO4)6Cl2) doped with lanthanide ions (Eu(3+), Er(3+) and Yb(3+)) and co-doped with silver ions (Ag(+)) were synthesized by a hydrothermal synthesis route. XRD, TEM, and SAED measurements indicated that the powders are single phased and crystallize with a hexagonal structure with good dispersion. The results showed well crystallized chlorapatite grains with a diameter of about 45 nm. The antimicrobial activity of the nanoparticles against Escherichia coli ATCC 11229 and ATCC 25922, Klebsiella pneumoniae ATCC 700603, and Pseudomonas aeruginosa PAO1 and ATCC 27853 was studied. The best activity was observed for the Eu(3+),Ag(+):Ca10(PO4)6Cl2 and Eu(3+),Ag(+),Yb(3+):Ca10(PO4)6Cl2 compositions. These multifunctional nanocrystalline powders could be used as a promising antimicrobial agent and material for bio-detection.

  16. Photocatalytic degradation of organic dyes under solar light irradiation combined with Er{sup 3+}:YAlO{sub 3}/Fe- and Co-doped TiO{sub 2} coated composites

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Rui; Li, Jia; Wang, Jun; Wang, Baoxin; Luan, Xiaoyu; Zhang, Xiangdong [Department of Chemistry, Liaoning University, Shenyang 110036 (China); Wang, Xiaofang; Liu, Bin [Department of Pharmacy, Liaoning University, Shenyang 110036 (China)

    2010-06-15

    In order to extend the photocatalytic performance of TiO{sub 2}, two new photocatalysts of Er{sup 3+}:YAlO{sub 3}/Fe- and Co-doped TiO{sub 2} coated composites were prepared by the sol-gel process and characterized by XRD and TG-DTA. And then, their photocatalytic activities through the degradation of azo fuchsine under solar light irradiation were evaluated by HPLC techniques and UV-vis spectra. The influencing factors such as the Er{sup 3+}:YAlO{sub 3} content, heat-treated temperature and heat-treated time on the photocatalytic activities of Er{sup 3+}:YAlO{sub 3}/Fe- and Co-doped TiO{sub 2} coated composites were reviewed. Otherwise, the solar light irradiation time, initial concentration of azo fuchsine, photocatalyst addition amount and kind of organic dyes on the photocatalytic degradation of azo fuchsine were also studied. All experimental results indicate that the Er{sup 3+}:YAlO{sub 3}/Fe- and Co-doped TiO{sub 2} coated composites are more effective than Fe- and Co-doped TiO{sub 2} powders. That is because the Er{sup 3+}:YAlO{sub 3} can transform the visible light into the ultraviolet light and enhance the photocatalytic activities of Fe- and Co-doped TiO{sub 2} powders. It is possible to provide a new way to utilize the Er{sup 3+}:YAlO{sub 3}/Fe- and Co-doped TiO{sub 2} coated composites under the solar light irradiation for the treatment of wastewater in the future. (author)

  17. Fluorine and sulfur simultaneously co-doped suspended graphene

    Science.gov (United States)

    Struzzi, C.; Sezen, H.; Amati, M.; Gregoratti, L.; Reckinger, N.; Colomer, J.-F.; Snyders, R.; Bittencourt, C.; Scardamaglia, M.

    2017-11-01

    Suspended graphene flakes are exposed simultaneously to fluorine and sulfur ions produced by the μ-wave plasma discharge of the SF6 precursor gas. The microscopic and spectroscopic analyses, performed by Raman spectroscopy, scanning electron microscopy and photoelectron spectromicroscopy, show the homogeneity in functionalization yield over the graphene flakes with F and S atoms covalently bonded to the carbon lattice. This promising surface shows potential for several applications ranging from biomolecule immobilization to lithium battery and hydrogen storage devices. The present co-doping process is an optimal strategy to engineer the graphene surface with a concurrent hydrophobic character, thanks to the fluorine atoms, and a high affinity with metal nanoparticles due to the presence of sulfur atoms.

  18. Microstructure and enhanced dielectric properties of yttrium and zirconium co-doped CaCu{sub 3}Ti{sub 4}O{sub 12} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Zunping, E-mail: xzp16213@163.com [Faculty of Materials and Energy, Southwest University, Chongqing 400715 (China); Qiang, Hua [College of Electromechanical Engineering, Chongqing College of Humanities, Science and Technology, Chongqing 401524 (China); Chen, Yi; Chen, Zhiqian [Faculty of Materials and Energy, Southwest University, Chongqing 400715 (China)

    2017-04-15

    CaCu{sub 3}Ti{sub 4}O{sub 12} (CCTO) ceramics doped with Y{sub 2}O{sub 3}, ZrO{sub 2}, and (Y{sub 2}O{sub 3}+ZrO{sub 2}) were prepared by the citrate-nitrate combustion derived powders in order to investigate the effect of dopants on the microstructure and electrical properties. The results showed that giant dielectric response was enhanced by co-doping of Y{sup 3+} and Zr{sup 4+} ions at the Ti site. Y{sub 2}O{sub 3} and ZrO{sub 2} additive can inhibit the grain growth. Compared with other samples, (Y{sub 2}O{sub 3}+ZrO{sub 2}) co-doped ceramics exhibit a dense and homogenous fine-grained microstructure. A much better temperature and frequency stability of dielectric properties were realized in these ceramics. The dielectric loss (tan δ) < 0.05 in the frequency range of 200 Hz–60 kHz at room temperature, and in the temperature range of 15–72 °C at 10 kHz was successfully accomplished in (Y{sub 2}O{sub 3}+ZrO{sub 2}) co-doped CCTO ceramics. Low tan δ ∼0.039 and high dielectric constant (ε{sub r} ∼10196) were observed at room temperature and 10 kHz for the above ceramic samples, and the characteristic frequency shifts to higher frequency with increasing measuring temperature. The present results indicate that (Y{sub 2}O{sub 3}+ZrO{sub 2}) co-doping may improve the dielectric properties and increase the grain boundary resistance of CCTO. - Highlights: • Y and Zr co-doped CCTO exhibits a dense and homogenous fine-grained microstructure. • Y and Zr co-doped CCTO performs a lower dielectric loss in wide-range of frequency. • Temperature and frequency stability of dielectric properties were greatly enhanced.

  19. Photochemical quenching of aqueous methylene blue by N, Nb co-doped TiO2 nanomaterials under visible light: a confirmatory UV/LC-MS study

    Science.gov (United States)

    Gupta, Kamini; Pandey, Ashutosh; Singh, R. P.

    2017-12-01

    Nanodimensional un-doped, Nb doped, N doped and N,Nb co-doped TiO2 particles have been prepared by the sol-gel procedure. Phase identification of the anatase particles was done by X-ray powder diffraction and Deby–Scherrer calculations revealed their particle sizes to range from 20 to 30 nm. The band gap energies of the samples were measured by UV–Vis-diffuse reflectance (UV-DRS) spectra. While un-doped TiO2 showed wide optical absorption in the UV region. The co-doped TiO2 particles exhibited narrow band gaps of ~2.7 eV, which showed absorption in the visible region. A decline in charge carrier recombination rates in the prepared samples was confirmed through photoluminescence (PL). The morphological appearances of the particles have been examined by scanning electron microscopy. X-ray photoelectron spectroscopy (XPS) of the samples confirmed the incorporations of N and Nb into the TiO2 matrices. The photocatalytic efficiencies of the prepared particles have been determined by the degradation of the non-biodegradable dye methylene blue (MB) under electromagnetic radiation. The co-doped sample showed superior photocatalytic activity under the visible light (λ  >  400) over the other samples. Photochemical quenching of aqueous MB was further analysed by UV/LC-MS which confirmed the attenuation of methylene blue.

  20. Electrochemical Properties for Co-Doped Pyrite with High Conductivity

    Directory of Open Access Journals (Sweden)

    Yongchao Liu

    2015-09-01

    Full Text Available In this paper, the hydrothermal method was adopted to synthesize nanostructure Co-doped pyrite (FeS2. The structural properties and morphology of the synthesized materials were characterized using X-ray diffraction (XRD and scanning electron microscopy (SEM, respectively. Co in the crystal lattice of FeS2 could change the growth rate of different crystal planes of the crystal particles, which resulted in various polyhedrons with clear faces and sharp outlines. In addition, the electrochemical performance of the doping pyrite in Li/FeS2 batteries was evaluated using the galvanostatic discharge test, cyclic voltammetry and electrochemical impedance spectroscopy. The results showed that the discharge capacity of the doped material (801.8 mAh·g−1 with a doping ratio of 7% was significantly higher than that of the original FeS2 (574.6 mAh·g−1 because of the enhanced conductivity. Therefore, the doping method is potentially effective for improving the electrochemical performance of FeS2.

  1. Spectroscopic characteristics of (Mn2+, Nd3+) co-doped zinc sulfide nanocrystals

    Science.gov (United States)

    Li, Yiyu; Wu, Yiquan

    2015-11-01

    The ZnS nanoparticles doped with Mn and Nd were synthesized by applying a wet chemical precipitation method using (NH4)2S as the sulfur source. The co-doped ZnS nanopowders with pure sphalerite phase were confirmed by X-ray diffraction (XRD). The influences of co-doped Mn and Nd on the ZnS crystallites, band-gap, and luminescence characteristics have been investigated. Ultraviolet-visible (UV-Vis) spectroscopy revealed the band gap enhancement of the co-doped ZnS. The photoluminescence in both visible and near infrared (NIR) regions, induced by incorporation of Mn2+ and Nd3+ into ZnS host, indicated that the co-doped ZnS nanocrystals can serve as a promising candidate for innovative photoluminescent materials.

  2. Defects in paramagnetic Co-doped ZnO films studied by transmission electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Kovács, A.; Duchamp, M.; Boothroyd, C. B.; Dunin-Borkowski, R. E. [Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons and Peter Grünberg Institute, Forschungszentrum Jülich, 52425 Jülich (Germany); Ney, A.; Ney, V. [Institut für Halbleiter- und Festkörperphysik, Johannes Kepler Universität, Altenberger Str. 69, 4040 Linz (Austria); Galindo, P. L. [Departamento de Ingeniería Informática, Universidad de Cádiz, 11510 Cádiz (Spain); Kaspar, T. C.; Chambers, S. A. [Fundamental and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99354 (United States)

    2013-12-28

    We study planar defects in epitaxial Co:ZnO dilute magnetic semiconductor thin films deposited on c-plane sapphire (Al{sub 2}O{sub 3}), as well as the Co:ZnO/Al{sub 2}O{sub 3} interface, using aberration-corrected transmission electron microscopy and electron energy-loss spectroscopy. Co:ZnO samples that were deposited using pulsed laser deposition and reactive magnetron sputtering are both found to contain extrinsic stacking faults, incoherent interface structures, and compositional variations within the first 3–4 Co:ZnO layers next to the Al{sub 2}O{sub 3} substrate. The stacking fault density is in the range of 10{sup 17} cm{sup −3}. We also measure the local lattice distortions around the stacking faults. It is shown that despite the relatively high density of planar defects, lattice distortions, and small compositional variation, the Co:ZnO films retain paramagnetic properties.

  3. Defects in paramagnetic Co-doped ZnO films studied by transmission electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Kovacs, Andras; Ney, A.; Duchamp, Martial; Ney, V.; Boothroyd, Chris; Galindo, Pedro L.; Kaspar, Tiffany C.; Chambers, Scott A.; Dunin-Borkowski, Rafal

    2013-12-23

    We have studied planar defects in epitaxial Co:ZnO dilute magnetic semiconductor thin films deposited on c-plane sapphire (Al2O3) and the Co:ZnO/Al2O3 interface structure at atomic resolution using aberration-corrected transmission electron microscopy (TEM) and electron energy-loss spectroscopy (EELS). Comparing Co:ZnO samples deposited by pulsed laser deposition and reactive magnetron sputtering, both exhibit extrinsic stacking faults, incoherent interface structures, and compositional variations within the first 3-4 Co:ZnO layers at the interface.. In addition, we have measured the local strain which reveals the lattice distortion around the stacking faults.

  4. Pseudocapacitance of Co doped NiO nanoparticles and its room temperature ferromagnetic behavior

    Science.gov (United States)

    Bharathy, G.; Raji, P.

    2018-02-01

    Co doped NiO nanoparticles CoxNi1-xO (x = 0.0, 0.1, 0.2, 0.3, 0.4) were synthesized by the Sol-gel technique. The impact of Co doping concentration on structural, functional and magnetic properties of NiO nanoparticles was analyzed by X-ray diffraction (XRD), FESEM with EDAX, FTIR and VSM. The average crystallite size was measured to be 34 nm and 11 nm for NiO and Co doped NiO nanoparticles respectively. FESEM reveals that particles are spherical in shape with average size around 30 nm. The elemental composition was analyzed by EDAX. FTIR spectra reveal the existence of NiO peaks in the prepared samples, room temperature ferromagnetism was observed for pure and Co doped NiO nanoparticles by VSM. Pure NiO particles shows ferromagnetic behavior with low coercivity and it increases gradually when doping ratio increases. Higher saturation magnetization was obtained for the sample 0.1 M of Co doped NiO nanoparticle as 22.09 emu/gm. An attempt has been made to study the pseudocapacitance behavior of pure and Co doped NiO nano particles in various scan rates. Electrochemical studies show that 0.4 M Co doped sample gives better charge storage capacity with maximum specific capacitance of 379 Fg-1 at a scan rate of 20 mVs-1. It reveals that it is a promising electrode material for super capacitor applications.

  5. The combined effect of alumina and silica co-doping on the ageing resistance of 3Y-TZP bioceramics.

    Science.gov (United States)

    Samodurova, Anastasia; Kocjan, Andraž; Swain, Michael V; Kosmač, Tomaž

    2015-01-01

    The combined effect of alumina and silica co-doping on the ageing resistance of 3Y-TZP bioceramics was investigated. In order to differentiate between the distinct contributions of two dopants to the overall resistance to low-temperature degradation (LTD), specimens were prepared by infiltration of silica sol into pre-sintered 3Y-TZP pellets, produced from commercially available powders, which were alumina-free or contained 0.05 and 0.25 wt.%. After sintering, specimens were exposed to accelerated ageing in distilled water at 134°C for 6-48 h. X-ray diffraction was applied to quantify the tetragonal-to-monoclinic (t-m) phase transformation associated with the LTD, while a focused ion beam-scanning electron microscopy technique was employed to study the microstructural features in the transformed layer. The results showed that the minor alumina and/or silica additions did not drastically change the densities, grain sizes or mechanical properties of 3Y-TZP, but they did significantly reduce LTD. The addition of either alumina or silica has the potential to influence both the nucleation and the propagation of moisture-induced transformation, but in different ways and to different extents. The co-doped ceramics exhibited predominantly transgranular fracture, reflecting strong grain boundaries (limiting microcracking of the transformed layer), for alumina doping, and rounded grains with a glassy phase at multiple grain junctions (reducing internal stresses) for silica-doped material. These two additives evidently have different dominant mechanisms associated with the deceleration of LTD of 3Y-TZP, but their combination increases resistance to ageing, importantly, without reducing the fracture toughness of this popular biomaterial. Copyright © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  6. Band gap tuning and room temperature ferromagnetism in Co doped Zinc stannate nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Sumithra, S., E-mail: ssmithra@gmail.com; Victor Jaya, N.

    2016-07-15

    The effect of Co doping on structural, optical and magnetic behavior of pure and Co doped Zinc stannate (ZTO) nanostructures was investigated. Pure and Co (1%, 3% & 5%) doped Zn{sub 2}SnO{sub 4} compounds were prepared through simple precipitation route. Formation of cubic inverse spinel structure and metal oxide vibrations of the samples were investigated using XRD and FTIR. Co doping influences the crystallite size producing micro strain in ZTO lattice. Poly dispersed rod like shape of the particles was examined by FESEM. Elemental composition of prepared samples was identified by EDAX analysis. Optical Absorption spectra shows significant red shift on increasing the dopant concentration which indicates the reduction in optical band gap. Visible luminescence observed from photoluminescence studies confirms the presence of oxygen vacancies and trap sites in the lattice. Magnetization analysis reveals the enhanced ferromagnetic behavior in all Co doped ZTO samples. The amplified ferromagnetic ordering in Co doped ZTO compounds has been explained in terms of defects serving as free spin polarized prophetic carriers.

  7. Structural, optical, magnetic and photocatalytic properties of Co doped CuS diluted magnetic semiconductor nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Sreelekha, N.; Subramanyam, K. [Department of Physics, Sri Venkateswara University, Tirupati 517502 (India); Department of Physics, Raghu Engineering College, Visakhapatnam, Andrapradesh 531162 (India); Amaranatha Reddy, D. [Department of Chemistry and Chemical Institute for Functional Materials, Pusan National University, Busan 609735 (Korea, Republic of); Murali, G. [Department of BIN Fusion Technology & Department of Polymer-Nano Science and Technology, Chonbuk National University, Jeonju, Jeonbuk (Korea, Republic of); Ramu, S. [Department of Physics, Sri Venkateswara University, Tirupati 517502 (India); Rahul Varma, K. [Department of Mechanical Engineering, University of California, Berkeley (United States); Vijayalakshmi, R.P., E-mail: vijayaraguru@gmail.com [Department of Physics, Sri Venkateswara University, Tirupati 517502 (India)

    2016-08-15

    Highlights: • Cu{sub 1−x}Co{sub x}S nanoparticles were synthesized via chemical co-precipitation method. • Structural, band gap, magnetization and photocatalysis studies were carried out. • All the doped samples exhibited intrinsic room temperature ferromagnetism. • Effect of magnetic properties on photocatalytic activity was analyzed. • CuS:Co nanoparticles may find applications in photocatalytic and spintronic devices. - Abstract: Pristine and Co doped covellite CuS nanoparticles were synthesized in aqueous solution by facile chemical co-precipitation method with Ethylene Diamine Tetra Acetic Acid (EDTA) as a stabilizing agent. EDAX measurements confirmed the presence of Co in the CuS host lattice. Hexagonal crystal structure of pure and Co doped CuS nanoparticles were authenticated by XRD patterns. TEM images indicated that sphere-shape of nanoparticles through a size ranging from 5 to 8 nm. The optical absorption edge moved to higher energies with increase in Co concentration as indicated by UV–vis spectroscopy. Magnetic measurements revealed that bare CuS sample show sign of diamagnetic character where as in Co doped nanoparticles augmentation of room temperature ferromagnetism was observed with increasing doping precursor concentrations. Photocatalytic performance of the pure and Co doped CuS nanoparticles were assessed by evaluating the degradation rate of rhodamine B solution under sun light irradiation. The 5% Co doped CuS nanoparticles provide evidence for high-quality photocatalytic activity.

  8. Visible-Light Photodegradation of Dye on Co-Doped Titania Nanotubes Prepared by Hydrothermal Synthesis

    Directory of Open Access Journals (Sweden)

    Jung-Pin Wang

    2012-01-01

    Full Text Available Highly porous Co-doped TiO2 nanotubes synthesized from a hydrothermal treatment were used to photodecompose methylene blue (MB in liquid phase under visible light irradiation. The anatase-type titania nanotubes were found to have high specific surface areas of about 289–379 m2/g. These tubes were shown to be hollow scrolls with outer diameter of about 10–15 nm and length of several micrometers. UV absorption confirmed that Co doping makes the light absorption of nanotubes shift to visible light region. With increasing the dopant concentration, the optical band gap of nanotubes became narrower, ranging from 2.4 eV to 1.8 eV, determined by Kubelka-Munk plot. The Co-doped nanotubes exhibit not only liquid-phase adsorption ability, but also visible-light-derived photodegradation of MB in aqueous solution. The synergetic effect involves two key factors in affecting the photocatalytic activity of Co-doped titania nanotubes under fluorescent lamp, that is, high porosity and optical band gap. The merit of the present work is to provide an efficient route for preparing Co-doped TiO2 nanotubes and to clarifying their adsorption and photocatalytic activity under fluorescent lamp.

  9. Spectral downshifting from blue to near infer red region in Ce3+-Nd3+ co-doped YAG phosphor

    Science.gov (United States)

    Sawala, N. S.; Omanwar, S. K.

    2016-07-01

    The YAG phosphors co-doped with Ce3+-Nd3+ ions by varying concentration of Nd3+ ion from 1 mol% to 15 mol% were successfully synthesized by conventional solid state reaction method. The phosphors were characterized by powder X-ray powder diffraction (XRD) and surface morphology was studied by scanning electronic microscope (SEM). The photoluminescence (PL) properties were studied in near infra red (NIR) and ultra violet visible (UV-VIS) region. The synthesized phosphors can convert a blue region photon (453 nm) into photons of NIR region (1063 nm). The energy transfer (ET) process was studied by time decay curve and PL spectra. The theoretical value of energy transfer efficiency (ETE) was calculated from time decay luminescence measurement and the maximum efficiency approached up to 82.23%. Hence this phosphor could be prime candidate as a downshifting (DS) luminescent convertor (phosphor) in front of crystalline silicon solar cell (c-Si) panels to reduce thermalization loss in the solar cells.

  10. Performance Study of CdS/Co-Doped-CdSe Quantum Dot Sensitized Solar Cells

    Directory of Open Access Journals (Sweden)

    Xiaoping Zou

    2014-01-01

    Full Text Available In order to optimize the charge transfer path in quantum dot sensitized solar cells (QDSCs, we employed successive ionic layer adsorption and reaction method to dope CdSe with Co for fabricating CdS/Co-doped-CdSe QDSCs constructed with CdS/Co-doped-CdSe deposited on mesoscopic TiO2 film as photoanode, Pt counter electrode, and sulfide/polysulfide electrolyte. After Co doping, the bandgap of CdSe quantum dot decreases, and the conduction band and valence band all improve, forming a cascade energy level which is more conducive to charge transport inside the solar cell and reducing the recombination of electron-hole thus improving the photocurrent and ultimately improving the power conversion efficiency. This work has not been found in the literature.

  11. Effects of sodium dodecyl benzene sulfonate on the crystal structures and photocatalytic performance of ZnO powders prepared by hydrothermal method

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Limin; Dong, Shuying; Li, Qilu; Li, Yifan; Pi, Yunqing; Liu, Menglin; Han, Xiao; Sun, Jianhui, E-mail: sunjh@htu.cn

    2015-11-15

    A facile and efficient route for the controllable synthesis of ZnO nanostructures by hydrothermal method using sodium dodecyl benzene sulfonate (SDBS) as surfactant was reported. The obtained products were well characterized with the aid of various techniques to probe their crystallographic, morphological, chemical, electrochemical and optical properties. The prepared products were used as photocatalysts in the application of the degradation of metronidazole (MNZ)-contained wastewater under visible light irradiation. A 4.5-fold augmentation of degradation efficiency was in turn observed for optimal ZnO (ZO-0.75) photocatalyst compared with that of sample without SDBS addition (ZO) under the visible light irradiation. The effects of SDBS dosage on the crystal structures of prepared samples as well as the crystal growth mechanism were also probed. - Graphical abstract: ZnO photocatalysts were fabricated through a facile and efficient hydrothermal method using SDBS as structure-directing surfactant in a controllable manner. In particular, the sample with different SDBS dosage exhibited distinct crystal structure and photocatalytic performance. - Highlights: • A rod-like ZnO photocatalyst was facilely synthesized by using SDBS as surfactant. • The effect of SDBS dosage on the crystal structure of photocatalyst was probed. • The probably crystal growth mechanism of prepared photocatalyst was explored. • The optimal ZnO with 0.75 g SDBS dosage displayed the best photocatalytic activity.

  12. Re-dispersible Li+ and Eu3+ co-doped CdS nanoparticles ...

    Indian Academy of Sciences (India)

    dispersible Li+ and Eu3+ co-doped CdS nanoparticles: Luminescence studies. N S Gajbhiye Raghumani Singh Ninghoujam Asar Ahmed D K Panda S S Umare S J Sharma. Contributed papers Volume 70 Issue 2 February 2008 pp 313-321 ...

  13. High rate performance of LiFePO4 cathode materials co-doped with ...

    Indian Academy of Sciences (India)

    Administrator

    ies applying to current and future portable electronic devices and electrical vehicles. In a word, co-doped LiFePO4 with carbon and metallic ion is a promising way to reinforce the electronic conduc- tivity of LiFePO4. It could improve the conductivity both between the LiFePO4 particles and the intrinsic electronic conductivity.

  14. Co-doped mesoporous titania photocatalysts prepared from a peroxo-titanium complex solution

    Energy Technology Data Exchange (ETDEWEB)

    El Saliby, Ibrahim [Faculty of Engineering and Information Technology, University of Technology Sydney, NSW 2007 (Australia); Erdei, Laszlo [Faculty of Engineering and Surveying, University of Southern Queensland, Toowoomba, QLD 4350 (Australia); McDonagh, Andrew [Faculty of Science, University of Technology Sydney, NSW 2007 (Australia); Kim, Jong-Beom; Kim, Jong-Ho [The Research Institute for Catalysis, Chonnam National University, Gwangju 500-757 (Korea, Republic of); Photo and Environmental Technology Co. Ltd., Gwangju 500-460 (Korea, Republic of); Shon, Ho Kyong, E-mail: hokyong.shon-1@uts.edu.au [Faculty of Engineering and Information Technology, University of Technology Sydney, NSW 2007 (Australia)

    2014-01-01

    Graphical abstract: - Highlights: • Peroxotitanium complex for the synthesis of doped photocatalysts. • Fabrication of N doped and N/Ag co-doped photocatalysts. • Characterization of photocatalysts by SEM, XRD, BET, DRS and XPS. • Bench scale photocatalysis under simulated solar light using crystal violet pollutant. - Abstract: In this study, nitrogen doped and nitrogen/silver co-doped TiO{sub 2} photocatalsysts were fabricated using a sol–gel method at room temperature. The obtained gels were neutralized, washed with pure water, and calcined at 400 °C for 4 h. The photocatalysts were characterized by scanning and transmission electron microscopy, X-ray diffraction, diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, and BET specific surface area. The results showed that spherical particles with anatase structure were produced after annealing at 400 °C. N 1s (400 eV) and Ag 3d (367.3 eV) states indicated that nitrogen doping and silver co-doping were in the form of NO bonds and AgO, respectively. The photocatalytic activity of photocatalysts was investigated using a batch reactor system exposed to artificial solar irradiation. Both nitrogen and silver/nitrogen co-doped materials were effective in the photocatalytic degradation of hexamethyl pararosaniline chloride.

  15. Evolution of Spin fluctuations in CaFe2As2 with Co-doping.

    Science.gov (United States)

    Sapkota, A.; Das, P.; Böhmer, A. E.; Abernathy, D. L.; Canfield, P. C.; Kreyssig, A.; McQueeney, R. J.; Goldman, A. I.

    Spin fluctuations are an essential ingredient for superconductivity in Fe-based supercondcutors. In Co-doped BaFe2As2, the system goes from the antiferromagnetic (AFM) state to the superconducting (SC) state with Co doping, and the spin fluctuations also evolve from well-defined spin waves with spin gap in the AFM regime to gapless overdamped or diffused fluctuations in the SC regime. CaFe2As2 has a stronger magneto-elastic coupling than BaFe2As2 and no co-existence of SC and AFM region as observed in BaFe2As2 with Co doping. Here, we will discuss the evolution of spin fluctuations in CaFe2As2 with Co doping. Work at the Ames Laboratory was supported by US DOE, Basic Energy Sciences, Division of Material Sciences and Engineering, under contract No. DE-AC02-07CH11358. This research used resources of SNS, a DOE office of science user facility operated by ORNL.

  16. Chemical composition gratings in Germanium doped and Boron-Germanium co-doped fibers

    Science.gov (United States)

    Barrera, D.; Finazzi, V.; Coviello, G.; Bueno, A.; Sales, S.; Pruneri, V.

    2010-04-01

    We have successfully created Chemical Composition Gratings (CCGs) into two different types of fiber: standard telecommunications Germanium doped fibers and photosensitive Germanium/Boron co-doped fibers. We will present results on the regeneration process, the sensing properties and also the high temperature decay and maximum operative temperature for the CCGs created in both types of fiber.

  17. Structure and luminescent properties of Co{sup 2+}/Cr{sup 3+} co-doped ZnGa{sub 2}O{sub 4} nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Duan, Xiulan, E-mail: xlduan@sdu.edu.cn; Liu, Jian; Wu, Yuanchun; Yu, Fapeng; Wang, Xinqiang

    2014-09-15

    Co{sup 2+}/Cr{sup 3+} co-doped ZnGa{sub 2}O{sub 4} nanoparticles were prepared by a citrate sol–gel method. Their structure and luminescent properties were studied by using X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and fluorescence spectrophotometer. The nanoparticles with the size of 18–50 nm were obtained when the precursor was annealed at 500 °C or above. Ga{sup 3+} ions occupied the octahedral sites as well as the tetrahedral sites, while Cr{sup 3+} ions only entered the octahedral sites by replacing Ga{sup 3+}. The as-synthesized samples had partially inverted spinel structure and the inversion degree slightly decreased with increasing temperature. The Cr{sup 3+}:ZnGa{sub 2}O{sub 4} sample exhibited an intense emission at 695 nm, corresponding to the {sup 2}E→{sup 4}A{sub 2} transition of octahedral Cr{sup 3+}. The emission intensity of Cr{sup 3+} was largely reduced when the sample was co-doped with Co{sup 2+}. However, the emission intensity of Co{sup 2+} in 2% Co/1% Cr co-doped ZnGa{sub 2}O{sub 4} is improved approximately 2 times when compared with 2% co-doped sample. This enhanced emission could be attributed to an efficient energy transfer from Cr{sup 3+} to Co{sup 2+}. The energy transfer mechanism is also discussed. - Highlights: • Co{sup 2+}/Cr{sup 3+}: ZnGa{sub 2}O{sub 4} nanoparticles have been synthesized by a citrate sol–gel method. • The chemical environments of Ga{sup 3+} and Cr{sup 3+} as a function of annealing temperature were studied. • Ga{sup 3+} ions occupy both the tetrahedral and octahedral sites of spinel structure in the samples. • The emission intensity of Co{sup 2+} is improved by Cr{sup 3+} codoping in ZnGa{sub 2}O{sub 4} with 550 nm excitation. • The possible energy transfer process was discussed.

  18. Role of glass structure in defining the chemical dissolution behavior, bioactivity and antioxidant properties of zinc and strontium co-doped alkali-free phosphosilicate glasses.

    Science.gov (United States)

    Kapoor, Saurabh; Goel, Ashutosh; Tilocca, Antonio; Dhuna, Vikram; Bhatia, Gaurav; Dhuna, Kshitija; Ferreira, José M F

    2014-07-01

    We investigated the structure-property relationships in a series of alkali-free phosphosilicate glass compositions co-doped with Zn(2+) and Sr(2+). The emphasis was laid on understanding the structural role of Sr(2+) and Zn(2+) co-doping on the chemical dissolution behavior of glasses and its impact on their in vitro bioactivity. The structure of glasses was studied using molecular dynamics simulations in combination with solid state nuclear magnetic resonance spectroscopy. The relevant structural properties are then linked to the observed degradation behavior, in vitro bioactivity, osteoblast proliferation and oxidative stress levels. The apatite-forming ability of glasses has been investigated by X-ray diffraction, infrared spectroscopy and scanning electron microscopy-energy-dispersive spectroscopy after immersion of glass powders/bulk in simulated body fluid (SBF) for time durations varying between 1h and 14 days, while their chemical degradation has been studied in Tris-HCl in accordance with ISO 10993-14. All the glasses exhibit hydroxyapatite formation on their surface within 1-3h of their immersion in SBF. The cellular responses were observed in vitro on bulk glass samples using human osteosarcoma MG63 cell line. The dose-dependent cytoprotective effect of glasses with respect to the concentration of zinc and strontium released from the glasses is also discussed. Copyright © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  19. Hydrothermal growth and characterization of aluminum-doped ZnO bulk crystals

    Science.gov (United States)

    Wang, Buguo; Mann, Matthew; Claflin, Bruce; Snure, Michael; Look, David C.

    2013-03-01

    Bulk ZnO crystals were grown by the hydrothermal technique with Al2O3 added to the solution in an attempt to obtain Al-doped ZnO crystals. Aluminum and indium co-doped ZnO were also grown by the same technique. Adding Al2O3 to the growth solution has a significant impact on the ZnO growth ⎯ either preventing overgrowth and dissolving the seed growth or degrading the crystalline quality; nevertheless, the resulting crystals of both Al:ZnO and Al/In:ZnO are highly conductive, similar to In and Ga doped ZnO crystals, with a resistivity approaching 0.01 Ω cm, as revealed by temperature-dependent Hall-effect measurements. Photoluminescence spectra at 18 K show Al0-bound-exciton peak energies of 3.3604 eV on the Zn face and 3.3609 eV on the O face for the Al-doped ZnO crystals. Similarly both an Al0- bound-exciton peak at 3.3604 eV and an In0-bound-exciton peak at 3.3575 eV were found on the Al/In-co-doped crystals. The electrical properties of all group III doped ZnO crystals grown hydrothermally are compared with each other and with Al:ZnO obtained by other growth methods.

  20. Preparation and Scintillating Properties of Sol-Gel Eu3+, Tb3+ Co-Doped Lu2O3 Nanopowders

    Directory of Open Access Journals (Sweden)

    Joel Moreno Palmerin

    2011-09-01

    Full Text Available Nanocrystalline Eu3+, Tb3+ co-doped Lu2O3 powders with a maximum size of 25.5 nm were prepared by the sol-gel process, using lutetium, europium and terbium nitrates as precursors, and ethanol as a solvent. Differential thermal analysis (DTA and infrared spectroscopy (IR were used to study the chemical changes during the xerogel annealing. After the sol evaporation at 100 °C, the formed gel was annealed from 300 to 900 °C for 30 min under a rich O2 atmosphere, and the yielded product was analyzed by X-ray diffraction (XRD to characterize the microstructural behavior and confirm the crystalline structure. The results showed that Lu2O3 nanopowders start to crystallize at 400 °C and that the crystallite size increases along with the annealing temperature. A transmission electron microscopy (TEM study of samples annealed at 700 and 900 °C was carried out in order to analyze the microstructure, as well as the size, of crystallites. Finally, in regard to scintillating properties, Eu3+ dopant (5 mol%, Tb3+ codoped Lu2O3 exhibited a typical red emission at 611 nm (Do→7F2, furthermore, the effect of Tb3+ molar content (0.01, 0.015 and 0.02% mol on the Eu3+ radioluminiscence was analyzed and it was found that the higher emission intensity corresponds to the lower Tb3+ content.

  1. Screen printed nanosized ZnO thick film

    Indian Academy of Sciences (India)

    Nanosized ZnO was prepared by polyol synthesis. Fluorescence spectrum of the ZnO colloid at varying pump intensities was studied. The powder was extracted and characterized by XRD and BET. The extracted powder was screen printed on glass substrates using ethyl cellulose as binder and turpinol as solvent.

  2. The effect of Co and In combinational or individual doping on the structural, optical and selective sensing properties of ZnO nanoparticles

    CSIR Research Space (South Africa)

    Maswanganye, MW

    2017-08-01

    Full Text Available Variably doped ZnO samples by the sol-gel process have been tested for response to humidity and industrial gases of CO, CH(sub4), NH(sub3) and H9sub2). The elements of Cobalt (Co) and Indium (In) either singly doped or co-doped at 5 wt% and annealed...

  3. Boron, bismuth co-doping of gallium arsenide and other compounds for photonic and heterojunction bipolar transistor devices

    Science.gov (United States)

    Mascarenhas, Angelo

    2015-07-07

    Isoelectronic co-doping of semiconductor compounds and alloys with acceptors and deep donors is sued to decrease bandgap, to increase concentration of the dopant constituents in the resulting alloys, and to increase carrier mobilities lifetimes. For example, Group III-V compounds and alloys, such as GaAs and GaP, are isoelectronically co-doped with, for example, B and Bi, to customize solar cells, and other semiconductor devices. Isoelectronically co-doped Group II-VI compounds and alloys are also included.

  4. Boron, bismuth co-doping of gallium arsenide and other compounds for photonic and heterojunction bipolar transistor devices

    Energy Technology Data Exchange (ETDEWEB)

    Mascarenhas, Angelo

    2017-08-01

    Isoelectronic co-doping of semiconductor compounds and alloys with acceptors and deep donors is used to decrease bandgap, to increase concentration of the dopant constituents in the resulting alloys, and to increase carrier mobilities lifetimes. For example, Group III-V compounds and alloys, such as GaAs and GaP, are isoelectronically co-doped with, for example, B and Bi, to customize solar cells, and other semiconductor devices. Isoelectronically co-doped Group II-VI compounds and alloys are also included.

  5. Anomalous enhancement of the thermoelectric figure of merit by V co-doping of Nb-SrTiO3

    KAUST Repository

    Ozdogan, K.

    2012-05-10

    The effect of V co-doping of Nb-SrTiO3 is studied by full-potential density functional theory. We obtain a stronger increase of the carrier density for V than for Nbdopants. While in Nb-SrTiO3 a high carrier density counteracts a high thermoelectric figure of merit, the trend is inverted by V co-doping. The mechanism leading to this behavior is explained in terms of a local spin-polarization introduced by the V ions. Our results indicate that magnetic co-doping can be a prominent tool for improving the thermoelectric figure of merit.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-12-01

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

  7. Ultraviolet light induced white light emission in Ag and Eu3+ co-doped oxyfluoride glasses.

    Science.gov (United States)

    Guo, Hai; Wang, Xiaofeng; Chen, Jindeng; Li, Fang

    2010-08-30

    Transparent Ag and Eu(3+) co-doped oxyfluoride glasses with composition 50SiO(2)-20Al(2)O(3)-30CaF(2) were prepared by melt-quenching technique. The structural and luminescent properties of glasses, energy transfer mechanism between luminescent centers were systematically investigated. The missing nanoparticles signals in absorption spectra, XRD patterns and TEM images, the additional broad excitation band at 325-375 nm indicate that the broad emission band at 400-700 nm is originated from very small molecule-like, non-plasmonic Ag particles (ML-Ag-particles). A perfect white light emission was realized by combining intense red emission of Eu(3+) with broad band emission of ML-Ag-particles. These results suggest that Ag and Eu(3+) co-doped oxyfluoride glasses could be potentially applied as white light-emitting phosphors for ultra-violet LED chips.

  8. Electronic structure, magnetic and superconducting properties of co-doped iron-arsenide superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Rosner, Helge; Schnelle, Walter; Nicklas, Michael; Leithe-Jasper, Andreas [MPI CPfS Dresden (Germany); Weikert, Franziska [Los Alamos National Laboratory, New Mexico (United States); HLD Dresden Rossendorf (Germany); Wosnitza, Joachim [HLD Dresden Rossendorf (Germany)

    2013-07-01

    We present a joint experimental and theoretical study of co-doped iron-arsenide superconductors of the 122 family A{sub 1-x}K{sub x}Fe{sub 2-y}T{sub y}As{sub 2} (A = Ba,Sr,Eu; T = Co,Ru,Rh). In these systems, the co-doping enables the separation of different parameters - like electron count, disorder or the specific geometry of the FeAs layer - with respect to the position of the respective compounds in the general 122 phase diagram. For a series of compounds, we investigate the relevance of the different parameters for the magnetic, thermodynamic and superconducting properties. Our experimental investigations are supported by density functional electronic structure calculations applying different approximations for doping and disorder.

  9. Vacancy mediated room temperature ferromagnetism in Co-doped Dy2O3

    Science.gov (United States)

    Bandyopadhyay, A.; Sutradhar, S.; Sarkar, B. J.; Deb, A. K.; Chakrabarti, P. K.

    2012-06-01

    Nanoparticles of Co doped dysprosium oxide [Dy1.90Co0.10O3] were prepared by co-precipitating the precursor salts in presence of air and argon gas. Crystallographic phase and substitution of Co-ion in Dy2O3 were confirmed by Rietveld analysis of the x-ray diffraction patterns. Magnetic susceptibility and magnetization as a function of temperature and magnetic field were measured by Faraday and Superconducting quantum inteference device (SQUID) magnetometers, which showed that the sample synthesized in the inert atmosphere is ferromagnetic at room temperature. But no such effect has been observed in the other sample. This observation confirmed that vacancy mediated ferromagnetism can be introduced in the Co-doped dysprosium oxide.

  10. First Principles Study of Electronic and Magnetic Properties of Co-Doped Armchair Graphene Nanoribbons

    Directory of Open Access Journals (Sweden)

    Biao Li

    2015-01-01

    Full Text Available Using the first principles calculations, we have studied the atomic and electronic structures of single Co atom incorporated with divacancy in armchair graphene nanoribbon (AGNR. Our calculated results show that the Co atom embedded in AGNR gives rise to significant impacts on the band structures and the FM spin configuration is the ground state. The presence of the Co doping could introduce magnetic properties. The calculated results revealed the arising of spin gapless semiconductor characteristics with doping near the edge in both ferromagnetic (FM and antiferromagnetic (AFM magnetic configurations, suggesting the robustness for potential application of spintronics. Moreover, the electronic structures of the Co-doped AGNRs are strongly dependent on the doping sites and the edge configurations.

  11. Nuclear magnetic resonance study of pure and Ni/Co doped LiFeAs

    Energy Technology Data Exchange (ETDEWEB)

    Grafe, Hans-Joachim; Baek, Seung-Ho; Hammerath, Franziska; Graefe, Uwe; Utz, Yannic; Harnagea, L.; Nacke, Claudia; Aswartham, Saicharan; Wurmehl, Sabine; Buechner, Bernd [Leibniz-Institut fuer Festkoerper- und Werkstoffforschung, Dresden (Germany)

    2011-07-01

    We present Nuclear Magnetic and Nuclear Quadrupole Resonance (NMR/NQR) measurements on pure, Ni and Co doped LiFeAs single crystals. The parent compound LiFeAs exhibits unconventional superconductivity with a transition temperature of about 17 K. Unlike other Fe based superconductors, where superconductivity is induced or stabilized by Co or Ni doping, replacement of Fe by these elements leads to a suppression of the superconducting transition temperature in LiFeAs. In case of Ni doping, a bulk magnetic order is induced below about 160 K. In contrast, for Co doping, the superconducting transition temperature is only reduced, but no magnetic order is observed. We discuss the nature and the origin of this magnetic order and its relation to unconventional superconductivity in pure LiFeAs.

  12. STM/STS study on Co-doped NaFeAs superconductor

    Energy Technology Data Exchange (ETDEWEB)

    Nag, Pranab Kumar; Baumann, Danny; Schlegel, Ronny; Pohle, Rico; Haenke, Torben; Beck, Robert; Aswartham, Saicharan; Wurmehl, Sabine; Hess, Christian [Institut fuer Festkoerperforschung IFW Dresden, (Germany); Scheffler, Martha; Buechner, Bernd [Institut fuer Festkoerperforschung IFW Dresden, (Germany); Institut fuer Festkoerperphysik TU Dresden (Germany)

    2013-07-01

    We have performed scanning tunneling microscopy/spectroscopy measurements on superconducting Co-doped NaFeAs as a function of temperature. After cleaving at low temperature and cryogenic vacuum we were able to investigate the electronic structure of the material by tunneling spectroscopy. The tunneling spectra (dI/dV) reveal several gap-like features near the Fermi level. We compare these result with recent data on LiFeAs.

  13. Sulfur and Nitrogen Co-Doped Graphene Electrodes for High-Performance Ionic Artificial Muscles.

    Science.gov (United States)

    Kotal, Moumita; Kim, Jaehwan; Kim, Kwang J; Oh, Il-Kwon

    2016-02-24

    Sulfur and nitrogen co-doped graphene electrodes for bioinspired ionic artificial muscles, which exhibit outstanding actuation performances (bending strain of 0.36%, 4.5 times higher than PSS electrodes, and 96% of initial strain after demonstration over 18 000 cycles), provide remarkable electro-chemo-mech anical properties: specific capacitance, electrical conductivity, and large surface area with mesoporosity. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Transition-metal-doped ZnO nanoparticles: Synthesis, characterization and photocatalytic activity under UV light

    Science.gov (United States)

    Saleh, Rosari; Djaja, Nadia Febiana

    2014-09-01

    ZnO nanoparticles doped with transition metals (Mn and Co) were prepared by a co-precipitation method. The synthesized nanoparticles were characterized using X-ray diffraction, scanning electron microscopy, energy dispersive X-rays, Fourier transform infrared spectroscopy, electron spin resonance spectroscopy and diffuse reflectance spectroscopy. The photocatalytic activities of the transition-metal-doped ZnO nanoparticles were evaluated in the degradation of methyl orange under UV irradiation. ZnO nanoparticles doped with 12 at.% of Mn and Co ions exhibited the maximum photodegradation efficiency. The experiment also demonstrated that the photodegradation efficiency of Mn-doped ZnO nanoparticles was higher than that of Co-doped ZnO nanoparticles. These results indicate that charge trapping states due to the doping were the decisive factor rather than the average particle size and energy gap. Moreover the effect of pH values on the degradation efficiency was discussed in the photocatalytic experiments using 12 at.% Mn- and Co-doped ZnO nanoparticles.

  15. Al/Ge co-doped large mode area fiber with high SBS threshold.

    Science.gov (United States)

    Li, Ming-Jun; Chen, Xin; Wang, Ji; Gray, Stuart; Liu, Anping; Demeritt, Jeffrey A; Ruffin, A B; Crowley, Alana M; Walton, Donnell T; Zenteno, Luis A

    2007-06-25

    We propose a novel approach of making large effective area laser fiber with higher threshold for the stimulated Brillouin scattering (SBS) using Al/Ge co-doping in the fiber core. The increased SBS threshold is achieved by reducing the acoustic-optic overlap integral while keeping the optical refractive index profile with a step structure. The manipulation of the overlap integral is done by adjusting the relative doping level between Al(2)O(3) and GeO(2) in the core. The mechanism is validated by detailed examples of numerical modeling. An Yb-doped double clad fiber with the core co-doped with Al(2)O(3) and GeO(2) was fabricated by the OVD process. Measured acoustic velocity profile using a scanning acoustic microscope verified that the acoustic velocity in the fiber core changes with the design. An amplifier utilizing the fiber demonstrated that the proposed fiber yielded 6 dB higher SBS threshold than a fiber without using the co-doping scheme.

  16. Photoluminescence properties of Mn2+/Yb3+ co-doped oxyfluoride glasses for solar cells application

    Science.gov (United States)

    Yan, Ying; Chen, Zeng; Jia, Xiyang; Li, Shengjun

    2018-01-01

    Mn2+/Yb3+ co-doped oxyfluoride glasses were facilely synthesized in the SiO2-Al2O3-Na2O-CaF2 system. Partial crystallization processed during the preparation of the glasses, by which small amounts of CaF2 nano-crystals were formed. Under ultraviolet and blue (370-500 nm) light excitation, an efficient down-conversion involving the emission of near-infrared is realized in the Mn2+/Yb3+ co-doped oxyfluoride glasses. The near-infrared emission peaks mainly at 976 nm and secondarily at 1020 nm, which is a comfortable match with the band gap of c-Si. The variation in visible and near-infrared spectra and the decay curves of Mn2+:4T1 → 6A1 emission have been investigated to verify the possible energy transfer from Mn2+ ions to Yb3+ ions. On analyzing the energy transfer processes theoretically and experimentally, we propose that quantum cutting and down-shifting processes may occur simultaneously in the samples. We suggest that the Mn2+-Yb3+ co-doped materials can provide a novel direction to realize UV-Vis to NIR down-conversion for Si solar cells.

  17. Carbon Nitrogen Co-Doped P25: Parameter Study on Photodegradation of Reactive Red 4

    Directory of Open Access Journals (Sweden)

    Azami M. S.

    2016-01-01

    Full Text Available Photocatalytic degradation rate of reactive red 4 (RR4 using carbon coated nitrogen doped TiO2 (C N co-doped TiO2 in photocatalysis process is main goal on this research. The main operating the parameters such as effect of initial dye concentration, catalyst loading, aeration flow rate and initial pH on degradation of RR4 under 45 W fluorescent lamp was investigated. photocatalytic activity of RR4 dye decreased with increasing RR4 dye concentration. The optimum loading is around 0.04 g and optimum aeration rate is about 25 mL min-1 of C N co-doped TiO2. Effect of pH was conducted based on the optimum loading and conclude that the photocatalytic degradation of RR4 became faster at pH 2 - 7. For the future work, the modification of doping with others element like non-metal or metal with C N co-doped TiO2 can be enhanced toward the higher efficieny of photodegradation under visible light. Moreover, the immobilized technique can be used in future to overcome the difficulty of filtration on suspension.

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

    Energy Technology Data Exchange (ETDEWEB)

    Anjana, R.; Subha, P. P.; Markose, Kurias K.; Jayaraj, M. K., E-mail: mkj@cusat.ac.in [Department of Physics, Cochin University of Science and Technology, Kochi, Kerala, India-682022 (India)

    2016-05-23

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

  19. Thermoelectric performance of intermetallic FeGa{sub 3} with Co doping

    Energy Technology Data Exchange (ETDEWEB)

    Ramachandran, B.; Syu, K.Z. [Department of Physics, National Dong Hwa University, Hualien 97401, Taiwan (China); Kuo, Y.K., E-mail: ykkuo@mail.ndhu.edu.tw [Department of Physics, National Dong Hwa University, Hualien 97401, Taiwan (China); Gippius, A.A. [Department of Physics, M.V. Lomonosov Moscow State University, Moscow 119991 (Russian Federation); Shevelkov, A.V.; Verchenko, V.Yu. [Department of Chemistry, M.V. Lomonosov Moscow State University, Moscow 119991 (Russian Federation); Lue, C.S. [Department of Physics, National Cheng Kung University, Tainan 70101, Taiwan (China)

    2014-09-01

    Highlights: • From the resistivity study of Fe{sub 1−x}Co{sub x}Ga{sub 3} (0.005 ⩽ x ⩽ 0.5), the metallic behavior is observed for the compounds with Co content of x ⩾ 0.125. • The Seebeck coefficient of these compounds has contribution from both diffusion thermoelectric power and phonon-drag effect. • A reduction in Seebeck coefficient with Co doping is observed, due to the modification in band gap and density of states at the Fermi level. • Low-temperature lattice thermal conductivity of FeGa{sub 3} is suppressed significantly by Co doping due to the phonon-point-defect scattering. • The maximum ZT value of ∼0.05 is achieved for Fe{sub 0.95}Co{sub 0.05}Ga{sub 3} at 400 K, ten times higher than that of the parent FeGa{sub 3}. - Abstract: Investigation on temperature-dependent electrical resistivity (ρ), Seebeck coefficient (S), and thermal conductivity (κ) of intermetallic Fe{sub 1−x}Co{sub x}Ga{sub 3} (0.005 ⩽ x ⩽ 0.5) compounds are carried out to probe their thermoelectric performance. From resistivity study, it is observed that increase in number of valence electrons introduced by Co doping leads to a change from semiconducting to metallic behavior, which occurs between x = 0.05 and 0.125. The characteristics of the Seebeck coefficient show a substantial decrease with the Co doping, due to the modifications in the band gap and the Fermi-level density of states. Analyses of thermal conductivity of the Co doped FeGa{sub 3} compounds reveal that thermal transport is essentially due to the lattice phonons. It is also noticed that the low-temperature peak in the lattice thermal conductivity of these compounds is reduced significantly with the increase in Co content, attributing to the enhanced scattering of phonons by point-defects. The value of the figure-of-merit, ZT = (S{sup 2}/ρκ)T, is estimated for all compounds, and the maximum room-temperature ZT value of about 0.02 was achieved for Fe{sub 0.95}Co{sub 0.05}Ga{sub 3}, and

  20. The effect of Co-doping on the humidity sensing properties of ordered mesoporous TiO2

    Science.gov (United States)

    Li, Zhong; Haidry, Azhar Ali; Gao, Bin; Wang, Tao; Yao, ZhengJun

    2017-08-01

    Monitoring of humidity is of utmost importance as it is essential part of almost every process in our life. Many commercial humidity sensors based on metal oxide semiconductors are available in the market, but there is still need to synthesize low-cost, fast and highly sensitive humidity sensors with no interference from background environment. The aim of this work was to fabricate the ordered mesoporous un-doped and Co-doped TiO2 (0.1-5 mol% Co) and to analyze its humidity sensing properties at room temperatures. The ordered mesoporous powders with high specific surface area (SSA) were prepared by multicomponent self-assembly procedure and then spray-coated onto the sensor substrates with interdigitated gold electrodes. The sensors exhibited excellent stability and reproducible resistance change under various relative humidity percentages (9-90% RH) with negligible effect of background environment. For instance, the response to 90% RH at room temperature was about five orders of magnitude (∼1.39 × 105) and the response time (Tres) was ∼24 s. The reaction/recovery times of the sensors were compared with commercial humidity sensor to show that the reaction times in this work are not given by the surface reaction of water vapor on the sensor surfaces, rather these are mainly influenced by the experimental setup. The sensor response increased up to 3 mol% Co-contents and then decreased for 5 mol% Co-contents. Based on the experimental results, the surface reaction of humidity is discussed related to specific surface area, average grain size and cobalt contents to understand the humidity sensing mechanism.

  1. N, S co-doped carbon dots with orange luminescence synthesized through polymerization and carbonization reaction of amino acids

    Energy Technology Data Exchange (ETDEWEB)

    Zeng, Ya-Wen [Nanomaterials and Chemistry Key Laboratory, Wenzhou University, Wenzhou, Zhejiang 325027 (China); Ma, De-Kun, E-mail: dkma@wzu.edu.cn [Nanomaterials and Chemistry Key Laboratory, Wenzhou University, Wenzhou, Zhejiang 325027 (China); Wang, Wei; Chen, Jing-Jing; Zhou, Lin; Zheng, Yi-Zhou [Department of Hematology, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang 325027 (China); Yu, Kang, E-mail: yukang62@126.com [Department of Hematology, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang 325027 (China); Huang, Shao-Ming, E-mail: smhuang@wzu.edu.cn [Nanomaterials and Chemistry Key Laboratory, Wenzhou University, Wenzhou, Zhejiang 325027 (China)

    2015-07-01

    Graphical abstract: N, S co-doped CDs with orange luminescence were synthesized through one-pot polymerization and carbonization reactions under hydrothermal conditions, using two different amino acids as raw materials. - Highlights: • N, S co-doped CDs were synthesized by one-pot carbonization reactions, using two different amino acids as raw materials. • The as-obtained N, S co-doped CDs showed unique orange fluorescence under excitation at room temperature. • The products could be applied in the imaging of peritoneal macrophages of mice without any functionalization. - Abstract: For practical application, it is highly desirable to obtain carbon dots (CDs) through environmentally benign synthetic route, using green raw materials. On the other hand, at present, most of CDs reported in the literature showed blue, green and yellow emission. Therefore it is still necessary to develop new strategy to obtain CDs with longer wavelength emission in order to expand their application range. Toward this end, in this study, N, S co-doped CDs were synthesized through one-pot condensation polymerization and carbonization reactions under hydrothermal conditions, using two different amino acids as raw materials. Taking the reaction of L-serine with L-cystine as an example, the as-obtained products were characterized by various techniques such as transmission electron microscopy, elemental analysis, Fourier-transform infrared spectrum, X-ray photoelectron spectra, and so on. Interestingly, N, S co-doped CDs displayed unique orange emission at room temperature. The possible photoluminescence mechanism of N, S co-doped CDs was proposed. Furthermore, the as-synthesized N, S co-doped CDs were directly applied in the imaging of peritoneal macrophages of mice.

  2. An ultrasensitive electrochemical sensor for simultaneous determination of xanthine, hypoxanthine and uric acid based on Co doped CeO{sub 2} nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Lavanya, N. [Department of Bioelectronics and Biosensors, Alagappa University, Karaikudi 630003, Tamilnadu (India); Sekar, C., E-mail: Sekar2025@gmail.com [Department of Bioelectronics and Biosensors, Alagappa University, Karaikudi 630003, Tamilnadu (India); Murugan, R.; Ravi, G. [Department of Physics, Alagappa University, Karaikudi 630003, Tamilnadu (India)

    2016-08-01

    A novel electrochemical sensor has been fabricated using Co doped CeO{sub 2} nanoparticles for selective and simultaneous determination of xanthine (XA), hypoxanthine (HXA) and uric acid (UA) in a phosphate buffer solution (PBS, pH 5.0) for the first time. The Co-CeO{sub 2} NPs have been prepared by microwave irradiation method and characterized by Powder XRD, Raman spectroscopy, HRTEM and VSM measurements. The electrochemical behaviours of XA, HXA and UA at the Co-CeO{sub 2} NPs modified glassy carbon electrode (GCE) were studied by cyclic voltammetry and square wave voltammetry methods. The modified electrode exhibited remarkably well-separated anodic peaks corresponding to the oxidation of XA, HXA and UA over the concentration range of 0.1–1000, 1–600 and 1–2200 μM with detection limits of 0.096, 0.36, and 0.12 μM (S/N = 3), respectively. For simultaneous detection by synchronous change of the concentrations of XA, HXA and UA, the linear responses were in the range of 1–400 μM each with the detection limits of 0.47, 0.26, and 0.43 μM (S/N = 3), respectively. The fabricated sensor was further applied to the detection of XA, HXA and UA in human urine samples with good selectivity and high reproducibility. - Highlights: • A novel electrochemical sensor has been fabricated for simultaneous determination of purine metabolites xanthine, hypoxanthine, and uric acid based on Co doped CeO{sub 2} nanoparticles. • The Co-CeO{sub 2} modified glassy carbon electrode exhibited wide linear range towards the detection of XA, HXA and UA than ever reported in the literature. • The fabricated sensor was successfully applied for the analysis of human urine samples with satisfactory results.

  3. Structure and photoluminescence of TiO{sub 2} nanocrystals doped and co-doped with N and rare earths (Y{sup 3+}, Pr{sup 3+})

    Energy Technology Data Exchange (ETDEWEB)

    Ricci, P.C., E-mail: carlo.ricci@dsf.unica.it [Dipartimento di Fisica, Università degli Studi di Cagliari, S.P. Monserrato-Sestu Km 0,700, 09042 Monserrato (Italy); Carbonaro, C.M.; Geddo Lehmann, A.; Congiu, F.; Puxeddu, B. [Dipartimento di Fisica, Università degli Studi di Cagliari, S.P. Monserrato-Sestu Km 0,700, 09042 Monserrato (Italy); Cappelletti, G.; Spadavecchia, F. [Dipartimento di Chimica, Università degli Studi di Milano, Via Golgi 19, 20133 Milano (Italy)

    2013-06-05

    Highlights: ► We studied singly and co-doped N, Y and Pr:TiO{sub 2} nanoparticles. ► A mixed anatase-brookite phase with average dimension lower than 10 nm was revealed. ► The nature of defects in the TiO{sub 2} structures depends on the doping elements. ► Bulk and surface defects are related to nitrogen in the TiO{sub 2} matrix. ► Y{sup 3+} ion acts as a surface stabilizer, Pr{sup 3+} generates surface recombination centers. -- Abstract: The structural and optical properties of sol–gel synthesized TiO{sub 2} nanoparticles doped and co-doped with N and rare earth ions (Y{sup 3+} and Pr{sup 3+}) are presented. Crystal structures, phase composition, and crystallite sizes are analyzed by powder X-ray diffraction and Raman spectroscopy. The analysis of intragap excited photoluminescence indicates the formation of radiative recombinations related to different defect centers in the TiO{sub 2} structure, generated by the presence of doping elements. In particular we assign the formation of bulk and surface defects to the presence of nitrogen in the TiO{sub 2} matrix, whereas we observe different effects on the defective TiO{sub 2} structure related to the two rare earths: the presence of Y{sup 3+} ion acts as a stabilizer of the TiO{sub 2} surface whereas the presence of Pr{sup 3+} generates surface recombination centers.

  4. Thermometry and up-conversion luminescence of Yb(3+)-Er(3+) co-doped Na2Ln2Ti3O10 (Ln = Gd, La) phosphors.

    Science.gov (United States)

    Zhang, Zhiyu; Guo, Chongfeng; Suo, Hao; Zhao, Xiaoqi; Zhang, Niumiao; Li, Ting

    2016-07-28

    Yb(3+)/Er(3+)-ion co-doped Na2Ln2Ti3O10 (Ln = Gd, La) up-conversion (UC) phosphors were successfully synthesized by a sol-gel method, and their crystal structures were characterized by powder X-ray diffraction. Dazzling yellow-greenish light was emitted under the excitation of 980 nm near-infrared (NIR) light, composing green and red emission bands from the (2)H11/2/(4)S3/2→(4)I15/2 and (4)F9/2→(4)I15/2 transitions of Er(3+), respectively. The optimal composition and synthesis parameters were determined according to their UC emission intensity. The photon absorption and emission processes were illustrated based on the UC mechanism, in which energy transfer (ET) from Yb(3+) to Er(3+) plays a pivotal role and has been proved by the variation of green emission lifetime in Er(3+) singly and Yb(3+)/Er(3+) co-doped Na2Ln2Ti3O10 samples. The temperature-dependent fluorescence intensity ratios (FIR) of the two thermal coupled energy level (TCL) emission from (2)H11/2→(4)I15/2 (526 nm) and (4)S3/2→(4)I15/2 (549 nm) were calculated in the range of 290-490 K, and their sensitivity values were approximately 0.0058 K(-1) for Na2Gd2Ti3O10 at 490 K and 0.0061 K(-1) for Na2La2Ti3O10 at 470 K, as potential optical temperature sensor.

  5. Synthesis, structure and optical properties of Co-doped MgGa2O4/SiO2 nano-glass-ceramic composites

    Science.gov (United States)

    Duan, Xiulan; Wu, Yuanchun; Wang, Xinqiang; Yu, Fapeng; Jiang, Huaidong

    2013-07-01

    Co-doped MgGa2O4/SiO2 nano-glass-ceramic composites with the composition of (1 - y) CoxMg1-xGa2O4-ySiO2 (0 ≤ x, y ≤ 1) were synthesized by the sol-gel method and characterized by X-ray powder diffraction and transmission electron microscopy. X-ray photoelectron spectroscopy was used to study the chemical environments of cations and oxygen in the nanocomposites as a function of annealing temperature, cobalt content and SiO2 content. The results show that Ga3+ and Mg2+ ions occupy both the tetrahedral and octahedral sites of spinel structure in the samples. The inversion parameter (two times the fraction of Ga3+ ions in the tetrahedral sites) of the nanocomposites is relatively larger in comparison with that of ZnGa2O4, and the value decreases with the increase of annealing temperature and silica concentration, while increases with cobalt-enrichment. All the Co-doped samples exhibit the intense absorption peak at ~600 nm, which is characteristic of tetrahedral Co2+. But only in the composites of Co0.3Mg0.7Ga2O4 and 0.6Co0.6Mg0.4Ga2O4-0.4SiO2, the absorption band at 300-500 nm characteristic of octahedral Co2+ ions is observed. The intensity of the absorption peak corresponding to octahedral Co2+ ions increases with decreasing annealing temperature for the Co0.3Mg0.7Ga2O4 nanocrystals.

  6. Electronic, optical and photocatalytic behavior of Mn, N doped and co-doped TiO{sub 2}: Experiment and simulation

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Ya Fei; Li, Can, E-mail: canli1983@gmail.com; Lu, Song; Liu, Ru Xi; Hu, Ji Yuan; Gong, Yin Yan; Niu, Leng Yuan

    2016-03-15

    The crystal phase structure, surface morphology, chemical states and optical properties of Mn, N mono-doped and co-doped TiO{sub 2} nanoparticles were investigated by X-ray powder diffractometry, Raman spectra, scanning electron microscopy, X-ray photoelectron spectroscopy and UV–vis diffuse reflectance spectroscopy. Meanwhile, geometry structures, formation energies, electronic and optical properties of all systems have been also analyzed by density functional theory. The results showed that the band gap values and the carrier mobility in the valence band, conduction band and impurity levels have a synergetic influence on the visible-light absorption and photocatalytic activity of the doped TiO{sub 2}. The number and the carrier mobility of impurity level jointly influence the photocatalytic activity of catalyst under visible-light. Especially, the photocatalytic activity of Mn-2N co-doped TiO{sub 2} beyond three-fold than that of pure TiO{sub 2} under visible-light. - Graphical abstract: The ILs formed by N-2p orbital in N single doped specimen lie above the VB, while the ILs formed by Mn-3d orbital in Mn single doped specimen appear below the CB. However, a large amount of ILs formed by N-2p orbital and Mn-3d orbital in N and Mn codoped specimens. The band gap values and the carrier mobility in the valence band, conduction band and impurity levels have a synergetic influence on the visible-light absorption and photocatalytic activity of the doped TiO{sub 2}. The number and the carrier mobility of impurity level jointly influence the photocatalytic activity of catalyst under visible-light.

  7. Low temperature synthesis of radio frequency magnetron sputtered gallium and aluminium co-doped zinc oxide thin films for transparent electrode fabrication

    Science.gov (United States)

    Muchuweni, E.; Sathiaraj, T. S.; Nyakotyo, H.

    2016-12-01

    Gallium and aluminium co-doped zinc oxide (GAZO) thin films were prepared on glass substrates at low temperatures by radio frequency (rf) magnetron sputtering and their physical properties were investigated. All films possessed a hexagonal wurtzite crystal structure with a strong growth orientation along the (0 0 2) c-axis. The (0 0 2) peak intensity and mean crystallite size increased with substrate temperature from room temperature (RT) to 75 °C and then decreased at 100 °C, indicating an improvement in crystallinity up to 75 °C and its deterioration at 100 °C. Scanning electron microscopy (SEM) micrographs revealed the strong dependency of surface morphology on substrate temperature and energy dispersive spectroscopy (EDS) confirmed the incorporation of Ga and Al into the ZnO films. All films exhibited excellent transmittances between 85 and 90% in the visible region and their optical band gap increased from 3.22 eV to 3.28 eV with substrate temperature. The Urbach energy decreased from 194 meV to 168 meV with increasing substrate temperature, indicating a decrease in structural disorders which was consistent with X-ray Diffraction (XRD) analysis. Films deposited at 75 °C exhibited the lowest electrical resistivity (2.4 Ωcm) and highest figure of merit (7.5 × 10-5 Ω-1), proving their potential as candidates for transparent electrode fabrication.

  8. Fabrication of Transparent Conductive Zinc Oxide Co-Doped with Fluorine and Zirconium Thin Solid Films by Ultrasonic Chemical Pyrolysis: Effects of Precursor Solution Aging and Substrate Temperature

    Directory of Open Access Journals (Sweden)

    Luis Castañeda

    2013-01-01

    Full Text Available Highly transparent, conducting zinc oxide [ZnO] thin films co-doped with fluorine and zirconium have been deposited on glass substrates by the ultrasonic chemical spraying technique. The effects of aging of the starting solution and substrate temperature on the structural, morphological, and electrical properties of the ZnO:F:Zr films have been studied. The resistivity of the films decreases with the aging time of the starting solution until the seventeenth day reaching a minimum of about 1.2×10−2 Ω cm and then increases. Though all the samples are of polycrystalline hexagonal wurtzite type and grow preferentially with (002 plane parallel to the substrate, their morphology depends strongly on the aging time of the reaction solution. The optical transmittance of all the films remained around 80% in the visible spectral range. These highly transparent, low resistive thin films are expected to be highly useful as transparent electrodes in the fabrication of thin film solar cells.

  9. Structural and electronic properties of V- and Co-doped single-walled ZnONT(8,0): Transition from semiconducting to metallic and half-metallic states

    Science.gov (United States)

    Taghavi Mendi, R.; Majidiyan Sarmazdeh, M.; Elahi, S. M.; Abolhassani, M. R.; Boochani, A.; Zelati, A.

    2015-02-01

    In this paper, some structural and electronic properties of V- and Co-doped single-walled ZnO nanotube (8,0), such as cohesive energy, geometric structure, density of states and band structure were investigated using first principles calculations. Our results showed that, first, the pure SWZnONT(8,0) can be stable and second, doped SWZnONTs(8,0) by V and Co atoms are more stable than pure SWZnONT(8,0) and TM impurities distort the structure of nanotubes around the TM impurities. The electronic results showed that pure SWZnONT(8,0) have a direct band gap about 1.443 eV and it is semiconductor. While with substituting V and Co instead of Zn in nanotube, a transition occurs from semiconducting to metallic and half-metallic states which these doped nanotubes as well as their magnetic properties are qualified for using in spintronic devices.

  10. Ionic conductivity of co-doped Sc2O3-ZrO2 ceramics

    DEFF Research Database (Denmark)

    Omar, Shobit; bin Najib, Waqas; Chen, Weiwu

    2012-01-01

    The oxide ionic conductivity of Sc0.18Zr0.82O1.91 doped with 0.5 mol.% of both Yb2O3 and In2O3 is evaluated at various temperatures in air. Among various co-doped compositions, In0.02Sc0.18Zr0.80O1.90 exhibits the highest grain ionic conductivity followed by Yb0.02Sc0.18Zr0.80O1.90 at 500°C. Howe...

  11. Enhanced Luminescent Properties in Tm3+/Dy3+ Co-doped Transparent Phosphate Glass Ceramic

    OpenAIRE

    Yao L. Q.; Chen G. H.; Zhong H. J.; Cui S. C.; Li F; Gan J.Y.

    2016-01-01

    Novel Tm3+/Dy3+ co-doped phosphate glass and glass ceramic samples for white light emitting diodes were prepared by melt quenching method. Under 353 nm excitation, the colors of the luminescence of the glass and glass ceramic samples are white. The CIE chromaticity coordinates (0.338, 0.328) of the emission from the glass ceramic is close to the standard white-light illumination (0.333, 0.333). Compared to the glass, the fluorescence intensity in the glass ceramic is greatly enhanced.

  12. Co-doping with antimony to control phosphorous diffusion in germanium

    KAUST Repository

    Tahini, H. A.

    2013-02-15

    In germanium, phosphorous and antimony diffuse quickly and as such their transport must be controlled in order to design efficient n-typed doped regions. Here, density functional theory based calculations are used to predict the influence of double donor co-doping on the migration activation energies of vacancy-mediated diffusion processes. The migration energy barriers for phosphorous and antimony were found to be increased significantly when larger clusters involving two donor atoms and a vacancy were formed. These clusters are energetically stable and can lead to the formation of even larger clusters involving a number of donor atoms around a vacancy, thereby affecting the properties of devices.

  13. Nuclear Magnetic Resonance Studies of Rare Earth co-doped Lanthanum Cuprates

    OpenAIRE

    Grafe, Hans-Joachim

    2005-01-01

    The work described in this thesis uses oxygen NMR to probe the electronic system of rare earth co-doped La_{2-x}Sr_xCuO_4, the prototypical high temperature superconducting cuprate (HTSC). Oxygen NMR turns out to be a powerful tool for this purpose. The nucleus is located directly inside the CuO_2 planes. It has a spin of 5/2 and a quadrupole moment and therefore can probe both, interactions with the magnetic hyperfine field as well as interactions through the electric field gradient of the c...

  14. Luminescence characteristics of Tl + ions co-doped RbCl:Eu 2+ crystals

    Science.gov (United States)

    Nagarajan, S.; Sudarkodi, R.

    2008-08-01

    RbCl:Eu 2+ single crystals which are co-doped with thallium display characteristic Eu 2+ emission around 420 nm and additional emission band at 312 nm with a weak shoulder around 390 nm attributable to centers involving Tl + ions. Additional excitation and emission bands observed in Tl + doped RbCl:Eu 2+ single crystals are attributed to the presence of Eu 2+ aggregates and complex centres involving both Eu 2+ and Tl + ions. Inclusion of Tl + ions in RbCl:Eu 2+ crystals is found to enhance the intensity of Eu 2+ emission at 420 nm due to an energy transfer from Tl + → Eu 2+ ions.

  15. Highly piezoelectric co-doped AlN thin films for wideband FBAR applications.

    Science.gov (United States)

    Yokoyama, Tsuyoshi; Iwazaki, Yoshiki; Onda, Yosuke; Nishihara, Tokihiro; Sasajima, Yuichi; Ueda, Masanori

    2015-06-01

    We report piezoelectric materials composed of charge-compensated co-doped (Mg, β)(x)Al(1-x)N (β = Zr or Hf) thin films. The effect of the dopant element into AlN on the crystal structure, and piezoelectric properties of co-doped AlN was determined on the basis of a first-principles calculation, and the theoretical piezoelectric properties were confirmed by experimentally depositing thin films of magnesium (Mg) and zirconium (Zr) co-doped AlN (Mg-Zr-doped AlN). The Mg-Zrdoped AlN thin films were prepared on Si (100) substrates by using a triple-radio-frequency magnetron reactive co-sputtering system. The crystal structures and piezoelectric coefficients (d33) were investigated as a function of the concentrations, which were measured by X-ray diffraction and a piezometer. The results show that the d33 of Mg-Zr-doped AlN at total Mg and Zr concentrations (both expressed as β) of 0.35 was 280% larger than that of pure AlN. The experimentally measured parameter of the crystal structure and d33 of Mg-Zr-doped AlN (plotted as functions of total Mg and Zr concentrations) were in very close agreement with the corresponding values obtained by the first-principle calculations. Thin film bulk acoustic wave resonators (FBAR) employing (Mg,Zr)0.13Al0.87N and (Mg, Hf)0.13 Al0.87N as a piezoelectric thin film were fabricated, and their resonant characteristics were evaluated. The measured electromechanical coupling coefficient increased from 7.1% for pure AlN to 8.5% for Mg-Zr-doped AlN and 10.0% for Mg- Hf-doped AlN. These results indicate that co-doped (Mg, β)(x)Al(1-x)N (β = Zr or Hf) films have potential as piezoelectric thin films for wideband RF applications.

  16. Co-doping effects on luminescence and scintillation properties of Ce doped Lu{sub 3}Al{sub 5}O{sub 12} scintillator

    Energy Technology Data Exchange (ETDEWEB)

    Kamada, Kei, E-mail: kamada@imr.tohoku.ac.jp [Tohoku University, New Industry Creation Hatchery Center, 6-6-10 Aoba, Aramaki, Aoba-ku, Sendai 980-8579, Miyagi (Japan); C& A Corporation, T-Biz, 6-6-10 Aoba, Aramaki, Aoba-ku, Sendai 980-8579, Miyagi (Japan); Nikl, Martin [Institute of Physics AS CR, Cukrovarnicka 10, 16253 Prague (Czech Republic); Kurosawa, Shunsuke [Tohoku University, New Industry Creation Hatchery Center, 6-6-10 Aoba, Aramaki, Aoba-ku, Sendai 980-8579, Miyagi (Japan); Tohoku University Institute for Material Reseach, 2-1-1 Katahira Aoba-ku, Sendai 980-8577, Miyagi (Japan); Beitlerova, Alena [Institute of Physics AS CR, Cukrovarnicka 10, 16253 Prague (Czech Republic); Nagura, Aya [Tohoku University Institute for Material Reseach, 2-1-1 Katahira Aoba-ku, Sendai 980-8577, Miyagi (Japan); Shoji, Yasuhiro [C& A Corporation, T-Biz, 6-6-10 Aoba, Aramaki, Aoba-ku, Sendai 980-8579, Miyagi (Japan); Tohoku University Institute for Material Reseach, 2-1-1 Katahira Aoba-ku, Sendai 980-8577, Miyagi (Japan); Pejchal, Jan [Tohoku University, New Industry Creation Hatchery Center, 6-6-10 Aoba, Aramaki, Aoba-ku, Sendai 980-8579, Miyagi (Japan); Institute of Physics AS CR, Cukrovarnicka 10, 16253 Prague (Czech Republic); Ohashi, Yuji [Tohoku University Institute for Material Reseach, 2-1-1 Katahira Aoba-ku, Sendai 980-8577, Miyagi (Japan); Yokota, Yuui [Tohoku University, New Industry Creation Hatchery Center, 6-6-10 Aoba, Aramaki, Aoba-ku, Sendai 980-8579, Miyagi (Japan); Yoshikawa, Akira [Tohoku University, New Industry Creation Hatchery Center, 6-6-10 Aoba, Aramaki, Aoba-ku, Sendai 980-8579, Miyagi (Japan); C& A Corporation, T-Biz, 6-6-10 Aoba, Aramaki, Aoba-ku, Sendai 980-8579, Miyagi (Japan); Tohoku University Institute for Material Reseach, 2-1-1 Katahira Aoba-ku, Sendai 980-8577, Miyagi (Japan)

    2015-05-11

    The Mg, Ca, Sr and Ba 200 ppm co-doped Ce:Lu{sub 3}Al{sub 5}O{sub 12} single crystals were prepared by micro pulling down method. Absorption and luminescence spectra were measured together with several other scintillation characteristics, namely the scintillation decay and light yield to reveal the effect of the co-doping. The scintillation decays were accelerated by both Mg and Ca co-dopants. The Mg co-doped samples showed the fastest decay and the highest light yield among the co-doped samples.

  17. Co-doping as a tool for tuning the optical properties of singlewalled carbon nanotubes: A first principles study

    Science.gov (United States)

    Sharma, Deepa; Jaggi, Neena

    2017-07-01

    This paper presents a first principles study on the effect of co-doping on various optical spectra of a zigzag single-walled carbon nanotube (SWCNT). Optical spectra of a pristine SWCNT, SWCNT co-doped with Aluminum (Al) & Phosphorus (P) and another one co-doped with Al, P and Nitrogen (N) have been calculated using density functional theory (DFT).The theory has been implemented using the Cambridge sequential total energy package (CASTEP) code available as a userfriendly module with the software 'Material Studio'. Polarized and unpolarized light as well as light through polycrystalline media have been considered. The dependence of various spectra on the status of incident light presents a clear evidence of anisotropicity in the optical properties. Analysis of the simulated spectra involves calculation and comparison of different optical properties like dielectric function, reflectivity, refractive index, conductivity and loss function for the pristine and co-doped SWCNTs. Noticeable variations are observed in the optical properties on simultaneously doping the SWCNT with Al and P and then further introducing N atom into the structure so that it can be concluded that co-doping (simultaneous doping with different combinations of dopants) can be evolved as a novel and effective tool for tailoring the optical properties of SWCNTs as per the requirements while designing an optical device. It will prove to be highly significant for effective designing of SWCNT based sensitive optical devices for a variety of technological applications.

  18. Nd and Ru co-doped bismuth titanate polycrystalline thin films with improved ferroelectric properties

    Science.gov (United States)

    Sahoo, Kishor Kumar; Singh Rajput, Shailendra; Gupta, Rajeev; Roy, Amritendu; Garg, Ashish

    2018-02-01

    We report the ferroelectric properties of pulsed laser deposited thin films of Nd and Ru co-doped bismuth titanate (Bi4‑x Nd x Ti3‑y Ru y O12). Structural analysis of the as-grown films, using x-ray diffraction, showed a single-phase formation with a polycrystalline structure. In comparison to un-doped and Nd-doped films, ferroelectric measurements on co-doped films demonstrated improved properties with remnant polarization (P r) ~ 12.5 µC cm‑2 and an enhanced electrical fatigue life for Bi3.25Nd0.75Ti2.8Ru0.20O12 films. The enhancement in remanent polarization is attributed to microscopic changes, such as local structural distortion and the modification of the dynamical/effective charges on constituent ions due to chemical strain upon simultaneous Bi- (A) and Ti- (B) site doping with Nd and Ru, which has a far stronger effect than only A-site doping with Nd. Piezoresponse force microscopy further confirmed the polar structure and domain switching at nanoscale. The films exhibit small yet finite magnetization at 10 K resulting from strain.

  19. Preparation of nitrogen and sulfur co-doped ordered mesoporous carbon for enhanced microwave absorption performance

    Science.gov (United States)

    Yuan, Xiaoyan; Xue, Xingkun; Ma, Hailong; Guo, Shouwu; Cheng, Laifei

    2017-09-01

    Ordered mesoporous carbon nanomaterials (OMCs) co-doped with homogeneous nitrogen and sulfur heteroatoms were prepared by nanocasting with the pyrrole oligomer catalyzed by sulfuric acid as a precursor and ordered mesoporous silica SBA-15 as a hard-template. By multi-technique approach utilization, it was demonstrated that the N and S co-doped OMCs possessed high ordered mesoporous structures, large surface areas and homogeneous distribution of heteroatoms. As a microwave absorber, the as-prepared materials exhibited a minimum reflection loss (RL) of -32.5 dB at the thickness of 2.5 mm and an absorption bandwidth of 3.2 GHz (RL < -10 dB) in X-band (8.2-12.4 GHz). The good microwave absorption performance was mainly originated from the high electrical conductivity induced by the high surface activity and special structures. And microwave energy can be effectively attenuated through multiple reflections and absorptions in complex conductive network. The design strategy in this work would contribute to the production of a lightweight absorber, presenting a strong absorbency and a wide bandwidth in microwave frequency.

  20. Optimizing thermochromic VO2 by co-doping with W and Sr for smart window applications

    Science.gov (United States)

    Dietrich, Marc K.; Kuhl, Florian; Polity, Angelika; Klar, Peter J.

    2017-04-01

    Smart windows possess the potential to contribute significantly to reducing the world-wide energy consumption in the future. The properties of the thermochromic metal oxide VO2 are closest to the material requirements set by economic considerations for the use as an active layer in thermochromic glazings. We show that the required parameters can be achieved by modifying VO2 on the atomic level, i.e., by simultaneous co-doping with Sr and W on the cation site. In particular, the transition temperature ϑ c can be adjusted in the range between 15 and 68 °C by varying W contents, whereas the incorporation of Sr mainly increases the band gap yielding a greyish color of the films. Interestingly, the simultaneous presence of W and Sr enhances both effects. The co-doping leads to values of the luminous transmittance T lum and the solar transmittance T sol fulfilling the requirements set by application. The variation of the solar transmittance Δ T sol of the plain thin films on a glass substrate already is larger than 5% for all samples promising that the required value of Δ T sol = 10 % is achievable by using such thin films as part of an optically engineered multilayer system.

  1. Sulfur and nitrogen co-doped carbon dots sensors for nitric oxide fluorescence quantification

    Energy Technology Data Exchange (ETDEWEB)

    Simões, Eliana F.C. [Centro de Investigação em Química da Universidade do Porto (CIQ-UP), Faculdade de Farmácia da Universidade de Coimbra, Pólo das Ciências da Saúde, 3000-548 Coimbra (Portugal); Centro de Investigação em Química da Universidade do Porto (CIQ-UP), Departamento de Geociências, Ambiente e Ordenamento do Território, Faculdade de Ciências da Universidade do Porto, R. Campo Alegre 687, 4169-007 Porto (Portugal); Leitão, João M.M., E-mail: jleitao@ff.uc.pt [Centro de Investigação em Química da Universidade do Porto (CIQ-UP), Faculdade de Farmácia da Universidade de Coimbra, Pólo das Ciências da Saúde, 3000-548 Coimbra (Portugal); Esteves da Silva, Joaquim C.G. [Centro de Investigação em Química da Universidade do Porto (CIQ-UP), Departamento de Geociências, Ambiente e Ordenamento do Território, Faculdade de Ciências da Universidade do Porto, R. Campo Alegre 687, 4169-007 Porto (Portugal)

    2017-04-01

    Microwave synthetized sulfur and nitrogen co-doped carbon dots responded selectively to nitric oxide (NO) at pH 7. Citric acid, urea and sodium thiosulfate in the proportion of 1:1:3 were used respectively as carbon, nitrogen and sulfur sources in the carbon dots microwave synthesis. For this synthesis, the three compounds were diluted in 15 mL of water and exposed for 5 min to a microwave radiation of 700 W. It is observed that the main factor contributing to the increased sensitivity and selectivity response to NO at pH 7 is the sodium thiosulfate used as sulfur source. A linear response range from 1 to 25 μM with a sensitivity of 16 μM{sup −1} and a detection limit of 0.3 μM were obtained. The NO quantification capability was assessed in standard and in fortified serum solutions. - Highlights: • S,N co-doped CDs were microwave synthetized from citric acid, urea and sodium thiosulfate. • The NO fluorescence sensing was evaluated at pH 7. • The selective and sensitive detection of NO at pH 7 was achieved. • Good NO quantification results in serum samples were obtained.

  2. Thermoelectric performance of co-doped SnTe with resonant levels

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Min; Han, Yemao; Li, Laifeng, E-mail: laifengli@mail.ipc.ac.cn, E-mail: wangheng83@gmail.com [Key Laboratory of Cryogenics, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190 (China); Gibbs, Zachary M. [Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E. California Blvd. Pasadena, California 91125 (United States); Wang, Heng, E-mail: laifengli@mail.ipc.ac.cn, E-mail: wangheng83@gmail.com [Materials Science, California Institute of Technology, 1200 California Blvd., Pasadena, California 91125 (United States); Snyder, G. Jeffrey [Materials Science, California Institute of Technology, 1200 California Blvd., Pasadena, California 91125 (United States); TMO University, Saint Petersburg 197101 (Russian Federation)

    2016-07-25

    Some group III elements such as Indium are known to produce the resonant impurity states in IV-VI compounds. The discovery of these impurity states has opened up new ways for engineering the thermoelectric properties of IV-VI compounds. In this work, resonant states in SnTe were studied by co-doping with both resonant (In) and extrinsic (Ag, I) dopants. A characteristic nonlinear relationship was observed between the Hall carrier concentration (n{sub H}) and extrinsic dopant concentration (N{sub I}, N{sub Ag}) in the stabilization region, where a linear increase of dopant concentration does not lead to linear response in the measured n{sub H}. Upon substituting extrinsic dopants beyond a certain amount, the n{sub H} changed proportionally with additional dopants (Ag, I) (the doping region). The Seebeck coefficients are enhanced as the resonant impurity is introduced, whereas the use of extrinsic doping only induces minor changes. Modest zT enhancements are observed at lower temperatures, which lead to an increase in the average zT values over a broad range of temperatures (300–773 K). The improved average zT obtained through co-doping indicates the promise of fine carrier density control in maximizing the favorable effect of resonant levels for thermoelectric materials.

  3. Ionic conductivity of co-doped Sc2O3-ZrO2 ceramics

    Science.gov (United States)

    Omar, Shobit; Najib, Waqas bin; Chen, Weiwu; Bonanos, Nikolaos

    2012-07-01

    The oxide ionic conductivity of Sc0.18Zr0.82O1.91 doped with 0.5 mol.% of both Yb2O3 and In2O3 is evaluated at various temperatures in air. Among various co-doped compositions, In0.02Sc0.18Zr0.80O1.90 exhibits the highest grain ionic conductivity followed by Yb0.02Sc0.18Zr0.80O1.90 at 500°C. However, it also possesses phase transformation from c- to β-phase at 475°C on cooling. In the present work, an attempt is made to completely stabilize the cphase in In0.02Sc0.18Zr0.80O1.90 by substituting 0.5 mol.% of In2O3 with Yb2O3, which can enhance the ionic conductivity in co-doped compositions.

  4. Photocatalytic decomposition of perfluorooctanoic acid by iron and niobium co-doped titanium dioxide

    Energy Technology Data Exchange (ETDEWEB)

    Renan Estrellan, Carl, E-mail: estrellan.c.ac@m.titech.ac.jp [Department of International Development Engineering, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550 (Japan); Salim, Chris; Hinode, Hirofumi [Department of International Development Engineering, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550 (Japan)

    2010-07-15

    The photocatalytic decomposition of perfluorooctanoic acid (PFOA) in aqueous solution using Fe and Nb co-doped TiO{sub 2} (Fe:Nb-TiO{sub 2}) prepared by sol-gel method was investigated. The photocatalytic activity of Fe:Nb-TiO{sub 2} towards PFOA degradation was compared to that of pure TiO{sub 2} synthesized using the same method, and that of the commercially available TiO{sub 2} photocatalyst, Aeroxide TiO{sub 2} P25 (AO-TiO{sub 2} P25). The photocatalysts were characterized by XRD, DRS, BET-N{sub 2} adsorption isotherm, and SEM-EDX techniques and the data were correlated to the photocatalytic activity. Fe:Nb-TiO{sub 2} showed the highest activity compared to the undoped TiO{sub 2} and the commercially available TiO{sub 2}. Such activity was attributable to the effects of co-doping both on the physico-chemical properties and surface interfacial charge transfer mechanisms. Perfluorocarboxylic acids (PFCAs) with shorter carbon chain length and fluoride ions were identified as photocatalytic reaction intermediates and products.

  5. Enhanced defect-mediated ferromagnetism in Cu2O by Co doping

    Science.gov (United States)

    Brandt, Iuri S.; Tumelero, Milton A.; Lima, Enio; da Silva, Douglas L.; Zysler, Roberto D.; Faccio, Ricardo; Pasa, André A.

    2017-11-01

    In this work an extensive characterization of Co doped Cu2O thin films grown by electrochemical deposition is presented. The doped films showed ferromagnetic behavior, with impressive Curie temperature up to 700 K. Undoped samples also presented magnetic moments at room temperature, but much reduced when compared to doped ones. The observed magnetism in undoped and doped samples was taken as an indicative of a defect-mediated ferromagnetism. Moreover, the sample magnetization was reduced as a consequence of a decreasing in defect density due to thermal annealing. Polarization-dependent X-ray absorption measurements demonstrated that oxygen derived states are the source of the observed magnetic moment and its magnetic dichroism depends on the amount of point defects. Structural, optical and electrical characterization provides information that confirms the incorporation of Co atoms in the Cu2O lattice, without the formation of secondary segregated Co phases. In addition, Electron Paramagnetic Resonance and Glow Discharge Optical Emission Spectroscopy measurements reject the existence of contaminants in the films, dismissing them as the source for the observed magnetism. Computational calculations have shown that Co doping shall locally increases the amount of defects, such as interstitial O, leading to highly oxidized regions from where the unpaired spin arises. This situation generates a picture similar to the magnetic polaron theory, but with the dopant ion pinning the defects.

  6. Enhanced photoluminescence in CaMoO4:Eu3+ by Gd3+ co-doping.

    Science.gov (United States)

    Singh, B P; Parchur, A K; Ningthoujam, R S; Ansari, A A; Singh, P; Rai, S B

    2014-03-28

    We have studied the luminescence property of CaMoO4:Eu(3+). The emission peaks at 590 ((5)D0→(7)F1) and 613 nm ((5)D0→(7)F2) for Eu(3+) are observed after excitation at 266 nm (i.e. Mo-O charge transfer band). The peak intensity of the latter dominates over the former indicating an asymmetric environment of Eu(3+) in EuO8 polyhedron or parity mixing. Luminescence intensity increases significantly with co-doping of Gd(3+). This is ascribed to energy transfer from Mo-O/Gd(3+) to Eu(3+). Luminescence intensity increases with annealing up to 900 °C due to the extent of decrease of non-radiative rates. Very high asymmetric values (A21) of 12-16 are found indicating a red emitter. As-prepared samples are dispersible in polar solvents like water, ethanol, methanol, dimethyl sulfoxide (DMSO) and ethylene glycol (EG); and among them, optimum luminescence is found in methanol. Polymer film shows red emission. The quantum yields of as-prepared 2 and 10 at% Gd(3+) co-doped CaMoO4:Eu(3+) under 277 nm (UV excitation) are 21 and 80%, respectively.

  7. W/Mo co-doped BiVO4 for photocatalytic treatment of polymer-containing wastewater in oilfield

    Science.gov (United States)

    Zhou, Ying; Li, Wei; Wan, Wenchao; Zhang, Ruiyang; Lin, Yuanhua

    2015-06-01

    Polymer flooding is an effective way to enhance oil recovery (EOR). However, the treatment of the oily wastewater becomes an urgent issue. Photocatalysis is a promising approach for this purpose. In this report, W/Mo co-doped BiVO4 particles are synthesized by hydrothermal method. W/Mo co-doping could promote an effective separation of photogenerated carriers reflecting from the 6 times higher photocurrent density compared to pure BiVO4. The photodegradation of partially hydrolyzed polyacrylamide (HPAM) over 0.5 at.% W and 1.5 at.% Mo co-doped BiVO4 is 43% under UV-vis light irradiation for 3 h, which is much higher than that of pure BiVO4 (18%).

  8. Novel band gap-tunable K–Na co-doped graphitic carbon nitride prepared by molten salt method

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Jiannan [Institute of Eco-environmental Sciences, Liaoning Shihua University, Fushun 113001 (China); School of Environmental and Biological Engineering, Liaoning Shihua University, Fushun 113001 (China); Ma, Lin [School of Petrochemical Engineering, Liaoning Shihua University, Fushun 113001 (China); Wang, Haoying; Zhao, Yanfeng [School of Environmental and Biological Engineering, Liaoning Shihua University, Fushun 113001 (China); Zhang, Jian [School of Petrochemical Engineering, Liaoning Shihua University, Fushun 113001 (China); Hu, Shaozheng, E-mail: hushaozhenglnpu@163.com [Institute of Eco-environmental Sciences, Liaoning Shihua University, Fushun 113001 (China)

    2015-03-30

    Graphical abstract: K and Na ions co-doped into g-C{sub 3}N{sub 4} crystal lattice can tune the position of CB and VB potentials, influence the structural and optical properties, and thus improve the photocatalytic degradation and mineralization ability. - Highlights: • K, Na co-doped g-C{sub 3}N{sub 4} was prepared in KCl/NaCl molten salt system. • The structural and optical properties of g-C{sub 3}N{sub 4} were greatly influenced by co-doping. • The position of VB and CB can be tuned by controlling the weight ratio of eutectic salts to melamine. • Co-doped g-C{sub 3}N{sub 4} showed outstanding photodegradation ability, mineralization ability, and catalytic stability. - Abstract: Novel band gap-tunable K–Na co-doped graphitic carbon nitride was prepared by molten salt method using melamine, KCl, and NaCl as precursor. X-ray diffraction (XRD), N{sub 2} adsorption, Scanning electron microscope (SEM), UV–vis spectroscopy, Photoluminescence (PL), and X-ray photoelectron spectroscopy (XPS) were used to characterize the prepared catalysts. The CB and VB potentials of graphitic carbon nitride could be tuned from −1.09 and +1.55 eV to −0.29 and +2.25 eV by controlling the weight ratio of eutectic salts to melamine. Besides, ions doping inhibited the crystal growth of graphitic carbon nitride, enhanced the surface area, and increased the separation rate of photogenerated electrons and holes. The visible-light-driven Rhodamine B (RhB) photodegradation and mineralization performances were significantly improved after K–Na co-doping.

  9. Low temperature synthesis of radio frequency magnetron sputtered gallium and aluminium co-doped zinc oxide thin films for transparent electrode fabrication

    Energy Technology Data Exchange (ETDEWEB)

    Muchuweni, E., E-mail: muchuweniedigar1@gmail.com; Sathiaraj, T.S.; Nyakotyo, H.

    2016-12-30

    Highlights: • Radio frequency magnetron sputtering was used to prepare gallium (Ga) and aluminium (Al) co-doped zinc oxide thin films. • The film’s crystallinity improved with substrate temperature from RT to 75 °C and then deteriorated at 100 °C. • The surface morphology was strongly dependent on substrate temperature. • Energy dispersive spectroscopy confirmed the incorporation of Ga and Al into the films. • Films deposited at 75 °C and 100 °C exhibited higher figure of merits suitable for transparent electrode applications. - Abstract: Gallium and aluminium co-doped zinc oxide (GAZO) thin films were prepared on glass substrates at low temperatures by radio frequency (rf) magnetron sputtering and their physical properties were investigated. All films possessed a hexagonal wurtzite crystal structure with a strong growth orientation along the (0 0 2) c-axis. The (0 0 2) peak intensity and mean crystallite size increased with substrate temperature from room temperature (RT) to 75 °C and then decreased at 100 °C, indicating an improvement in crystallinity up to 75 °C and its deterioration at 100 °C. Scanning electron microscopy (SEM) micrographs revealed the strong dependency of surface morphology on substrate temperature and energy dispersive spectroscopy (EDS) confirmed the incorporation of Ga and Al into the ZnO films. All films exhibited excellent transmittances between 85 and 90% in the visible region and their optical band gap increased from 3.22 eV to 3.28 eV with substrate temperature. The Urbach energy decreased from 194 meV to 168 meV with increasing substrate temperature, indicating a decrease in structural disorders which was consistent with X-ray Diffraction (XRD) analysis. Films deposited at 75 °C exhibited the lowest electrical resistivity (2.4 Ωcm) and highest figure of merit (7.5 × 10{sup −5} Ω{sup −1}), proving their potential as candidates for transparent electrode fabrication.

  10. Highly luminescent S, N co-doped graphene quantum dots with broad visible absorption bands for visible light photocatalysts

    Science.gov (United States)

    Qu, Dan; Zheng, Min; Du, Peng; Zhou, Yue; Zhang, Ligong; Li, Di; Tan, Huaqiao; Zhao, Zhao; Xie, Zhigang; Sun, Zaicheng

    2013-11-01

    A facile hydrothermal synthesis route to N and S, N co-doped graphene quantum dots (GQDs) was developed by using citric acid as the C source and urea or thiourea as N and S sources. Both N and S, N doped GQDs showed high quantum yield (78% and 71%), excitation independent under excitation of 340-400 nm and single exponential decay under UV excitation. A broad absorption band in the visible region appeared in S, N co-doped GQDs due to doping with sulfur, which alters the surface state of GQDs. However, S, N co-doped GQDs show different color emission under excitation of 420-520 nm due to their absorption in the visible region. The excellent photocatalytic performance of the S, N co-doped GQD/TiO2 composites was demonstrated by degradation of rhodamine B under visible light. The apparent rate of S, N:GQD/TiO2 is 3 and 10 times higher than that of N:GQD/TiO2 and P25 TiO2 under visible light irradiation, respectively.A facile hydrothermal synthesis route to N and S, N co-doped graphene quantum dots (GQDs) was developed by using citric acid as the C source and urea or thiourea as N and S sources. Both N and S, N doped GQDs showed high quantum yield (78% and 71%), excitation independent under excitation of 340-400 nm and single exponential decay under UV excitation. A broad absorption band in the visible region appeared in S, N co-doped GQDs due to doping with sulfur, which alters the surface state of GQDs. However, S, N co-doped GQDs show different color emission under excitation of 420-520 nm due to their absorption in the visible region. The excellent photocatalytic performance of the S, N co-doped GQD/TiO2 composites was demonstrated by degradation of rhodamine B under visible light. The apparent rate of S, N:GQD/TiO2 is 3 and 10 times higher than that of N:GQD/TiO2 and P25 TiO2 under visible light irradiation, respectively. Electronic supplementary information (ESI) available: More XPS and UV-Vis spectra. See DOI: 10.1039/c3nr04402e

  11. Study on the Emission Property of YBO{sub 3} with Co-doping of Ce and Gd Ions

    Energy Technology Data Exchange (ETDEWEB)

    Jang, Soyeong; Lim, Junhwi; Lee, Y. S. [Soongsil University, Seoul (Korea, Republic of)

    2017-08-15

    We investigated the co-doping effect of Ce{sup 3+} and Gd{sup 3+} ions on the visible emission in vaterite-type orthoborate YBO{sub 3}. By using photoluminescence and photoluminescence excitation spectroscopy, we found that the co-doping of the Gd{sup 3+} ions increased the violet-blue emission of the Ce ions significantly. In basis of the optical spectroscopic data, we discussed our results in terms of the energy transfer between Ce{sup 3+} and Gd{sup 3+} ions.

  12. Nickel Oxide and Nickel Co-doped Graphitic Carbon Nitride Nanocomposites and its Octylphenol Sensing Application

    KAUST Repository

    Gong, Wanyun

    2015-11-16

    Nickel oxide and nickel co-doped graphitic carbon nitride (NiO-Ni-GCN) nanocomposites were successfully prepared by thermal treatment of melamine and NiCl2 6H2O. NiO-Ni-GCN nanocomposites showed superior electrochemical catalytic activity for the oxidation of octylphenol to pure GCN. A detection method of octylphenol in environmental water samples was developed based at NiO-Ni-GCN nanocomposites modified electrode under infrared light irradiation. Differential pulse voltammetry was used as the analytic technique of octylphenol, exhibiting stable and specific concentration-dependent oxidation signal in the presence of octylphenol in the range of 10nM to 1μM and 1μM to 50μM, with a detection limit of 3.3nM (3S/N). © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Crystallization studies on rare-earth co-doped fluorozirconate-based glasses.

    Science.gov (United States)

    Paßlick, C; Johnson, J A; Schweizer, S

    2013-07-01

    This work focuses on the structural changes of barium chloride (BaCl2) nanoparticles in fluorochlorozirconate-based glass ceramics when doped with two different luminescent activators, in this case rare-earth (RE) ions, and thermally processed using a differential scanning calorimeter. In a first step, only europium in its divalent and trivalent oxidation states, Eu(2+) and Eu(3+), is investigated, which shows no significant influence on the crystallization of hexagonal phase BaCl2. However, higher amounts of Eu(2+) increase the activation energy of the phase transition to an orthorhombic crystal structure. In a second step, nucleation and nanocrystal growth are influenced by changing the structural environment of the glasses by co-doping with Eu(2+) and trivalent Gd(3+), Nd(3+), Yb(3+), or Tb(3+), due to the different atomic radii and electro-negativity of the co-dopants.

  14. Structural and dielectric properties of Nd/Ca co-doped bi-ferrite multiferroics

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Ashwini, E-mail: vdinesh33@rediffmail.com, E-mail: ashu.dhanda@gmail.com; Sharma, Poorva, E-mail: vdinesh33@rediffmail.com, E-mail: ashu.dhanda@gmail.com; Varshney, Dinesh, E-mail: vdinesh33@rediffmail.com, E-mail: ashu.dhanda@gmail.com [School of Physics, Vigyan Bhawan, Devi Ahilya University, Khandwa Road Campus, Indore 452001 (India)

    2014-04-24

    Single-phase polycrystalline samples of Bi{sub 0.8}Nd{sub 0.2−x}Ca{sub x}FeO{sub 3} (x = 0.0, 0.1) were synthesized by chemical coprecipitation method. X-ray diffraction patterns accompanied by Rietveld-refined crystal structure parameters reveal the phase transition of Bi{sub 0.8}Nd{sub 0.1}Ca{sub 0.1}FeO{sub 3} with rhombohedral R3c symmetry to triclinic structure of Bi{sub 0.8}Nd{sub 0.2}FeO{sub 3} sample. Frequency dependence of dielectric constant (ε') and dielectric loss (tanδ), infers enhancement of both ε' (tanδ) in narrow band gap of Nd/Ca co-doped BFO as compare to wide band pristine BFO.

  15. Phase transitions in ZnTe co-doped with Mg and oxygen

    Energy Technology Data Exchange (ETDEWEB)

    Elyukhin, V.A.; Sorokina, L.P. [Departamento de Ingenieria Electrica, CINVESTAV-IPN, Av. IPN 2508, Mexico, D.F., 07360 (Mexico); Rodriguez de Santiago, M. [Departamento de Ingenieria Quimica Petrolera, IPN, Edif. 8, Mexico, D.F., 07738 (Mexico)

    2007-05-15

    Self-assembling of 1O4Mg tetrahedral clusters in ZnTe isoelectronically co-doped with Mg and oxygen in the ultra dilute oxygen impurity limit is described by a phase diagram. The occurrence of 1O4Mg clusters is a result of the second-order transition. The final stage of self-assembling when all oxygen impurities are in 1O4Mg clusters has to be reached also as a result of the second-order transition at the temperature close to the temperature of the occurrence of these clusters. The conditions of these phase transitions are obtained. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  16. Ultrahigh volumetric capacitance and cyclic stability of fluorine and nitrogen co-doped carbon microspheres

    Science.gov (United States)

    Zhou, Junshuang; Lian, Jie; Hou, Li; Zhang, Junchuan; Gou, Huiyang; Xia, Meirong; Zhao, Yufeng; Strobel, Timothy A.; Tao, Lu; Gao, Faming

    2015-09-01

    Highly porous nanostructures with large surface areas are typically employed for electrical double-layer capacitors to improve gravimetric energy storage capacity; however, high surface area carbon-based electrodes result in poor volumetric capacitance because of the low packing density of porous materials. Here, we demonstrate ultrahigh volumetric capacitance of 521 F cm-3 in aqueous electrolytes for non-porous carbon microsphere electrodes co-doped with fluorine and nitrogen synthesized by low-temperature solvothermal route, rivaling expensive RuO2 or MnO2 pseudo-capacitors. The new electrodes also exhibit excellent cyclic stability without capacitance loss after 10,000 cycles in both acidic and basic electrolytes at a high charge current of 5 A g-1. This work provides a new approach for designing high-performance electrodes with exceptional volumetric capacitance with high mass loadings and charge rates for long-lived electrochemical energy storage systems.

  17. Computational model for operation of 2 mum co-doped Tm,Ho solid state lasers.

    Science.gov (United States)

    Louchev, Oleg A; Urata, Yoshiharu; Saito, Norihito; Wada, Satoshi

    2007-09-17

    A computational model for operation of co-doped Tm,Ho solid-state lasers is developed coupling (i) 8-level rate equations with (ii) TEM00 laser beam distribution, and (iii) complex heat dissipation model. Simulations done for Q-switched approximately 0.1 J giant pulse generation by Tm,Ho:YLF laser show that approximately 43% of the 785 nm light diode side-pumped energy is directly transformed into the heat inside the crystal, whereas approximately 45% is the spontaneously emitted radiation from (3)F(4), (5)I(7) , (3)H(4) and (3)H(5) levels. In water-cooled operation this radiation is absorbed inside the thermal boundary layer where the heat transfer is dominated by heat conduction. In high-power operation the resulting temperature increase is shown to lead to (i) significant decrease in giant pulse energy and (ii) thermal lensing.

  18. Co-doped sodium chloride crystals exposed to different irradiation temperature

    Energy Technology Data Exchange (ETDEWEB)

    Ortiz-Morales, A. [Unidad Profesional Interdisciplinaria de Ingenieria y Tecnologias Avanzadas, IPN, Av. Instituto Politecnico Nacional 2580, Col. La Laguna Ticoman, 07340 Mexico D.F., Mexico and Unidad de Irradiacion y Segurid (Mexico); Cruz-Zaragoza, E.; Furetta, C. [Unidad de Irradiacion y Seguridad Radiologica, Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, A.P. 70-543, 04510 Mexico D.F (Mexico); Kitis, G. [Nuclear Physics Laboratory, Aristotle University of Thessaloniki, Thessaloniki 54124 (Greece); Flores J, C.; Hernandez A, J.; Murrieta S, H. [Instituto de Fisica, Universidad Nacional Autonoma de Mexico, AP. 20-364, 01000 Mexico D.F (Mexico)

    2013-07-03

    Monocrystals of NaCl:XCl{sub 2}:MnCl{sub 2}(X = Ca,Cd) at four different concentrations have been analyzed. The crystals were exposed to different irradiation temperature, such as at room temperature (RT), solid water (SW), dry ice (DI) and liquid nitrogen (LN). The samples were irradiated with photon from {sup 60}Co irradiators. The co-doped sodium chloride crystals show a complex structure of glow curves that can be related to different distribution of traps. The linearity response was analyzed with the F(D) index. The F(D) value was less than unity indicating a sub-linear response was obtained from the TL response on the function of the dose. The glow curves were deconvoluted by using the CGCD program based on the first, second and general order kinetics.

  19. Synthesis and structural analysis of Co-doped BaTiO3

    Science.gov (United States)

    Padilla-Campos, L.; Diaz-Droguett, D. E.; Lavín, R.; Fuentes, S.

    2015-11-01

    BaTiO3 doped with various percentages of Co (1-5 mol%) was synthesized using a combined sol-gel-hydrothermal method. The structural characteristics of the compounds were investigated using X-ray diffraction and Raman spectroscopy. Surface chemical information and oxidation states were studied using X-ray photoelectron spectroscopy. The magnetic properties of the samples were studied using magnetization curves. In addition, quantum chemical calculations were performed to elucidate the electronic structure of the samples and to understand the possible substitution mechanisms during Co-doping. The results indicated that Co effectively endowed the BaTiO3 structure with intrinsic magnetic properties, which decreased as the Co percentage increased. In addition, the increase in the Co mol% produced a gradual loss of the non-perovskite structure, leading to a decrease in the ferroelectric behaviour.

  20. ANN Modeling of Electronic Nose Based on Co-doped SnO2 Nanofiber Sensor

    Directory of Open Access Journals (Sweden)

    S. KHALDI

    2016-05-01

    Full Text Available We present in this paper a novel neural network based technique to create a model incorporates intelligence for electronic nose. The idea is to create intelligent models; the first one, called selector, can select exactly the nature of gas detected. The second intelligent model is a corrector, which can automatically compensate the electronic nose’s response characteristics and discriminating exactly the detected gas (nature and concentration, and make the response increases all time when the temperature increases. The electronic nose is based on Co-doped SnO2 nanofiber sensor. The MATLAB environment is used during the design phase and optimization. The method discriminates qualitatively and quantitatively between six gases. The advantage of the method is that it uses a small representative database so we can easily implement the model in an electrical simulator.

  1. Fabrication and characterization of ZnO and Li doped ZnO by a sol-gel method

    Science.gov (United States)

    Fadillah, L.; Soegijono, B.; Budiawanti, S.; Mudzakir, I.

    2017-07-01

    The substitution of group-I and or group V elements on Zn-site and O-site respectively are challenge that needs to be overcome for the realization of the most ZnO based application materials. The process of fabrication to obtain high quality crystal samples in various structures should be handled carefully with precaution. ZnO and Li doped ZnO have been fabricated via sol-gel method. The samples have been observed by means of X-ray diffractometer, Thermal gravimetry analyzer (TGA), and FTIR. The characterization results show similar to commercial powder for undoped ZnO while Li doped ZnO show a shifting in crystallographic properties. It concludes that fabrication of high quality ZnO and Li doped ZnO was accomplished.

  2. Er{sup 3+}/Yb{sup 3+}co-doped bismuth molybdate nanosheets upconversion photocatalyst with enhanced photocatalytic activity

    Energy Technology Data Exchange (ETDEWEB)

    Adhikari, Rajesh; Gyawali, Gobinda; Cho, Sung Hun [Research Center for Eco-Multifunctional Nanomaterials, Sun Moon University (Korea, Republic of); Narro-García, R. [Centro de Investigaciones en Óptica, A. P.1-948, León, Gto. 37150, México (Mexico); Sekino, Tohru [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University (Japan); Lee, Soo Wohn, E-mail: swlee@sunmoon.ac.kr [Research Center for Eco-Multifunctional Nanomaterials, Sun Moon University (Korea, Republic of)

    2014-01-15

    In this paper, we report the microwave hydrothermal synthesis of Er{sup 3+}/Yb{sup 3+} co-doped Bi{sub 2}MoO{sub 6} upconversion photocatalyst. Crystal structure, morphology, elemental composition, optical properties and BET surface area were analyzed in detail. Infrared to visible upconversion luminescence at 532 nm and 546 nm of the co-doped samples was investigated under excitation at 980 nm. The results revealed that the co-doping of Er{sup 3+}/Yb{sup 3+} into Bi{sub 2}MoO{sub 6} exhibited enhanced photocatalytic activity for the decomposition of rhodamine B under simulated solar light irradiation. Enhanced photocatalytic activity can be attributed to the energy transfer between Er{sup 3+}/Yb{sup 3+} and Bi{sub 2}MoO{sub 6} via infrared to visible upconversion from Er{sup 3+}/Yb{sup 3+} ion and higher surface area of the Bi{sub 2}MoO{sub 6} nanosheets. Therefore, this synthetic approach may exhibit a better alternative to fabricate upconversion photocatalyst for integral solar light absorption. - Graphical abstract: Schematic illustration of the upconversion photocatalysis. Display Omitted - Highlights: • Er{sup 3+}/Yb{sup 3+} co-doped Bi{sub 2}MoO{sub 6} upconversion photocatalyst is successfully synthesized. • We obtained the nanosheets having high surface area. • Upconversion of IR to visible light was confirmed. • Upconversion phenomena can be utilized for effective photocatalysis.

  3. Synthesis of Co-Doped CdS Nanocrystals by Direct Thermolysis of Cadmium and Cobalt Thiolate Clusters

    Directory of Open Access Journals (Sweden)

    Jianing Zhao

    2015-01-01

    Full Text Available Co-doped CdS (Co:CdS nanocrystals with controllable morphology (quantum dots and nanorods were easily synthesized by direct thermolysis of (Me4N2[Co4(SC6H510] and (Me4N4[S4Cd10(SPh16] under different precursor concentration, in virtue of the ions exchange of molecular clusters. The Co:CdS quantum dots were produced under low precursor concentration, and the Co:CdS nanorods could be obtained under higher precursor concentration. The Co-doping effect on the structure, growth process, and property of CdS nanocrystals was also investigated. The results indicated that the Co-doping was favorable for the formation of the nanorod structures for a short reaction time. In addition, the Co-doping in the CdS lattice resulted in the ferromagnetic property of the Co:CdS quantum dots at room temperature. Moreover, compared with the CdS quantum dots, the Co:CdS quantum dots exhibited obvious quantum confinement effect and photoluminescence emission with slightly red-shift.

  4. Tunable luminescence mediated by energy transfer in Tm3+/Dy3+ co-doped phosphate glasses under UV excitation

    Science.gov (United States)

    Chen, Yong; Chen, Guohua; Liu, Xiangyu; Yuan, Changlai; Zhou, Changrong

    2017-11-01

    Tm3+/Dy3+ co-doped phosphate glasses for white light-emitting diodes were synthesized by a conventional melting-quenching method. A spectroscopic research based on optical, photoluminescence spectrum and decay time curves in Tm3+/Dy3+ co-doped phosphate glasses was carried out. The color of luminescence could be tuned by altering the concentrations of Tm3+ ions. Under UV light excitation, the CIE chromaticity coordinates (0.3471, 0.3374) and color correlate temperature (CCT = 4866.21 K) close to the standard white-light illumination (0.333, 0.333 and CCT = 5454.12 K) could be achieved in 0.4 Tm3+/0.6 Dy3+ (mol %) co-doped glass sample. The decrease of the Dy3+ emission decay time in existence of Tm3+ ascertained that non-radiative energy transfer from Dy3+ to Tm3+ occurred. Moreover, the research of energy transfers between Dy3+ and Tm3+ based on the Inokuti-Hirayama model revealed that an electric quadrupole-quadrupole interaction might be the predominant mechanism participated in the energy transfer. This finding suggests that the as-prepared Tm3+/Dy3+ co-doped phosphate glasses may be promising candidate for white LEDs and other display devices.

  5. Synthesis of Pyridinic-Rich N, S Co-doped Carbon Quantum Dots as Effective Enzyme Mimics

    Science.gov (United States)

    Liu, Teng; Cui, Zhi-wei; Zhou, Jun; Wang, Ying; Zou, Zhi-gang

    2017-05-01

    N and S co-doped carbon quantum dots (N, S-CQDs) with high N- and S-doping level were synthesized by microwave solid-phase pyrolysis within 50 s. Owing to the dominant pyridinic N injection into the conjugated framework, both high enzyme mimics catalytic activity and photoluminescence quantum yield are achieved simultaneously.

  6. Structural and magnetic properties of Zn{sub 1-x}Mn{sub x}O nanocrystalline powders and thin films

    Energy Technology Data Exchange (ETDEWEB)

    Mera, J.; Cordoba, C. [Centro de Investigaciones en Materiales, Facultad de Ingenieria, Universidad de Narino, Ciudad Universitaria Torobajo, Pasto (Colombia); Doria, J. [Laboratorio de Materiales Ceramicos y Vitreos, Departamento de Fisica, Universidad Nacional de Colombia, Campus Medellin, A.A. 568, Medellin (Colombia); Gomez, A. [Laboratorio de caracterizacion de materiales, Universidad Nacional de Colombia, Campus Medellin, A.A. 568, Medellin (Colombia); Paucar, C. [Laboratorio de Materiales Ceramicos y Vitreos, Departamento de Fisica, Universidad Nacional de Colombia, Campus Medellin, A.A. 568, Medellin (Colombia); Fuchs, D. [Karlsruhe Institute of Technology, Institute for Solid State Physics, P.O. Box 3640, Karlsruhe Germany (Germany); Moran, O., E-mail: omoranc@unal.edu.co [Laboratorio de Materiales Ceramicos y Vitreos, Departamento de Fisica, Universidad Nacional de Colombia, Campus Medellin, A.A. 568, Medellin (Colombia)

    2012-12-15

    The structural and magnetic properties of Zn{sub 1-x}Mn{sub x}O (x = 0, 0.02, 0.05, 0.1) nanocrystalline powders and thin epitaxial films were studied in detail. Epitaxial films were fabricated by pulsed laser deposition on c-Al{sub 2}O{sub 3} substrates. To this end, ablation targets were prepared by pressing nano-sized powders of Zn{sub 1-x}Mn{sub x}O (x = 0, 0.02, 0.1) synthesized by the wet polymeric precursor method. The method was chosen in order to improve purity and homogeneity of the grain-size distribution. The epitaxial growth was optimized with respect to crystalline quality by varying deposition parameters such as substrate temperature, laser fluence and background gas conditions. Films prepared under optimized conditions show a mosaic spread < 0.3 Degree-Sign and a bulk-like c-axis lattice parameter of 5.198 A. The structural data indicate the substitution of Zn{sup 2+} by the Mn{sup 2+} cations in the wurtzite structure of pristine ZnO. The influence of Mn on the lattice dynamics of ZnO is confirmed by Raman scattering. It is found that Mn doping increases the lattice defects and induces two Raman vibration modes of 275 and 526 cm{sup -1}. Magnetic measurements, in turn, show while thin films, grown in vacuum, are ferromagnetic at RT, the growth in an oxygen atmosphere results in a dramatic decrease of the magnetic properties, demonstrating that oxygen vacancies are most likely responsible for the magnetic exchange. The co-doping with nitrogen has no major influence on the structural and magnetic properties of the ZnO films. A correct Mn doping concentration seems to be crucial for making a viable diluted magnetic semiconductor. - Highlights: Black-Right-Pointing-Pointer Growth of Zn{sub 1-x}Mn{sub x}O thin films by pulsed laser deposition is optimized. Black-Right-Pointing-Pointer Blue-shift of the absorption edge with increasing Mn is observed. Black-Right-Pointing-Pointer Deffect density in Zn{sub 1-x}Mn{sub x}O increases with increasing Mn

  7. Effect of co-doping on luminescence of LiCaAlF{sub 6}:Eu phosphor

    Energy Technology Data Exchange (ETDEWEB)

    Rahangdale, S.R.; Palikundwar, U.A. [Department of Physics, Nagpur University, Nagpur 440033 (India); Wankhede, S.P. [Department of Physics, K.D.K. College of Engineering, Nagpur (India); Dhabekar, Bhushan; Kadam, Sonal [Radiological Physics and Advisory Division, Bhabha Atomic Research Centre (BARC), Mumbai 400085 (India); Moharil, S.V., E-mail: svmoharil@yahoo.com [Department of Physics, Nagpur University, Nagpur 440033 (India)

    2015-11-15

    Abstracts: LiCaAlF{sub 6} is a versatile host material. Applications of this host as scintillation detector and solid state laser have been reported quite frequently. Thermoluminescence studies on LiCaAlF{sub 6}:Eu have also been reported. They are, however, not consistent. The glow curve structure depends on the synthesis route. At least two glow peaks are observed, around 180 °C and 240 °C. Effects of co-doping on the glow curve are reported. Co-doping with Y (0.5 mol%) suppresses the 240 °C peak and increases the intensity of 180 °C peak nearly 3 fold and shifts it to slightly higher temperature of 190 °C. Co-doping with La (0.8 mol%), on the other hand, removes 180 °C peak and intense peak at 240 °C can be observed. Thus co-doping produces a relatively simple glow curve with only one dominant peak. LiCaAlF{sub 6}:Eu phosphor also shows intense optically stimulated luminescence (OSL). The OSL sensitivity of LiCaAlF{sub 6}:Eu codoped with Y is about 7 times that of commercially available Al{sub 2}O{sub 3}:C. Other OSL properties useful for dosimetry applications are also reported in this paper. - Highlights: • Precipitation synthesis of LiCaAlF{sub 6}:Eu, Yttrium co-doping simplifies glow curve. • TL sensitivity is 3 times that of CaSO{sub 4}:Dy. • OSL sensitivity is 7 times that of Al{sub 2}O{sub 3}:C (Landauer). • Linear OSL response in the range 3 mGy to 1 kGy. • Negligible fading over 40 days.

  8. Multimodal emissions from Tb3+/Yb3+ co-doped lithium borate glass: Upconversion, downshifting and quantum cutting

    Science.gov (United States)

    Bahadur, A.; Yadav, R. S.; Yadav, R. V.; Rai, S. B.

    2017-02-01

    This paper reports the optical properties of Tb3+/Yb3+ co-doped lithium borate (LB) glass prepared by melt quench method. The absorption spectrum of the Yb3+ doped LB glass contains intense NIR band centered at 976 nm due to 2F7/2→2F5/2 transition. The emission spectra of the prepared glasses have been monitored on excitation with 266, 355 and 976 nm. The Yb3+ doped glass emits a broad NIR band centered at 976 nm whereas the Tb3+ doped glass gives off visible bands on excitations with 266 and 355 nm. When the Tb3+ and Yb3+ ions are co-doped together, the emission intensity in the visible region decreases whereas it increases in the NIR region significantly. The increase in the emission intensity in the NIR region is due to efficient cooperative energy transfer (CET) from Tb3+ to Yb3+ ions. The quantum cutting efficiency for Tb3+/Yb3+ co-doped glass has been calculated and compared for 266 and 355 nm excitations. The quantum cutting efficiency is larger for 355 nm excitation (137%). The Tb3+/Yb3+ co-doped LB glass also emits upconverted visible bands on excitation with 976 nm. The mechanisms involved in the energy transfer have been discussed using schematic energy level diagram. The Tb3+/Yb3+ co-doped LB glass may be used in the optical devices and in solar cell for solar spectral conversion and behaves as a multi-modal photo-luminescent material.

  9. Co-doping effects of Mg and Be on properties of ZnMgBeGaO UV-range transparent conductive oxide films prepared by RF magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jang-Ho; Cuong, Hoang Ba [Photonic and Electronic Thin Film Laboratory, Department of Materials Science and Engineering, Chonnam National University, 300, Yong-bong dong, Gwangju 500-757 (Korea, Republic of); Jeong, Sang-Hun, E-mail: shjeong@kbsi.re.kr [Gwangju Center, Korea Basic Science Institute, 300, Yong-bong dong, Gwangju 500-757 (Korea, Republic of); Lee, Byung-Teak, E-mail: btlee@jnu.ac.kr [Photonic and Electronic Thin Film Laboratory, Department of Materials Science and Engineering, Chonnam National University, 300, Yong-bong dong, Gwangju 500-757 (Korea, Republic of)

    2014-12-05

    Highlights: • Zn{sub 0.96−x−y}Mg{sub x}Be{sub y}Ga{sub 0.04}O TCO films with wide band-gap were prepared by sputtering. • Controlling of band-gap and conductivity was tried by co-doping Mg and Be. • Maximum band-gap energy reached 3.88 eV at 5 at.% Mg and 10 at.% Be contents. • Post-growth annealing was performed in Ar + H{sub 2} ambient gas to improve conductivity. • The lowest resistivity was obtained from the annealed film at 400 °C. - Abstract: In this work, the Zn{sub 0.96-x−y}Mg{sub x}Be{sub y}Ga{sub 0.04}O films co-doped with different Mg and Be doping levels of 3 ∼10 at.% were prepared using an RF magnetron sputtering, and the correlation between the film properties and the doping levels was investigated. With an increase in Mg or Be doping level, the film crystal quality gradually deteriorated and the ZnO c-axis parameter was contracted or expanded due to the difference in ionic radii of Mg and Be ions, resulting in the shift of the ZnO (0 0 0 2) XRD peak position to lower 2θ or higher 2θ values and the broadening of the ZnO (0 0 0 2) XRD peak. All the grown films were highly transparent with a transmittance above 85% in the visible wavelength region and the band-gap widened from 3.74 eV to 3.88 eV at high doping level of 5 at.% Mg and 10 at.% Be, whereas the resistivity was degraded from 1.6 × 10{sup −3} Ω cm at low doping level to 1–4 × 10{sup −1} Ω cm at high doping level. In the Zn{sub 0.88}Mg{sub 0.05}Be{sub 0.03}Ga{sub 0.04}O film post growth annealed at 400 °C in Ar + H{sub 2} mixture ambient, the lowest resistivity of 8.17 × 10{sup −4} Ω cm, the highest electron concentration of 5.26 × 10{sup 20} cm{sup −3}, and the large band-gap of 3.8 eV were obtained, which is attributed to the hydrogen incorporation in film during annealing and the improved film crystal quality.

  10. Energy transfer phenomena in GdF sub 3 :Mn co-doped with Ce sup 3 sup + , Pr sup 3 sup + or Zr sup 4 sup +

    CERN Document Server

    Kobayashi, M; Ishii, M; Solovieva, N; Nikl, M

    2003-01-01

    We studied the effects of Mn sup 2 sup + doping and Ce sup 3 sup + or Pr sup 3 sup + or Zr sup 4 sup + co-doping on the scintillation characteristics of GdF sub 3 powder crystals including excitation-emission spectra and decay time for UV excitation, light yield (LY) and luminescence spectra for X-rays. In GdF sub 3 :Mn sup 2 sup + , the dominant Mn sup 2 sup + emission occurred at 515 nm with a decay constant tau - 24 ms for excitation at 275 nm. The LY increased monotonically as the Mn sup 2 sup + concentration decreased from 1 at.% down to 20 at.ppm, indicating very efficient Gd sup 3 sup + -> Mn sup 2 sup + energy transfer and possible concentration quenching at large Mn sup 2 sup + concentrations. The maximum LY for X-rays was about 19% of Gd sub 2 O sub 2 S:Pr sup 3 sup + , Ce sup 3 sup + , one of the brightest ceramics scintillators employed in X-ray computed tomography. While efficient energy transfers of Ce sup 3 sup + -> Gd sup 3 sup + and Ce sup 3 sup + -> (Gd sup 3 sup +) sub n -> Mn sup 2 sup + w...

  11. Enhanced photoluminescence of Gd2O3:Eu3+ nanophosphors with alkali (M=Li+, Na+, K+) metal ion co-doping.

    Science.gov (United States)

    Dhananjaya, N; Nagabhushana, H; Nagabhushana, B M; Rudraswamy, B; Shivakumara, C; Narahari, K; Chakradhar, R P S

    2012-02-01

    Gd(1.95)Eu(0.04)M(0.01)O(3) (M=Li(+), Na(+), K(+)) nanophosphors have been synthesized by a low temperature solution combustion (LSC) method. Powder X-ray diffraction pattern (PXRD), scanning electron microscopy (SEM), UV-vis and photoluminescence (PL) measurements were carried out to characterize their structural and luminescent properties. The excitation and emission spectra indicated that the phosphor could be well excited by UV light (243 nm) and emit red light about 612 nm. The effect of alkali co-dopant on PL properties has been examined. The results showed that incorporation of Li(+), Na(+) and K(+) in to Gd(2)O(3):Eu(3+) phosphor would lead to a remarkable increase of photoluminescence. The PL intensity of Gd(2)O(3):Eu(3+) phosphor was improved evidently by co-doping with Li(+) ions whose radius is less than that of Gd(3+) and hardly with Na(+), K(+) whose radius is larger than that of Gd(3+). The effect of co-dopants on enhanced luminescence was mainly regarded as the result of a suitable local distortion of crystal field surrounding the Eu(3+) activator. These results will play an important role in seeking some more effective co-dopants. Copyright © 2011. Published by Elsevier B.V.

  12. NIR luminescence studies on Er{sup 3+}:Yb{sup 3+} co-doped sodium telluroborate glasses for lasers and optical amplifer applications

    Energy Technology Data Exchange (ETDEWEB)

    Annapoorani, K.; Marimuthu, K., E-mail: mari-ram2000@yahoo.com [Department of Physics, Gandhigram Rural Institute - Deemed University, Gandhigram – 624 302 (India); Murthy, N. Suriya [Radiological Safety Division, Indira Gandhi Centre for Atomic Research, Kalpakkam–603 102 (India)

    2016-05-23

    Er{sup 3+}:Yb{sup 3+} co-doped Sodium telluroborate glasses were prepared with the chemical composition (49.5–x)B{sub 2}O{sub 3}+25TeO{sub 2}+5Li{sub 2}CO{sub 3}+10ZnO+10NaF+0.5Er{sub 2}O{sub 3}+xYb{sub 2}O{sub 3} (where x= 0.1, 0.5, 1.0 and 2.0 in mol %) following the melt quenching technique. With the addition of Yb{sup 3+} ions into Er{sup 3+} ions in the prepared glasses, the absorption cross-section values were found to increase due to the effective energy transfer from {sup 2}F{sub 5/2} level of Yb{sup 3+} ions to the {sup 4}I{sub 11/2} level of Er{sup 3+} ions. The fluorescence around 1550 nm correspond to the {sup 4}I{sub 13/2}→{sup 4}I{sub 15/2} transition was observed under 980 nm pumping. Among the present glasses, integrated intensity was found to be higher for 1.0 mol% Yb{sup 3+} ion glass. The parameters such as stimulated emission cross- section, Gain bandwidth and quantum efficiency of the {sup 4}I{sub 13/2}→{sup 4}I{sub 15/2} transition was found to be higher for the NTBE1.0Y glass and the same is suggested for potential NIR lasers and optical amplifier applications.

  13. Tm3+ and Tm(3+)-Ho3+ co-doped tungsten tellurite glass single mode fiber laser.

    Science.gov (United States)

    Li, Kefeng; Zhang, Guang; Wang, Xin; Hu, Lili; Kuan, Peiwen; Chen, Danping; Wang, Meng

    2012-04-23

    We investigated the ~2 μm spectroscopic and lasing performance of Tm(3+) and Tm(3+)-Ho(3+) co-doped tungsten tellurite glass single mode fibers with a commercial 800 nm laser diode. The double cladding single mode (SM) fibers were fabricated by using rod-in-tube method. The propagation loss of the fiber was ~2.5 dB/m at 1310 nm. The spectroscopic properties of the fibers were analyzed. A 494 mW laser operating at ~1.9 μm was achieved in a Tm(3+) doped 20 cm long fiber, the slope efficiency was 26%, and the laser beam quality factor M(2) was 1.09. A 35 mW ~2.1 μm laser output was also demonstrated in a 7 cm long of Tm(3+)-Ho(3+) co-doped tungsten tellurite SM fiber. © 2012 Optical Society of America

  14. Cobalt and sulfur co-doped nano-size TiO2 for photodegradation of various dyes and phenol

    KAUST Repository

    Siddiqa, Asima

    2015-11-01

    Various compositions of cobalt and sulfur co-doped titania nano-photocatalyst are synthesized via sol–gel method. A number of techniques including X-ray diffraction (XRD), ultraviolet–visible (UV–Vis), Rutherford backscattering spectrometry (RBS), thermal gravimetric analysis (TGA), Raman, N2 sorption, electron microscopy are used to examine composition, crystalline phase, morphology, distribution of dopants, surface area and optical properties of synthesized materials. The synthesized materials consisted of quasispherical nanoparticles of anatase phase exhibiting a high surface area and homogeneous distribution of dopants. Cobalt and sulfur co-doped titania demonstrated remarkable structural and optical properties leading to an efficient photocatalytic activity for degradation of dyes and phenol under visible light irradiations. Moreover, the effect of dye concentration, catalyst dose and pH on photodegradation behavior of environmental pollutants and recyclability of the catalyst is also examined to optimize the activity of nano-photocatalyst and gain a better understanding of the process.

  15. Intrinsic and Extrinsic Ferromagnetism in Co-Doped Indium Tin Oxide Revealed Using X-Ray Magnetic Circular Dichroism

    Directory of Open Access Journals (Sweden)

    A. M. H. R. Hakimi

    2017-01-01

    Full Text Available The effects of high-temperature annealing on ferromagnetic Co-doped Indium Tin Oxide (ITO thin films have been investigated using X-ray diffraction (XRD, magnetometry, and X-Ray Magnetic Circular Dichroism (XMCD. Following annealing, the magnetometry results indicate the formation of Co clusters with a significant increase in the saturation magnetization of the thin films arising from defects introduced during cluster formation. However, sum rule analysis of the element-specific XMCD results shows that the magnetic moment at the Co sites is reduced after annealing. The effects of annealing demonstrate that the ferromagnetism observed in the as-deposited Co-doped ITO films arises from intrinsic defects and cannot be related to the segregation of metallic Co clusters.

  16. Biocompatible Er, Yb co-doped fluoroapatite upconversion nanoparticles for imaging applications

    Science.gov (United States)

    Anjana, R.; K. M., Kurias; M. K., Jayaraj

    2017-08-01

    Upconversion luminescence, visible emission on infra red (IR) excitation was achieved in a biocompatible material, fluoroapatite. Fluoroapatite crystals are well known biomaterials, which is a component of tooth enamel. Also it can be considered as an excellent host material for lanthanide doping since the ionic radii of lanthanide is similar to that of calcium ion(Ca2+) hence successful incorporation of dopants within the lattice is possible. Erbium (Er), Ytterbium (Yb) co-doped fluorapatite (FAp) nanoparticles were prepared by precipitation method. The particles show intense visible emission when excited with 980 nm laser. Since upconversion luminescence is a multiphoton process the excitation power dependence on emission will give number of photons involved in the emission of single photon. Excitation power dependence studies show that two photons are involved in the emission of single photons. The value of slope was different for different emission peak because of the difference in intermediate energy level involved. The crystal structure and morphology of the particle were determined using X-ray diffractometer (XRD) and field emission scanning electron microscope (FESEM). These particles with surface functionalisation can be used for live cell imaging.

  17. Carbon and nitrogen co-doping self-assembled MoS2 multilayer films

    Science.gov (United States)

    Zhang, Xiaoqin; Xu, Jiao; Chai, Liqiang; He, Tengfei; Yu, Fucheng; Wang, Peng

    2017-06-01

    Mo-S-C-N composite films were prepared using reactive magnetron sputtering of graphite and MoS2 targets in argon and nitrogen atmospheres. The effects of carbon/nitrogen co-doping and carbon concentration on the composition, microstructure, mechanical and tribological properties of deposited films have been investigated by various characterization techniques. The results show that the deposited films comprise MoS2 nanocrystalline and amorphous carbon, and the incorporating nitrogen forms Mo-N and C-N chemical bonds. Increasing carbon concentration leads to the increase of sp2 carbon fraction in the films. Furthermore, the high-resolution transmission electron microscopy reveals that a self-assembled multilayer structure with periodicity in the nanometer scale is formed in the Mo-S-C-N film. Benefiting from the composite and self-assembled multilayer structures, the hardness of Mo-S-C-N film deposited at optimized parameter reaches up to 9.76 GPa, and corresponding friction experiment indicates that this composite films display low friction coefficient and high wear resistance both in vacuum and ambient air conditions.

  18. Sulfur and nitrogen co-doped carbon dots sensors for nitric oxide fluorescence quantification.

    Science.gov (United States)

    Simões, Eliana F C; Leitão, João M M; Esteves da Silva, Joaquim C G

    2017-04-01

    Microwave synthetized sulfur and nitrogen co-doped carbon dots responded selectively to nitric oxide (NO) at pH 7. Citric acid, urea and sodium thiosulfate in the proportion of 1:1:3 were used respectively as carbon, nitrogen and sulfur sources in the carbon dots microwave synthesis. For this synthesis, the three compounds were diluted in 15 mL of water and exposed for 5 min to a microwave radiation of 700 W. It is observed that the main factor contributing to the increased sensitivity and selectivity response to NO at pH 7 is the sodium thiosulfate used as sulfur source. A linear response range from 1 to 25 μM with a sensitivity of 16 μM-1 and a detection limit of 0.3 μM were obtained. The NO quantification capability was assessed in standard and in fortified serum solutions. Copyright © 2017 Elsevier B.V. All rights reserved.

  19. Visible light carrier generation in co-doped epitaxial titanate films

    Energy Technology Data Exchange (ETDEWEB)

    Comes, Ryan B., E-mail: ryan.comes@pnnl.gov; Kaspar, Tiffany C.; Chambers, Scott A. [Fundamental and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99354 (United States); Smolin, Sergey Y.; Baxter, Jason B. [Department of Chemical and Biological Engineering, Drexel University, Philadelphia, Pennsylvania 19104 (United States); Gao, Ran [Department of Materials Science and Engineering, University of California-Berkeley, Berkeley, California 94720 (United States); Apgar, Brent A. [Department of Materials Science and Engineering, University of California-Berkeley, Berkeley, California 94720 (United States); Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Champaign, Illinois 61801 (United States); Martin, Lane W. [Department of Materials Science and Engineering, University of California-Berkeley, Berkeley, California 94720 (United States); Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Bowden, Mark E. [Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99354 (United States)

    2015-03-02

    Perovskite titanates such as SrTiO{sub 3} (STO) exhibit a wide range of important functional properties, including ferroelectricity and excellent photocatalytic performance. The wide optical band gap of titanates limits their use in these applications; however, making them ill-suited for integration into solar energy harvesting technologies. Our recent work has shown that by doping STO with equal concentrations of La and Cr, we can enhance visible light absorption in epitaxial thin films while avoiding any compensating defects. In this work, we explore the optical properties of photoexcited carriers in these films. Using spectroscopic ellipsometry, we show that the Cr{sup 3+} dopants, which produce electronic states immediately above the top of the O 2p valence band in STO reduce the direct band gap of the material from 3.75 eV to 2.4–2.7 eV depending on doping levels. Transient reflectance spectroscopy measurements are in agreement with the observations from ellipsometry and confirm that optically generated carriers are present for longer than 2 ns. Finally, through photoelectrochemical methylene blue degradation measurements, we show that these co-doped films exhibit enhanced visible light photocatalysis when compared to pure STO.

  20. Visible light carrier generation in co-doped epitaxial titanate films

    Energy Technology Data Exchange (ETDEWEB)

    Comes, Ryan B.; Smolin, Sergey Y.; Kaspar, Tiffany C.; Gao, Ran; Apgar, Brent A.; Martin, Lane W.; Bowden, Mark E.; Baxter, Jason; Chambers, Scott A.

    2015-03-02

    Perovskite titanates such as SrTiO3 (STO) exhibit a wide range of important functional properties, including high electron mobility, ferroelectricity—which may be valuable in photovoltaic applications—and excellent photocatalytic performance. The wide optical band gap of titanates limits their use in these applications, however, making them ill-suited for integration into solar energy harvesting technologies. Our recent work has shown that by doping STO with equal concentrations of La and Cr we can enhance visible light absorption in epitaxial thin films while avoiding any compensating defects. In this work, we explore the optical properties of photoexcited carriers in these films. Using spectroscopic ellipsometry, we show that the Cr3+ dopants, which produce electronic states immediately above the top of the O 2p valence band in STO reduce the direct band gap of the material from 3.75 eV to between 2.4 and 2.7 eV depending on doping levels. Transient reflectance measurements confirm that optically generated carriers have a recombination lifetime comparable to that of STO and are in agreement with the observations from ellipsometry. Finally, through photoelectrochemical yield measurements, we show that these co-doped films exhibit enhanced visible light photocatalysis when compared to pure STO.

  1. IR-to-visible frequency upconversion in Yb3+/Tm3+ co-doped phosphate glass

    Science.gov (United States)

    Rego-Filho, F. G.; Dantas, N. O.; Silva, A. C. A.; Vermelho, M. V. D.; Jacinto, C.; Gouveia-Neto, A. S.

    2017-11-01

    Frequency upconversion luminescence in Yb3+/Tm3+ co-doped 60P2O5·15ZnO·5Al2O3·10BaO·10PbO glass (PZABP) excited at 980 nm is reported. Pump power dependence, lifetime measurements, and the absorption spectra of the Tm3+ ions in the visible to IR region are investigated as a function of sensitizer (Yb3+) concentration. Blue light at 475 nm and red light at 660 nm generation was observed. Intensity saturation behavior is observed for the 475 nm (1G4 - 3H6), 650-664 nm (1G4 - 3F4 and/or 3F2,3 - 3H6) and 793 nm (3H4 - 3H6) upconversion emissions, when laser power was above ∼ 75 mW (∼1.9 kW/cm2). The radiative lifetimes measured for the observed emissions were 270 μs (475 nm), 195 μs (650 nm), 177 μs (664 nm), 184 μs (793 nm) and 335 μs (1211 nm). The application of the Davis-Mott model detected a slight change of 6.6% in the value of the energy bandgap for the highest doping concentration in comparison with the undoped sample. Results indicate that the PZABP glass matrix herein reported is a promising contender as host for rare-earth doped based photonic devices.

  2. Intrinsic and Extrinsic Ferromagnetism in Co-Doped Indium Tin Oxide Revealed Using X-Ray Magnetic Circular Dichroism

    OpenAIRE

    Hakimi, A. M. H. R.; Schoofs, F.; Blamire, M. G.; S. Langridge; Dhesi, S. S.

    2017-01-01

    The effects of high-temperature annealing on ferromagnetic Co-doped Indium Tin Oxide (ITO) thin films have been investigated using X-ray diffraction (XRD), magnetometry, and X-Ray Magnetic Circular Dichroism (XMCD). Following annealing, the magnetometry results indicate the formation of Co clusters with a significant increase in the saturation magnetization of the thin films arising from defects introduced during cluster formation. However, sum rule analysis of the element-specific XMCD resul...

  3. Structural and electronic properties of Mg and Mg-Nb co-doped TiO2 (101) anatase surface

    Energy Technology Data Exchange (ETDEWEB)

    Sasani, Alireza [Department of Science, Karaj Islamic Azad University, Karaj, Alborz, P.O. Box 31485-313 (Iran, Islamic Republic of); Baktash, Ardeshir [Institute of Nano Science and Nano Technology, University of Kashan, Kashan, P.O. Box 87317-51167 (Iran, Islamic Republic of); Mirabbaszadeh, Kavoos, E-mail: mirabbas@aut.ac.ir [Department of Energy Engineering and Physics, Amirkabir University of Technology, Tehran, P. O. Box 15875-4413 (Iran, Islamic Republic of); Khoshnevisan, Bahram [Institute of Nano Science and Nano Technology, University of Kashan, Kashan, P.O. Box 87317-51167 (Iran, Islamic Republic of)

    2016-10-30

    Highlights: • Formation energy of Mg and Mg-Nb co-doped TiO{sub 2} anatase surface (101) is studied. • Effect of Mg defect to the TiO{sub 2} anatase (101) surface and bond length distribution of the surface is studied and it is shown that Mg defects tend to stay far from each other. • Effect of Mg and Nb to the bond length distribution of the surface studied and it is shown that these defects tend to stay close to each other. • Effects of Mg and Mg-Nb defects on DSSCs using TiO{sub 2} anatase hosting these defects are studied. - Abstract: In this paper, by using density functional theory, Mg and Nb-Mg co-doping of TiO{sub 2} anatase (101) surfaces are studied. By studying the formation energy of the defects and the bond length distribution of the surface, it is shown that Mg defects tend to stay as far as possible to induce least possible lattice distortion while Nb and Mg defects stay close to each other to cause less stress to the surface. By investigating band structure of the surface and changes stemmed from the defects, potential effects of Mg and Mg-Nb co-doping of TiO{sub 2} surface on dye-sensitized solar cells are investigated. In this study, it is shown that the Nb-Mg co-doping could increase J{sub SC} of the surface while slightly decreasing V{sub OC} compared to Mg doped surface, which might result in an increase in efficiency of the DSSCs compared to Nb or Mg doped surfaces.

  4. Three-dimensional nitrogen and boron co-doped graphene for high-performance all-solid-state supercapacitors

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Zhong-Shuai; Chen, Long; Sun, Yi; Muellen, Klaus [Max-Planck-Institut fuer Polymerforschung, Ackermannweg 10, 55128 Mainz (Germany); Winter, Andreas; Turchanin, Andrey [Universitaet Bielefeld, Fakultaet fuer Physik, Physik Supramolekularer Systeme und Oberflaechen, Universitaetsstr. 25D, 33615 Bielefeld (Germany); Feng, Xinliang [Max-Planck-Institut fuer Polymerforschung, Ackermannweg 10, 55128 Mainz (Germany); School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, 200240, Shanghai (China)

    2012-09-25

    A simplified prototype device of high-performance all-solid-state supercapacitors (ASSSs) based on 3D nitrogen and boron co-doped monolithic graphene aerogels (BN-GAs) is demonstrated for the first time. The resulting ASSSs show high specific capacitance, good rate capability, and enhanced energy density or power density. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  5. Paramagnetic behavior of Co doped TiO{sub 2} nanocrystals controlled by self-purification mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Anitha, B. [Centre for Nanoscience and Nanotechnology, University of Kerala, Kariavattom, Thiruvananthapuram 695 581 (India); Khadar, M. Abdul, E-mail: mabdulkhadar@rediffmail.com [Centre for Nanoscience and Nanotechnology, University of Kerala, Kariavattom, Thiruvananthapuram 695 581 (India); Banerjee, Alok [UGC-DAE Consortium for Scientific Research (CSR), Khandwa Road, Indore 452 001 (India)

    2016-07-15

    Doping in nanocrystals is a challenging process because of the self- purification mechanism which tends to segregate out the dopants resulting in a greater dopant concentration near the surface than at the interior of nanocrystals. In the present work nanocrystals of TiO{sub 2} doped with different atom % of Co were synthesized by peroxide gel method. XRD analysis confirmed the tetragonal anatase structure and HRTEM images showed the rod-like morphology of the samples. Raman modes of anatase phase of TiO{sub 2} along with weak intensity peaks of Co{sub 3}O{sub 4} for higher Co dopant concentrations were observed for the samples. EPR measurements revealed the presence of cobalt in +2 oxidation state in the TiO{sub 2} matrix. SQUID measurements indicated paramagnetic behavior of the Co doped TiO{sub 2} nanocrystals. The paramagnetic behavior is attributed to an increased concentration of Co{sup 2+} ions and an increased presence of Co{sub 3}O{sub 4} phase near the surface of the TiO{sub 2} nanocrystals due to self-purification mechanism. - Graphical abstract: Variation of the intensity ratios of XRD peaks as a function of atomic ratio of Co. Inset: variation of structure factor for (101) reflection as a function of atomic ratio of Co. Display Omitted - Highlights: • Co doped TiO{sub 2} nanocrystals were synthesized by peroxide gel method. • HRTEM images showed Co doped TiO{sub 2} nanocrystals to be rod-like. • EPR spectra showed +2 oxidation states for Co in the samples. • Co doped TiO{sub 2} nanocrystals showed paramagnetic behavior.

  6. Synergistic Effects of Sm and C Co-Doped Mixed Phase Crystalline TiO₂ for Visible Light Photocatalytic Activity.

    Science.gov (United States)

    Peng, Fuchang; Gao, Honglin; Zhang, Genlin; Zhu, Zhongqi; Zhang, Jin; Liu, Qingju

    2017-02-21

    Mixed phase TiO₂ nanoparticles with element doping by Sm and C were prepared via a facile sol-gel procedure. The UV-Vis light-diffuse reflectance spectroscopy analysis showed that the absorption region of co-doped TiO₂ was shifted to the visible-light region, which was attributed to incorporation of samarium and carbon into the TiO₂ lattice during high-temperature reaction. Samarium effectively decreased the anatase-rutile phase transformation. The grain size can be controlled by Sm doping to achieve a large specific surface area useful for the enhancement of photocatalytic activity. The photocatalytic activities under visible light irradiation were evaluated by photocatalytic degradation of methylene blue (MB). The degradation rate of MB over the Sm-C co-doped TiO₂ sample was the best. Additionally, first-order apparent rate constants increased by about 4.3 times compared to that of commercial Degusssa P25 under the same experimental conditions. Using different types of scavengers, the results indicated that the electrons, holes, and •OH radicals are the main active species for the MB degradation. The high visible-light photocatalytic activity was attributed to low recombination of the photo-generated electrons and holes which originated from the synergistic effect of the co-doped ions and the heterostructure.

  7. High-temperature ferromagnetism in Co-doped CeO2 synthesized by the coprecipitation technique.

    Science.gov (United States)

    Colis, S; Bouaine, A; Schmerber, G; Ulhaq-Bouillet, C; Dinia, A; Choua, S; Turek, P

    2012-05-28

    The aim of the present study is to check the influence of annealing under vacuum and a mixture of N(2)-H(2) atmosphere on the magnetic properties of polycrystalline Co-doped CeO(2) diluted magnetic oxides (DMOs) with Co concentrations of 5 at% synthesized using the coprecipitation technique. X-Ray diffraction (XRD) patterns and transmission electron microscopy (TEM) showed for all samples the expected CeO(2) cubic fluorite-type structure and that Co ions are uniformly distributed inside the samples. Room-temperature Raman and photoluminescence (PL) spectroscopies indicate an increase in the concentration of oxygen vacancies upon Co doping and further annealing. Field dependent magnetization measurements revealed a paramagnetic behavior for as-prepared Co-doped CeO(2), while a ferromagnetic behavior appears when the same samples are annealed under vacuum or N(2)-H(2) atmosphere. Temperature dependent magnetization measurements suggest that the observed ferromagnetism is due to the presence of metallic Co clusters with nanometric size and broad size distribution. These results are supported by electron paramagnetic resonance studies.

  8. Effects of Li+ co-doping on properties of Eu3+ activated TiO2 anatase nanoparticles

    Science.gov (United States)

    Milićević, Bojana; Đorđević, Vesna; Vuković, Katarina; Dražić, Goran; Dramićanin, Miroslav D.

    2017-10-01

    Sol-gel technique for the synthesis of anatase TiO2 at 420 °C produces nanocrystals of 10-20 nm in size with Ti4+ in crystal volume and Ti3+ at terminal planes of the crystal. The study of Li+ co-doping effects on the structure, morphology, absorption, and luminescence of Eu3+ activated TiO2 anatase nanocrystals is presented. Pure anatase structure is achieved up to 9 at.% Li, with significant improvement in crystallinity of europium doped anatase TiO2. The Li+ co-doping reduces the unit cell volume of the crystal, induces the blue shift of the absorption edge, lengthens the lifetime of Eu3+5D0 excited state, and improves the Eu3+ emission intensity up to 37.5%. Judd-Ofelt analysis of Eu3+ emission showed enhancement of quantum efficiency from 66.4% to 98.7% when TiO2:Eu3+ was co-doped with 9 at.% of Li.

  9. The effect of K-na co-doping on the formation and particle size of Bi-2212 phase

    Energy Technology Data Exchange (ETDEWEB)

    Kır, M. Ebru [Department of Physics, Faculty of Arts and Sciences, Mersin University, Çiftlikköy, 33343 Mersin (Turkey); Özkurt, Berdan, E-mail: berdanozkurt@mersin.edu.tr [Department of Physics, Faculty of Arts and Sciences, Mersin University, Çiftlikköy, 33343 Mersin (Turkey); Department of Energy Systems Engineering, Faculty of Tarsus Technology, Mersin University, Mersin (Turkey); Advanced Technology Research and Application Center, Mersin University, Yenişehir, TR-33343 Mersin (Turkey); Aytekin, M. Ersin [Advanced Technology Research and Application Center, Mersin University, Yenişehir, TR-33343 Mersin (Turkey)

    2016-06-01

    Superconducting K-Na co-doped Bi{sub 2}Sr{sub 2}K{sub x}Ca{sub 1}Cu{sub 1.75}Na{sub 0.25}O{sub y} (x=0, 0.05, 0.1 and 0.25) ceramics are prepared by a solid-state reaction method. It is clearly determined from XRD data that the characteristic peaks of Bi-2212 phase are observed in all samples. The resistivity measurements show that T{sub c} (onset) values is gradually increasing as K content is increased. It is also found that K-Na co-doping influence the grain sizes for Bi-2212 phase significantly. The critical current densities as a function of magnetic field have been calculated from M–H hysteresis loops of samples according to Bean's critical model, indicating that K-Na co-doping cause higher J{sub c} values than the pure ones.

  10. Influence of Fe Buffer Layer on Co-Doped BaFe2As2 Superconducting Thin Films

    Directory of Open Access Journals (Sweden)

    C. Bonavolontà

    2015-01-01

    Full Text Available A systematic characterization of Co-doped BaFe2As2 (Ba-122 thin films has been carried out. Two samples were available, one grown on CaF2 substrate and the other on MgO with an Fe buffer layer. The goal was to investigate films’ magnetic and superconducting properties, their reciprocal interplay, and the role played by the Fe buffer layer in modifying them. Morphological characterization and Energy Dispersive X-ray analyses on the Fe-buffered sample demonstrate the presence of diffused Fe close to the Co-doped Ba-122 outer surface as well as irregular holes in the overlying superconducting film. These results account for hysteresis loops obtained with magneto-optic Kerr effect measurements and observed at both room and low temperatures. The magnetic pattern was visualized by magneto-optical imaging with an indicator film. Moreover, we investigated the onset of superconductivity through a measure of the superconducting energy gap. The latter is strictly related to the decay time of the excitation produced by an ultrashort laser pulse and has been determined in a pump-probe transient reflectivity experiment. A comparison of results relative to Co-doped Ba-122 thin films with and without Fe buffer layer is finally reported.

  11. Effect of (Nd, Ni) co-doped on the multiferroic and photocatalytic properties of BiFeO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Vanga, Pradeep Reddy [Nanomaterials Laboratory, Department of Physics, National Institute of Technology, Tiruchirapalli 620 015 (India); Mangalaraja, R.V. [Department of Materials Engineering, University of Concepcion, Concepcion (Chile); Ashok, M., E-mail: ashokm@nitt.edu [Nanomaterials Laboratory, Department of Physics, National Institute of Technology, Tiruchirapalli 620 015 (India)

    2015-12-15

    Highlights: • Sol–gel synthesis. • Saturation magnetization and ferroelectricity increases in Ni co-doped samples. • Conduction mechanism is different in Nd doped and (Nd, Ni) co-doped samples. • Samples show good photocatalytic activity in the presence of H{sub 2}O{sub 2}. - Abstract: Bi{sub 0.95}Nd{sub 0.05}Fe{sub 1−x}Ni{sub x}O{sub 3} (x = 0, 0.01, 0.03 and 0.05) samples are synthesized by solgel method. The phase and crystal structure of the samples are confirmed by X-ray diffraction studies, Rietveld refinement is performed to calculate the structural parameters. The reflectance spectra show bands in UV and visible region and the optical band gap is calculated using Kulbeka–Munk function. The magnetization and leakage current density are strongly influenced by doping. Different conduction mechanisms are observed in Nd doped and Ni co-doped samples. All the samples exhibit ferroelectric nature at various frequencies. Photocatalytic activities of the samples are determined by the degradation of methylene blue dye in the presence of visible light and H{sub 2}O{sub 2} which shows samples are good photo-Fenton like catalyst.

  12. Structural, electrical and magnetic properties of rare-earth and transition element co-doped bismuth ferrites

    Energy Technology Data Exchange (ETDEWEB)

    Verma, Vivek, E-mail: vermavivek.neel@gmail.com

    2015-08-25

    Highlights: • Sm-doping increases the symmetry and decreases the second phase formation. • Ferromagnetic, ferroelectric and dielectric properties enhanced with doping. • M–H loops represents weak ferromagnetic (FM) behavior. • A modification in dielectric constant is observed due to doping of Mn, Co and Cr. • Saturation polarization (P{sub s}), remnant polarization (P{sub r}) and coercive field (E{sub c}) increased with doping. - Abstract: Pure and doped multiferroic samples of bismuth ferrites (BFO) were successfully synthesized by the sol–gel technique. Detailed investigations were made on the influence of (Sm and Mn, Co, Cr) co-doping on structural, electrical, ferroelectric and magnetic properties of the BFO. A structural phase transformation from rhombohedral to orthorhombic with co-doping is confirmed through XRD. It is also observed that Sm-doping increases the symmetry and decreases the second phases noticeably. Microstructure investigation using the scanning electron microscope showed a reduction of grain size with doping in BFO. Magnetic hysteresis loops showed that retentivity (Mr), coercivity (Hc) and saturation magnetization (Ms) of the doped samples were improved. Furthermore, the co-doping enhances the dielectric properties as a result of the reduction in the Fe{sup 2+} ions and oxygen vacancies. The room temperature P–E loop study shows that ferroelectric properties are strongly depend on doping.

  13. The influence of Pr3+ co-doping on the photoluminescence and cathodoluminescence properties of SiO2:Eu3+/Tb3+

    CSIR Research Space (South Africa)

    Mhlongo, GH

    2011-07-01

    Full Text Available Tb3+-Pr3+, and Eu3+-Pr3+ ion pairs co-doped in a SiO2 matrix were prepared by a sol-gel method. Co-doping of Eu3+ and Tb3+ ions with Pr3+ in SiO2 resulted in the quenching of Eu3+ and Tb3+ emissions with increasing Pr3+ concentrations. The quenching...

  14. 1-D and 2-D morphology of metal cation co-doped (Zn, Mn) TiO2 and investigation of their photocatalytic activity

    Science.gov (United States)

    Benjwal, Poonam; De, Bibekananda; Kar, Kamal K.

    2018-01-01

    Morphology and electronic bandgap of titania (TiO2) are considered to be the primary factors for determining the photocatalytic efficiency, as they determine the number of active sites for the photocatalytic reactions. In the present study, two different morphologies of TiO2 (nanosphere and nanorod) with varying Zn and Mn co-doping were synthesized by solvothermal and hydrothermal methods to examine their photocatalytic efficiency by methylene blue degradation. The co-doped photocatalysts were characterized by XRD, XPS, SEM, TEM, Raman, FTIR and UV-vis DRS. Further, a comparison has been made with co-doped TiO2 nanospheres and TiO2 nanorods, where Zn, Mn co-doped TiO2 nanorods show higher photocatalytic activity compared to nanospheres. This higher photocatalytic activity of co-doped TiO2 is attributed to its polymorphic phases, as they act as heterojunctions for TiO2. Further, being 1-D nanostructure, the TiO2 nanorods exhibit the straight diffusion path for charge carriers, which reduces the recombination possibilities. The obtained results suggest that the photocatalysis efficiency of TiO2 can be significantly enhanced by tailoring the shape and co-doping concentration, which enforce a new concept for developing the new nanostructures of TiO2.

  15. The effect of boron on the doping efficiency of nitrogen in ZnO

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Xingyou [State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033 (China); State Key Laboratory of Function Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Zhang, Zhenzhong, E-mail: exciton@163.com [State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033 (China); Yao, Bin, E-mail: binyao@jlu.edu.cn [State Key Laboratory of Superhard Materials and College of Physics, Jilin University, Changchun 130023 (China); Zhang, Yonggang; Gu, Yi [State Key Laboratory of Function Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Zhao, Pengcheng; Li, Binghui; Shen, Dezhen [State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033 (China)

    2016-07-05

    Stable p-type boron–nitrogen codoped ZnO thin films were prepared by plasma-assisted molecular beam epitaxy. The incorporations of boron and nitrogen into ZnO, identified by X-ray diffraction and X-ray photoelectron spectroscopy, led to improvement in p-type conductivity of ZnO with respect to nitrogen monodoped ZnO. It was ascribed to the marked enhancement of nitrogen doping efficiency due to the existence of two types of chemical states of nitrogen atoms: the nitrogen substituting at oxygen site with nearest neighbor of Zinc atom (N{sub O}–Zn bonding), and the nitrogen locating at the nearest neighbor of boron atom (N{sub O}–B bonding). The strong interaction between the boron and nitrogen makes the complex of B{sub Zn}-nN{sub O} (n = 3 or 4) be a shallow acceptor, which is responsible for the observed p-type behavior. - Highlights: • P-type ZnO was fabricated using boron–nitrogen codoping by RF-plasma source. • The boron–nitrogen codoped ZnO showed high hole concentration and low resistivity. • Co-doping by boron and nitrogen increased the number of N-related acceptors. • The effect of incorporation of B atom on the chemical states of N was discussed.

  16. Structural and magnetic properties of cobalt-doped ZnO thin films on sapphire (0 0 0 1) substrate deposited by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Shanying, E-mail: yshy_150@163.com [Laiwu Vocational and Technical College, Laiwu, Shandong Province, 271100 (China); Lv, Rongqing [Laiwu Vocational and Technical College, Laiwu, Shandong Province, 271100 (China); Wang, Changzheng [School of Physics Science and Information Engineering, Liaocheng University, Liaocheng, Shandong Province, 252059 (China); Liu, Yunyan [School of Science, Shandong University of Technology, Zibo, Shandong Province, 255049 (China); Song, Zeqing [Laiwu Vocational and Technical College, Laiwu, Shandong Province, 271100 (China)

    2013-12-05

    Highlights: •Co-doped ZnO thin films on sapphire (0 0 0 1) substrates were deposited. •ZnLMM Auger spectrum indicated that Zn interstitials existed in thin films. •The lattice constant increasing was ascribed to the stress and interstitial atoms. •The average moment per Co atom related to the distribution of Co{sup 2+} ions and defects. -- Abstract: Co-doped ZnO thin films on sapphire (0 0 0 1) substrates were deposited by PLD at various substrate temperatures in a one Pa oxygen ambient condition. The structural and magnetic properties of as-grown thin films were characterized by using XRD, UV–Visible absorption spectrophotometer, XPS and AGM. All samples possessed wurtzite hexagonal structure of ZnO. Co atoms incorporated into ZnO matrix and substituted for Zn in ZnO lattice, and Zn interstitials existed in as-grown thin films. The c-axis lattice constants of as-deposited thin films were larger than the standard data. Crystallization of as-prepared thin films increased and then decreased with substrate temperatures enhancing. All samples exhibited room-temperature ferromagnetism. The average moment per Co atom was much smaller than that of Co{sup 2+} (3d{sup 7}), due to the different distribution of Co{sup 2+} ions and defects, as well as the different defect concentrations in thin films.

  17. Erbium and ytterbium co-doped transparent oxyfluoride glass-ceramics optical fibers

    Science.gov (United States)

    Czerska, Elwira; Wiśniewski, Krzysztof; Augustyn, ElŻbieta; Koepke, Czesław; Lisiecki, Radosław; Kepińska, Mirosława; Żelechower, Michał

    2017-08-01

    According to the earlier author's papers, the erbium/ytterbium co-doped oxyfluoride glass-ceramics fibers should demonstrate better 1550 nm emission under 488/515/980 nm excitation (the erbium Er3+ ion transition 4I13/2->4I15/2) than corresponding glass fibers (the batch composition 48SiO211Al2O3-7Na2CO3-10CaO-10PbO-12PbF2- 1.5/0.6YbF3-0.5/0.2ErF3). Glass fibers provided as a core of standard multimode waveguide (the diameter of 62 μm) have been drawn with the mini-tower to the diameter between 50 μm and 80 μm, then annealed in the two-step regime (580°C/1h - nucleation of nano-crystals; 760oC/15/30 min - nano-crystals growth). This kind of heat treatment ensures the transparent glass-ceramics fibers with the microstructure of homogeneously distributed nano-crystals (lead, erbium and ytterbium enriched cubic fluorite-like crystals and hexagonal PbF2 crystals) embedded in a glassy host. Their transmission covers the range of 80-90% and seems to be sufficient with respect to their provided limited length ( 2m). The luminescence intensity for glass-ceramics fibers at 1530 nm is higher than that of respective glass fibers and the lifetimes of the erbium ion excited state 4I13/2 are of the same order ( 5 ms). In that context the glass-ceramics fibers discussed above seem to be promising candidates for cores of fiber lasers at the 1550 nm band.

  18. Investigation of structural and magnetic properties of Zr-Co doped nickel ferrite nanomaterials

    Science.gov (United States)

    Ali, Rajjab; Khan, Muhammad Azhar; Manzoor, Alina; Shahid, Muhammad; Haider, Sajjad; Malik, Abdul Sattar; Sher, Muhammad; Shakir, Imran; FarooqWarsi, Muhammad

    2017-05-01

    Nano-sized Zr-Co doped nickel ferrites with nominal composition, NiZrxCoxFe2-2xO4 (x=0.0, 0.2, 0.4, 0.6, 0.8) were synthesized using the micro-emulsion route. The structural elucidation of the synthesized materials was carried out by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. The XRD analysis confirmed face centered cubic (FCC) structure of all compositions of NiZrxCoxFe2-2xO4 nanocrystallites. Crystallite size was calculated by Scherrer's formula found in the range 10-15 nm. The variation in lattice parameter as determined by XRD data agreed with size variation of host (Fe3+) and guest (Zr4+ and Co2+) cations. FTIR spectra of doped NiFe2O4 exhibited the typical octahedral bands at 528.4 cm-1 which is the characteristic feature of spinel structure of spinel ferrites. The characterized spinel NiZrxCoxFe2-2xO4 nano-ferrites were evaluated for their potential applications by magnetic hysteresis loops and dielectric measurements. The value of saturation magnetization (Ms) decreased from 47.9 to 13.09 emu/g up to x=0.8 with ups and downs fluctuations in between x=0.0 to x=0.8. The high values of Ms of some compositions predicted the potential applications in high density perpendicular recording media and microwave devices. The frequency dependent behavior of permittivity (ε') is recorded and discussed with the help of hopping mechanism of both holes and electrons. The dielectric and magnetic data of NiZrxCoxFe2-2xO4 nano-ferrites suggested the potential applications of these ferrite nanoparticles in high frequency and magnetic data storage devices fabrication.

  19. Novel tannin-based Si, P co-doped carbon for supercapacitor applications

    Science.gov (United States)

    Ramasahayam, Sunil Kumar; Nasini, Udaya B.; Shaikh, Ali U.; Viswanathan, Tito

    2015-02-01

    Increasing environmental pollution and population compounded by a decrease in the availability of non-renewable resources and fossil fuels has propelled the need for sustainable alternate energy storage technologies particularly in the last two decades. An attempt to meet this crisis was carried out by a unique, microwave-assisted method which has enabled the generation of a novel Si, P co-doped carbon (SiPDC) for supercapacitor applications. The microwave-assisted method is useful in developing SiPDC at a rapid and economical fashion that does not employ any inert or reducing gases, but is high yielding. Varying proportions of precursor materials were utilized to generate four SiPDCs (SiPDC-1, SiPDC-2, SiPDC-3 and SiPDC-4) with varying contents of dopants as evidenced by X-ray photoelectron spectroscopic (XPS) results. Surface area and pore size analysis revealed that SiPDC-2 has a surface area of 641.51 m2 g-1, abundant micropores, mesopores and macropores which are critical for electrical double layer capacitance (EDLC). Of all the SiPDCs, SiPDC-2 exhibited highest capacitance of 276 F g-1 in 1 M H2SO4 and 244 F g-1 in 6 M KOH at a scan rate of 5 mV s-1. Galvanostatic charge-discharge studies performed in 6 M KOH establish the high capacitance of SiPDC-2. SiPDC-2 also exhibited excellent electrochemical stability in 1 M H2SO4 and 6 M KOH.

  20. Nature of ferromagnetic coupling in Cobalt-doped ZnO; Ursache der magnetischen Kopplung in Kobalt-dotiertem ZnO

    Energy Technology Data Exchange (ETDEWEB)

    Nielsen, K.W.

    2007-12-12

    Aim of this thesis was on the one hand to produce Co doped ZnO films, which exhibit a ferromagnetic signal and on the other hand to study the cause of the magnetic coupling. For this purpose Zn{sub 0.95}Co{sub 0.05} films wer fabricated by pulsed laser deposition. Three different substrate materials ((0001)ZnO, (0001)Al{sub 2}O{sub 3}, and (0001)ScAlMgO{sub 4}) were applied anf the growth temperature T{sub g} varied between 300 C and 600 C. Furthermore non-transition-metal doped films were grown at T{sub g}=320 C. By means of X-ray diffractometry the samples were studied concerning their structure, phase purity, and mosaicism. In the films on ZnO a foreign phase was detected, which can be explained by metallic Co inclusions. An estimation of the particle sizes yielded diameters between 2.2 nm and 5.4 nm. With SQID magnetometry measurements of the magnetization M were performed in dependence on the magnetic field H and the temperature T. At 300 K in all Co doped samples on ZnO and in samples on Al{sub 2}O{sub 3} and ScAlMgO{sub 4} with T{sub g}<400 C in the M(H) curves a distinct magnetic moment was observed, which cannot be explained by paramagnetic CO{sup 2+}. The magnetization measurements prove the existence of superparamegnetic nanoparticles. By means of high-resolution transmission electron microscopy it was possible to detect the Co inclusions in the Co doped film on ZnO with T{sub g}=500 C. For the Co and the non-transition-metal-doped samples on Al{sub 2}O{sub 3} and ScAlMgO{sub 4} with T{sub g}=320 C the electric trasnport properties were determined in dependence on H and T.

  1. Comparison of In doped and In, Pb co-doped Cd{sub 0.9}Zn{sub 0.1}Te

    Energy Technology Data Exchange (ETDEWEB)

    Zaman, Yasir, E-mail: yasirzaman31@yahoo.com; Jie, Wanqi; Wang, Tao; Xu, Lingyan; He, Yihui; Xu, Yadong; Zha, Gangqiang; Guo, Rongrong; Fu, Xu

    2015-08-01

    In doped CdZnTe (CdZnTe:In) and In and Pb co-doped CdZnTe (CdZnTe:In,Pb) single crystals were comparatively studied by using thermally stimulated current (TSC) and photoluminescence (PL) measurements. The resistivity for both the wafers was found in the region of 10{sup 9}–10{sup 10} Ωcm; however, In doped CdZnTe crystals had seven different traps, but In and Pb co-doped CdZnTe crystals had thirteen different traps. PL spectra showed that neutral acceptor exciton (A{sup 0}, X) and neutral donor exciton (D{sup 0}, X) had higher PL intensity for In and Pb co-doped CdZnTe crystals than in the case of CdZnTe: In, while the donor–acceptor pair (DAP) had lower PL intensity for In doped CdZnTe crystals than co-doped CdZnTe:(In,Pb). Channel numbers of CdZnTe:In were also found higher as compared to co-doped CdZnTe:(In,Pb). The comparative analysis showed that CdZnTe:In had better detector performance than co-doped CdZnTe:(In,Pb). - Highlights: • Comparison of In doped and In, Pb co-doped Cd{sub 0.9}Zn{sub 0.1}Te. • Resistivity for the two different wafers is in the region 10{sup 9}–10{sup 10} Ω cm. • In and Pb co-doped CdZnTe have thirteen different traps, which are almost double of CdZnTe:In. • Channel numbers of CdZnTe:In are higher compared to co-doped CdZnTe:(In,Pb) reflecting better detector performance. • Charge collection efficiency is much better for In doped CdZnTe compared to In and Pb co-doped CdZnTe.

  2. Properties and local environment of p-type and photoluminescent rare earths implanted into ZnO single crystals

    CERN Document Server

    Rita, EMC; Wahl, U; Soares, JC

    This thesis presents an experimental study of the local environment of p-type and Rare- Earth dopants implanted in ZnO single-crystals (SCs). Various nuclear and bulk property techniques were combined in the following evaluations: Implantation damage annealing was evaluated in ZnO SCs implanted with Fe, Sr and Ca. P-type dopants Cu and Ag implanted ZnO SCs were studied revealing that the solubility of Cu in substituting Zn is considerably higher than that of Ag. These results are discussed within the scope of the ZnO p-type doping problematic with these elements. Experimental proofs of the As “anti-site” behavior in ZnO were for the first time attained, i.e., the majority of As atoms are substitutional at the Zn site (SZn), possibly surrounded by two Zn vacancies (VZn). This reinforces the theoretical prediction that As acts as an acceptor in ZnO via the AsZn-2VZn complex formation. The co-doping of ZnO SC with In (donor) and As (acceptor) was addressed. The most striking result is the possible In-As “p...

  3. Nickel phosphide nanoparticles decorated nitrogen and phosphorus co-doped porous carbon as efficient hybrid catalyst for hydrogen evolution

    Science.gov (United States)

    Lin, Yan; Zhang, Jun; Pan, Yuan; Liu, Yunqi

    2017-11-01

    The design of efficient and robust Ni2P-based hybrid catalysts for hydrogen evolution reaction (HER) is still in challenge. In this work, a hybrid catalyst composed of monodispersed Ni2P nanoparticles (NPs) and N, P co-doped porous carbon (NPPC) was synthesized through a facile thermal decomposition and used as an efficient electrocatalyst for the HER in 0.5 M H2SO4 solution. Series technologies including X-ray diffraction, Raman, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and N2 sorption are used to characterize the as-synthesized catalysts. The electrochemisty experiments suggested that the as-synthesized Ni2P/NPPC displayed efficient electrocatalytic performance with a low onset overpotential (51 mV), small Tafel slope (74 mV dec-1), high exchange current density (0.12 mA cm-2), large electrochemical double-layer capacitance (21.97 mF cm-2) and high conductivity for the HER. The needed overpotentials are 159 and 184 mV to reach to the current density of 10 and 20 mA cm-2, respectively. Simultaneously, Ni2P/NPPC also displayed good stability in acid solution. The more defects and active sites on the porous carbon which are offered by the co-doped N and P atoms as well as the synergistic effect between NPPC and Ni2P NPs are contributed to the excellent catalytic performance for HER. The current study suggests that introducing the N, P heteroatoms co-doped carbon materials to the Ni2P-based catalysts could enhance HER electrocatalytic performance efficiently.

  4. Analysis of thermal and structural properties of germanate glasses co-doped with Yb(3+)/Tb(3+) ions.

    Science.gov (United States)

    Zmojda, J; Kochanowicz, M; Miluski, P; Dorosz, D; Jelen, P; Sitarz, M

    2014-10-15

    In the work the new glass compositions in the GeO2-GaO-BaO system have been prepared and thermal, structural properties of in germanate glasses co-doped with Yb(3+)/Tb(3+)ions were studied. Glasses were obtained by conventional high-temperature melt-quenching technique. The study of the crystallization kinetics processes of glasses co-doped with 0.7Yb2O3:0.7Tb2O3 was performed with DSC measurements. The activation energies have been calculated using Freedman analysis and verified with the Flynn-Wall-Ozawa method. In this order, the DSC curves have been registered with different heating rates, between 5 and 15 degrees/min. The structure of fabricated glasses has been studied by infrared and Raman spectroscopes. The effect of heat treatment on the structural properties was determined. In all glass samples the dominated infrared absorbance band at 800cm(-1) corresponds to asymmetric stretching motions of GeO4 tetrahedra containing bridging (Ge-O(Ge)) and non-bridging (Ge-O(-)) oxygens. Additionally, the influence of heat treatment on the luminescent properties was evaluated. Strong luminescence at 489, 543, 586 and 621nm corresponding to (5)D4→(7)FJ (J=6, 5, 4, 3) transitions was measured. The highest upconversion emission intensity was obtained in the germanate glass co-doped with 0.7Yb2O3/0.7Tb2O3. Copyright © 2014 Elsevier B.V. All rights reserved.

  5. Photocatalytic performance of magnetically separable Fe, N co-doped TiO{sub 2}-cobalt ferrite nanocomposite

    Energy Technology Data Exchange (ETDEWEB)

    Gaikwad, P.N. [Department of Chemistry, Shivaji University, Kolhapur 416004 (India); Hankare, P.P., E-mail: p_hankarep@rediffmail.com [Department of Chemistry, Shivaji University, Kolhapur 416004 (India); Wandre, T.M.; Garadkar, K.M. [Department of Chemistry, Shivaji University, Kolhapur 416004 (India); Sasikala, R., E-mail: sasikala@barc.gov.in [Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India)

    2016-03-15

    Graphical abstract: - Highlights: • FeN-TiO{sub 2}-cobalt ferrite shows enhanced photocatalytic activity compared to TiO{sub 2}. • Increased visible light absorption is observed for the composite catalyst. • Fe, N doped TiO{sub 2} exists as a dispersed phase on cobalt ferrite. • The composite catalyst is stable for prolonged use and magnetically separable. - Abstract: Photocatalytic activity of a magnetically separable cobalt ferrite (CoFe{sub 2}O{sub 4}, CF) coupled with Fe and N co-doped TiO{sub 2} nanocomposite was investigated for the degradation of methyl orange. TiO{sub 2} and Fe, N co-doped TiO{sub 2} existed as anatase phase of TiO{sub 2}. The presence of both anatase TiO{sub 2} and CF was indicated in the XRD pattern. The UV–visible spectra of all samples showed absorption in the visible region. The photocatalytic activity of these samples was examined in both UV and visible light. TiO{sub 2} co-doped with Fe and N exhibited the highest activity. Though the photocatalytic activity of the composite was slightly less than that of doped TiO{sub 2}, it showed improved activity compared to TiO{sub 2}. Besides, the composite has an added advantage that it is magnetically separable from the solution, which is a desired property for industrial applications. The increased photocatalytic activity is attributed to the increased optical absorption property compared to single phase TiO{sub 2}.

  6. Amorphous Si layers co-doped with B and Mn: Thin film growth and steering of magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Drera, G. [I-LAMP, Dipartimento di Matematica e Fisica, Università Cattolica del Sacro Cuore, Via dei Musei 41, 25121 Brescia (Italy); Mozzati, M.C. [CNISM, Dipartimento di Fisica, Università di Pavia, Via Bassi 6, 27100 Pavia (Italy); Colombi, P. [CSMT Gestione s.c.a.r.l, Via Branze 45, 25123 Brescia (Italy); Salvinelli, G.; Pagliara, S.; Visentin, D. [I-LAMP, Dipartimento di Matematica e Fisica, Università Cattolica del Sacro Cuore, Via dei Musei 41, 25121 Brescia (Italy); Sangaletti, L., E-mail: sangalet@dmf.unicatt.it [I-LAMP, Dipartimento di Matematica e Fisica, Università Cattolica del Sacro Cuore, Via dei Musei 41, 25121 Brescia (Italy)

    2015-09-01

    Amorphous silicon thin films co-doped with manganese (5% at.) and boron (1.8% at.) have been prepared by RF sputtering on Al{sub 2}O{sub 3} substrates held at room temperature (RT). The films, with an average thickness of about 0.9 μm, were carefully characterized by micro-Raman and X-ray photoemission spectroscopies. A ferromagnetic (FM) behavior up to RT was observed. In order to discuss and possibly rule out extrinsic effects usually related to segregations of ferromagnetic impurities in the samples, magnetization measurements were carried out on the Al{sub 2}O{sub 3} substrates, as well as on Si:B and Si:Mn films grown with the same RF sputtering system. Only the Si:B:Mn films displayed a FM behavior up to RT. Since amorphous films doped with Mn alone did not display any signature of FM ordering, boron co-doping results to be crucial for the onset of the FM behavior. The conductivity of the samples is not affected by boron doping that, therefore, does not appear to significantly contribute to a possible carrier-mediated FM interaction between Mn ions by supplying extra charges to the system. On this basis, the capability of B to hinder the quenching of the Mn 3d magnetic moments has also to be regarded as a possible role of this co-dopant in the observed magnetization. - Highlights: • We successfully deposited amorphous silicon thin films co-doped with Mn and B. • Structural, electronic, and magnetic properties have been carefully characterized. • A ferromagnetic behavior up to room temperature was detected. • The extrinsic origin of magnetism is excluded. • Boron can play a relevant role to avoid quenching of magnetic moment in Mn ions.

  7. Corrosion protection of AISI 1018 steel using Co-doped TiO{sub 2}/polypyrrole nanocomposites in 3.5% NaCl solution

    Energy Technology Data Exchange (ETDEWEB)

    Ladan, Magaji, E-mail: ladanmagaji@yahoo.com [Department of Chemistry, Faculty of Science, University of Malaya, Kuala Lumpur, 50603 (Malaysia); Department of Pure and Industrial Chemistry, Bayero University Kano (Nigeria); Basirun, Wan Jeffrey, E-mail: jeff@um.edu.my [Department of Chemistry, Faculty of Science, University of Malaya, Kuala Lumpur, 50603 (Malaysia); Institute of Nanotechnology and Catalysis (NanoCat), University of Malaya, Kuala Lumpur, 50603 (Malaysia); Kazi, Salim Newaz; Rahman, Fariza Abdul [Department of Mechanical Engineering, Faculty of Engineering, University of Malaya, Kuala Lumpur, 50603 (Malaysia)

    2017-05-01

    A polypyrrole nanocomposites (PPy NTCs) have been effectively synthesized in the presence of TiO{sub 2} and Co-doped TiO{sub 2} nanoparticles (NPs) by an in situ chemical oxidative polymerization. Field Emission Scanning Electron Microscopy and Transmission Electron Microscopy revealed a tube shape structure of the PPy. The TEM results confirmed that the nanocomposite size of Co-doped TiO{sub 2}/PPy NTCs was smaller than TiO{sub 2}/PPy NTCs thereby increasing the interaction between the PPy nanotube and the AISI steel surface. The corrosion performance of the coatings was evaluated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurements in 3.5% NaCl solution. The EIS results show that the log |Z| of AISI 1018 coated with Co-doped TiO{sub 2}/PPy NTCs and TiO{sub 2}/PPy NTCs reached about 8.2 and 6.0 respectively after 30 days of exposure in 3.5% NaCl solution. This is likely due to the increased surface area of the PPy synthesized in the presence of Co-doped TiO{sub 2} NPs. The EIS results are confirmed by the potentiodynamic polarization and open circuit potential values of the Co-doped TiO{sub 2}/PPy which indicated little changes between 1 and 30 days of exposure which confirms the protection ability of this coating. . It is evident that the presence of Co-doped TiO{sub 2} NPs can enhance the resistance against corrosion at the steel/electrolyte interface. - Highlights: • Polymerization of pyrrole monomer in the presence of Co-doped TiO{sub 2} decreases the size of the polypyrrole nanotube (PPy NT). • The corrosion protection increases with the increase in PPy NT dispersion. • The corrosion resistance of steel coated with Co-doped TiO{sub 2}/PPy NTCs is considerably higher. • TiO{sub 2}/PPy with Co doping reduces the charge transfer across the electrolyte/AISI 1018 steel interface.

  8. Enhanced photocatalytic degradation of dye under visible light on mesoporous microspheres by defects in manganese- and nitrogen-co-doped TiO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Lu; Jiang, Heng, E-mail: hjiang78@hotmail.com [Liaoning Shihua University, School of Chemistry and Materials Science (China); Zou, Mingming; Xiong, Fengqiang; Ganeshraja, Ayyakannu Sundaram; Pervaiz, Erum [Chinese Academy of Sciences, Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics (China); Liu, Yinan; Zou, Shunying [Dalian Environmental Protection Laboratory (China); Yang, Minghui, E-mail: myang@dicp.ac.cn [Chinese Academy of Sciences, Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics (China)

    2016-09-15

    Manganese- and nitrogen-co-doped mesoporous TiO{sub 2} microsphere photocatalysts are prepared by a simple sol–gel method with controllable sizes in the range of 400–500 nm and high surface area of 112 m{sup 2} g{sup −1}. Manganous acetate is the Mn source, and ammonia gas is the nitrogen source used. The dopants are found to be uniformly distributed in the TiO{sub 2} matrix. Interestingly, in (Mn,N)-co-doped TiO{sub 2}, we observe an effective indirect band gap of ~2.58 eV. (Mn,N)-co-doped mesoporous TiO{sub 2} microspheres show higher photocatalytic activity than Mn–TiO{sub 2} microspheres under visible light irradiation. Among the samples reported in this work, 0.2 at.% Mn doping and 500 °C 2-h nitriding condition give the highest photocatalytic activity. The observed photocatalytic activity in the (Mn,N)-co-doped TiO{sub 2} is attributed to the contribution from improved absorption due to trap levels of Mn, oxygen vacancies and N doping.Graphical AbstractManganese- and nitrogen-co-doped mesoporous TiO{sub 2} microspheres containing substitutional N, interstitial N and O vacancies show high visible light photocatalytic activity.

  9. A DFT study of the electronic structures and optical properties of (Cr, C) co-doped rutile TiO2

    Science.gov (United States)

    Chen, Hao; Li, Xuechao; Wan, Rundong; Kao-Walter, Sharon; Lei, Ying

    2018-02-01

    To get an effective doping model of rutile TiO2, we systematically study geometrical parameters, density of states, electron densities, dielectric functions, optical absorption spectra for the pure, C mono-doping, Cr mono-doping and (Cr,C) co-doping rutile TiO2, using density functional calculations. We find that a C doped system presents higher stability under Ti-rich condition, while Cr doped and (Cr,C) co-doped systems are more stable under O-rich condition. For (Cr,C) co-doping situation, the imaginary part of the dielectric function reflects the higher energy absorption efficiency for incident photons. Moreover, co-doping system exhibits much bigger red-shift of optical absorption edge compared with Cr/C single doping systems, because of the great reduction of the direct band gap. The calculated optical absorption spectra show that the (Cr,C) co-doping rutile TiO2 has higher photocatalytic activity in the visible light region.

  10. Structural, optical, and magnetic properties of polycrystalline Co-doped TiO{sub 2} synthesized by solid-state method

    Energy Technology Data Exchange (ETDEWEB)

    Bouaine, Abdelhamid, E-mail: abdelhamidfethi@yahoo.fr [Laboratoire d' Etude des Materiaux (LEM), Departement de Physique, Faculte des Sciences Exactes et des Sciences de la Nature et de la vie, Universite de Jijel, cite Oued-Aissa, B.P 98, Jijel 18000 (Algeria); Institut de Physique et Chimie des Materiaux de Strasbourg (IPCMS), UMR 7504 CNRS - UdS, 23 rue du Loess, B.P. 43, 67034 Strasbourg Cedex 2 (France); Schmerber, G.; Ihiawakrim, D.; Derory, A. [Institut de Physique et Chimie des Materiaux de Strasbourg (IPCMS), UMR 7504 CNRS - UdS, 23 rue du Loess, B.P. 43, 67034 Strasbourg Cedex 2 (France)

    2012-11-01

    Highlights: Black-Right-Pointing-Pointer Influence of Co doping on the TiO{sub 2} tetragonal structure. Black-Right-Pointing-Pointer Decrease of the energy band gap after doping with Co atoms. Black-Right-Pointing-Pointer Appearance of ferromagnetism in Co-doped TiO{sub 2} diluted magnetic semiconductors. - Abstract: We have used a solid-state method to synthesize polycrystalline Co-doped TiO{sub 2} diluted magnetic semiconductors (DMSs) with Co concentrations of 0, and 0.5 at.%. X-ray diffraction patterns reveal that Co doped TiO{sub 2} crystallizes in the rutile tetragonal structure with no additional peaks. Transmission electron microscopy (TEM) did not indicate the presence of magnetic parasitic phases and confirmed that Co ions are uniformly distributed inside the samples. Optical absorbance measurements showed an energy band gap which decreases after doping with the Co atoms into the TiO{sub 2} matrix. Magnetization measurements revealed a paramagnetic behavior for the as-prepared Co-doped TiO{sub 2} and a ferromagnetic behavior for the same samples after annealed under a mixture of H{sub 2}/N{sub 2} atmosphere.

  11. Photocatalytic performance of nitrogen, osmium co-doped TiO2 for removal of eosin yellow in water under simulated solar radiation.

    Science.gov (United States)

    Kuvarega, Alex T; Krause, Rui W M; Mamba, Bhekie B

    2013-07-01

    Nitrogen, osmium co-doped TiO2 photocatalysts were prepared by a modified sol-gel method using ammonia as the nitrogen source and osmium tetroxide as the source of osmium. The role of rutile phase OsO2 in enhancing the photocatalytic activity of rutile TiO2 towards the degradation of Eosin Yellow was investigated. The materials were characterised by various techniques that include FTIR, Raman, XRD, SEM, EDS, TEM, TGA and DRUV-Vis. The amorphous, oven dried sample was transformed to the anatase and then the rutile phase with increasing calcination temperature. DRUV-Vis analysis revealed a red shift in absorption with increasing calcination temperature, confirmed by a decrease in the band gap of the material. The photocatalytic activity of N, Os co-doped TiO2 was evaluated using eosin yellow degradation and activity increased with increase in calcination temperature under simulated solar irradiation. The rutile phase of the co-doped TiO2 was found to be more effective in degrading the dye (k(a) = 1.84 x 10(-2) min(-1)) compared to the anatase co-doped phase (k(a) = 9.90 x 10(-3) min(-1)). The enhanced photocatalytic activity was ascribed to the synergistic effects of rutile TiO2 and rutile OsO2 in the N, Os co-doped TiO2.

  12. Obtaining ZnO nanocrystalline through methods of combustion and precipitation; Obtencao de ZnO nanocristalino atraves dos metodos de combustao e de precipitacao

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, A.P.; Guaglianoni, W.C.; Cunha, M.A.; Basegio, T.M.; Bergmann, C.P., E-mail: anapquimica@yahoo.com.br [Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS (Brazil). Lab. de Materiais Ceramicos

    2012-07-01

    Zinc oxide is important technological applications in rubber and industrial paints. The chemical properties and microstructure of ZnO powder depends on the synthesis method employed. In this work, it was obtained nanosized ZnO using different synthesis processes, such as solution combustion and precipitation, varying the concentrations of reactants and the working temperature. The obtained powders were characterized by SEM, BET, XRD, crystallite size determination and thermal analysis (TGA and DTA). It was possible to obtain nanosized ZnO with the methods used. (author)

  13. Superior supercapacitors based on nitrogen and sulfur co-doped hierarchical porous carbon: Excellent rate capability and cycle stability

    Science.gov (United States)

    Zhang, Deyi; Han, Mei; Wang, Bing; Li, Yubing; Lei, Longyan; Wang, Kunjie; Wang, Yi; Zhang, Liang; Feng, Huixia

    2017-08-01

    Vastly improving the charge storage capability of supercapacitors without sacrificing their high power density and cycle performance would bring bright application prospect. Herein, we report a nitrogen and sulfur co-doped hierarchical porous carbon (NSHPC) with very superior capacitance performance fabricated by KOH activation of nitrogen and sulfur co-doped ordered mesoporous carbon (NSOMC). A high electrochemical double-layer (EDL) capacitance of 351 F g-1 was observed for the reported NSHPC electrodes, and the capacitance remains at 288 F g-1 even under a large current density of 20 A g-1. Besides the high specific capacitance and outstanding rate capability, symmetrical supercapacitor cell based on the NSHPC electrodes also exhibits an excellent cycling performance with 95.61% capacitance retention after 5000 times charge/discharge cycles. The large surface area caused by KOH activation (2056 m2 g-1) and high utilized surface area owing to the ideal micro/mesopores ratio (2.88), large micropores diameter (1.38 nm) and short opened micropores structure as well as the enhanced surface wettability induced by N and S heteroatoms doping and improved conductivity induced by KOH activation was found to be responsible for the very superior capacitance performance.

  14. High-power graphene mode-locked Tm/Ho co-doped fiber laser with evanescent field interaction.

    Science.gov (United States)

    Li, Xiaohui; Yu, Xuechao; Sun, Zhipei; Yan, Zhiyu; Sun, Biao; Cheng, Yuanbing; Yu, Xia; Zhang, Ying; Wang, Qi Jie

    2015-11-16

    Mid-infrared ultrafast fiber lasers are valuable for various applications, including chemical and biomedical sensing, material processing and military applications. Here, we report all-fiber high-power graphene mode-locked Tm/Ho co-doped fiber laser at long wavelength with evanescent field interaction. Ultrafast pulses up to 7.8 MHz are generated at a center wavelength of 1879.4 nm, with a pulse width of 4.7 ps. A graphene absorber integrated with a side-polished fiber can increase the damage threshold significantly. Harmonics mode-locking can be obtained till to the 21(th) harmonics at a pump power of above 500 mW. By using one stage amplifier in the anomalous dispersion regime, the laser can be amplified up to 450 mW and the narrowest pulse duration of 1.4 ps can be obtained simultaneously. Our work paves the way to graphene Tm/Ho co-doped mode-locked all-fiber master oscillator power amplifiers as potentially efficient and economic laser sources for high-power laser applications, such as special material processing and nonlinear optical studies.

  15. Ce(3+) /Tb(3+) non-/single-/co-doped K-Lu-F materials: synthesis, optical properties, and energy transfer.

    Science.gov (United States)

    Cao, Chunyan; Xie, An; Noh, Hyeon Mi; Jeong, Jung Hyun

    2016-08-01

    Using a hydrothermal method, Ce(3+) /Tb(3+) non-/single-/co-doped K-Lu-F materials have been synthesized. The X-ray diffraction (XRD) results suggest that the Ce(3+) and/or Tb(3+) doping had great effects on the crystalline phases of the final samples. The field emission scanning electron microscopy (FE-SEM) images indicated that the samples were in hexagonal disk or polyhedron morphologies in addition to some nanoparticles, which also indicated that the doping also had great effects on the sizes and the morphologies of the samples. The energy-dispersive spectroscopy (EDS) patterns illustrated the constituents of different samples. The enhanced emissions of Tb(3+) were observed in the Ce(3+) /Tb(3+) co-doped K-Lu-F materials. The energy transfer (ET) efficiency ηT were calculated based on the fluorescence yield. The ET mechanism from Ce(3+) to Tb(3+) was confirmed to be the dipole-quadrupole interaction inferred from the theoretical analysis and the experimental data. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

  16. Intrinsic Enhancement of Dielectric Permittivity in (Nb + In) co-doped TiO2 single crystals.

    Science.gov (United States)

    Kawarasaki, Masaru; Tanabe, Kenji; Terasaki, Ichiro; Fujii, Yasuhiro; Taniguchi, Hiroki

    2017-07-13

    The development of dielectric materials with colossal permittivity is important for the miniaturization of electronic devices and fabrication of high-density energy-storage devices. The electron-pinned defect-dipoles has been recently proposed to boost the permittivity of (Nb + In) co-doped TiO2 to 105. However, the follow-up studies suggest an extrinsic contribution to the colossal permittivity from thermally excited carriers. Herein, we demonstrate a marked enhancement in the permittivity of (Nb + In) co-doped TiO2 single crystals at sufficiently low temperatures such that the thermally excited carriers are frozen out and exert no influence on the dielectric response. The results indicate that the permittivity attains quadruple of that for pure TiO2. This finding suggests that the electron-pinned defect-dipoles add an extra dielectric response to that of the TiO2 host matrix. The results offer a novel approach for the development of functional dielectric materials with large permittivity by engineering complex defects into bulk materials.

  17. Broadband ∼3 μm mid-infrared emission in Dy3+/Yb3+ co-doped germanate glasses

    Science.gov (United States)

    Shen, Lingling; Wang, Ning; Dou, Aoju; Cai, Yangjian; Tian, Ying; Huang, Feifei; Xu, Shiqing; Zhang, Junjie

    2018-01-01

    The Dy3+/Yb3+ co-doped germanate glasses with good thermal stability have been prepared by the conventional melt quenching method. The J-O intensity parameters and radiative properties such as spontaneous transition probilities (Arad), fluorescence branching ratios (β) and radiative lifetimes (τrad) were investigated according to the absorption spectrum based on Judd-Ofelt theory. An intense emission around ∼3 μm with the FWHM reaching to 322 nm was obtained in present glasses excited by 980 nm LD. The high spontaneous transition probability (63.94 s-1), large emission cross section (6.0 × 10-21 cm2) and superior gain performance corresponding to the Dy3+: 6H13/2 → 6H15/2 transition were obtained. Moreover, the energy transfer mechanism was analyzed qualitatively, and it was found that the energy transfer from Yb3+: 2F5/2 to Dy3+: 6H5/2 level could be quite efficient. Hence, the results indicated that the prepared Dy3+/Yb3+ co-doped germanate glass could be a potential candidate for ∼3 μm mid-infrared solid state lasers.

  18. Crystal growth, electronic structure and luminescence properties of Nb/Yb co-doped RbTiOPO4 crystals

    Science.gov (United States)

    Liu, Jian; Li, Ziqing; Zhu, Pengfei; Duan, Xiulan

    2018-01-01

    Nb/Yb co-doped RbTiOPO4 (RTP) crystals were successfully grown by a top-seeded solution growth method from two different kinds of flux systems. 5%Nb/3%Yb: RTP crystal with more transparency was obtained from the mixed solvent containing MoO3. The chemical composition was analyzed by Electron Probe Microanalyzer (EPMA), and the result indicated that co-doping of Nb and Yb into RTP can greatly increase the concentration of Yb in RTP crystal. The addition of MoO3 into self-flux system can improve the quality of as-grown crystals, but it is not helpful to introduce Yb into crystal. The electronic structures of Nb/Yb: RTP crystals were analyzed using X-ray photoelectron spectra (XPS). The results show that the binding energy difference between O 1s and P 2p levels (ΔBE (O-P)) increases firstly with the increase of Yb content, and then decreases with Nb content increasing, which is associated with the covalency change of O-P bonds in crystals. However, the doping has little influence on the chemical bond properties of O-Ti. The FL spectra of Nb/Yb: RbTiOPO4 crystals were also analyzed, and five emission peaks characteristic of Yb3+ ions were observed.

  19. Structural, magnetic and spectroscopic study of a diluted magnetic oxide: Co doped CeO{sub 2-{delta}}

    Energy Technology Data Exchange (ETDEWEB)

    Vodungbo, B; Vidal, F; Zheng, Y; Marangolo, M; Demaille, D; Etgens, V H [Institut des NanoSciences de Paris, UMR 7588 CNRS, Universites Pierre et Marie Curie et Denis Diderot, Campus Boucicaut, 140 rue de Lourmel, 75015 Paris (France); Varalda, J; Oliveira, A J A de [Departamento de Fisica, Universidade Federal de Sao Carlos, 13565-905, S. Carlos SP (Brazil); Maccherozzi, F; Panaccione, G [TASC Laboratory INFM-CNR, in Area Science Park, S.S.14, Km 163.5, I-34012 Trieste (Italy)], E-mail: franck.vidal@insp.jussieu.fr

    2008-03-26

    A structural, spectroscopic and magnetic study of Co doped CeO{sub 2-{delta}} diluted magnetic oxide (DMO) thin films grown by pulsed laser deposition is presented. No secondary phase or metallic clusters could be detected. The samples are ferromagnetic at room temperature and epitaxial films display a large magnetic anisotropy with an out-of-plane easy axis. The evolution of the magnetization with temperature did not reveal any superparamagnetic signal related to nanosized clusters, reinforcing the conclusion that the ferromagnetism is intrinsic in this system. The magnetization at saturation has the same magnitude ({approx}1.4-1.5 {mu}{sub B}/Co) in epilayers and textured films and shows no clear dependence on the structural quality, contrary to other DMOs. It is also shown that ferromagnetism is not restricted to a particular region of the films, such as the interface. The ferromagnetic signal depends sensitively on the oxygen pressure during growth and post-growth annealing. The valence of Ce and Co was deduced from x-ray spectroscopies, revealing a predominant Co{sup 2+} state. The origin of ferromagnetism in Co doped CeO{sub 2-{delta}} is discussed in connection with possible charge-compensating defects and existing models describing indirect exchange in DMOs.

  20. Structural, magnetic and electric properties of Nd and Ni co-doped BiFeO3 materials

    Directory of Open Access Journals (Sweden)

    Dao Viet Thang

    2017-09-01

    Full Text Available Multiferroic Bi1−xNdxFe0.975Ni0.025O3 (x = 0.00, 0.05, 0.10, 0.125, and 0.15 (BNFNO and BiFeO3 (BFO materials were synthesized by a sol-gel method. Crystal structure, ferromagnetic and ferroelectric properties of the as-synthesized materials were investigated. Results showed that Nd3+ and Ni2+ co-doping affected to the electrical leakage, enhanced ferroelectric polarization and magnetization of BiFeO3. Co-doped sample with 12.5 mol% of Nd3+ and 2.5 mol% of Ni2+ exhibited an enhancement in both ferromagnetism and ferroelectric properties up to MS ~ 0.528 emu/g and PS ~ 18.35 μC/cm2 with applied electric field at 5 kV/cm, respectively. The origins of ferromagnetism and ferroelectricity enhancement were discussed in the paper.

  1. Fluorine and boron co-doped diamond-like carbon films deposited by pulsed glow discharge plasma immersion ion processing

    CERN Document Server

    He, X M; Peters, A M; Taylor, B; Nastasi, M

    2002-01-01

    Fluorine (F) and boron (B) co-doped diamond-like carbon (FB-DLC) films were prepared on different substrates by the plasma immersion ion processing (PIIP) technique. A pulse glow discharge plasma was used for the PIIP deposition and was produced at a pressure of 1.33 Pa from acetylene (C sub 2 H sub 2), diborane (B sub 2 H sub 6), and hexafluoroethane (C sub 2 F sub 6) gas. Films of FB-DLC were deposited with different chemical compositions by varying the flow ratios of the C sub 2 H sub 2 , B sub 2 H sub 6 , and C sub 2 F sub 6 source gases. The incorporation of B sub 2 H sub 6 and C sub 2 F sub 6 into PIIP deposited DLC resulted in the formation of F-C and B-C hybridized bonding structures. The levels of the F and B concentrations effected the chemical bonding and the physical properties as was evident from the changes observed in density, hardness, stress, friction coefficient, and contact angle of water on films. Compared to B-doped or F-doped DLC films, the F and B co-doping of DLC during PIIP deposition...

  2. Yellow laser performance of Dy$^{3+}$ in co-doped Dy,Tb:LiLuF$_4$

    CERN Document Server

    Bolognesi, Giacomo; Calonico, Davide; Costanzo, Giovanni Antonio; Levi, Filippo; Metz, Philip Werner; Kränkel, Christian; Huber, Günter; Tonelli, Mauro

    2015-01-01

    We present laser results obtained from a Dy$^{3+}$-Tb$^{3+}$ co-doped LiLuF$_{4}$ crystal, pumped by a blue emitting InGaN laser diode, aiming for the generation of a compact 578 nm source. We exploit the yellow Dy$^{3+}$ transition $^{4}$F$_{9/2}$ $\\Longrightarrow$ $^{6}$H$_{13/2}$ to generate yellow laser emission. The lifetime of the lower laser level is quenched via energy transfer to co-doped Tb$^{3+}$ ions in the fluoride crystal. We report the growth technique, spectroscopic study and room temperature continuous wave (cw) laser results in a hemispherical cavity at 574 nm and with a highly reflective output coupler at 578 nm. A yellow laser at 578 nm is very relevant for metrological applications, in particular for pumping of the forbidden $^{1}$S$_{0} \\Longrightarrow ^{3}$P$_{0}$ Ytterbium clock transition, which is recommended as a secondary representation of the second in the international system (SI) of units. This paper was published in Optics Letters and is made available as an electronic reprint ...

  3. The Structure, Electronic, Magnetic and Optical Properties of the Mn-X (X = B, C, N and O) Co-Doped Monolayer WS2

    Science.gov (United States)

    Xie, Ling-Yun; Zhang, Jian-Min

    2017-11-01

    To expand the potential application of monolayer WS2 systems, the structure, electronic, magnetic and optical properties of pure and Mn-X (X = B, C, N and O) co-doped monolayer WS2 systems are theoretically studied using first-principles methods based on the density function theory. The pure monolayer WS2 system is a nonmagnetic semiconductor with a direct band gap E g of 1.82 eV, and the Mn-B and Mn-N co-doped monolayer WS2 systems remain of nonmagnetic semiconducting character with smaller band gaps E_{{g}} of 1.09 eV and 0.84 eV, respectively. While the Mn-C and Mn-O co-doped monolayer WS2 systems exhibit magnetic semiconducting characters with a total magnetic moment M_{{tot}} of 1 μ_{{B}} , and spin-up gaps E_{{g}}^{ \\uparrow } (spin-down gaps E_{{g}}^{ \\downarrow } ) of 0.54 (1.17) eV and 0.61 (1.44) eV, respectively. Although the pure monolayer WS2 system has the highest transmittance in the low energy region, the Mn-B co-doped monolayer WS2 system has the highest static dielectric constants ɛ1 (0) and ɛ2 (0) , reflectivity r(0) , refractive indices n(0) and k(0) . Meanwhile, the Mn-X (X = B, C, N and O) co-doped monolayer WS2 systems are more suitable to make infrared photodetector due to their red-shift phenomenon. In particularly, the Mn-B co-doped monolayer WS2 system becomes of great interest to researchers since the absorption edge shifts to the mid-infrared spectral region.

  4. Solvothermal syntheses of Bi and Zn co-doped TiO{sub 2} with enhanced electron-hole separation and efficient photodegradation of gaseous toluene under visible-light

    Energy Technology Data Exchange (ETDEWEB)

    Li, Juan-Juan [Center for Excellence in Regional Atmospheric Environment, and Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021 (China); Cai, Song-Cai [Center for Excellence in Regional Atmospheric Environment, and Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021 (China); University of Chinese Academy of Sciences, Beijing, 100049 (China); Xu, Zhen [Center for Excellence in Regional Atmospheric Environment, and Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021 (China); Chen, Xi [Center for Excellence in Regional Atmospheric Environment, and Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021 (China); University of Chinese Academy of Sciences, Beijing, 100049 (China); Chen, Jin [Center for Excellence in Regional Atmospheric Environment, and Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021 (China); Jia, Hong-Peng, E-mail: hpjia@iue.ac.cn [Center for Excellence in Regional Atmospheric Environment, and Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021 (China); Chen, Jing, E-mail: jing.chen@fjirsm.ac.cn [State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002 (China)

    2017-03-05

    Highlights: • Bi-Zn co-doped TiO{sub 2} catalysts were prepared by solvothermal route. • The incorporation of Bi doping into the TiO{sub 2} generates intermediate energy levels. • Bi and Zn doping showed the enhanced absorption in visible-light region. • Zn dopant acts as a mediator of interfacial charge transfer. • TiBi{sub 1.9%}Zn{sub 1%}O{sub 2} exhibited high photocatalytic degradation for toluene. - Abstract: This study investigated the effects of Bi doped and Bi-Zn co-doped TiO{sub 2} on photodegradation of gaseous toluene. The doped TiO{sub 2} with various concentration of metal was prepared using the solvothermal route and characterized by SEM, XRD, Raman, BET, DRS, XPS, PL and EPR. Their photocatalytic activities under visible-light irradiation were drastically influenced by the dopant content. The results showed that moderate metal doping levels were obviously beneficial for the toluene degradation, while high doping levels suppressed the photocatalytic activity. The photocatalytic degradation of toluene over TiBi{sub 1.9%}O{sub 2} and TiBi{sub 1.9%}Zn{sub 1%}O{sub 2} can reach to 51% and 93%, respectively, which are much higher than 25% of TiO{sub 2}. Bi doping into TiO{sub 2} lattice generates new intermediate energy level of Bi below the CB edge of TiO{sub 2}. The electron excitation from the VB to Bi orbitals results in the decreased band gap, extended absorption of visible-light and thus enhances its photocatalytic efficiency. Zn doping not only further enhances the absorption in this visible-light region, but also Zn dopant exists as the form of ZnO crystallites located on the interfaces of TiO{sub 2} agglomerates and acts as a mediator of interfacial charge transfer to suppress the electron-hole recombination. These synergistic effects are responsible for the enhanced photocatalytic performance.

  5. Effects of rare-earth co-doping on the local structure of rare-earth phosphate glasses using high and low energy X-ray diffraction

    OpenAIRE

    Cramer, Alisha J.; Cole, Jacqueline M.; Fitzgerald, Vicky; Honkimaki, Veijo; Roberts, Mark A.; Brennan, Tessa; Martin, Richard A.; Saunders, George A.; Newport, Robert J.

    2013-01-01

    Rare-earth co-doping in inorganic materials has a long-held tradition of facilitating highly desirable optoelectronic properties for their application to the laser industry. This study concentrates specifically on rare-earth phosphate glasses, (R2O3) x(R�2O3)y(P2O 5)1-(x+y), where (R, R�) denotes (Ce, Er) or (La, Nd) co-doping and the total rare-earth composition corresponds to a range between metaphosphate, RP3O9, and ultraphosphate, RP 5O14. Thereupon, the effects of rare-earth co-dopin...

  6. Facile synthesis and enhanced visible light photocatalytic activity of N and Zr co-doped TiO2 nanostructures from nanotubular titanic acid precursors

    Science.gov (United States)

    Zhang, Min; Yu, Xinluan; Lu, Dandan; Yang, Jianjun

    2013-12-01

    Zr/N co-doped TiO2 nanostructures were successfully synthesized using nanotubular titanic acid (NTA) as precursors by a facile wet chemical route and subsequent calcination. These Zr/N-doped TiO2 nanostructures made by NTA precursors show significantly enhanced visible light absorption and much higher photocatalytic performance than the Zr/N-doped P25 TiO2 nanoparticles. Impacts of Zr/N co-doping on the morphologies, optical properties, and photocatalytic activities of the NTA precursor-based TiO2 were thoroughly investigated. The origin of the enhanced visible light photocatalytic activity is discussed in detail.

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

    Science.gov (United States)

    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.

  8. Synthetic and spectroscopic studies of vanadate glaserites I: Upconversion studies of doubly co-doped (Er, Tm, or Ho):Yb:K{sub 3}Y(VO{sub 4}){sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Kimani, Martin M., E-mail: kimani@g.clemson.edu; Chen, Hongyu, E-mail: hongyuc@g.clemson.edu; McMillen, Colin D., E-mail: cmcmill@g.clemson.edu; Anker, Jeffery N., E-mail: janker@clemson.edu; Kolis, Joseph W., E-mail: kjoseph@clemson.edu

    2015-03-15

    The synthesis and upconversion properties of trigonal glaserite-type K{sub 3}Y(VO{sub 4}){sub 2} co-doped with Er{sup 3+}/Yb{sup 3+}, Ho{sup 3+}/Yb{sup 3+}, or Tm{sup 3+}/Yb{sup 3+} were studied. Powder samples were synthesized by solid state reactions at 1000 °C for 48 h, while well-formed hexagonal single crystals of the same were grown hydrothermally using 10 M K{sub 2}CO{sub 3} at 560–650 °C. Infrared-to-visible upconversion by Er{sup 3+}/Yb{sup 3+}, Ho{sup 3+}/Yb{sup 3+}, or Tm{sup 3+}/Yb{sup 3+} codoped-K{sub 3}Y(VO{sub 4}){sub 2} glaserite powder and single crystals was observed, and the upconversion spectral properties were studied as a function of different Er{sup 3+}, Tm{sup 3+}, Ho{sup 3+}, and Yb{sup 3+} ion concentrations. The process is observed under 980 nm laser diode excitation and leads to strong green (552 nm) and red (659 nm) emission for Er{sup 3+}/Yb{sup 3+}, green (549 nm) and red (664 nm) emission for Ho{sup 3+}/Yb{sup 3+}, and blue (475 nm) and red (647 nm) emission for Tm{sup 3+}/Yb{sup 3+}. The main mechanism that allows for up-conversion is attributed the energy transfer among Yb{sup 3+} and the various Er{sup 3+}/Ho{sup 3+}/Tm{sup 3+} ions in excited states. These results illustrate the large potential of co-doped alkali double vanadates for photonic applications involving optoelectronics devices. - Graphical abstract: Synthesis and upconversion in vanadate glaserites. - Highlights: • K{sub 3}Y(VO{sub 4}){sub 2} codoped with Er, Tm, or Ho:Yb were synthesized via solid-state and hydrothermal routes. • Upconversion properties are investigated. • The codoped compounds revealed efficient infrared-to-visible upconversion. • The presented compounds are potential host for solid state lighting.

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

    DEFF Research Database (Denmark)

    Bøjesen, Espen Drath

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

  10. Multimodal emissions from Tb{sup 3+}/Yb{sup 3+} co-doped lithium borate glass: Upconversion, downshifting and quantum cutting

    Energy Technology Data Exchange (ETDEWEB)

    Bahadur, A.; Yadav, R.S.; Yadav, R.V.; Rai, S.B., E-mail: sbrai49@yahoo.co.in

    2017-02-15

    This paper reports the optical properties of Tb{sup 3+}/Yb{sup 3+} co-doped lithium borate (LB) glass prepared by melt quench method. The absorption spectrum of the Yb{sup 3+} doped LB glass contains intense NIR band centered at 976 nm due to {sup 2}F{sub 7/2}→{sup 2}F{sub 5/2} transition. The emission spectra of the prepared glasses have been monitored on excitation with 266, 355 and 976 nm. The Yb{sup 3+} doped glass emits a broad NIR band centered at 976 nm whereas the Tb{sup 3+} doped glass gives off visible bands on excitations with 266 and 355 nm. When the Tb{sup 3+} and Yb{sup 3+} ions are co-doped together, the emission intensity in the visible region decreases whereas it increases in the NIR region significantly. The increase in the emission intensity in the NIR region is due to efficient cooperative energy transfer (CET) from Tb{sup 3+} to Yb{sup 3+} ions. The quantum cutting efficiency for Tb{sup 3+}/Yb{sup 3+} co-doped glass has been calculated and compared for 266 and 355 nm excitations. The quantum cutting efficiency is larger for 355 nm excitation (137%). The Tb{sup 3+}/Yb{sup 3+} co-doped LB glass also emits upconverted visible bands on excitation with 976 nm. The mechanisms involved in the energy transfer have been discussed using schematic energy level diagram. The Tb{sup 3+}/Yb{sup 3+} co-doped LB glass may be used in the optical devices and in solar cell for solar spectral conversion and behaves as a multi-modal photo-luminescent material. - Graphical abstract: The Tb{sup 3+}/Yb{sup 3+} co-doped lithium borate (LB) glass prepared by melt quench method emits upconverted visible emissions through upconversion CET from Yb{sup 3+} to Tb{sup 3+} ions and quantum cutting emissions through downconversion CET from Tb{sup 3+} to Yb{sup 3+} ions. Therefore, the Tb{sup 3+}/Yb{sup 3+} co-doped LB glass may find applications in optical devices and solar cell and behaves as a multi-modal photo-luminescent material. - Highlights: • The Tb{sup 3+}/Yb{sup 3

  11. Facile Hydrothermal Approach to ZnO Nanorods at Mild Temperature

    Directory of Open Access Journals (Sweden)

    Yang Jiao

    2013-01-01

    Full Text Available In this work, ZnO nanorods are obtained through a facile hydrothermal route. The structure and morphology of the resultant products are characterized by X-ray diffraction (XRD and scanning electron microscope (SEM. The experimental results indicated that the as-synthesized ZnO nanorods have an average diameter of approximate 100 nm. A possible growth mechanism for ZnO nanorods was proposed based on the experimental results and found that Zn powder plays a critical role for the morphology of the products. Room temperature photoluminescence property of ZnO nanorods shows an ultraviolet emission peak at 390 nm.

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

    Energy Technology Data Exchange (ETDEWEB)

    Krishnakanth, Katturi Naga; Sunandana, C. S. [School of Physics, University of Hyderabad, Hyderabad-50046 (India); Rajesh, Desapogu, E-mail: rajesh.esapogu@gmail.com, E-mail: mperd@nus.edu.sg [School of Physics, University of Hyderabad, Hyderabad-50046 (India); Dept. of Mechanical Engineering, National University of Singapore (Singapore)

    2016-05-23

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

  13. Preparation and studies of Eu{sup 3+} and Tb{sup 3+} co-doped Gd{sub 2}O{sub 3} and Y{sub 2}O{sub 3} sol-gel scintillating films

    Energy Technology Data Exchange (ETDEWEB)

    Morales Ramirez, A. de J, E-mail: amoralesra@ipn.m [Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada (CICATA) Unidad Altamira Instituto Politecnico Nacional Km. 14.5 Carr. Tampico-Puerto Industrial, C.P. 89600, Altamira, Tamaulipas (Mexico); Depto. de Ingenieria Metalurgica, ESIQIE-Instituto Politecnico Nacional UPALM C.P. 07738, Mexico D.F. (Mexico); Garcia Murillo, A.; Carrillo Romo, F. de J [Depto. de Ingenieria Metalurgica, ESIQIE-Instituto Politecnico Nacional UPALM C.P. 07738, Mexico D.F. (Mexico); Ramirez Salgado, J. [Programa de Ingenieria Molecular, Instituto Mexicano del Petroleo, Eje Lazaro Cardenas No. 152, CP 07730, Mexico D.F. (Mexico); Le Luyer, C. [LPCML, CNRS-UMR 5620/Universite Claude Bernard Lyon 1/69622 Villeurbanne Cedex (France); Chadeyron, G.; Boyer, D. [Laboratoire des Materiaux Inorganiques, CNRS-UMR 6002, Universite Blaise Pascal, 24 Ave des Landais F 63177 Aubiere Cedex (France); Moreno Palmerin, J. [Depto. de Ingenieria Metalurgica, ESIQIE-Instituto Politecnico Nacional UPALM C.P. 07738, Mexico D.F. (Mexico)

    2009-10-30

    Eu{sup 3+} (2.5 at.%) and Tb{sup 3+} (0.005-0.01 at.%) co-doped gadolinium and yttrium oxide (Gd{sub 2}O{sub 3} and Y{sub 2}O{sub 3}) powders and films have been prepared using the sol-gel process. High density and optical quality thin films were prepared with the dip-coating technique. Gadolinium (III) 2,4-pentadionate and yttrium (III) 2,4-pentadionate were used as precursors, and europium and terbium in their nitrate forms were used as doping agents. Chemical and structural analyses (infrared spectroscopy, X-ray diffraction and high-resolution transmission electron microscopy) were conducted on both sol-gel precursor powders and dip-coated films. The morphology of thin films heat-treated at 700 {sup o}C was studied by means of atomic force microscopy. It was shown that the highly dense and very smooth films had a root mean roughness (RMS) of 2 nm {+-} 0.2 (A = 0.0075 Tb{sup 3+}) and 24 nm {+-} 3.0 (B = 0.01 Tb{sup 3+}). After treatment at 700 {sup o}C, the crystallized films were in the cubic phase and presented a polycrystalline structure made up of randomly oriented crystallites with grain sizes varying from 20 to 60 nm. The X-ray induced emission spectra of Eu{sup 3+}- and Tb{sup 3+}-doped Gd{sub 2}O{sub 3} and Y{sub 2}O{sub 3} powders showed that Tb{sup 3+} contents of 0.005, 0.0075 and 0.01 at.% affected their optical properties. Lower Tb{sup 3+} concentrations (down to 0.005 at.%) in both systems enhanced the light yield.

  14. Thermal barrier coating by electron beam-physical vapor deposition of zirconia co-doped with yttria and niobia

    Directory of Open Access Journals (Sweden)

    Daniel Soares de Almeida

    2010-08-01

    Full Text Available The most usual ceramic material for coating turbine blades is yttria doped zirconia. Addition of niobia, as a co-dopant in the Y2O3-ZrO2 system, can reduce the thermal conductivity and improve mechanical properties of the coating. The purpose of this work was to evaluate the influence of the addition of niobia on the microstructure and thermal properties of the ceramic coatings. SEM on coatings fractured cross-section shows a columnar structure and the results of XRD show only zirconia tetragonal phase in the ceramic coating for the chemical composition range studied. As the difference NbO2,5-YO1,5 mol percent increases, the tetragonality increases. A significant reduction of the thermal conductivity, measured by laser flash technique in the zirconia coating co-doped with yttria and niobia when compared with zirconia-yttria coating was observed.

  15. Pressure dependence of magneto-structural properties of Co-doped off-stoichiometric Ni2MnGa alloys

    Directory of Open Access Journals (Sweden)

    Arnold Z.

    2013-01-01

    Full Text Available A strong effect of pressure on magnetization and paramagnetic moment of the Co-doped Mn-rich Ni50-xCoxMn25+yGa25-y (x = 5,7,9 and y = 5,6,7,8 Heusler alloys is presented and compared with very weak pressure sensitivity of magnetization of the stoichiometric Ni2MnGa alloy. The effects of both, the pressure and the magnetic field, on temperature of the structural martensitic transition in the alloys are discussed with a use of the Clausius-Clapeyron relations. An analysis of pressure and field effects provides a possibility to evaluate structural and magnetic parts of latent heat of the martensitic transitions in the studied alloys. The Curie temperature of martensite phase of the Co-rich alloys is not affected by pressure.

  16. Thermoluminescence dosimetry properties and kinetic parameters of lithium potassium borate glass co-doped with titanium and magnesium oxides.

    Science.gov (United States)

    Hashim, S; Alajerami, Y S M; Ramli, A T; Ghoshal, S K; Saleh, M A; Abdul Kadir, A B; Saripan, M I; Alzimami, K; Bradley, D A; Mhareb, M H A

    2014-09-01

    Lithium potassium borate (LKB) glasses co-doped with TiO2 and MgO were prepared using the melt quenching technique. The glasses were cut into transparent chips and exposed to gamma rays of (60)Co to study their thermoluminescence (TL) properties. The TL glow curve of the Ti-doped material featured a single prominent peak at 230 °C. Additional incorporation of MgO as a co-activator enhanced the TL intensity threefold. LKB:Ti,Mg is a low-Z material (Z(eff)=8.89) with slow signal fading. Its radiation sensitivity is 12 times lower that the sensitivity of TLD-100. The dose response is linear at doses up to 10(3) Gy. The trap parameters, such as the kinetics order, activation energy, and frequency factor, which are related to the glow peak, were determined using TolAnal software. Copyright © 2014 Elsevier Ltd. All rights reserved.

  17. Study of electro-caloric effect in Ca and Sn co-doped BaTiO3 ceramics

    Science.gov (United States)

    Upadhyay, Sanjay Kumar; Fatima, Iram; Raghavendra Reddy, V.

    2017-04-01

    The present work deals with the study of structural, ferroelectric, dielectric and electro-caloric effects in lead free ferroelectric polycrystalline Ba1-x Ca x Ti0.95Sn0.05O3 (x  =  2, 5 and 10%) i.e. Ca, Sn co-doped BaTiO3 (BTO). Phase purity of the samples is confirmed from x-ray data by using Rietveld refinement. 119Sn Mössbauer reveals homogenous phase as well as iso-valent substitution of Sn at Ti site. Enhancements in ferroelectric and dielectric properties have been observed. Indirect method which is based on Maxwell equation has been used to determine the electro-caloric (EC) effect in the studied ferroelectric ceramics and maximum EC coefficient is observed for Ba0.95Ca0.05Ti0.95Sn0.05O3.

  18. Optical and Piezoelectric Study of KNN Solid Solutions Co-Doped with La-Mn and Eu-Fe

    Directory of Open Access Journals (Sweden)

    Jesús-Alejandro Peña-Jiménez

    2016-09-01

    Full Text Available The solid-state method was used to synthesize single phase potassium-sodium niobate (KNN co-doped with the La3+–Mn4+ and Eu3+–Fe3+ ion pairs. Structural determination of all studied solid solutions was accomplished by XRD and Rietveld refinement method. Electron paramagnetic resonance (EPR studies were performed to determine the oxidation state of paramagnetic centers. Optical spectroscopy measurements, excitation, emission and decay lifetime were carried out for each solid solution. The present study reveals that doping KNN with La3+–Mn4+ and Eu3+–Fe3+ at concentrations of 0.5 mol % and 1 mol %, respectively, improves the ferroelectric and piezoelectric behavior and induce the generation of optical properties in the material for potential applications.

  19. A quantum chemical analysis of Zn and Sb doping and co-doping in SnO2

    Directory of Open Access Journals (Sweden)

    Luis Villamagua

    2017-10-01

    Full Text Available This work presents a quantum chemical study of Zn and Sb doping and co-doping in SnO2 carried out by a DFT+U method. The analysis has been developed by introducing three different modifications in the otherwise pure SnO2 system. In the first place, an oxygen vacancy was introduced within the crystal. Following, such a system was doped (separately by Zn or Sb impurities. Finally, the best energetic positions for both Zn and Sb atoms were simultaneously introduced within the lattice. Results of the simulations show that the confined charge that appeared due to the introduction of the oxygen vacancy interacts with the dopants atoms, being this interaction mostly responsible of the observed effects, i.e., EG shrinkage, F-centers formations, and magnetic momentum rise.

  20. Electronic Structure on (001) Surface of Co-doped BaFe2As2 Studied with Scanning Tunneling Spectroscopy

    Science.gov (United States)

    Li, A.; Jayasundara, D. R.; Xuan, Y.; O'Neal, J. P.; Chen, Y.; Kim, W.; Ting, C. S.; Pan, S. H.; Jin, R.; Plummer, E. W.; Jin, R.; Sefat, A. S.; McGuire, M. A.; Sales, B. C.; Mandrus, D.

    2009-03-01

    Co-doping makes the pnictide compound BaFe2As2 superconducting. We cleave the single crystals of this compound in UHV and study their surfaces with a low temperature STM. In this talk, we present the scanning tunneling spectrums obtained on the (001) surface of the optimally doped BaFe2As2 single crystals (Tc = 23K) and compare these spectrums with the ones obtained on the surface of the parent compound. We have found that the major feature of the spectrums on the superconducting compounds is the opening of a superconducting gap of about 6 meV for the optimally doped one. We have also observed other detailed spectrum features. We will discuss the relation between spectrum features and the local environment and also present some theoretical fit to the superconducting energy gap spectrum.

  1. Structural and spectroscopic properties of Li+ co-doped MgAl2O4: Eu3+ nanophosphors

    Science.gov (United States)

    Faizan, Mohd.; Ahmad, Shabbir

    2016-05-01

    The red light emitting highly-luminescent Li+ co-doped magnesium aluminates (MgAl2O4: Eu3+) nanophosphors were synthesized by combustion synthesis method. The phosphors were characterized by XRD, FTIR, UV-visible and photoluminescence (PL) spectroscopy. The crystal structure and phase of the phosphors were investigated using XRD. The band gap of pure, Eu3+ doped and Li+ codoped MgAl2O4 phosphor were obtained from the DR spectra using the K-M function F(R∞). The photoluminescence spectra of MgAl2O4:Eu3+ and Li+ codoped MgAl2O4:Eu3+ phosphors were described by well known 5D0-7Fj transitions (J=0, 1, 2, 3, 4). The emission intensity of MgAl2O4:Eu3+ phosphor is enhanced with Li+ codoping.

  2. Optical and electrical properties of aluminum and boron co-doped zinc thin films as functions of the substrate temperature

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Hyun-il [Sungkyunkwan University, Suwon (Korea, Republic of); Lee, Kyu-il [Hyosung Corporation, Anyang (Korea, Republic of)

    2010-08-15

    Aluminum and boron co-doped zinc-oxide (AZOB) transparent conductive oxide (TCO) films were prepared by DC magnetron sputtering. We investigated the optical and the electrical properties of AZOB thin films as functions of the substrate temperature. A highly c-axis-oriented (002) plane was obtained in all AZOB thin films. The lowest electrical resistivity was 5.16 x 10{sup -4} {Omega}cm in AZOB thin films sputtered at 500 .deg. C. An average transmittance above 85% was obtained in AZOB thin films sputtered at substrate temperatures above 300 .deg. C. The optical absorption energy edge of the AZOB thin films sputtered at temperatures above 300 .deg. C showed a shift toward lower energy.

  3. Mid-infrared spectroscopic properties and energy transfer of Er3+/Yb3+ co-doped bismuth germanate glass.

    Science.gov (United States)

    Zhao, Guoying; Wang, Shikai; Fan, Huiyan; Hu, Lili

    2013-01-15

    An Er3+/Yb3+ co-doped bismuth germanate glass is synthesized and analyzed. The radiative characteristics and mid-infrared spectroscopic properties are investigated under excitation of a conventional 980 nm laser diode. The prepared glass possesses higher spontaneous transition probability (68.82 s(-1)) and larger calculated emission cross-section (7.73×10(-21) cm2) corresponding to the 4I11/2→4I13/2 transition. The calculated energy migration coefficient (CDD) among Yb3+ ions is larger than the energy transfer coefficient (CDA) from Yb3+ to Er3+, indicating the energy transfer process assisted with energy migration. The excellent spectroscopic properties along with the outstanding thermal stability suggest that this glass may become an attractive host for developing solid state lasers operating in the mid-infrared range. Crown Copyright © 2012. Published by Elsevier B.V. All rights reserved.

  4. Elaboration of translucent ZnO ceramics by spark plasma sintering under low temperature

    Science.gov (United States)

    Lin, Debao; Fan, Lingcong; Shi, Ying; Xie, Jianjun; Lei, Fang; Ren, Dudi

    2017-09-01

    ZnO is considered to be a potential ultrafast scintillator. In this work, nanosized ZnO powders were synthesized via thermal decomposition of precursors prepared by indirect-precipitation method from zinc nitrate and urea in aqueous solutions. The resultant single phased ZnO powder calcined at 600 °C for 2 h had a primary grain size of 66.0 nm with good dispersity showing excellent sinterability. Translucent ZnO ceramic with a relative density of 99.2% was fabricated successfully by spark plasma sintering at 850 °C for 10 min under the pressure of 80 MPa. The obtained ZnO ceramic exhibited fully dense and homogenous microstructure with average grain size of ∼1 μm, leading to an in-line optical transmission of 11.8% at a wavelength of 950 nm.

  5. The role of air annealing on the optical and scintillation properties of Mg co-doped Pr:LuAG transparent ceramics

    Czech Academy of Sciences Publication Activity Database

    Hu, Z.; Cao, M.; Chen, H.; Shi, Y.; Kou, H.; Xie, T.; Wu, L.; Pan, Y.; Feng, X.; Vedda, A.; Beitlerová, Alena; Nikl, Martin; Li, J.

    2017-01-01

    Roč. 72, Oct (2017), s. 201-207 ISSN 0925-3467 R&D Projects: GA ČR GA16-15569S Institutional support: RVO:68378271 Keywords : Mg co-doped Pr:LuAG * transparent ceramics * annealing effect * luminescence Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.238, year: 2016

  6. Biomass-Derived Oxygen and Nitrogen Co-Doped Porous Carbon with Hierarchical Architecture as Sulfur Hosts for High-Performance Lithium/Sulfur Batteries

    Directory of Open Access Journals (Sweden)

    Yan Zhao

    2017-11-01

    Full Text Available In this work, a facile strategy to synthesize oxygen and nitrogen co-doped porous carbon (ONPC is reported by one-step pyrolysis of waste coffee grounds. As-prepared ONPC possesses highly rich micro/mesopores as well as abundant oxygen and nitrogen co-doping, which is applied to sulfur hosts as lithium/sulfur batteries’ appropriate cathodes. In battery testing, the sulfur/oxygen and nitrogen co-doped porous carbon (S/ONPC composite materials reveal a high initial capacity of 1150 mAh·g−1 as well as a reversible capacity of 613 mAh·g−1 after the 100th cycle at 0.2 C. Furthermore, when current density increases to 1 C, a discharge capacity of 331 mAh·g−1 is still attainable. Due to the hierarchical porous framework and oxygen/nitrogen co-doping, the S/ONPC composite exhibits a high utilization of sulfur and good electrochemical performance via the immobilization of the polysulfides through strong chemical binding.

  7. Enhanced coercivity in Co-doped α-Fe2O3 cubic nanocrystal assemblies prepared via a magnetic field-assisted hydrothermal synthesis

    Directory of Open Access Journals (Sweden)

    Kinjal Gandha

    2017-05-01

    Full Text Available Ferromagnetic Co-doped α-Fe2O3 cubic shaped nanocrystal assemblies (NAs with a high coercivity of 5.5 kOe have been synthesized via a magnetic field (2 kOe assisted hydrothermal process. The X-ray diffraction pattern and Raman spectra of α-Fe2O3 and Co-doped α-Fe2O3 NAs confirms the formation of single-phase α-Fe2O3 with a rhombohedral crystal structure. Electron microscopy analysis depict that the Co-doped α-Fe2O3 NAs synthesized under the influence of the magnetic field are consist of aggregated nanocrystals (∼30 nm and of average assembly size 2 μm. In contrast to the NAs synthesized with no magnetic field, the average NAs size and coercivity of the Co-doped α-Fe2O3 NAs prepared with magnetic field is increased by 1 μm and 1.4 kOe, respectively. The enhanced coercivity could be related to the well-known spin–orbit coupling strength of Co2+ cations and the redistribution of the cations. The size increment indicates that the small ferromagnetic nanocrystals assemble into cubic NAs with increased size in the magnetic field that also lead to the enhanced coercivity.

  8. Enhanced coercivity in Co-doped α-Fe2O3 cubic nanocrystal assemblies prepared via a magnetic field-assisted hydrothermal synthesis

    Science.gov (United States)

    Gandha, Kinjal; Mohapatra, Jeotikanta; Poudyal, Narayan; Elkins, Kevin; Liu, J. Ping

    2017-05-01

    Ferromagnetic Co-doped α-Fe2O3 cubic shaped nanocrystal assemblies (NAs) with a high coercivity of 5.5 kOe have been synthesized via a magnetic field (2 kOe) assisted hydrothermal process. The X-ray diffraction pattern and Raman spectra of α-Fe2O3 and Co-doped α-Fe2O3 NAs confirms the formation of single-phase α-Fe2O3 with a rhombohedral crystal structure. Electron microscopy analysis depict that the Co-doped α-Fe2O3 NAs synthesized under the influence of the magnetic field are consist of aggregated nanocrystals (˜30 nm) and of average assembly size 2 μm. In contrast to the NAs synthesized with no magnetic field, the average NAs size and coercivity of the Co-doped α-Fe2O3 NAs prepared with magnetic field is increased by 1 μm and 1.4 kOe, respectively. The enhanced coercivity could be related to the well-known spin-orbit coupling strength of Co2+ cations and the redistribution of the cations. The size increment indicates that the small ferromagnetic nanocrystals assemble into cubic NAs with increased size in the magnetic field that also lead to the enhanced coercivity.

  9. Biomass-Derived Oxygen and Nitrogen Co-Doped Porous Carbon with Hierarchical Architecture as Sulfur Hosts for High-Performance Lithium/Sulfur Batteries.

    Science.gov (United States)

    Zhao, Yan; Wang, Li; Huang, Lanyan; Maximov, Maxim Yu; Jin, Mingliang; Zhang, Yongguang; Wang, Xin; Zhou, Guofu

    2017-11-21

    In this work, a facile strategy to synthesize oxygen and nitrogen co-doped porous carbon (ONPC) is reported by one-step pyrolysis of waste coffee grounds. As-prepared ONPC possesses highly rich micro/mesopores as well as abundant oxygen and nitrogen co-doping, which is applied to sulfur hosts as lithium/sulfur batteries' appropriate cathodes. In battery testing, the sulfur/oxygen and nitrogen co-doped porous carbon (S/ONPC) composite materials reveal a high initial capacity of 1150 mAh·g-1 as well as a reversible capacity of 613 mAh·g-1 after the 100th cycle at 0.2 C. Furthermore, when current density increases to 1 C, a discharge capacity of 331 mAh·g-1 is still attainable. Due to the hierarchical porous framework and oxygen/nitrogen co-doping, the S/ONPC composite exhibits a high utilization of sulfur and good electrochemical performance via the immobilization of the polysulfides through strong chemical binding.

  10. Enhanced photocatalytic degradation of dye under visible light on mesoporous microspheres by defects in manganese- and nitrogen-co-doped TiO2

    Science.gov (United States)

    Feng, Lu; Jiang, Heng; Zou, Mingming; Xiong, Fengqiang; Ganeshraja, Ayyakannu Sundaram; Pervaiz, Erum; Liu, Yinan; Zou, Shunying; Yang, Minghui

    2016-09-01

    Manganese- and nitrogen-co-doped mesoporous TiO2 microsphere photocatalysts are prepared by a simple sol-gel method with controllable sizes in the range of 400-500 nm and high surface area of 112 m2 g-1. Manganous acetate is the Mn source, and ammonia gas is the nitrogen source used. The dopants are found to be uniformly distributed in the TiO2 matrix. Interestingly, in (Mn,N)-co-doped TiO2, we observe an effective indirect band gap of 2.58 eV. (Mn,N)-co-doped mesoporous TiO2 microspheres show higher photocatalytic activity than Mn-TiO2 microspheres under visible light irradiation. Among the samples reported in this work, 0.2 at.% Mn doping and 500 °C 2-h nitriding condition give the highest photocatalytic activity. The observed photocatalytic activity in the (Mn,N)-co-doped TiO2 is attributed to the contribution from improved absorption due to trap levels of Mn, oxygen vacancies and N doping.

  11. Hydrothermal synthesis, characterization and enhanced visible-light photocatalytic activity of Co-doped Zn2SnO4 nanoparticles

    Science.gov (United States)

    Hu, Xiaofei; Hao, Hongshun; Guo, Weihua; Jin, Shanshan; Li, Hong; Hou, Hongman; Zhang, Gongliang; Yan, Shuang; Gao, Wenyuan; Liu, Guishan

    2017-06-01

    Various molar concentrations of Co-doped Zn2SnO4 nanoparticles were synthesized by hydrothermal method. The as-prepared samples were characterized by XRD, XPS, FESEM, TEM, UV-Vis and PL. The result of XPS revealed that the Co dopant displayed a chemical state of Co2+ in Zn2SnO4 lattice. UV-Vis results revealed that the absorption edge of samples shifted towards visible light region gradually with the increase of Co doping content. The PL intensity weakened significantly for the Co-doped Zn2SnO4, which indicates that the recombination of photo-generated electrons and holes was suppressed strongly. The photocatalytic activity of Zn2SnO4 was observed by photodegradation of RhB under visible light irradiation. The influences of Co doping content on photocatalytic activity of Zn2SnO4 were investigated. The experiment results indicated that the maximum degradation rate of RhB was 93% in 120 min when Co2+ molar concentration was 2 mol%. Furthermore, a possible mechanism of photocatalytic degradation of RhB was discussed.

  12. Luminescent properties and quenching effects of Pr3+ co-doping in SiO2:Tb3+/Eu3+ nanophosphors

    CSIR Research Space (South Africa)

    Mhlongo, GH

    2014-02-01

    Full Text Available Luminescence properties of Pr(sup3+) single doped SiO2 and Pr(sup3+) co-doped SiO(sub2):Tb(sup3+)/Eu(sup3+) nanophosphors synthesized using sol–gel method were investigated. X-ray diffraction (XRD), and scanning electron microscope (SEM) were used...

  13. Hydrothermal fabrication of multi-functional Eu3+ and Tb3+ co-doped BiPO4: Photocatalytic activity and tunable luminescence properties

    Science.gov (United States)

    Wang, Yao; Huang, Hongwei; Quan, Chaoming; Tian, Na; Zhang, Yihe

    2016-01-01

    We demonstrated for first time the tunable photoluminescence (PL) properties and photocatalytic activity of the Tb3+ and Eu3+ co-doped BiPO4 assemblies. They are fabricated via a facile hydrothermal approach. Through co-doping of Eu3+ and Tb3+ ions and changing the doping ratio, the emission color of the co-doped BiPO4 phosphors can be tuned precisely from green to yellow and red. Meanwhile, a very efficient energy transfer from Tb3+ to Eu3+ can be observed. Fascinatingly, a warmwhite color has been realized in the co-doped sample by tuning the ratio of Tb3+/Eu3+ to a certain value as displayed in the CIE chromaticity diagram. The doped BiPO4 samples also exhibit significantly enhanced photocatalytic activity compared to the pristine BiPO4 pertaining to Rhodamine (RhB) degradation under UV light. This enhancement should be attributed to the trapping electron effect induced by ion doping that endows BiPO4 with high separation of photoinduced electron-hole pairs, thereby greatly promoting the photocatalytic reactivity. It was corroborated by the electrochemical impedance spectra (EIS). Moreover, the crystal structure, microstructure and optical properties of as-prepared samples were investigated in details.

  14. Defects induced in Yb3+/Ce3+ co-doped aluminosilicate fiber glass preforms under UV and γ-ray irradiation

    DEFF Research Database (Denmark)

    Chiesa, Mario; Mattsson, Kent Erik; Taccheo, Stefano

    2014-01-01

    A set of Ce-/Yb-co-doped silica optical fiber preform cores, differing in terms of dopant concentrations are studied by Electron Paramagnetic Resonance (EPR) spectroscopy before and after irradiation of the samples with excimer UV laser light and γ-rays. Evidence of Yb3+ clustering in the case...

  15. Computational investigation of the co-doping effect of sulphur and nitrogen on the electronics of CsTaWO6

    Directory of Open Access Journals (Sweden)

    Liuxie Liu

    2017-03-01

    Full Text Available CsTaWO6 is a typical AMWO6-type compound and the photocatalysis of the pure and doped phases has been extensively studied experimentally. In this work, the electronic structures of sulphur (S and nitrogen (N co-doped CsTaWO6 have been studied in the framework of density functional theory, in particular the S/N co-doping effect has been investigated. It is found that, (i S/N co-dopants prefer to be separated; (ii middle-gap states are introduced by N and S-dopant at the edges of valence band and conduction band; and (iii Co-doping not only narrows the band gap, but also promotes the separation of photo-excited electrons and holes. Feature (iii has been identified as a key reason why S/N co-doped CsTaWO6 is more efficient in photocatalytic water-splitting. A general doping strategy has been further suggested: co-dopants which can dominate the frontier states and favour to be separated can offer excellent photocatalysis performance.

  16. The enhanced and broadband near-infrared emission in Pr3+/Nd3+ co-doped tellurite glass

    Science.gov (United States)

    Zhou, Zizhong; Zhou, Yaxun; Cheng, Pan; Zhou, Minghan; Su, Xiue; Li, Jun

    2017-11-01

    This paper reports an enhanced and broadband near-infrared fluorescence emission in the Pr3+/Nd3+ co-doped tellurite glass, which was prepared using melt-quenching technique. Under the excitation of 488 nm laser diode (LD), three near-infrared emission bands at around 0.9, 1.04 and 1.30 μm from 3P1,0 → 1G4, 1G4→3H4 and 1G4→3H5 radiative transitions respectively were observed in the Pr3+ single-doped glass, and the fluorescence intensities increased further with the introduction of Nd3+ ions, which is mainly attributed to the energy transfers from Nd3+ to Pr3+ emissions. Meanwhile, the spectral overlapping of Pr3+:1G4→3H4 and Nd3+:4F3/2 → 4I11/2 radiative transitions resulted in a broadband emission ranging from 1000 to 1100 nm, whose full-width at half-maximum (FWHM) reached about 66 nm. Additionally, the spectroscopic properties of Nd3+ and Pr3+ ions were analyzed using Judd-Ofelt theory and the thermal stability property of prepared glass was characterized by the differential scanning calorimeter (DSC) measurement, and larger than 134 °C for the difference ΔT(=Tx -Tg) was observed, which indicates its feasibility for later fiber drawing. The enhanced fluorescence and broadband emission indicate that Pr3+/Nd3+ co-doped tellurite glass can be applied in the near-infrared band tunable lasers and broadband optical amplifiers.

  17. Visible light-responded C, N and S co-doped anatase TiO{sub 2} for photocatalytic reduction of Cr(VI)

    Energy Technology Data Exchange (ETDEWEB)

    Lei, X.F., E-mail: leixuefei69@163.com [School of Resources and Materials, Northeastern University at Qinhuangdao, Qinhuangdao 066004 (China); Institute of Metallurgical Resource and Environmental Engineering, Northeastern University, Shenyang 110819 (China); Liaoning Key Laboratory of Metallurgical Resource Recycling Science, Shenyang 110819 (China); Liaoning Engineering and Technology Research Center of Boron Resource, Comprehensive, Utilization, Shenyang 110819 (China); Liaoning Provincial Universities Key Laboratory of Boron Resource Ecological, Utilization, Technology and Boron Materials, Shenyang 110819 (China); Xue, X.X.; Yang, H. [Institute of Metallurgical Resource and Environmental Engineering, Northeastern University, Shenyang 110819 (China); Liaoning Key Laboratory of Metallurgical Resource Recycling Science, Shenyang 110819 (China); Liaoning Engineering and Technology Research Center of Boron Resource, Comprehensive, Utilization, Shenyang 110819 (China); Liaoning Provincial Universities Key Laboratory of Boron Resource Ecological, Utilization, Technology and Boron Materials, Shenyang 110819 (China); Chen, C.; Li, X.; Pei, J.X.; Niu, M.C.; Yang, Y.T.; Gao, X.Y. [School of Resources and Materials, Northeastern University at Qinhuangdao, Qinhuangdao 066004 (China)

    2015-10-15

    The (C, N and S) co-doped TiO{sub 2} (TH-TiO{sub 2}) samples were synthesized by a sol-gel method calcined at 500 °C, employing butyl titanate as the titanium source and thiourea as the dopant. The structures of TH-TiO{sub 2} samples were characterized by X-ray diffraction (XRD), Transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectra (DRS), photoluminescence (PL) spectroscopy, Thermo gravimetry and differential thermal analysis (TG-DTA), Scanning electron microscopy (SEM) and nitrogen adsorption–desorption isotherms. The photocatalytic activities were checked through the photocatalytic reduction of Cr(VI) as a model compound under visible light irradiation. The results showed that the thiourea content played an important role on the microstructure and photocatalytic activity of the samples. According to XPS results, (C, N and S) atoms were successfully co-doped into the nanostructures of TH-TiO{sub 2} samples. TH-TiO{sub 2} samples with thiourea: Ti molar ratio of 1.5 exhibits higher photocatalytic activity than that of the other samples under visible light irradiation, which can be attributed to the synergic effect of the pure anatase structure, the higher light absorption characteristics in visible regions, separation efficiency of electron–hole pairs, the specific surface area and the optimum (C, N and S) content. - Graphical abstract: (C, N and S) co-doped TiO{sub 2} samples show good photocatalytic activity for Cr (VI) reduction under visible light irradiation. - Highlights: • (C, N and S) co-doping in TH-TiO{sub 2} samples can promote the formation of the pure anatase structure. • (C, N and S) atoms were successfully co-doped into the nanostructures of TH-TiO{sub 2} samples. • The band gap energy of TH-TiO{sub 2} samples reduced after (C, N and S) co-doping. • (C, N and S) co-doped TiO{sub 2} samples were effective for the photocatalytic reduction of Cr(VI) under visible light

  18. Trapping of cubic ZnO nanocrystallites at ambient conditions

    DEFF Research Database (Denmark)

    Decremps, F.; Pellicer-Porres, J.; Datchi, F.

    2002-01-01

    Dense powder of nanocrystalline ZnO has been recovered at ambient conditions in the metastable cubic structure after a heat treatment at high pressure (15 GPa and 550 K). Combined x-ray diffraction (XRD) and x-ray absorption spectroscopy (XAS) experiments have been performed to probe both long...

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

    Indian Academy of Sciences (India)

    2017-05-13

    May 13, 2017 ... dry at room temperature, and then stored in a desiccator for further use. 2.3 Heat treatment. Pre-weighed powder sample of the selected batch of the ... Figure 1. SEM images of the ZnO particles obtained by heating reactant solutions of different pH values, containing ..... [5] Prasad A S 1995 Nutrition 11 39.

  20. Microstructure and mechanical properties of Ti/Al co-doped DLC films: Dependence on sputtering current, source gas, and substrate bias

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Ting [Key Laboratory of Marine Materials and Related Technologies, Zhejiang Key Laboratory of Marine Materials and Protective Technologies, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); School of Materials Science and Engineering, Shanghai University, Shanghai 200444 (China); Kong, Cuicui [Key Laboratory of Marine Materials and Related Technologies, Zhejiang Key Laboratory of Marine Materials and Protective Technologies, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Ningbo University, Ningbo 315201 (China); Li, Xiaowei, E-mail: lixw@nimte.ac.cn [Key Laboratory of Marine Materials and Related Technologies, Zhejiang Key Laboratory of Marine Materials and Protective Technologies, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Guo, Peng; Wang, Zhenyu [Key Laboratory of Marine Materials and Related Technologies, Zhejiang Key Laboratory of Marine Materials and Protective Technologies, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Wang, Aiying, E-mail: aywang@nimte.ac.cn [Key Laboratory of Marine Materials and Related Technologies, Zhejiang Key Laboratory of Marine Materials and Protective Technologies, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China)

    2017-07-15

    Highlights: • Ti/Al co-doped diamond-like carbon films were fabricated by a hybrid ion beam method. • Process parameters affected the structure and chemical state of co-doped Ti and Al. • The relation between microstructure and properties was investigated systematically. • The guidance to tailor the Ti/Al-DLC films with high performance was provided. - Abstract: Co-doping two metal elements into diamond-like carbon (DLC) films can reach the desirable combined properties, but the preparation and commercialized application of metal co-doped DLC films with well-defined structural properties are currently hindered by the non-comprehensive understanding of structural evolutions under different process parameters. Here, we fabricated the Ti/Al-DLC films using a unique hybrid ion beam system which enabled the independent control of metal content and carbon structure. The evolutions of microstructure, residual compressive stress and mechanical properties induced by the different process parameters including sputtering currents, C{sub 2}H{sub 2} or CH{sub 4} source gases and bias voltages were investigated systematically in order to perform in-depth analysis on the relation between the structure and properties in Ti/Al-DLC films. Results revealed that the variations of process parameters seriously affected the concentration and chemical bond state of co-doped Ti/Al atoms in amorphous carbon matrix or incident energies of C ions, which brought the complicated effect on amorphous carbon structures, accounting for the change of residual compressive stress, hardness and toughness. The present results provide the guidance for suitable, effective parameters selection to tailor the Ti/Al-DLC films with high performance for further applications.

  1. Study of hyperfine parameters in Co-doped tin dioxide using PAC spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ramos, Juliana M.; Carbonari, Artur W.; Martucci, Thiago; Costa, Messias S.; Saxena, Rajendra N. [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Vianden, R.; Kessler, P.; Geruschke, T.; Steffens, M., E-mail: vianden@hiskp.uni-bonn.d [Rheinische Friedrich-Wilhelms-Universitaet Bonn (HISKP- Bonn) (Germany). Helmholtz - Institut fuer Strahlen- und Kernphysik

    2011-07-01

    PAC technique has been used to measure the hyperfine interactions in nano-structured powder samples of semiconducting SnO{sub 2} doped with Co. The aim of this work is to compare the results of PAC measurements using two different techniques of introducing the radioactive {sup 111}In probe nuclei in the sample of SnO{sub 2} doped with Co. The perturbed gamma-gamma angular correlation (PAC) spectroscopy is used for the measurements of the magnetic hyperfine field (MHF) and the electric field gradient (EFG) at {sup 111}Cd sites in SnO{sub 2} doped with 1% and 2% Co. The measurement of EFG is used to study the defects introduced in the semiconductor material and also for the identification of different phases formed within the compound. The techniques utilized for introducing the radioactive {sup 111}In in the sample are the ion-implantation using radioactive ion beam of {sup 111}In and the chemical process in which {sup 111}InCl{sub 3} solution is added during the preparation of SnO{sub 2} doped with Co using sol gel method. The ion-implantation of {sup 111}In in SnO{sub 2} doped with Co was carried out using the University of Bonn ion-implanter with beam energy of 160 keV. The PAC measurements were carried out with four BaF{sub 2} detector gamma spectrometer in the temperature range of 10-295 K. The results show no significant difference in the values of hyperfine parameters. Both techniques show practically the same electric quadrupole interaction for the substitutional site. The results were compared with previous PAC and Moessbauer measurements of SnO{sub 2} powder samples using {sup 111}In-{sup 111}Cd probe. (author)

  2. Preparation of nanometer sized Mn doped Zn based oxides powder for DMS applications

    CSIR Research Space (South Africa)

    Das, J

    2009-01-01

    Full Text Available In order to study the size dependent DMS (Diluted Magnetic Semiconductor) behavior of Mn doped ZnO, the authors have systematically prepared a series of nanosized green powder based on Mn doped ZnO (Zn 1-x Mn x O, where x=0.02 - 0.1) materials using...

  3. Synergistic effects of Mo and F doping on the quality factor of ZnO thin films prepared by a fully automated home-made nebulizer spray technique

    Science.gov (United States)

    Ravichandran, K.; Dineshbabu, N.; Arun, T.; Manivasaham, A.; Sindhuja, E.

    2017-01-01

    Transparent conducting oxide films of undoped, Mo doped, Mo + F co-doped ZnO were deposited using a facile homemade nebulizer spray pyrolysis technique. The effects of Mo and F doping on the structural, optical, electrical and surface morphological properties were investigated using XRD, UV-vis-NIR spectroscopy, I-V and Hall probe techniques, FESEM and AFM, and XPS, respectively. The XRD analysis confirms that all the films are well crystallized with hexagonal wurtzite structure. All the synthesized samples exhibit high transmittance (above 85%) in the visible region. The current-voltage (I-V) characteristics show the ohmic conduction nature of the films. The Hall probe measurements show that the synergistic effects of Mo and F doping cause desirable improvements in the quality factor of the ZnO films. A minimum resistivity of 5.12 × 10-3 Ω cm with remarkably higher values of mobility and carrier concentration is achieved for Mo (2 at.%) + F (15 at.%) co-doped ZnO films. A considerable variation in the intensity of deep level emission caused by Mo and F doping is observed in the photoluminescence (PL) studies. The presence of the constituent elements in the samples is confirmed by XPS analysis.

  4. Structural interpretation of chemically synthesized ZnO nanorod and its application in lithium ion battery

    Energy Technology Data Exchange (ETDEWEB)

    Kundu, Samapti; Sain, Sumanta [Materials Science Division, Department of Physics, The University of Burdwan, Golapbag, Burdwan 713104, West Bengal (India); Yoshio, Masaki [Advanced Research and Education Centre, Saga University, 1341 Yoga-machi, Saga 840-0047 (Japan); Kar, Tanusree [Department of Materials Science, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, West Bengal (India); Gunawardhana, Nanda, E-mail: nandagunawardhana@pdn.ac.lk [International Research Centre, Senate Building, University of Peradeniya, Peradeniya 20400 (Sri Lanka); Pradhan, Swapan Kumar, E-mail: skpradhan@phys.buruniv.ac.in [Materials Science Division, Department of Physics, The University of Burdwan, Golapbag, Burdwan 713104, West Bengal (India)

    2015-02-28

    Graphical abstract: - Highlights: • ZnO nanorods are synthesized at room temperature via a simple chemical route. • Growth direction of ZnO nanorods has been determined along 〈0 0 2〉. • ZnO nanorods constructed anode shows a high discharge capacity in first cycle. • It retains good reversible capacity compared to other ZnO morphologies. - Abstract: ZnO nanorods are synthesized at room temperature via a simple chemical route without using any template or capping agent and its importance is evaluated as a suitable candidate for anode material in lithium ion battery. Structural and microstructure characterizations of these nanorods are made by analyzing the X-ray diffraction data employing the Rietveld method of powder structure refinement. It reveals that the ZnO nanorods are grown up with a preferred orientation and elongated along 〈0 0 2〉. FESEM images reveal that these uniform cylindrical shaped nanorods are of different lengths and diameters. These synthesized ZnO nanorods are tested as an anode material for lithium ion batteries. The nano grain size of the ZnO rods results in less volume expansion and/or contraction during the alloying/de-alloying process and causes in good cyclability. In addition, synthesized ZnO nanorods deliver high charge/discharge capacities compared to other reported ZnO materials.

  5. High-Throughput Continuous Hydrothermal Synthesis of Transparent Conducting Aluminum and Gallium Co-doped Zinc Oxides.

    Science.gov (United States)

    Howard, Dougal P; Marchand, Peter; McCafferty, Liam; Carmalt, Claire J; Parkin, Ivan P; Darr, Jawwad A

    2017-04-10

    High-throughput continuous hydrothermal flow synthesis was used to generate a library of aluminum and gallium-codoped zinc oxide nanoparticles of specific atomic ratios. Resistivities of the materials were determined by Hall Effect measurements on heat-treated pressed discs and the results collated into a conductivity-composition map. Optimal resistivities of ∼9 × 10-3 Ω cm were reproducibly achieved for several samples, for example, codoped ZnO with 2 at% Ga and 1 at% Al. The optimum sample on balance of performance and cost was deemed to be ZnO codoped with 3 at% Al and 1 at% Ga.

  6. Effects of rare-earth co-doping on the local structure of rare-earth phosphate glasses using high and low energy X-ray diffraction.

    Science.gov (United States)

    Cramer, Alisha J; Cole, Jacqueline M; FitzGerald, Vicky; Honkimaki, Veijo; Roberts, Mark A; Brennan, Tessa; Martin, Richard A; Saunders, George A; Newport, Robert J

    2013-06-14

    Rare-earth co-doping in inorganic materials has a long-held tradition of facilitating highly desirable optoelectronic properties for their application to the laser industry. This study concentrates specifically on rare-earth phosphate glasses, (R2O3)x(R'2O3)y(P2O5)(1-(x+y)), where (R, R') denotes (Ce, Er) or (La, Nd) co-doping and the total rare-earth composition corresponds to a range between metaphosphate, RP3O9, and ultraphosphate, RP5O14. Thereupon, the effects of rare-earth co-doping on the local structure are assessed at the atomic level. Pair-distribution function analysis of high-energy X-ray diffraction data (Q(max) = 28 Å(-1)) is employed to make this assessment. Results reveal a stark structural invariance to rare-earth co-doping which bears testament to the open-framework and rigid nature of these glasses. A range of desirable attributes of these glasses unfold from this finding; in particular, a structural simplicity that will enable facile molecular engineering of rare-earth phosphate glasses with 'dial-up' lasing properties. When considered together with other factors, this finding also demonstrates additional prospects for these co-doped rare-earth phosphate glasses in nuclear waste storage applications. This study also reveals, for the first time, the ability to distinguish between P-O and P[double bond, length as m-dash]O bonding in these rare-earth phosphate glasses from X-ray diffraction data in a fully quantitative manner. Complementary analysis of high-energy X-ray diffraction data on single rare-earth phosphate glasses of similar rare-earth composition to the co-doped materials is also presented in this context. In a technical sense, all high-energy X-ray diffraction data on these glasses are compared with analogous low-energy diffraction data; their salient differences reveal distinct advantages of high-energy X-ray diffraction data for the study of amorphous materials.

  7. Near-infrared quantum cutting in Ho{sup 3+}/Yb{sup 3+} co-doped BaZr{sub 0.8}Y{sub 0.2}O{sub 3-δ}

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Tiejin; Yang, Xiaoliang, E-mail: xiaoliangy@xtu.edu.cn; Xia, Wenbin; Gao, Xuejun; Li, Wei; Xiao, Siguo

    2016-09-15

    Highlights: • Ho{sup 3+}/Yb{sup 3+} co-doped BaZr{sub 0.8}Y{sub 0.2}O{sub 3-δ} quantum cutting phosphor is prepared with co-precipitation method. • Ho{sup 3+}/Yb{sup 3+} co-doped BaZr{sub 0.8}Y{sub 0.2}O{sub 3-δ} powder gives strong and pure emission of Ho{sup 3+} in the near infrared region. • Efficient Ho{sup 3+} → Yb{sup 3+}→ Ho{sup 3+} multi-step energy transfer is responsible for the novel quantum cutting properties. • A new method based on luminescence intensity ratio is developed to estimate the quantum cutting efficiency. - Abstract: A novel Ho{sup 3+} → Yb{sup 3+} → Ho{sup 3+} multi-step energy transfer caused quantum cutting under 455 nm excitation is observed in Ho{sup 3+}/Yb{sup 3+} co-doped BaZr{sub 0.8}Y{sub 0.2}O{sub 3-δ} phosphor. During the quantum cutting process, Yb{sup 3+} ions efficiently increase the particle population of {sup 5}I{sub 6} level of H{sub O}{sup 3+}, resulting in 10 and 8 times of enhancement of Ho{sup 3+} emission at 1216 nm ({sup 5}I{sub 6} → {sup 5}I{sub 8}) and 1926 nm ({sup 5}I{sub 7} → {sup 5}I{sub 8}), respectively. It is interesting that the {sup 2}F{sub 5/2} → {sup 2}F{sub 7/2} emission of Yb{sup 3+} ions themselves is very weak although the quantum cutting is performed by the Ho{sup 3+}/Yb{sup 3+} ion-pairs. The result indicates that the Yb{sup 3+} → Ho{sup 3+} back energy transfer in the BaZr{sub 0.8}Y{sub 0.2}O{sub 3-δ} phosphor is quite efficient and helpful for the enhancement of Ho{sup 3+} emission in near infrared region. A new valid method based on luminescence intensity ratio is developed to estimate the quantum cutting efficiency. It is found that the energy transfer form Ho{sup 3+} to Yb{sup 3+} is 52.8% in the phosphor with optimum Ho{sup 3+}/Yb{sup 3+} doping concentration and 90% of near infrared emission of Ho{sup 3+} is performed by the multi-step energy transfer induced quantum cutting.

  8. Spectroscopic properties of tellurite glasses co-doped with Er{sup 3+} and Yb{sup 3+}

    Energy Technology Data Exchange (ETDEWEB)

    Leal, J.J. [Instituto Politécnico Nacional CICATA-Unidad Altamira, Tamaulipas 89600 (Mexico); Narro-García, R., E-mail: roberto.narro@gmail.com [Centro de Física Aplicada y Tecnología Avanzada, Universidad Nacional Autónoma de México, A.P. 1-1010, Querétaro 76000, Querétaro México (Mexico); Desirena, H. [Centro de Investigaciones en Óptica, A.P. 1-948, León, Gto. 37150 (Mexico); Marconi, J.D. [Universidade Federal do ABC, SP (Brazil); Rodríguez, E. [Instituto Politécnico Nacional CICATA-Unidad Altamira, Tamaulipas 89600 (Mexico); Linganna, K. [Department of Physics, Sri Venkateswara University, Tirupati 517502 (India); De la Rosa, E. [Centro de Investigaciones en Óptica, A.P. 1-948, León, Gto. 37150 (Mexico)

    2015-06-15

    Spectroscopic characterization of Er{sup 3+}/Yb{sup 3+} co-doped tellurite glasses 70.8TeO{sub 2}–5Al{sub 2}O{sub 3}–13K{sub 2}O–(11−x)–BaO–0.2Er{sub 2}O{sub 3}–xYb{sub 2}O{sub 3}, where x=0, 0.4, 0.8, 1.2 and 2 mol% has been carried out through X-ray diffraction, Raman, absorption and luminescence spectra. The Judd–Ofelt intensity parameters were calculated for 0.2 mol% Er{sup 3+}-doped glass and are used to evaluate radiative properties such as transition probabilities, branching ratios and radiative lifetime. The emission cross-section of the {sup 4}I{sub 13/2}→{sup 4}I{sub 15/2} transition has been calculated from the absorption data using McCumber's theory. The emission intensity of both, visible and infrared signals as a function of Yb{sub 2}O{sub 3}, have been studied under 980 nm and 375 nm laser excitation. The physical mechanisms responsible for both, visible and infrared signals in the tellurite samples have been explained in terms of the energy transfer and excited state absorption process. The FWHM of the {sup 4}I{sub 13/2}→{sup 4}I{sub 15/2} transition as a function of Yb{sub 2}O{sub 3} mol% and distance (δ) between the laser focusing point and the end-face of the glass has been reported. It was observed both, experimentally and numerically, a change in the FWHM with variations of δ less than 8 mm. The latter was attributed to the radiation trapping effect. - Highlights: • Er{sup 3+}/Yb{sup 3+} co-doped tellurite glasses were fabricated by the melt-quenching technique. • The structural, thermal and optical properties of the tellurite glasses were studied. • The radiation trapping effect has been observed in small tellurite glass samples. • Tellurite glasses could be a potential material for fiber fabrication.

  9. Highly luminescent N, S- Co-doped carbon dots and their direct use as mercury(II) sensor

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yu [Key Lab of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China); Department of Advanced Organic Materials Science and Engineering, Kyungpook National University, Daegu, 702-701 (Korea, Republic of); Kim, Sung-Hoon, E-mail: shokim@knu.ac.kr [Department of Advanced Organic Materials Science and Engineering, Kyungpook National University, Daegu, 702-701 (Korea, Republic of); Feng, Liang, E-mail: fengl@dicp.ac.cn [Key Lab of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China)

    2015-08-26

    Heteroatom doping has been proven as an efficient way to improve the fluorescent efficiency of carbon dots. Co-doping with heteroatoms may introduce more active sites to carbon dots, which would broaden applications of CDs in sensing. In this work, highly luminescent nitrogen and sulfur co-doped carbon dots (NSCDs) were synthesized through a facile one-step microwave assisted method by using citric acid and rubeanic acid as carbon, nitrogen, and sulfur sources. The well-isolated NSCDs not only exhibit an enhanced fluorescent efficiency with a relatively high quantum yield up to 17.6%, but also show potential use as a multi-sensing platform based on their fluorescence “on-off-on” and color changing behaviors. The NSCDs can be directly used for the selective determination of mercury cations without any functionalization. The detection limit is approximately calculated as 0.18 μM and linear range is 0–20 μM. The sensing mechanism is proposed as coordination reaction induced by oligomers upon the carbon core. Furthermore, in the presence of cyanide anions, the fluorescence shows linear recovery associated with the concentration of cyanide, indicating its potential usage for the detection of cyanide ion. The optimized pH range for such fluorescence “on-off-on” sensing system is investigated as pH 6–8, suggesting potential applications in bio-sensing and imaging area. In addition, by adding hydrosulfide anion to NSCDs@Hg{sup 2+} complex, a notable color change could be clearly observed due to the formation of fuscous HgS. In application, a handy test paper for direct and rapid detection of Hg{sup 2+} is manufactured for the evaluation of usage of NSCDs in the real circumstance. - Highlights: • NSCDs were synthesized by using citric acid and rubeanic acid. • NSCDs exhibited an enhanced fluorescent efficiency with high QY up to 17.6%. • NSCDs presented good sensing performance to mercury ions. • NSCDs showed potential use as a multi-sensing platform.

  10. The effect of Bi{sup 3+} and Li{sup +} co-doping on the luminescence characteristics of Eu{sup 3+}-doped aluminum oxide films

    Energy Technology Data Exchange (ETDEWEB)

    Padilla-Rosales, I., E-mail: ipadilla@cinvestav.mx [Centro de Investigación y de Estudios Avanzados del IPN, Nanociencias y Nanotecnología, Av. IPN 2508, Col. San Pedro Zacatenco, CP 07360 México D.F. (Mexico); Martinez-Martinez, R. [Instituto de Física y Matemáticas, Universidad Tecnológica de la Mixteca, Carretera a Acatlima Km. 2.5, CP 69000 Huajuapan de León, Oax, México (Mexico); Cabañas, G. [Centro de Investigación y de Estudios Avanzados del IPN, Nanociencias y Nanotecnología, Av. IPN 2508, Col. San Pedro Zacatenco, CP 07360 México D.F. (Mexico); Falcony, C. [Centro de Investigación y de Estudios Avanzados del IPN, Departamento de Física, Av. IPN 2508, Col. San Pedro Zacatenco, CP 07360 México D.F. (Mexico)

    2015-09-15

    The incorporation of Bi{sup 3+} and Li{sup +} as co-dopants in Eu{sup 3+}-doped aluminum oxide films deposited by the ultrasonic spray pyrolysis technique and its effect on the luminescence characteristics of this material are described. Both Bi{sup 3+} and Li{sup +} do not introduce new luminescence features but affect the luminescence intensity of the Eu{sup 3+} related emission spectra as well as the excitation spectra. The introduction of Bi{sup 3+} generates localized states in the aluminum oxide host that result in a quenching of the luminescence intensity, while Li{sup +} and Bi{sup 3+} co-doping increase the luminescence intensity of these films. - Highlights: • Li and Bi co-doping increase the luminescence. • Bi creates localized states in the Al{sub 2}O{sub 3} host. • Li was incorporated as a co-activator.

  11. Energy response and thermoluminescence properties of lithium potassium borate Glass co-doped with Cu and SnO2 nanoparticles

    Directory of Open Access Journals (Sweden)

    Haydar Aboud

    2017-01-01

    Full Text Available SnO2 nanoparticles doped lithium potassium borate with Cu-doped was prepared by melt-quenching technique. The field emission scanning electron microscope was used to examine morphology of samples. The TLD-Reader 4500 was used to measurement of thermoluminescence. The glow curves position of Cu-doped and co-doped SnO2 glass were recorded at about 205 °C and 215 °C respectively. The linear relationship of dose-TL intensity was observed for both samples. The TLD sensitivity shows that the co-doped SnO2 glass has almost 6 time higher sensitivity compared to Cu-doped glass. It was found that the theoretical calculations are in good agreement with the experimental results for relative energy response. The activation energy and frequency factor of TL glow peak are determined by using the peak shape method.

  12. Characterization, Degradation, and Reaction Pathways of Indoor Toluene over Visible-light-driven S, Zn Co-doped TiO2

    Science.gov (United States)

    Chu, H.; Lin, Y. H.; Lin, C. Y.

    2017-01-01

    Sulfur and Zinc co-doped TiO2 prepared by a sol-gel method to degrade toluene under a fluorescent lamp was investigated. The results indicate that S,Zn co-doped TiO2 photocatalysts are mainly nano-size with an anatase phase structure. The degradation reactions of toluene were performed under various operation conditions. The results show that the toluene conversion increases with increasing toluene concentration and decreasing relative humidity. Based on the results of activity test, S0.05Zn0.001/TiO2 was chosen for further studies. The main oxidation products of toluene photodegradation are CO2, H2O, benzyl alcohol, acetone, butadiene and acetic acid. Two possible mechanisms have been developed for photodegradation of toluene in a dry and a humid environment.

  13. Enhanced 1.8 µm emission in Cr3+/Tm3+ co-doped fluorogermanate glasses for a multi-wavelength pumped near-infrared lasers

    Directory of Open Access Journals (Sweden)

    W. C. Wang

    2014-10-01

    Full Text Available Cr3+/Tm3+ co-doped fluorogermanate glasses were prepared by melt-quenching technique, and their luminescent properties were investigated under excitation of Xenon lamp and 808 nm laser diode, respectively. Through strong sensitization of Cr3+, an enhanced 1.8 µm emission band of Tm3+: 3F4→3H6 can be achieved in an extremely extended excitation band of 380-900 nm. The possible energy transfer mechanism between Cr3+ and Tm3+ is rationally discussed. On the basis of experimental data, the highest energy transfer efficiency is up to 91.70%. Our results suggest this efficient Cr3+/Tm3+ co-doping system provides a selective pump mechanism for obtaining 1.8 µm laser and thus shows attractive applications in near-infrared fiber lasers and amplifiers.

  14. Rod-like polyaniline supported on three-dimensional boron and nitrogen-co-doped graphene frameworks for high-performance supercapacitors

    Science.gov (United States)

    Liao, Kexuan; Gao, Jialu; Fan, Jinchen; Mo, Yao; Xu, Qunjie; Min, Yulin

    2017-12-01

    In this work, novel three-dimensional (3D) boron and nitrogen-co-doped three-dimensional (3D) graphene frameworks (BN-GFs) supporting rod-like polyaniline (PANI) are facilely prepared and used as electrodes for high-performance supercapacitors. The results demonstrated that BN-GFs with tuned electronic structure can not only provide a large surface area for rod-like PANI to anchor but also effectively facilitate the ion transfer and charge storage in the electrode. The PANI/BN-GF composite with wrinkled boron and nitrogen-co-doped graphene sheets interconnected by rod-like PANI exhibits excellent capacitive properties with a maximum specific capacitance of 596 F/g at a current density of 0.5 A/g. Notably, they also show excellent cycling stability with more than 81% capacitance retention after 5000 charge-discharge cycles.

  15. Zirconium and silver co-doped TiO2 nanoparticles as visible light catalyst for reduction of 4-nitrophenol, degradation of methyl orange and methylene blue.

    Science.gov (United States)

    Naraginti, Saraschandra; Stephen, Finian Bernard; Radhakrishnan, Adhithya; Sivakumar, A

    2015-01-25

    Catalytic activity of Zr and Ag co-doped TiO2 nanoparticles on the reduction of 4-nitrophenol, degradation of methylene blue and methyl orange was studied using sodium borohydride as reducing agent. The nanoparticles were characterized using X-ray diffraction, energy dispersive X-ray, high resolution transmission electron microscopy, selected area electron diffraction and UV-Vis spectroscopy. The rate of the reduction/degradation was found to increase with increasing amount of the photocatalyst which could be attributed to higher dispersity and small size of the nanoparticles. The catalytic activity of Zr and Ag co-doped TiO2 nanoparticles showed no significant difference even after recycling the catalyst four times indicating a promising potential for industrial application of the prepared photocatalyst. Copyright © 2014 Elsevier B.V. All rights reserved.

  16. Crystal structure, electrical conductivity and thermal expansion of Ni and Nb co-doped LaCoO3.

    Science.gov (United States)

    Øygarden, Vegar; Grande, Tor

    2013-02-28

    The effect of co-doping LaCoO(3) with Ni and Nb has been investigated in the two solid solution series (1 - x)LaCoO(3)-xLaNi(2/3)Nb(1/3)O(3) and (1 - y)LaCo(2/3)Ni(1/3)O(3)-yLaNi(2/3)Nb(1/3)O(3). The materials were shown to be stoichiometric with respect to oxygen. The compositional effect on the evolution of the crystal structure, thermal expansion and electrical conductivity is reported. The chemical stability of LaCoO(3) in a reducing atmosphere was improved and the thermal expansion was suppressed at higher levels of Nb-substitution. The materials with mixed oxidation states on the B-site possessed superior electrical transport properties compared to solid solutions with cations in mainly isovalent oxidation states. The evolution of the electronic conductivity, thermal expansion and crystal structural is discussed with emphasis on the oxidation states of Ni and Co, and the spin transitions of Co.

  17. High sensitivity of gold nanoparticles co-doped with Gd2O3 mesoporous silica nanocomposite to nasopharyngeal carcinoma cells

    Science.gov (United States)

    Wang, Hui; Zhang, Songjin; Tian, Xiumei; Liu, Chufeng; Zhang, Lei; Hu, Wenyong; Shao, Yuanzhi; Li, Li

    2016-10-01

    Nanoprobes for combined optical and magnetic resonance imaging have tremendous potential in early cancer diagnosis. Gold nanoparticles (AuNPs) co-doped with Gd2O3 mesoporous silica nanocomposite (Au/Gd@MCM-41) can produce pronounced contrast enhancement for T1 weighted image in magnetic resonance imaging (MRI). Here, we show the remarkably high sensitivity of Au/Gd@MCM-41 to the human poorly differentiated nasopharyngeal carcinoma (NPC) cell line (CNE-2) using fluorescence lifetime imaging (FLIM). The upconversion luminescences from CNE-2 and the normal nasopharyngeal (NP) cells (NP69) after uptake of Au/Gd@MCM-41 show the characteristic of two-photon-induced-radiative recombination of the AuNPs. The presence of the Gd3+ ion induces a much shorter luminescence lifetime in CNE-2 cells. The interaction between AuNPs and Gd3+ ion clearly enhances the optical sensitivity of Au/Gd@MCM-41 to CNE-2. Furthermore, the difference in the autofluorescence between CNE-2 and NP69 cells can be efficiently demonstrated by the emission lifetimes of Au/Gd@MCM-41 through the Forster energy transfers from the endogenous fluorophores to AuNPs. The results suggest that Au/Gd@MCM-41 may impart high optical resolution for the FLIM imaging that differentiates normal and high-grade precancers.

  18. Hydrogen-assisted versus hydroxyl-assisted CO dissociation over Co-doped Cu(111): A DFT study

    Science.gov (United States)

    Zha, Hao; Dong, Xiuqin; Yu, Yingzhe; Zhang, Minhua

    2018-03-01

    First principle based density functional theory (DFT) was used to calculate the step-by-step hydrogenation and dissociation reaction network of carbon monoxide (CO) over Co-doped Cu(111) surface as a model for understanding the lateral interaction of surface hydroxyl species (OH) on these reactions. We discussed the Csbnd O bond length and the adsorption energy changes of reaction intermediates under different adsorption circumstances for purpose of making out the effect of surface hydroxyl on the reaction selectivity. Reaction intermediates co-adsorbed with H atom and hydroxyl could undergo H-assisted or OH-assisted routes. The calculations show that the OH-assisted route prefers with the formation of COH, CHOH and CH2OH while general H-assisted route prefers with the formation of HCO, CH2O and CH3O. Considering the rather low activation barrier of COH, CHOH and CH2OH to form CHX, the existence of hydroxyl on the surface is in favor of boosting the CHX and suppressing the methanol.

  19. Enhanced lithium ion storage in TiO2 nanoparticles, induced by sulphur and carbon co-doping

    Science.gov (United States)

    Ivanov, Svetlozar; Barylyak, Adriana; Besaha, Khrystyna; Dimitrova, Anna; Krischok, Stefan; Bund, Andreas; Bobitski, Jaroslav

    2016-09-01

    Sulphur and carbon codoped anatase nanoparticles are synthesized by one-step approach based on interaction between thiourea and metatitanic acid. Electron microscopy shows micrometer-sized randomly distributed crystal aggregates, consisting of many 25-40 nm TiO2 nanoparticles. The obtained phase composition and chemical states of the elements in the structure are analyzed by means of X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). XRD shows that after doping the tetragonal anatase structure is preserved. Further data assessment by Rietveld refinement allows detection of a slight increase of the c lattice parameter and volume related to incorporation of the doping elements. XPS confirms the coexistence of both elemental and oxide carbon forms, which are predominantly located on the TiO2 particle surface. According to XPS analysis sulphur occupies titanium sites and the element is present in S6+ sulfate environment. Analysis based on cyclic voltammetry and galvanostatic intermittent titration (GITT) suggests an accelerated Li+ transport in the doped TiO2 structure. The synthesized S and C co-doped anatase has an excellent electrochemical performance in terms of capacity and very fast lithiation kinetics, superior to the non-doped TiO2. The material displays 83% capacity retention for 500 galvanostatic cycles and nearly 100% current efficiency.

  20. CuO nanoparticles supported on nitrogen and sulfur co-doped graphene nanocomposites for non-enzymatic glucose sensing

    Energy Technology Data Exchange (ETDEWEB)

    Li, Meixia [Hebei University of Engineering, Faculty of Material Science and Engineering (China); Guo, Qingbin, E-mail: guoqingbinhue@163.com [Hebei University of Engineering, Academic Affairs office (China); Xie, Juan; Li, Yongde; Feng, Yapeng [Hebei University of Engineering, Faculty of Material Science and Engineering (China)

    2017-01-15

    Developing highly active catalysts to promote the electrocatalytic glucose oxidation (EGO) is a crucial demand for non-enzymatic glucose sensing. Herein, we reported the use of nitrogen and sulfur co-doped graphene (NSG) as a novel support material for anchoring CuO nanoparticles and obtained CuO/NSG was employed as an efficient EGO catalyst for non-enzymatic glucose sensing. The results showed that the NSG endowed the CuO/NSG with large surface area, increased structural defects, improved conductivity, and strong covalent coupling between NSG and CuO. Owing to the significant contribution of NSG and the synergistic effect of NSG and CuO, the CuO/NSG exhibited a remarkably higher EGO activity than CuO and CuO/reduced graphene oxide. The CuO/NSG-based sensor displayed excellent glucose sensing performances with a considerably low detection limit of 0.07 μM. These findings elucidate that the NSG is a promising support material for non-enzymatic glucose detection.

  1. Effect of Co doping on optical properties of chemically synthesized delafossite structured CuCrO2 thin film

    Science.gov (United States)

    Bera, A.; Deb, K.; Sarkar, K.; Saha, B.

    2017-05-01

    In this communication, thin films of delafossite structured oxide material of CuCrO2 with different concentration of cobalt (0%, 1%, 2% and 3%) have been grown on quartz substrate by sol-gel spin coating method. Prepared films were annealed at 800 °C in ambient condition for 5 hours. The microstructure, surface topography and optical properties of as prepared Co doped CuCrO2 thin films were analyzed by using X-ray diffractometer (XRD) with Cu-Kα radiation, Atomic Force Microscopy (AFM) and UV-Vis NIR photospectrometer respectively. Maximum transparency was found to be 50% from transmittance spectra. Red shifts of optical energy band gap have been observed due to increase of carrier concentration of cobalt in CuCrO2 thin films. The doping of cobalt in CuCrO2 thin films have a significant influence on the optical properties of CuCrO2 which can be used to shape up smart semiconductor devices.

  2. Highly efficient transition metal and nitrogen co-doped carbide-derived carbon electrocatalysts for anion exchange membrane fuel cells

    Science.gov (United States)

    Ratso, Sander; Kruusenberg, Ivar; Käärik, Maike; Kook, Mati; Puust, Laurits; Saar, Rando; Leis, Jaan; Tammeveski, Kaido

    2018-01-01

    The search for an efficient electrocatalyst for oxygen reduction reaction (ORR) to replace platinum in fuel cell cathode materials is one of the hottest topics in electrocatalysis. Among the many non-noble metal catalysts, metal/nitrogen/carbon composites made by pyrolysis of cheap materials are the most promising with control over the porosity and final structure of the catalyst a crucial point. In this work we show a method of producing a highly active ORR catalyst in alkaline media with a controllable porous structure using titanium carbide derived carbon as a base structure and dicyandiamide along with FeCl3 or CoCl2 as the dopants. The resulting transition metal-nitrogen co-doped carbide derived carbon (M/N/CDC) catalyst is highly efficient for ORR electrocatalysis with the activity in 0.1 M KOH approaching that of commercial 46.1 wt.% Pt/C. The catalyst materials are also investigated by scanning electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy to characterise the changes in morphology and composition causing the raise in electrochemical activity. MEA performance of M/N/CDC cathode materials in H2/O2 alkaline membrane fuel cell is tested with the highest power density reached being 80 mW cm-2 compared to 90 mW cm-2 for Pt/C.

  3. MOF-derived Co-doped nickel selenide/C electrocatalysts supported on Ni foam for overall water splitting

    KAUST Repository

    Ming, Fangwang

    2016-09-01

    It is of prime importance to develop dual-functional electrocatalysts with good activity for overall water splitting, which remains a great challenge. Herein, we report the synthesis of a Co-doped nickel selenide (a mixture of NiSe and NiSe)/C hybrid nanostructure supported on Ni foam using a metal-organic framework as the precursor. The resulting catalyst exhibits excellent catalytic activity toward the oxygen evolution reaction (OER), which only requires an overpotential of 275 mV to drive a current density of 30 mA cm. This overpotential is much lower than those reported for precious metal free OER catalysts. The hybrid is also capable of catalyzing the hydrogen evolution reaction (HER) efficiently. A current density of -10 mA cm can be achieved at 90 mV. In addition, such a hybrid nanostructure can achieve 10 and 30 mA cm at potentials of 1.6 and 1.71 V, respectively, along with good durability when functioning as both the cathode and the anode for overall water splitting in basic media.

  4. Nickel cobaltite nanosheets strongly anchored on boron and nitrogen co-doped graphene for high-performance asymmetric supercapacitors

    Science.gov (United States)

    Jiao, Xinyan; Xia, Xifeng; Liu, Peng; Lei, Wu; Ouyang, Yu; Hao, Qingli

    2017-08-01

    Strongly coupled boron and nitrogen co-doped graphene (BN-G) hybrids with nickel cobaltite (NiCo2O4) nanosheets (NCO/BN-G) were fabricated by a facile soft-chemical method for asymmetric supercapacitors with high-performance. The strong interaction between BN-G and NiCo2O4 nanosheets are explored by various techniques. The effect of heteroatom doping on electrochemical properties of the hybrids is systematically investigated. The strong synergistic effect between NiCo2O4 and BN-G leads to a specific capacitance of 106.5 mA h g-1 at the current density of 0.5 A g-1 and capacitance retention of 96.8% after 10 000 cycles at 5 A g-1, much better than those of the pure NiCo2O4 and its hybrid with N-doped graphene. Moreover, an asymmetric supercapacitor device, assembled with NCO/BN-G and activated carbon (NCO/BN-G//AC), exhibits a maximum energy density of 45.6 Wh kg-1 and an excellent cycling stability. The improved electrochemical performance of the NCO/BN-G hybrid is attributed to the good conductivity of BN-G and the synergistic effect between NiCo2O4 nanosheets and BN-G combined together through a plane-to-plane contact mode.

  5. Facile and controllable synthesis of N/P co-doped graphene for high-performance supercapacitors

    Science.gov (United States)

    Xia, Kaisheng; Huang, Zhiyuan; Zheng, Lin; Han, Bo; Gao, Qiang; Zhou, Chenggang; Wang, Hongquan; Wu, Jinping

    2017-10-01

    Improving the energy density of carbon-based supercapacitors is one of the most urgent demands for developing high-power energy supplies, which in general requires delicate engineering of the carbon composition and textures. By pre-functionalization of graphene nanosheets and successive one-step (NH4)3PO4 activation, we prepared a type of nitrogen and phosphorus co-doped graphene (NPG) with high specific surface areas, hierarchical pore structures as well as tunable N and P contents. The as-obtained NPG shows high specific capacitances of 219 F g-1 (123 F cm-3) at 0.25 A g-1 and 175 F g-1 (98 F cm-3) at 10 A g-1, respectively. Accordingly, the NPG-based symmetrical supercapacitor device, working at a potential window of 1.3 V, could deliver an enhanced energy density of 8.2 Wh kg-1 (4.6 Wh L-1) at a power density of 162 W kg-1 (91 W L-1), which still retains 6.7 Wh kg-1 at 6.5 kW kg-1. In particular, under a current density of 5 A g-1, the device endows an 86% capacitance retention of initial after 20,000 cycles, displaying superior cycle stability. Our results imply the feasibility of NPG as a promising candidate for high-performance supercapacitors.

  6. The effect of Pr co-doping on the densification and electrical properties of Sr-LaAlO3

    Directory of Open Access Journals (Sweden)

    L. A. Villas-Boas

    2013-01-01

    Full Text Available Perovskite-type materials have been investigated extensively in the attempt to discover new electrolyte materials for solid oxide fuel cells (SOFC operating at low temperatures. These materials include LaAlO3-based perovskite, which, when adequately doped, presents high ionic conductivity. However, despite the high conductivity of doped LaAlO3, two characteristics limit its application as solid electrolyte: low sinterability and p-type electronic conductivity in oxidizing conditions. The purpose of this work was to investigate the effect of Pr co-doping on the densification and electrical conductivity of Sr-doped LaAlO3. The addition of Pr eliminated the deficiencies mentioned above. Pr in solid solution acts as a perfect sintering aid because promoted densification without forming secondary phase which should be detrimental for electrical conduction. The addition of Pr also increased the bulk electrical conductivity measured in air atmosphere but had no effect at low oxygen partial pressure. However, the addition of Pr had a strong effect on the grain boundary, improving the ionic grain boundary electrical conductivity at air atmosphere which was attributed to the Pr influence on the space charge layer.

  7. Effect of Mg co-doping on cathodoluminescence properties of LuGAGG:Ce single crystalline garnet films

    Science.gov (United States)

    Schauer, P.; Lalinský, O.; Kučera, M.; Lučeničová, Z.; Hanuš, M.

    2017-10-01

    Mg2+ co-doped (LuGd)3(GaAl)5O12:Ce (LuGAGG:Ce,Mg) multicomponent single crystalline epitaxial garnet films were prepared and their cathodoluminescence (CL) and thermoluminescence (TSL) properties were studied in this paper. The films were prepared using the liquid phase epitaxy from lead-free BaO-B2O3-BaF2 flux and their scintillation properties were characterized using the 10 keV collimated e-beam. More specifically, temperature dependent CL intensity, CL emission spectra, CL decay characteristics as well as TSL emission characteristics of the mentioned films were measured. At the highest content of Mg (700 ppm), the CL decay time was as low as 28 ns and the CL afterglow was as low as 0.01% at 1 μs after the e-beam excitation cut-off, which are important parameters for electron detectors in e-beam devices. The CL temperature quenching of the studied films began above room temperature. An increase of Mg concentration to or above 280 ppm quenched the characteristic CL emission of LuGAGG:Ce,Mg. The TSL measurements show that the trap population in studied garnet samples is considerably suppressed. The LuGAGG:Ce,Mg multicomponent single crystalline epitaxial films were evaluated as the perspective fast scintillators for the electron detectors in the e-beam devices.

  8. Effect of WO 3 on the spectroscopic properties in Er 3+/Yb 3+ co-doped bismuth-borate glasses

    Science.gov (United States)

    Wang, Jun; Zhou, Yaxun; Dai, Shixun; Xu, Tiefeng; Nie, Qiuhua

    2007-11-01

    The spectroscopic properties of Er 3+/Yb 3+ co-doped Bi 2O 3-B 2O 3-WO 3 (BBW) glasses were analyzed and discussed. The effect of WO 3 content on the absorption spectra, the Judd-Ofelt parameters Ω t ( t=2, 4, 6), emission spectra and the lifetime of the 4I 13/2 level and the quantum efficiency of Er 3+: 4I 13/2→ 4I 15/2 transition were also investigated. With the substitution of WO 3 for B 2O 3, the measured lifetime of the 4I 13/2 level and the quantum efficiency of Er 3+: 4I 13/2→ 4I 15/2 transition increase from 0.98 to 1.31 ms and from 38.2% to 49.2%, respectively. The effective width of emission band and the emission cross-section both decrease slightly. And the emission spectra is analyzed via the different curve ( σe- σa) of BBW glasses, the influence of OH - is also discussed.

  9. Post-annealed gallium and aluminum co-doped zinc oxide films applied in organic photovoltaic devices

    Science.gov (United States)

    Chang, Shang-Chou

    2014-10-01

    Gallium and aluminum co-doped zinc oxide (GAZO) films were produced by magnetron sputtering. The GAZO films were post-annealed in either vacuum or hydrogen microwave plasma. Vacuum- and hydrogen microwave plasma-annealed GAZO films show different surface morphologies and lattice structures. The surface roughness and the spacing between adjacent (002) planes decrease; grain growth occurs for the GAZO films after vacuum annealing. The surface roughness increases and nanocrystals are grown for the GAZO films after hydrogen microwave plasma annealing. Both vacuum and hydrogen microwave plasma annealing can improve the electrical and optical properties of GAZO films. Hydrogen microwave plasma annealing improves more than vacuum annealing does for GAZO films. An electrical resistivity of 4.7 × 10-4 Ω-cm and average optical transmittance in the visible range from 400 to 800 nm of 95% can be obtained for the GAZO films after hydrogen microwave plasma annealing. Hybrid organic photovoltaic (OPV) devices were fabricated on the as-deposited, vacuum-annealed, and hydrogen microwave plasma-annealed GAZO-coated glass substrates. The active layer consisted of blended poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) in the OPV devices. The power conversion efficiency of the OPV devices is 1.22% for the hydrogen microwave plasma-annealed GAZO films, which is nearly two times higher compared with that for the as-deposited GAZO films.

  10. Photoluminescence study of Sm{sup 3+}–Yb{sup 3+}co-doped tellurite glass embedding silver nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Reza Dousti, M., E-mail: mrdousti@ifsc.usp.br [Laboratório de Espectroscopia de Materiais Funcionais (LEMAF), Instituto de Fisica de São Carlos, Universidade de São Paulo, Av. Trabalhador So-carlense 400, São Carlos, SP 13566-590 (Brazil); Department of Physics, Tehran-North Branch, Islamic Azad University Tehran (Iran, Islamic Republic of); Department of Physics, Faculty of Science, Universiti Teknologi Malaysia, Skudai 81310, Johor (Malaysia); Amjad, R.J. [Department of Physics, Faculty of Science, Universiti Teknologi Malaysia, Skudai 81310, Johor (Malaysia); Department of Physics, COMSATS Institute of Information Technology, Lahore 54000 (Pakistan); Hosseinian S, R.; Salehi, M.; Sahar, M.R. [Department of Physics, Faculty of Science, Universiti Teknologi Malaysia, Skudai 81310, Johor (Malaysia)

    2015-03-15

    We report on the upconversion emission of Sm{sup 3+} ions doped tellurite glass in the presence of Yb{sup 3+} ions and silver nanoparticles. The enhancement of infrared-to-visible upconversion emissions is achieved under 980 nm excitation wavelength and attributed to the high absorption cross section of Yb{sup 3+} ions and an efficient energy transfer to Sm{sup 3+} ions. Further enhancements are attributed to the plasmonic effect via metallic nanoparticles resulting in the large localized field around rare earth ions. However, under excitation at 406 nm, the addition of Yb{sup 3+} content and heat-treated silver nanoparticles quench the luminescence of Sm{sup 3+} ions likely due to quantum cutting and plasmonic diluent effects, respectively. - Highlights: • Sm{sup 3+} tellurite glasses co-doped with Yb{sup 3+} ions and tri-doped with Yb{sup 3+}:Ag NPs were prepared. • In first step, Yb{sup 3+} ions enhanced the upconversion emissions of Sm{sup 3+} doped samples. • In second step, Ag NPs further enhanced the upconversion emissions in tri-doped glasses. • Finally, the quench in luminescence under 406 nm excitation is observed and discussed.

  11. Enhanced red emission from BaMoO4 : Eu3+ by Bi3+ co-doping.

    Science.gov (United States)

    Luo, Wenqin; Ling, Danping; Bao, Susu; Xiong, Huifang; Zhang, Rui; Li, Bin; Wu, Haiyan

    2017-10-23

    A series of Bi3+ ,Eu3+ -doped BaMoO4 phosphors was synthesized using a hydrothermal method. The crystal structure, morphology and optical properties of the phosphors were studied using X-ray diffraction (XRD), scanning electron microscope (SEM) and photoluminescence (PL) measurements. Three different particle morphologies were detected in the SEM observation. The energy dispersive spectroscopy (EDS) results indicated that the solubility of Bi3+ in spherical or rugby-like BaMoO4 particles was very low and the excess Bi3+ element was cumulated in the irregular particles. Characteristic emissions of Eu3+ ions (5 D0  → 7 FJ ; J = 0, 1, 2, 3, 4) were observed under excitation in ultraviolet (UV) light, with the most intense transition being the 5 D0  → 7 F2 transition. Energy transfer from MoO42- and Bi3+ to Eu3+ can be readily achieved. Red emission intensity of Eu3+ was enhanced by a factor of two by co-doping with a small amount of Bi3+ . Optical properties as a function of Bi3+ content were studied and the optimum Bi3+ content in BaMoO4 nanocrystals was determined to be 0.4 mol%. Copyright © 2017 John Wiley & Sons, Ltd.

  12. N, S co-doped carbon dots with high quantum yield: tunable fluorescence in liquid/solid and extensible applications

    Science.gov (United States)

    Yang, Mei; Meng, Xinlei; Li, Baoyan; Ge, Shusheng; Lu, Yun

    2017-06-01

    A set of the highly fluorescent N, S co-doped carbon dots (NSCDs) were prepared through one-step hydrothermal synthesis at different temperature with citric acid as the carbon source and cysteamine as the N, S source. The NSCDs synthesized at 200 °C show significant quantum yield (81%) due to its optimal structure. The structure of the NSCDs changed with varying degrees of carbonization/aromatization and different content of multifunctional groups of C=O, -NH2, -OH, -SH, and N, S-aromatic heterocycte under different preparation temperatures, thus exhibiting tunable fluorescence. Especially, the obtained NSCDs exhibited a blue fluorescence in solution state and changed from strong blue to yellowish-green in its solid state under UV light as a result of the increase in preparation temperature. The as-prepared NSCDs can be used in selective detection of complex anions such as Cr2O7 2- and Fe(CN)6 3-, cell imaging, and preparation of fluorescent composite films.

  13. Effect of Ag doping on structural, optical, and photocatalytic properties of ZnO nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Hosseini, S.M.; Sarsari, I. Abdolhosseini, E-mail: abdolhosseini@cc.iut.ac.ir; Kameli, P.; Salamati, H.

    2015-08-15

    Highlights: • Hexagonal-wurtzite phase of ZnO were synthesized by thermal treatment of ball milled precursors at 400 °C. • Silver may be a good candidate for producing p-type ZnO. • Photocatalytic activity of ZnO nanoparticles increased by silver doping. • Reduction the optical energy gap of ZnO by silver doping is an advantage for use in optoelectronic devices. • The Ag 3d binding energy shifts to lower energies via XPS study. - Abstract: Silver-doped ZnO nanoparticles were successfully fabricated at 400 °C via a simple and rapid method based on short time solid state milling and calcination of precursor powders. The effect of Ag dilute doping on the structural, optical, and photocatalytic properties of ZnO nanoparticles was investigated by X-ray diffraction (XRD), UV–vis spectrophotometer and photoluminescence (PL) spectroscopy. X-ray analysis revealed that Ag doped ZnO solidified in hexagonal wurtzite structure. The intensity of deep level emission was reduced with increasing silver doping in PL measurement. The X-ray photoelectron spectroscopy (XPS) measurement predicted that Ag was mainly in the metallic state and ZnO was in the wurtzite structure. This metallic state accompanied by unique zinc oxide properties decolorized the methyl violet, efficiently. The first-principles calculation represented Ag deep level in ZnO with an n-type behavior, while in ZnO structure with grain boundary p-type nature via shallow states is dominant same as powder samples as studied in this present work. It was suggested that these Ag-doped ZnO nanoparticles may have good applications in optoelectronics, spintronics and wastewater treatment.

  14. Thermal Stability and Electrical Transport Properties of Single-Crystalline β-Zn4Sb3 Co-doped by Ga/Sn

    Science.gov (United States)

    Deng, Shuping; Tang, Yu; Li, Decong; Liu, Hongxia; Chen, Zhong; Shen, Lanxian; Deng, Shukang

    2017-12-01

    In this study, Ga/Sn co-doped single-crystal β-Zn4Sb3 were prepared by a Sn-flux method based on stoichiometric ratios of Zn4- x Sb3Ga x Sn3 ( x = 0, 0.25, 0.5, 0.6 and 0.75). The effect of Ga/Sn co-doping on the thermal stability and electrical transport properties of the obtained samples were investigated. All the prepared samples exhibit p-type conduction, and carrier concentration varies from 4.71 × 1019 cm-3 to 10.44 × 1019 cm-3, while carrier mobility changes from 34.2 cm2 V-1 s-1 to 68.9 cm2 V-1 s-1 at room temperature. Structure analysis indicates that all samples are β-Zn4Sb3 with space group R\\bar{3}c. Thermal analysis results show that the Ga/Sn co-doped samples possess an excellent thermal stability. The results of crystal compositions indicate that both Ga and Sn atoms tend to replace Zn atoms, and the electrical transport properties of the samples were optimized by co-doping Ga and Sn. Meanwhile, the calculated values of the carrier effective mass, band gap and relaxation time agree with the result obtained from a band structure calculation. Consequently, the sample with Ga initial content x = 0.5 possesses excellent electrical properties, which obtains a maximal power factor of 1.56 × 10-3 W m-1 K-2 at 450 K.

  15. Effects of Yttrium and Iron co-doping on the high temperature thermoelectric properties of Ca3Co4O9+δ

    DEFF Research Database (Denmark)

    Wu, NingYu; Van Nong, Ngo; Pryds, Nini

    2015-01-01

    A series of Y and Fe co-doped Ca3−xYxCo4−yFeyO9+δ (0 ⩽ x ⩽ 0.3, 0 ⩽ y ⩽ 0.1) samples synthesized by auto-combustion reaction and followed by a spark plasma sintering (SPS) processing with the effects of Fe and Y doping on the high temperature (RT to 800 °C) thermoelectric properties were systemat......A series of Y and Fe co-doped Ca3−xYxCo4−yFeyO9+δ (0 ⩽ x ⩽ 0.3, 0 ⩽ y ⩽ 0.1) samples synthesized by auto-combustion reaction and followed by a spark plasma sintering (SPS) processing with the effects of Fe and Y doping on the high temperature (RT to 800 °C) thermoelectric properties were...... systematically investigated. For the Fe-doped system (x = 0, y ⩽ 0.1), the electrical resistivity (ρ) decreased over the whole measured temperature range, while the Seebeck coefficient (S) remained almost the same. For the co-doped system, at any fixed Fe doping content, both ρ and S tended to increase...... with increasing Y dopants, however, the effect is more substantial on ρ than on S, particularly in the low temperature regime. In contrast to ρ and S, the in-plane thermal conductivity (κ) is only slightly influenced by Y and Fe substitutions. Among all the investigated samples, the co-doped sample with x = 0...

  16. Electrical and optical properties of ZnO bulk crystals with and without lithium grown by the hydrothermal technique

    Science.gov (United States)

    Wang, Buguo; Claflin, Bruce; Callahan, Michael; Fang, Z.-.; Look, David

    2014-03-01

    Lithium is usually added into the solution to improve ZnO hydrothermal growth; however, lithium doping affects the properties of the resulting crystals. Optical and electrical properties of hydrothermal ZnO bulk crystals without lithium, have been studied by photoluminescence and Hall-effect measurements. High quality ZnO crystals without lithium were grown in H2O/D2O and in NH3-H2O solutions. The crystals grown from H2O/D2O are conductive with resistivities of 0.6-0.7 Ωcm and mobilities of ~ 100 cm2/Vs, while lithium doped ZnO crystals typically have resistivities of ~ 103Ω-cm and mobilities of ~ 200 cm2/Vs, but can be varied from dozens to 1010 Ω-cm depending on lithium concentration. Lithium-free but nitrogen doped crystals grown in NH3-H2O solution have resistivities of 1×100 Ω-cm and sometimes show p-type conduction; the resistivity increases to ~ 1×108 Ω-cm after annealing at 600° C in air. Lithium and nitrogen co-doped ZnO crystals have resistivities of 108-1012 Ω-cm and are semi-insulating after annealling. Electronic irradiation also increases the ZnO resistivity. For lithium-doped samples, a 3.357 eV peak can be seen in the photoluminescence spectra. This is close to the donor-exciton peaks in indium-doped ZnO where 3.3586 eV and 3.357 eV were found on the C+ and C- faces, respectively. More studies are needed to identify lithium-related complexes (defects).

  17. Structural and Magnetic Properties of Mn doped ZnO Thin Film Deposited by Pulsed Laser Deposition

    KAUST Repository

    Baras, Abdulaziz

    2011-07-01

    Diluted magnetic oxide (DMO) research is a growing field of interdisciplinary study like spintronic devices and medical imaging. A definite agreement among researchers concerning the origin of ferromagnetism in DMO has yet to be reached. This thesis presents a study on the structural and magnetic properties of DMO thin films. It attempts to contribute to the understanding of ferromagnetism (FM) origin in DMO. Pure ZnO and Mn doped ZnO thin films have been deposited by pulsed laser deposition (PLD) using different deposition conditions. This was conducted in order to correlate the change between structural and magnetic properties. Structural properties of the films were characterized using x-ray diffraction (XRD) and scanning electron microscopy (SEM). The superconducting quantum interference device (SQUID) was used to investigate the magnetic properties of these films. The structural characterizations showed that the quality of pure ZnO and Mn doped ZnO films increased as oxygen pressure (PO) increased during deposition. All samples were insulators. In Mn doped films, Mn concentration decreased as PO increased. The Mn doped ZnO samples were deposited at 600˚C and oxygen pressure from 50-500mTorr. All Mn doped films displayed room temperature ferromagnetism (RTFM). However, at 5 K a superparamagnetic (SPM) behavior was observed in these samples. This result was accounted for by the supposition that there were secondary phase(s) causing the superparamagnetic behavior. Our findings hope to strengthen existing research on DMO origins and suggest that secondary phases are the core components that suppress the ferromagnetism. Although RTFM and SPM at low temperature has been observed in other systems (e.g., Co doped ZnO), we are the first to report this behavior in Mn doped ZnO. Future research might extend the characterization and exploration of ferromagnetism in this system.

  18. Optical function of bionic nanostructure of ZnO

    Energy Technology Data Exchange (ETDEWEB)

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

    2007-10-15

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

  19. Room temperature ferromagnetism in ZnO prepared by microemulsion

    Directory of Open Access Journals (Sweden)

    Qingyu Xu

    2011-09-01

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

  20. Synthesis, characteristics and antimicrobial activity of ZnO nanoparticles

    Science.gov (United States)

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

    2015-06-01

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

  1. Synthesis of ZnO Nanocrystal-Graphene Composite by Mechanical Milling and Sonication-Assisted Exfoliation

    Science.gov (United States)

    Arora, Sweety; Srivastava, Chandan

    2017-02-01

    A ZnO nanocrystal-graphene composite was synthesized by a two-step method involving mechanical milling and sonication-assisted exfoliation. Zn metal powder was first ball-milled with graphite powder for 30 h in water medium. This ball-milled mixture was then subjected to exfoliation by sonication in the presence of sodium lauryl sulfate surfactant to produce graphene decorated with spherical agglomerates of ultrafine nanocrystalline ZnO. The presence of a few layers of graphene was confirmed by Raman spectroscopy and atomic force microscopy measurements. The size, phase identity and composition of the ZnO nanocrystals was determined by transmission electron microscopy measurements.

  2. Low-temperature CO oxidation over Cu/Pt co-doped ZrO2 nanoparticles synthesized by solution combustion

    Directory of Open Access Journals (Sweden)

    Amit Singhania

    2017-07-01

    Full Text Available Zirconia (ZrO2 nanoparticles co-doped with Cu and Pt were applied as catalysts for carbon monoxide (CO oxidation. These materials were prepared through solution combustion in order to obtain highly active and stable catalytic nanomaterials. This method allows Pt2+ and Cu2+ ions to dissolve into the ZrO2 lattice and thus creates oxygen vacancies due to lattice distortion and charge imbalance. High-resolution transmission electron microscopy (HRTEM results showed Cu/Pt co-doped ZrO2 nanoparticles with a size of ca. 10 nm. X-ray diffraction (XRD and Raman spectra confirmed cubic structure and larger oxygen vacancies. The nanoparticles showed excellent activity for CO oxidation. The temperature T50 (the temperature at which 50% of CO are converted was lowered by 175 °C in comparison to bare ZrO2. Further, they exhibited very high stability for CO reaction (time-on-stream ≈ 70 h. This is due to combined effect of smaller particle size, large oxygen vacancies, high specific surface area and better thermal stability of the Cu/Pt co-doped ZrO2 nanoparticles. The apparent activation energy for CO oxidation is found to be 45.6 kJ·mol−1. The CO conversion decreases with increase in gas hourly space velocity (GHSV and initial CO concentration.

  3. The Gadolinium (Gd3+) and Tin (Sn4+) Co-doped BiFeO3 Nanoparticles as New Solar Light Active Photocatalyst

    Science.gov (United States)

    Irfan, Syed; Rizwan, Syed; Shen, Yang; Li, Liangliang; Asfandiyar; Butt, Sajid; Nan, Ce-Wen

    2017-02-01

    The process of photocatalysis is appealing to huge interest motivated by the great promise of addressing current energy and environmental issues through converting solar light directly into chemical energy. However, an efficient solar energy harvesting for photocatalysis remains a critical challenge. Here, we reported a new full solar spectrum driven photocatalyst by co-doping of Gd3+ and Sn4+ into A and B-sites of BiFeO3 simultaneously. The co-doping of Gd3+ and Sn4+ played a key role in hampering the recombination of electron-hole pairs and shifted the band-gap of BiFeO3 from 2.10 eV to 2.03 eV. The Brunauer-Emmett-Teller (BET) measurement confirmed that the co-doping of Gd3+ and Sn4+ into BiFeO3 increased the surface area and porosity, and thus the photocatalytic activity of the Bi0.90Gd0.10Fe0.95Sn0.05O3 system was significantly improved. Our work proposed a new photocatalyst that could degrade various organic dyes like Congo red, Methylene blue, and Methyl violet under irradiation with different light wavelengths and gave guidance for designing more efficient photocatalysts.

  4. X-ray photoelectron spectroscopy studies of Co-doped ZnO-Ga 2O 3-SiO 2 nano-glass-ceramic composites

    Science.gov (United States)

    Duan, Xiulan; Song, Chunfeng; Yu, Fapeng; Yuan, Duorong; Li, Xiaoyu

    2011-02-01

    Co-doped ZnO-Ga2O3-SiO2 nano-glass-ceramic composites were prepared by sol-gel method. X-ray diffraction patterns showed that the crystallization temperature was 800 °C. X-ray photoelectron spectroscopy (XPS) was used to study the effect of heat-treatment temperature on the electronic structure of Co-doped ZnO-Ga2O3-SiO2 nano-glass-ceramic composites. The Zn (2p3/2), Ga (2p3/2) and O (1s) XPS spectra for the glass-ceramics heat-treated at 800-1000 °C could be deconvoluted into two peaks corresponding to these elements in glass network and in nanocrystals, respectively. The results indicate that the material is composed of an amorphous silicate network and ZnGa2O4 nanocrystalline particles. The amount of nanocrystals increases with the annealing temperature. The photoelectron peak of Si (2p) shifts to higher binding energy at higher annealing temperature, revealing the charge transfer from Si to O increased. The relationship between the microstructure of Co-doped ZnO-Ga2O3-SiO2 sample and its absorption properties was discussed, and the suitable heat-treatment temperature was proposed.

  5. Preparation and Characterization of Mn/N Co-Doped TiO2 Loaded on Wood-Based Activated Carbon Fiber and Its Visible Light Photodegradation

    Directory of Open Access Journals (Sweden)

    Xiaojun Ma

    2015-09-01

    Full Text Available Using MnSO4·H2O as manganese source and urea as nitrogen source, Mn/N co-doped TiO2 loaded on wood-based activated carbon fiber (Mn/Ti-N-WACF was prepared by sol–gel method. Mn/Ti-N-WACF with different Mn doping contents was characterized by scanning electron microscopy, X-ray diffraction (XRD and X-ray photoelectron spectroscopies (XPS, and ultraviolet-visible spectrophotometer. Results showed that the loading rate of TiO2 in Mn/Ti-N-WACF was improved by Mn/N co-doping. After calcination at 450 °C, the degree of crystallinity of TiO2 was reduced due to Mn/N co-doption in the resulting Mn/Ti-N-WACF samples, but the TiO2 crystal phase was not changed. XPS spectra revealed that some Ti4+ ions from the TiO2 lattice of Mn/Ti-N-WACF system were substituted by doped Mn. Moreover, new bonds formed within N–Ti–N and Ti–N–O because of the doped N that substituted some oxygen atoms in the TiO2 lattice. Notably, the degradation rate of methylene blue for Mn/Ti-N-WACF was improved because of the co-doped Mn/N under visible-light irradiation.

  6. Evidences of grain boundary capacitance effect on the colossal dielectric permittivity in (Nb + In) co-doped TiO2 ceramics.

    Science.gov (United States)

    Li, Jinglei; Li, Fei; Li, Chao; Yang, Guang; Xu, Zhuo; Zhang, Shujun

    2015-02-06

    The (Nb + In) co-doped TiO2 ceramics were synthesized by conventional solid-state sintering (CSSS) and spark plasma sintering (SPS) methods. The phases and microstructures were studied by X-ray diffraction, Raman spectra, field-emission scanning electron microscopy and transmission electron microscopy, indicating that both samples were in pure rutile phase while showing significant difference in grain size. The dielectric and I-V behaviors of SPS and CSSS samples were investigated. Though both possess colossal permittivity (CP), the SPS samples exhibited much higher dielectric permittivity/loss factor and lower breakdown electric field when compared to their CSSS counterparts. To further explore the origin of CP in co-doped TiO2 ceramics, the I-V behavior was studied on single grain and grain boundary in CSSS sample. The nearly ohmic I-V behavior was observed in single grain, while GBs showed nonlinear behavior and much higher resistance. The higher dielectric permittivity and lower breakdown electric field in SPS samples, thus, were thought to be associated with the feature of SPS, by which reduced space charges and/or impurity segregation can be achieved at grain boundaries. The present results support that the grain boundary capacitance effect plays an important role in the CP and nonlinear I-V behavior of (Nb + In) co-doped TiO2 ceramics.

  7. Effect of Mg$^{2+}$ ions co-doping on timing performance and radiation tolerance of Cerium doped Gd$_{3}$Al$_{2}$Ga$_{3}$O$_{12}$ crystals

    CERN Document Server

    Lucchini, M.T.; Bohacek, P.; Gundacker, S.; Kamada, K.; Nikl, M.; Petrosyan, A.; Yoshikawa, A.; Auffray, E.

    2016-01-01

    Inorganic scintillators with high density and high light yield are of major interest for applications in medical imaging and high energy physics detectors. In this work, the optical and scintillation properties of Mg co-doped Ce:Gd3Al2Ga3O12 crystals, grown using Czochralski technique, have been investigated and compared with Ce:Gd3Al2Ga3O12 ones prepared with identical technology. Improvements in the timing performance of the Mg co-doped samples with respect to Ce:Gd3Al2Ga3O12 ones have been measured, namely a substantial shortening of the rise time and scintillation decay components and lower afterglow were achieved. In particular, a significantly better coincidence time resolution of 233 ps FWHM, being a fundamental parameter for TOF-PET devices, has been observed in Mg co-doped crystals. The samples have also shown a good radiation tolerance under high doses of γ-rays, making them suitable candidates for applications in harsh radiation environments, such as detectors at future collider experiments.

  8. Broadband 2.9 μm emission and high energy transfer efficiency in Er3+/Dy3+ co-doped fluoroaluminate glass

    Science.gov (United States)

    Wang, Tao; Huang, Feifei; Ren, Guangyu; Cao, Wenqian; Tian, Ying; Lei, Ruoshan; Zhang, Junjie; Xu, Shiqing

    2018-01-01

    2.9 μm fluorescence properties and energy transfer mechanism in our prepared Er3+/Dy3+ co-doped fluoroaluminate glass (AYFT) have been investigated in this paper. As far as we know, it is the first time to report a broadband emission extending from 2500 to 3100 nm with a full width at half maximum (FWHM) of 270 nm obtained in Er3+/Dy3+ co-doped fluoroaluminate glass under 980 nm pump. The large spontaneous transition probability (59.46 s-1) calculated based on the Judd-Ofelt theory indicates the intensive Dy3+: 6H13/2 → 6H15/2 transition which has happened to coincide with the emission spectra. Moreover, the high energy transfer efficiencies of Er3+: 4I13/2 to Dy3+: 6H11/2 (90.3%) and Er3+: 4I11/2 to Dy3+: 6H5/2 (85.1%) further confirmed the efficient population inversion of Dy3+: 2.9 μm emission. This present work suggests that Er3+/Dy3+ co-doped fluoroaluminate glass can be a potential candidate for mid-infrared broadband integrated amplifier.

  9. Li{sup +} co-doping effect on the photoluminescence time decay behavior of Y{sub 2}O{sub 3}:Er{sup 3+} films

    Energy Technology Data Exchange (ETDEWEB)

    Meza-Rocha, A.N., E-mail: ameza@fis.cinvestav.mx [Centro de Investigación y de Estudios Avanzados del IPN. Departamento de Física, Av. IPN 2508 Col. San Pedro Zacatenco, CP 07360 México D.F. (Mexico); Huerta, E.F.; Caldiño, U. [Departamento de Física, Universidad Autónoma Metropolitana-Iztapalapa, Av. San Rafael Atlixco 186, CP 09340 México D.F. (Mexico); Zaleta-Alejandre, E. [Centro de Investigación y de Estudios Avanzados del IPN. Departamento de Física, Av. IPN 2508 Col. San Pedro Zacatenco, CP 07360 México D.F. (Mexico); Murrieta S, H.; Hernández A, J.M.; Camarillo, E. [Instituto de Física UNAM, A.P. 20-364 Del. A. Obregón 01000 México D.F. (Mexico); Rivera-Álvarez, Z. [Centro de Investigación y de Estudios Avanzados del IPN. Departamento de Física, Av. IPN 2508 Col. San Pedro Zacatenco, CP 07360 México D.F. (Mexico); Righini, G.C. [Instituto di Fisica Applicata Nello Carrara, C.N.R., Via Madonna del Piano 10, Sesto Fiorentino, 50019 Florence (Italy); Museo Storico della Fisica e Centro Studi e Ricerche Enrico Fermi, Piazza del Viminale 2, 00184 Rome (Italy); Falcony, C. [Centro de Investigación y de Estudios Avanzados del IPN. Departamento de Física, Av. IPN 2508 Col. San Pedro Zacatenco, CP 07360 México D.F. (Mexico)

    2014-10-15

    The effect of Li{sup +} co-doping on photoluminescence time decay characteristics of Y{sub 2}O{sub 3}:Er{sup 3+} is reported for films deposited by ultrasonic spray pyrolysis at 500 °C. The Er{sup 3+} content was fixed at 1.5 at% while the Li{sup +} content in the spraying solution was varied from 1 to 4 at% in relation to Y{sup 3+}. It is observed that the addition of Li{sup +} content up to 2 at%, besides resulting in an increase of the luminescence emission intensity, modifies the luminescence time decay behavior as well. A simple model in which charge transfer from localized centers to the Er{sup 3+} ions is used to describe the evolution with time of the luminescence emission. The introduction of Li{sup +} ions in Y{sub 2}O{sub 3}:Er{sup 3+} seems to have an impact on the charge transfer process and on the total number of Er{sup 3+} ions contributing to the luminescence emission. - Highlights: • Luminescence time decay characteristics of Y{sub 2}O{sub 3}:Er{sup 3+} films were measured as a function of the Li{sup +} co-doping. • The time decay behaviors were analyzed by a simple charge transfer model. • The Li{sup +} co-doping creates localized states which have an impact on the Er{sup 3+} emission.

  10. Synergistic Effects of Sm and C Co-Doped Mixed Phase Crystalline TiO2 for Visible Light Photocatalytic Activity

    Directory of Open Access Journals (Sweden)

    Fuchang Peng

    2017-02-01

    Full Text Available Mixed phase TiO2 nanoparticles with element doping by Sm and C were prepared via a facile sol-gel procedure. The UV-Vis light-diffuse reflectance spectroscopy analysis showed that the absorption region of co-doped TiO2 was shifted to the visible-light region, which was attributed to incorporation of samarium and carbon into the TiO2 lattice during high-temperature reaction. Samarium effectively decreased the anatase-rutile phase transformation. The grain size can be controlled by Sm doping to achieve a large specific surface area useful for the enhancement of photocatalytic activity. The photocatalytic activities under visible light irradiation were evaluated by photocatalytic degradation of methylene blue (MB. The degradation rate of MB over the Sm-C co-doped TiO2 sample was the best. Additionally, first-order apparent rate constants increased by about 4.3 times compared to that of commercial Degusssa P25 under the same experimental conditions. Using different types of scavengers, the results indicated that the electrons, holes, and •OH radicals are the main active species for the MB degradation. The high visible-light photocatalytic activity was attributed to low recombination of the photo-generated electrons and holes which originated from the synergistic effect of the co-doped ions and the heterostructure.

  11. Synthesis, thermal expansion and high-temperature electrical conductivity of Co-doped (Y,Ca)FeO{sub 3−δ} with orthorhombic perovskite structure

    Energy Technology Data Exchange (ETDEWEB)

    Kalyuzhnaya, A.S.; Drozhzhin, O.A. [M. V. Lomonosov Moscow State University, 119991 Moscow (Russian Federation); Istomin, S.Ya., E-mail: istomin@icr.chem.msu.ru [M. V. Lomonosov Moscow State University, 119991 Moscow (Russian Federation); Gippius, A.A.; Kazakov, S.M. [M. V. Lomonosov Moscow State University, 119991 Moscow (Russian Federation); Lyskov, N.V. [Institute of Problems of Chemical Physics RAS, Academician Semenov Av. 1, Chernogolovka, Moscow District 142432 (Russian Federation); Rozova, M.G.; Antipov, E.V. [M. V. Lomonosov Moscow State University, 119991 Moscow (Russian Federation)

    2015-06-15

    Highlights: • (Y,Ca)(Fe,Co)O{sub 3−δ} was prepared via citrate-based route with annealing at 1150–1200 °C. • Y{sub 0.9}Ca{sub 0.1}Fe{sub 0.8}Co{sub 0.2}O{sub 3−δ} demonstrates low thermal expansion coefficient of 11.9 ppm K{sup −1}. • Oxides do not react with YSZ and GDC up to 1000 °C and 1100 °C, respectively. • Compounds demonstrate higher electrical conductivity in comparison with Y{sub 0.9}Ca{sub 0.1}FeO{sub 3}. • Pr-doped (Y,Ca)(Fe,Co)O{sub 3−δ} demonstrate both higher electrical conductivity and TEC. - Abstract: Orthorhombic perovskites Y{sub 1−x}Ca{sub x}Fe{sub 1−y}Co{sub y}O{sub 3−δ} (0.1 ≤ x ≤ 0.2, 0.1 ≤ y ≤ 0.2 and x = 0.1, y = 0.3) were synthesized in air by the citrate route at 1150–1300 °C. High-temperature X-ray powder diffraction (HT XRPD) data for Y{sub 0.9}Ca{sub 0.1}Fe{sub 0.8}Co{sub 0.2}O{sub 3−δ} at 25–800 °C showed no phase transition with calculated thermal expansion coefficient (TEC) of 11.9 ppm K{sup −1}. High-temperature electrical conductivity measurements revealed almost composition independent conductivity values of 22–27 S/cm at 900 °C. No chemical interaction of Y{sub 0.8}Ca{sub 0.2}Fe{sub 0.9}Co{sub 0.1}O{sub 3−δ} with (Zr,Y)O{sub 2−x} (YSZ) or (Ce,Gd)O{sub 2−x} (GDC) was observed up to 1000 °C and 1100 °C, respectively. Partial replacement of Y by Pr according to formula Y{sub 0.8−z}Pr{sub z}Ca{sub 0.2}Fe{sub 0.7}Co{sub 0.3}O{sub 3−δ}, 0.1 ≤ z ≤ 0.35, leads to an increase of both electrical conductivity up to 50 S/cm (z = 0.3) at 900 °C and dilatometry measured TEC up to 15.1 ppm K{sup −1}. Moderate values of electrical conductivity in combination with low TEC and stability towards chemical interaction with typical SOFC electrolytes make Co-doped Y{sub 1−x}Ca{sub x}FeO{sub 3−δ} promissing cathode materials for intermediate temperature solid oxide fuel cells (IT-SOFC)

  12. Photocatalytic degradation of methylene blue by C3N4/ZnO: the ...

    Indian Academy of Sciences (India)

    Abstract. The C3N4/ZnO composite photocatalysts were synthesized by mechanical milling combined with a calcination process. Various ratios of melamine and ZnO powders were milled by a planetary ball mill for 10 h. After heating at 540◦C for 3 h in air, melamine was converted to C3N4 but the formation of C3N4 ...

  13. ZnO Micro- and Nanostructures Obtained by Thermal Oxidation: Microstructure, Morphogenesis, Optical, and Photoluminescence Properties

    OpenAIRE

    Alejandro Escobedo-Morales; Rubén J. Aranda-García; Ernesto Chigo-Anota; Armando Pérez-Centeno; Antonio Méndez-Blas; Carlos G. Arana-Toro

    2016-01-01

    ZnO micro- and nanostructures were obtained through thermal oxidation of Zn powders at high temperature under air atmosphere. A detailed study of the microstructure, morphology, optical, and photoluminescence properties of the generated products at different stages of thermal oxidation is presented. It was found that the exposure time has a strong influence on the resulting morphology. The morphogenesis of the different ZnO structures is discussed, and experimental parameters for fabricating ...

  14. Effect of photocatalytic reduction of carbon dioxide by N-Zr co-doped nano TiO2.

    Science.gov (United States)

    Zhang, Ru; Wang, Li; Kang, Zhuo; Li, Qiang; Pan, Huixian

    2017-11-01

    Modified sol-gel method was adopted to prepare TiO2, Zr-TiO2 and N/Zr-TiO2 composite catalyst. The as-synthesized photocatalysts were characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, Brunner- Emmet- Teller measurement and UV-Vis diffuse reflectance spectroscopy. And the photocatalytic performance toward CO2 reduction was evaluated under ultraviolet light. The catalyst particles were demonstrated in the nanometer level size. When N and Zr are co-doped, on the one hand, Ti4+ can be replaced by Zr4 +, which leads to lattice distortion and inhibits electron-hole recombination. On the other hand, N enters into TiO2 lattice gap to form O-Ti-N bond structure, and partial Ti4+ are reduced to Ti3+. Compared with pristine TiO2, the specific surface area and the band gap of N/Zr-TiO2 were improved and reduced, respectively. The N and Zr synergistically contribute to the obviously strengthened absorption intensity in visible region, as well as significantly improved photocatalytic activity. In the gas phase reactor, when the calcination temperature was 550°C, 0.125N/0.25Zr-TiO2 composite performed the highest photocatalytic activity UV irradiation for 8 h, and the corresponding CH4 yield was 11.837 µmol/g, which was 87.8% higher than that of pristine TiO2. For the visible light, the CH4 yield was 9.003 µmol/g after 8 h irradiation, which was 83.9% higher than that of pristine TiO2.

  15. Structural and dielectric studies of Co doped MgTiO3 thin films fabricated by RF magnetron sputtering

    Directory of Open Access Journals (Sweden)

    T. Santhosh Kumar

    2014-06-01

    Full Text Available We report the structural, dielectric and leakage current properties of Co doped MgTiO3 thin films deposited on platinized silicon (Pt/TiO2/SiO2/Si substrates by RF magnetron sputtering. The role of oxygen mixing percentage (OMP on the growth, morphology, electrical and dielectric properties of the thin films has been investigated. A preferred orientation of grains along (110 direction has been observed with increasing the OMP. Such evolution of the textured growth is explained on the basis of the orientation factor analysis followed the Lotgering model. (Mg1-xCoxTiO3 (x = 0.05 thin films exhibits a maximum relative dielectric permittivity of ɛr = 12.20 and low loss (tan δ ∼ 1.2 × 10−3 over a wide range of frequencies for 75% OMP. The role of electric field frequency (f and OMP on the ac-conductivity of (Mg0.95Co0.05TiO3 have been studied. A progressive increase in the activation energy (Ea and relative permittivity ɛr values have been noticed up to 75% of OMP, beyond which the properties starts deteriorate. The I-V characteristics reveals that the leakage current density decreases from 9.93 × 10−9 to 1.14 × 10−9 A/cm2 for OMP 0% to 75%, respectively for an electric field strength of 250 kV/cm. Our experimental results reveal up to that OMP ≥ 50% the leakage current mechanism is driven by the ohmic conduction, below which it is dominated by the schottky emission.

  16. Gram-scale production of B, N co-doped graphene-like carbon for high performance supercapacitor electrodes

    Science.gov (United States)

    Chen, Zhuo; Hou, Liqiang; Cao, Yan; Tang, Yushu; Li, Yongfeng

    2018-03-01

    Boron and nitrogen co-doped graphene-like carbon (BNC) with a gram scale was synthesized via a two-step method including a ball-milling process and a calcination process and used as electrode materials for supercapacitors. High surface area and abundant active sites of graphene-like carbon were created by the ball-milling process. Interestingly, the nitrogen atoms are doped in carbon matrix without any other N sources except for air. The textual and chemical properties can be easily tuned by changing the calcination temperature, and at 900 oC the BNC with a high surface area (802.35 m2/g), a high boron content (2.19 at%), a hierarchical pore size distribution and a relatively high graphitic degree was obtained. It shows an excellent performance of high specific capacitance retention about 78.2% at high current density (199 F/g at 100 A/g) of the initial capacitance (254 F/g at 0.25 A/g) and good cycling stability (90% capacitance retention over 1000 cycles at 100 A/g) measured in a three-electrode system. Furthermore, in a two-electrode system, a specific capacitance of 225 F/g at 0.25 A/g and a good cycling stability (93% capacitance retention over 20,000 cycles at 25 A/g) were achieved by using BNC as electrodes. The strategy of synthesis is facile and effective to fabricate multi-doped graphene-like carbon for promising candidates as electrode materials in supercapacitors.

  17. Co-doping TiO{sub 2} with boron and/or yttrium elements: Effects on antimicrobial activity

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yuzheng [School of Materials Science and Engineering, Shenyang University of Technology, Shenyang 110870 (China); Wu, Yusheng, E-mail: henanwys@sina.com [School of Materials Science and Engineering, Shenyang University of Technology, Shenyang 110870 (China); Yang, He; Xue, Xiangxin; Liu, Zhihua [Institute of Metallurgical Resources and Environmental Engineering, Northeastern University, Shenyang 110819 (China)

    2016-09-15

    Highlights: • B-Y/TiO{sub 2} nano materials firstly applied to the fields of antibacterial materials. • Systems analysis the existence state of boron and yttrium ion in TiO{sub 2}. • Doping B and Y greatly strengthened the antibacterial activity of TiO{sub 2}. - Abstract: Pure TiO{sub 2}, boron and/or yttrium doped TiO{sub 2} nano-materials were synthesized by a sol–gel method and characterized by XRD, SEM, XPS and PL. XRD analysis indicates that, in the pure TiO{sub 2} and B single doped TiO{sub 2} (B-TiO{sub 2}) nano-materials calcinated at 700 °C, the presence of TiO{sub 2} is a mixture of anatase and rutile; in the Y single doped (Y-TiO{sub 2}), B and Y co-doped TiO{sub 2} nano-materials (B/Y-TiO{sub 2}), the presence of TiO{sub 2} is anatase. SEM image shows the prepared materials have a common round morphology and hexagonal plate morphology caused by the agglomeration of particles. Boron atoms are partially embedded into the TiO{sub 2} interstitial structure or incorporated into the TiO{sub 2} lattice through occupying the position of the oxygen atoms. The results of antimicrobial experiment show that B/Y-TiO{sub 2} material has a remarkable antimicrobial activity. Compared with the visible light irradiation, antimicrobial activity of B/Y-TiO{sub 2} in dark is significant poor.

  18. Aminosilane Functionalization and Cytotoxicity Effects of Upconversion Nanoparticles YO and GdO Co-Doped with Yband Er

    Directory of Open Access Journals (Sweden)

    Dalia Holanda Chavez

    2016-01-01

    Full Text Available In this study, luminescent upconversion nanoparticles (UCNPs Y 2 O 3 and Gd 2 O 3 co-doped with Yb 3+ and Er 3+ were prepared by the sol-gel method (SG. These NPs are able to absorb near infrared photons and upconvert them into visible radiation with a direct application in bioimaging, as an important tool to diagnose and visualize cancer cells. The UCNPs were coated with a thin silica shell and functionalized with amino groups for further folic acid conjugation to allow their interaction with folate ligands on the cell surface. Their physical properties were analysed by Transmission Electron Microscopy (TEM, Fourier transform infrared spectroscopy (FTIR and photoluminescence (PL measurements. The PL results revealed excellent luminescence properties on all core-shell UCNPs. Cytotoxicity experiments with concentrations of bare and aminosilane coated/functionalized UCNPs between 0.001 μg/mL to 1 μg/mL were tested on two different cell lines from human cervix carcinoma (HeLa and human colorectal adenocarcinoma (DLD-1 with a colorimetric assay based on the reduction of MTT reagent (methy-134-thiazolyltetrazolium. The assays show that some concentrations of bare UCNPs were cytotoxic for cervical adenocarcinoma cells (HeLa; however, for human colorectal adenocarcinoma all UCNPs are non-cytotoxic. After UCNPs functionalization with silica-aminosilane (APTES/TEOS, all of the nanoparticles tested were found to be non-cytotoxic for both cell lines. The UCNPs functionalized in this work can be further conjugated with specific ligands and used as biolabels for detection of cancer cells.

  19. Green method for producing hierarchically assembled pristine porous ZnO nanoparticles with narrow particle size distribution

    Energy Technology Data Exchange (ETDEWEB)

    Escobedo-Morales, A., E-mail: alejandro.escobedo@correo.buap.mx [Facultad de Ingeniería Química, Benemérita Universidad Autónoma de Puebla, C.P. 72570 Puebla, Pue. (Mexico); Téllez-Flores, D.; Ruiz Peralta, Ma. de Lourdes [Facultad de Ingeniería Química, Benemérita Universidad Autónoma de Puebla, C.P. 72570 Puebla, Pue. (Mexico); Garcia-Serrano, J.; Herrera-González, Ana M. [Centro de Investigaciones en Materiales y Metalurgia, Universidad Autónoma del Estado de Hidalgo, Carretera Pachuca Tulancingo Km 4.5, Pachuca, Hidalgo (Mexico); Rubio-Rosas, E. [Centro Universitario de Vinculación y Transferencia de Tecnología, Benemérita Universidad Autónoma de Puebla, C.P. 72570 Puebla, Pue. (Mexico); Sánchez-Mora, E. [Instituto de Física, Benemérita Universidad Autónoma de Puebla, Apdo. Postal J-48, 72570 Puebla, Pue. (Mexico); Olivares Xometl, O. [Facultad de Ingeniería Química, Benemérita Universidad Autónoma de Puebla, C.P. 72570 Puebla, Pue. (Mexico)

    2015-02-01

    A green method for producing pristine porous ZnO nanoparticles with narrow particle size distribution is reported. This method consists in synthesizing ZnO{sub 2} nanopowders via a hydrothermal route using cheap and non-toxic reagents, and its subsequent thermal decomposition at low temperature under a non-protective atmosphere (air). The morphology, structural and optical properties of the obtained porous ZnO nanoparticles were studied by means of powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and nitrogen adsorption–desorption measurements. It was found that after thermal decomposition of the ZnO{sub 2} powders, pristine ZnO nanoparticles are obtained. These particles are round-shaped with narrow size distribution. A further analysis of the obtained ZnO nanoparticles reveals that they are hierarchical self-assemblies of primary ZnO particles. The agglomeration of these primary particles at the very early stage of the thermal decomposition of ZnO{sub 2} powders provides to the resulting ZnO nanoparticles a porous nature. The possibility of using the synthesized porous ZnO nanoparticles as photocatalysts has been evaluated on the degradation of rhodamine B dye. - Highlights: • A green synthesis method for obtaining porous ZnO nanoparticles is reported. • The obtained ZnO nanoparticles have narrow particle size distribution. • This method allows obtaining pristine ZnO nanoparticles avoiding unintentional doping. • A growth mechanism for the obtained porous ZnO nanoparticles is proposed.

  20. Sintesis de ceramicos de ZnO dopados con praseodimio y cobalto

    Directory of Open Access Journals (Sweden)

    Ana Milena Cruz

    2003-06-01

    Full Text Available Zinc oxide, ZnO, is a very interesting compound in science and electronic ceramics technology. ZnO ceramics containing some additives were reported to show varistor action with excellent nonlinearity in current - voltage characteristics. However, investigations were restricted to the ZnO - Bi2O3 ceramic system. Other type of varistor, which contains praseodymium oxide, also present nonlinear behaviour. In this work, results obtained in the synthesis Zn-Pr-Co powder are shown. In order to determine and control the several stages of the chemical method, potentiometric titration was used. The solid phase obtained was pressed and sintered.

  1. Magnetic properties of Sn-substituted Ni-Zn ferrites synthesized from nano-sized powders of NiO, ZnO, Fe2O3, and SnO2

    Science.gov (United States)

    Ali, MA; Uddin, MM; Khan, MNI; Chowdhury, FUZ; Hoque, SM; Liba, SI

    2017-06-01

    A series of Ni0.6-x/2Zn0.4-x/2Sn x Fe2O4 (x = 0.0, 0.05, 0.1, 0.15, 0.2, and 0.3) (NZSFO) ferrite composities have been synthesized from nano powders using a standard solid state reaction technique. The spinel cubic structure of the investigated samples has been confirmed by x-ray diffraction (XRD). The magnetic properties such as saturation magnetization ({M}{{s}}), remanent magnetization ({M}{{r}}), coercive field ({H}{{c}}), and Bohr magneton (μ) are calculated from the hysteresis loops. The value of {M}{{s}} is found to decrease with increasing Sn content in the samples. This change is successfully explained by the variation of A-B interaction strength due to Sn substitution in different sites. The compositional stability and quality of the prepared ferrite composites have also been endorsed by the fairly constant initial permeability ({μ }^{\\prime }) over a wide range of frequency. The decreasing trend of {μ }^{\\prime } with increasing Sn content has been observed. Curie temperature {T}{{C}} has been found to increase with the increase in Sn content. A wide spread frequency utility zone indicates that the NZSFO can be considered as a good candidate for use in broadband pulse transformers and wide band read-write heads for video recording. The composition of x = 0.05 shows unusual results and the possible reason is also mentioned with the established formalism.

  2. Powder diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Hart, M.

    1995-12-31

    the importance of x-ray powder diffraction as an analytical tool for phase identification of materials was first pointed out by Debye and Scherrer in Germany and, quite independently, by Hull in the US. Three distinct periods of evolution lead to ubiquitous application in many fields of science and technology. In the first period, until the mid-1940`s, applications were and developed covering broad categories of materials including inorganic materials, minerals, ceramics, metals, alloys, organic materials and polymers. During this formative period, the concept of quantitative phase analysis was demonstrated. In the second period there followed the blossoming of technology and commercial instruments became widely used. The history is well summarized by Parrish and by Langford and Loueer. By 1980 there were probably 10,000 powder diffractometers in routine use, making it the most widely used of all x-ray crystallographic instruments. In the third, present, period data bases became firmly established and sophisticated pattern fitting and recognition software made many aspects of powder diffraction analysis routine. High resolution, tunable powder diffractometers were developed at sources of synchrotron radiation. The tunability of the spectrum made it possible to exploit all the subtleties of x-ray spectroscopy in diffraction experiments.

  3. Photocatalytic degradation of organic dyes by Er3+: YAlO3/Co- and Fe-doped ZnO coated composites under solar irradiation

    Science.gov (United States)

    Chen, Yang; Lu, Chunxiao; Tang, Liang; Song, Yahui; Wei, Shengnan; Rong, Yang; Zhang, Zhaohong; Wang, Jun

    2016-12-01

    In this work, the Er3+: YAlO3/Co- and Fe-doped ZnO coated composites were prepared by the sol-gel method. Then, they were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDX). Photo-degradation of azo fuchsine (AF) as a model dye under solar light irradiation was studied to evaluate the photocatalytic activity of the Er3+: YAlO3/Co- and Fe-doped ZnO coated composites. It was found that the photocatalytic activity of Co- and Fe-doped ZnO composites can be obviously enhanced by upconversion luminescence agent (Er3+: YAlO3). Besides, the photocatalytic activity of Er3+: YAlO3/Fe-doped ZnO is better than that of Er3+: YAlO3/Co-doped ZnO. The influence of experiment conditions, such as the concentration of Er3+: YAlO3, heat-treatment temperature and time on the photocatalytic activity of the Er3+: YAlO3/Co- and Fe-doped ZnO coated composites was studied. In addition, the effects of solar light irradiation time, dye initial concentration, Er3+: YAlO3/Co- and Fe-doped ZnO amount on the photocatalytic degradation of azo fuchsine in aqueous solution were investigated in detail. Simultaneously, some other organic dyes, such as Methyl Orange (MO), Rhodamine B (RM-B), Acid Red B (AR-B), Congo Red (CR), and Methyl Blue (MB) were also studied. The possible excitation principle of Er3+: YAlO3/Co- and Fe-doped ZnO coated composites under solar light irradiation and the photocatalytic degradation mechanism of organic dyes were discussed.

  4. Vacuum-annealing induced enhancements in the transparent conducting properties of Mo  +  F doped ZnO thin films

    Science.gov (United States)

    Dineshbabu, N.; Ravichandran, K.

    2017-09-01

    The decisive aim of the present study is to enhance the transparent conducting properties of Mo  +  F co-doped ZnO films through annealing. In this work, Mo  +  F co-doped ZnO (MFZO) films were deposited on glass substrates at a deposition temperature of 350 °C using a home-made nebulizer spray pyrolysis technique and the prepared samples were annealed under air and vacuum atmosphere at 400 °C for 2 h. The structural, electrical, optical, surface morphological and elemental properties of as-deposited, air-annealed and vacuum-annealed samples were compared using various analytical techniques. The vacuum-annealed sample shows lowest resistivity of 1.364  ×  10-3 Ω cm and high transmittance of 90% in the visible region with high ohmic conducting nature. The optical bandgap of the sample was found to be increased to 3.36 eV after vacuum annealing treatment. The XRD patterns of the films confirmed the polycrystalline nature. The PL measurements show the defect levels of the deposited films. The FESEM and AFM studies show an increase in the grain size and roughness of the films, respectively, after vacuum-annealing treatment. The presence of the elements before and after annealing treatment was confirmed using XPS analysis.

  5. In-Doped ZnO Hexagonal Stepped Nanorods and Nanodisks as Potential Scaffold for Highly-Sensitive Phenyl Hydrazine Chemical Sensors

    National Research Council Canada - National Science Library

    Ahmad Umar; Sang Hoon Kim; Rajesh Kumar; Mohammad S. Al-Assiri; A. E. Al-Salami; Ahmed A. Ibrahim; Sotirios Baskoutas

    2017-01-01

    Herein, we report the growth of In-doped ZnO (IZO) nanomaterials, i.e., stepped hexagonal nanorods and nanodisks by the thermal evaporation process using metallic zinc and indium powders in the presence of oxygen...

  6. Defects and the optical absorption in nanocrystalline ZnO

    Science.gov (United States)

    Dutta, Sreetama; Chattopadhyay, Sanjay; Sutradhar, Manas; Sarkar, Anindya; Chakrabarti, Mahuya; Sanyal, Dirtha; Jana, Debnarayan

    2007-06-01

    The correlation between the structural and optical properties of mechanically milled high purity ZnO powder is reported in the present work. Reduction of average grain size and enhancement of strain as a result of milling have been estimated from the broadening of x-ray powder diffraction patterns. After milling, the optical bandgap, revealed from absorption spectroscopy, has been red-shifted and the width of the localized states, calculated from the analysis of the Urbach tail below the absorption edge, has been extended more and more into the bandgap. Moreover, the band tailing parameter is seen to vary exponentially with the inverse of the grain size. Finally, the positron annihilation technique has been employed to identify the nature of defects present (or generated due to milling) in the system and thereby to correlate the defect mediated modification of optical absorption in ZnO.

  7. Defects and the optical absorption in nanocrystalline ZnO

    Energy Technology Data Exchange (ETDEWEB)

    Dutta, Sreetama [Department of Physics, University of Calcutta, 92 Acharya Prafulla Chandra Road, Kolkata 700 009 (India); Chattopadhyay, Sanjay [Department of Physics, Taki Government College, Taki 743429 (India); Sutradhar, Manas [Department of Chemistry, University of Calcutta, 92 Acharya Prafulla Chandra Road, Kolkata 700 009 (India); Sarkar, Anindya [Department of Physics, Bangabasi Morning College, 19 Rajkumar Chakraborty Sarani, Kolkata 700 009 (India); Chakrabarti, Mahuya [Variable Energy Cyclotron Centre, 1/AF, Bidhannagar, Kolkata 700 064 (India); Sanyal, Dirtha [Variable Energy Cyclotron Centre, 1/AF, Bidhannagar, Kolkata 700 064 (India); Jana, Debnarayan [Department of Physics, University of Calcutta, 92 Acharya Prafulla Chandra Road, Kolkata 700 009 (India)

    2007-06-13

    The correlation between the structural and optical properties of mechanically milled high purity ZnO powder is reported in the present work. Reduction of average grain size and enhancement of strain as a result of milling have been estimated from the broadening of x-ray powder diffraction patterns. After milling, the optical bandgap, revealed from absorption spectroscopy, has been red-shifted and the width of the localized states, calculated from the analysis of the Urbach tail below the absorption edge, has been extended more and more into the bandgap. Moreover, the band tailing parameter is seen to vary exponentially with the inverse of the grain size. Finally, the positron annihilation technique has been employed to identify the nature of defects present (or generated due to milling) in the system and thereby to correlate the defect mediated modification of optical absorption in ZnO.

  8. (YSZ) powders

    Indian Academy of Sciences (India)

    Unknown

    XRD pattern for YSZ gel calcined at 900°C. Figure 3. Particle size distribution of the dry and wet ground slurries (20 vol.% solid content at a pH of 3). A. powder dry ground for 1 h; B, C, D, E. wet ground for 1, 2, 4, 10 h, res- pectively. Figure 4. Zeta-potential variation with pH for aqueous sus- pensions of 900°C calcined YSZ ...

  9. Ba and Ti co-doped BiFeO3 thin films via a modified chemical route with synchronous improvement in ferroelectric and magnetic behaviors

    Science.gov (United States)

    Wang, Yao; Li, Jing; Chen, Jingyi; Deng, Yuan

    2013-03-01

    A modified chemical route via the layer-by-layer alternative deposition of BaTiO3 and BiFeO3 two compositions followed by the solution processing has been developed to prepare Ba and Ti co-doped multiferroic BiFeO3 thin films. The Ba and Ti co-doped BiFeO3 films crystallize in single perovskite phase and are composed of uniformly distributed grains of tens of nanometers as evidenced by X-ray diffraction and scanning electron microscopy images, respectively. But the films show local composition fluctuation with further high-resolution transmission electron microscope analysis, which leads to increased inner strain and thus a phase transition from R3c to P4mm occurs as Ba and Ti contents reach 50 mol. %. Accompanying the structural phase transition, a saturated P-E hysteresis loop with Pr ˜ 27 μC/cm2 and Ps ˜ 87 μC/cm2 and, moreover, a transition from antiferromagnetic to ferromagnetic state with Mr ˜ 1.46 emu/cm3 and Hc ˜ 1000 Oe have been observed. A strain induced structural change is proposed to explain for the observed synchronous enhancement in ferroelectric and magnetic properties, and elastic energy calculation is carried out to verify the viewpoint on magnetic behavior. The modified multiferroic behaviors of Ba, Ti co-doped BiFeO3 film imply an improved magnetoelectric coupling, which makes the material good candidate as memory devices and sensors.

  10. A simple preparation method and characterization of B and N co-doped TiO{sub 2} nanotube arrays with enhanced photoelectrochemical performance

    Energy Technology Data Exchange (ETDEWEB)

    Georgieva, J., E-mail: jenia@ipc.bas.bg [Rostislaw Kaischew Institute of Physical Chemistry, Bulgarian Academy of Sciences (Bulgaria); Valova, E.; Armyanov, S.; Tatchev, D. [Rostislaw Kaischew Institute of Physical Chemistry, Bulgarian Academy of Sciences (Bulgaria); Sotiropoulos, S. [Department of Chemistry, Aristotle University of Thessaloniki (Greece); Avramova, I. [Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences (Bulgaria); Dimitrova, N. [Rostislaw Kaischew Institute of Physical Chemistry, Bulgarian Academy of Sciences (Bulgaria); Hubin, A.; Steenhaut, O. [Research Group Electrochemical and Surface Engineering (SURF), Vrije Universiteit Brussel (Belgium)

    2017-08-15

    Highlights: • An environment-sparing method for preparation of B,N-co-doped TNTA is realized. • N and B promote additionally the reduction of Ti(IV) to Ti(III) during the crystallization annealing. • N and B dopants are predominantly in interstitial positions. • B,N-TNTA exhibited better photoelectrochemical performance and photoelectrocatalytic degradation of MO. - Abstract: Highly ordered TiO{sub 2} nanotube arrays (TNTA) have attracted much attention due to the excellent photocatalytic, optical and electrical properties. However, their absorption range is limited to ultraviolet (UV) spectrum only due to the wide band gap (3.2 eV). One of the strategies to overcome this problem is doping with boron and nitrogen. They are produced via titanium sheet anodization and subsequent electrochemical treatment of titania in an electrolyte containing boric acid. The as-prepared B-TNTA are annealed in N{sub 2} atmosphere at 500 °C for 2 h to obtain B,N-TNTA. The samples are characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), UV–vis diffuse reflectance spectroscopy (DRS) and X-ray photoelectron spectroscopy (XPS). The B,N-TNTA consist of uniform and well aligned nanotubes with an average inner diameter of 80–100 nm and a length not exceeding 1 μm. The photocurrent response measurements of undoped TNTA, N-doped and B,N-co-doped samples are performed under UV and visible light (Vis) illumination and a comparison is made. The obtained results show that the B,N-doping leads to remarkable photocurrent enhancement and better photocatalytic activity for methyl orange (MO) degradation due to the synergistic effects of B,N-co-doping and lower electron-hole recombination rates.

  11. Luminescent properties and energy transfer of Gd{sup 3+}/Eu{sup 3+} co-doped high uniform meso-silica nanorods

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Chunming; Song, Yanhua; Gao, Fei; Zhou, Xiuqing; Sheng, Ye [College of Chemistry, Jilin University, Changchun 130012 (China); Shi, Zhan [State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun 130012 (China); Zou, Haifeng, E-mail: haifengzou0431@gmail.com [College of Chemistry, Jilin University, Changchun 130012 (China)

    2015-02-15

    Eu{sup 3+} and Gd{sup 3+} ions co-doped amorphous silica nanorods were prepared using a simple sol–gel method, and their luminescent properties were studied under the excitation of ultraviolet light. X-ray diffraction (XRD), Energy-dispersive X-ray (EDX) spectroscopy, Fourier transform infrared spectrum (FT-IR), Scanning electron microscope (SEM), Transmission electron microscopy (TEM), and Photoluminescence (PL) spectra were employed to characterize the products in detail. The nanorods are uniform and their diameters and lengths are in the range of 200–300 nm and 500–700 nm, respectively. Energy transfer process in Gd{sup 3+} and Eu{sup 3+} co-doped silica, where a ground state of Gd{sup 3+}, {sup 8}S{sub 7/2}, was selectively excited to a {sup 6}I{sub J} state under the excitation of 274 nm, was studied in terms of luminescence spectra, which indict that the energy transfer of Gd{sup 3+}–Eu{sup 3+} is efficient. The mechanism of energy transfer from Gd{sup 3+} to Eu{sup 3+} is a resonant transfer, in which electric dipole–dipole interaction plays a leading role. Furthermore, the doping concentration-dependence of Eu{sup 3+} ions on the energy transfer efficiency was also investigated. - Highlights: • Uniform silica nanorods co-doped with Gd{sup 3+} and Eu{sup 3+} have been prepared using cetyltrimethylammonium bromide (CTAB) as surfactant template by the sol–gel method. • Rare earths doping enhanced the luminescence activity under UV excitation. • Energy transfer from Gd{sup 3+} to Eu{sup 3+} is a resonant transfer, in which electric dipole–dipole interaction plays a leading role. • The effect of doping concentrations of Eu{sup 3+} ions on the energy transfer efficiency was investigated.

  12. Enhanced photorefractive properties in Hf, Ce and Cu co-doped LiNbO{sub 3} crystals for holographic application

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Tao, E-mail: tzhang_hit02@yahoo.com [Key Laboratory of In-fiber Integrated Optics, Ministry of Education of China, Harbin Engineering University, Harbin 150001 (China); College of Science, Harbin Engineering University, Harbin 150001 (China); Postdoctoral Research Station of Mechanical Engineering, College of Mechanical and Electrical Engineering, Harbin Engineering University, Harbin 150001 (China); Wang, Xin; Geng, Tao; Tong, Chengguo [Key Laboratory of In-fiber Integrated Optics, Ministry of Education of China, Harbin Engineering University, Harbin 150001 (China); College of Science, Harbin Engineering University, Harbin 150001 (China); Kang, Chong [Key Laboratory of In-fiber Integrated Optics, Ministry of Education of China, Harbin Engineering University, Harbin 150001 (China); College of Science, Harbin Engineering University, Harbin 150001 (China); Postdoctoral Research Station of Mechanical Engineering, College of Mechanical and Electrical Engineering, Harbin Engineering University, Harbin 150001 (China)

    2015-04-25

    Graphical abstract: Correlation spots of 200 holograms in a Hf, Ce and Cu co-doped LiNbO{sub 3}. - Highlights: • Several doped LiNbO{sub 3} crystals with various level of Hf doping were grown by Cz method. • IR peak shift is attributed to the complex defect change at different level of Hf. • Enhanced photorefractive properties have been got with higher Hf-doping level. • Reduced defect and increased photoconductivity are responsible for optical properties. • 200 holograms’ experiment is realized in a coherent volume 0.073 cm{sup 3}. - Abstract: Hf, Ce and Cu co-doped LiNbO{sub 3} crystals with various level of Hf doping were grown in air by a conventional Cz method. The infrared spectra were measured to discuss the defect structures and the mechanism of the absorption peak shift in these crystals. The light-induced scattering of the crystals was evaluated by the transmitted light method. The influence of the Hf-doping level on the photorefractive properties of Hf, Ce and Cu co-doped LiNbO{sub 3} crystals was studied via two-beam coupling. It is found that proper doping Hf is an efficient method to enhance the comprehensive photorefractive properties of the LiNbO{sub 3}. Using one of these crystals as medium, 200 holograms storage and correlation experiments based on angle fractal multiplexing have been realized in a coherent volume 0.073 cm{sup 3}. Moreover the diffraction efficiency is uniform and the storage density has reached 2.2 Gb/cm{sup 3}.

  13. Characterisation, phase stability and surface chemical properties of photocatalytic active Zr and Y co-doped anatase TiO2 nanoparticles

    Science.gov (United States)

    Mattsson, Andreas; Lejon, Christian; Bakardjieva, Snejana; Štengl, Vaclav; Österlund, Lars

    2013-03-01

    We report on the characterization, phase stability, surface chemical and photocatalytic properties of Zr and Y co-doped anatase TiO2 nanoparticles prepared by homogenous hydrolysis methods using urea as precipitating agent. The materials were analyzed by scanning electron microscopy, X-ray diffraction, Raman spectroscopy, BET isotherm and BJH pore size distribution measurements. It is shown that Y and Zr ions replace Ti ions in the anatase TiO2 structures up to a critical total dopant concentration of approximately 13 wt%. The co-doped particles show increased phase stability compared to pure anatase TiO2 nanoparticles. The anatase to rutile phase transformation is shown to be preceded by cation segregation and dissolution with concomitant precipitation of Y2Ti2-xZrxO7 and ZrTiO4. Co-doping modifies the optical absorption edge with a resulting attenuation of the Urbach tail. The band gap is slightly blue-shifted at high doping concentrations, and red shifted at lower doping concentrations. Formic acid adsorption was used as a probe molecule to investigate surface chemical properties and adsorbate structures. It was found that the relative abundance of monodentate formate compared to bidentate coordinated formate decreases with increasing doping concentration. This is attributed to an increased surface acidity with increasing dopant concentration. Photodegradation of formic acid occurred on all samples. With mode-resolved in situ FTIR spectroscopy it is shown that the rate of photodegradation of monodentate formate species are higher than for bidentate formate species. Thus our results show that the trend of decreasing photo-degradation rate with increasing dopant concentration can be explained by the adsorbate structure, which is controlled by the acidity of the surface.

  14. Enhancment of ferromagnetism in Ba and Er co-doped BiFeO{sub 3} nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Naeimi, A.S., E-mail: naeimi.a.s@gmail.com [Department of Physics, Aliabad Katoul Branch, Islamic Azad University, Aliabad Katoul (Iran, Islamic Republic of); Dehghan, E.; Sanavi Khoshnoud, D. [Department of Physics, Semnan University, Semnan 35195-363 (Iran, Islamic Republic of); Gholizadeh, A. [School of Physics, Damghan University (DU), Damghan (Iran, Islamic Republic of)

    2015-11-01

    Bi{sub 1−y−x}Ba{sub y}Er{sub x}FeO{sub 3} [BB{sub y}E{sub x}FO, (0.13≤y≤0.17, 0≤x≤0.2)] nanoparticles were successfully synthesized by a sol–gel method. The structural, microstructural and magnetic properties have been investigated, using X-ray diffraction, Raman scattering, field emission scanning electron microscopy (FE-SEM) and magnetometry measurements at room temperature. The refinement of X-ray diffraction pattern of BB{sub 0.15}E{sub 0}FO indicates a phase transition from rhombohedral (R3c) to tetragonal (P4mm) with increasing Ba content and a transition from the coexistence of rhombohedral–tetragonal phase to orthorhombic (Pbnm) in BB{sub 0.15}E{sub x}FO samples with increasing Er concentration. The Raman analysis confirms crystal phase transition in BB{sub 0.15}E{sub x}FO compounds. The FE-SEM and TEM analysis show that the average nanoparticle size is about 50–100 nm and it decreases with Er concentration. The remnant magnetisation of BB{sub 0.15}E{sub 0.1}FO sample (M{sub r}=0.98 emu/g) is approximately two times greater than compared to BB{sub 0.15}E{sub 0}FO (M{sub r}=0.51 emu/g) that may be attributed to the collapse of spin structure and modifying exchange interactions because of Er{sup +3} doping. This enhancement in magnetic properties at room temperature can play an important role for the practical applications. - Highlights: • Bi{sub 1−y−x}Ba{sub y}Er{sub x}FeO{sub 3} nanoparticles were successfully synthesized by a sol–gel route. • X-ray diffraction and Raman spectroscopy measurements confirmed a phase transition from rhombohedral–orthorhombic. • Considerable enhancement in magnetisation of BiFeO{sub 3} is obtained with Ba and Er co-doping.

  15. Processing and Characterization of In-Situ Generated Nanosilver and Er3+ Co-Doped Bromoborosilicate Glass Nanocomposites.

    Science.gov (United States)

    Sarkar, Jit; Tarafder, Anal; Karmakar, Basudeb

    2015-09-01

    In the present investigation, bromoborosilicate glass of composition 6Na2O-19K2O-10BaBr2- 2Al2O3-15B2O3-48SiO2 (mole %) added with 0.2 wt% SnO, co-doped with 0.001 wt% Ag and 0.7 wt% Er2O3 in excess amount, was prepared by melt-quench technique. The metal-glass nanocomposites were derived involving a single-step in-situ thermochemical reduction of the precursor glass subjecting an isothermal heat-treatment protocol. The precursor glass and metal glass nanocomposites were characterized by dilatometer, differential scanning calorimeter, X-ray diffractometer, field emission scanning electron microscope, transmission electron microscope, Fourier transform infrared spectrometer, UV-Vis-NIR spectrophotometer, fluorimeter etc. XRD spectra represent the amorphous nature of the samples and without having any sharp peaks of silver (Ag0) and barium bromide (BaBr2). But the FESEM micrograph shows the presence of BaBr2 crystallites in clusters and the TEM micrograph shows the presence of AgO nanoparticles of different shapes and sizes. The precursor glass sample shows sharp absorption peak at 378 nm and 521 nm due to the 4G11,2 and 2H11/2 energy levels of Er3+ but glass nanocomposites exhibit another band at 410 nm due to the surface plasmon resonance of Ag0 nanoparticles. They also show sharp emis- sion peak at 1542 nm due to 4115/2 -+4l13/2 transition of Er3+ ions and prominent upconverted peaks at 630 nm (red, medium) and 645 nm (red, strong) due to 4F9/2 + 1 15/2 transition. The intensity of the absorption and upconverted peaks increases with the duration of heat treatment, having maximum intensity at 5 h and the intensity of the emission peak increases with heat treatment upto 1 h and then decreases for 5 h. Thus these metal-glass nanocomposites show enhanced photoluminescence upconversion and are promising material for different photonic applications.

  16. Aminosilane Functionalization and Cytotoxicity Effects of Upconversion Nanoparticles Y2O3 and Gd2O3 Co-doped with Yb3+ and Er3+

    OpenAIRE

    Dalia Holanda Chavez; Karla Juarez-Moreno; Gustavo Alonso Hirata

    2016-01-01

    In this study, luminescent upconversion nanoparticles (UCNPs) Y2O3 and Gd2O3 co-doped with Yb3+ and Er3+ were prepared by the sol-gel method (SG). These NPs are able to absorb near infrared photons and upconvert them into visible radiation with a direct application in bioimaging, as an important tool to diagnose and visualize cancer cells. The UCNPs were coated with a thin silica shell and functionalized with amino groups for further folic acid conjugation to allow their interaction with fola...

  17. Understanding the infrared to visible upconversion luminescence properties of Er{sup 3+}/Yb{sup 3+} co-doped BaMoO{sub 4} nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Adhikari, Rajesh; Choi, Jinhyuk [Research Center for Eco-Multifunctional Nanomaterials, SunMoon University, Asan (Korea, Republic of); Narro-García, R.; De la Rosa, E. [Centro de Investigaciones en Óptica, A. P.1-948, León, Gto. 37150 (Mexico); Sekino, Tohru [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai (Japan); Lee, Soo Wohn, E-mail: swlee@sunmoon.ac.kr [Research Center for Eco-Multifunctional Nanomaterials, SunMoon University, Asan (Korea, Republic of)

    2014-08-15

    In this paper we report the infrared to visible upconversion luminescence properties of Er{sup 3+}/Yb{sup 3+} co-doped BaMoO{sub 4} nanocrystals synthesized via microwave assisted sol–gel processing route. Structural, morphological and upconversion luminescence properties were investigated by X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), UV–vis diffuse reflectance spectroscopy (UV–vis DRS) and Upconversion Photoluminescence spectra analysis. Results revealed that the oval shaped BaMoO{sub 4} nanocrystals ranging in size from 40 to 60 nm having tetragonal scheelite crystal structure were obtained by sol–gel route. The infrared to visible upconversion luminescence has been investigated in Er{sup 3+}/Yb{sup 3+} co-doped in BaMoO{sub 4}with different Yb{sup 3+} concentrations. Intense green upconversion emissions around 528, 550 nm, and red emission at 657 nm corresponding to the {sup 2}H{sub 11/2}, {sup 4}S{sub 3/2}, and {sup 4}F{sub 9/2} transitions, respectively to the {sup 4}I{sub 15/2} ground state were observed when excited by CW laser radiation at 980 nm. The green emissions were greatly enhanced after the addition of sensitizer (Yb{sup 3+} ions). The effect of Yb{sup 3+} on the upconversion luminescence intensity was analyzed and explained in terms of the energy transfer process based. The reported work establishes the understanding of molybdates as an alternative host material for upconversion luminescence. - Graphical abstract: Infrared to visible upconversion luminescence of Er{sup 3+}/Yb{sup 3+} co-doped BaMoO{sub 4} nanocrystals. - Highlights: • Nanocrystals were synthesized by microwave assisted sol–gel processing route. • Strong green emissions were observed in Er{sup 3+}/Yb{sup 3+} co-doped BaMoO{sub 4} nanocrystals. • Provides an insight on Upconversion luminescence properties of oxides host materials.

  18. One-pot Synthesis of Nitrogen and Phosphorus Co-doped Graphene and Its Use as High-performance Electrocatalyst for Oxygen Reduction Reaction.

    Science.gov (United States)

    Dong, Liye; Hu, Chuangang; Huang, Xianke; Chen, Nan; Qu, Liangti

    2015-12-01

    In this study, N,P co-doped graphene (NPG) was prepared by a one-step pyrolysis using a mixture of graphene oxide and hexachlorocyclotriphosphazene (HCCP), in which HCCP was used as both the N and P source. Furthermore, it is shown that NPG electrodes, as efficient metal-free electrocatalysts, have a high onset potential, high current density, and long-term stability for the oxygen reduction reaction. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Curie temperature of Co-doped TiO2 as functions of carrier density and Co content evaluated from electrical transport and magnetization at low temperature regime

    Directory of Open Access Journals (Sweden)

    Thantip S. Krasienapibal

    2016-05-01

    Full Text Available Curie temperature (TC of anatase Co-doped TiO2 epitaxial thin films was systematically investigated as functions of carrier density (n and Co content (x by electrical transport and magnetization measurements at low temperature regime. The estimated TC from both measurements showed similar TC. For x = 0.03, 0.05, and 0.07, non-monotonic TC vs. n relations were observed, whereas TC was monotonically increasing function of n for x = 0.10. Possible mechanism of high TC ferromagnetism for this compound was discussed.

  20. Structure and optical properties of Dy3+/Tm3+ co-doped oxyfluoride glass ceramics containing β-NaGdF4 nanocrystals

    Science.gov (United States)

    Sun, Xiao; Zhao, Shilong; Fei, Yong; Huang, Lihui; Xu, Shiqing

    2014-12-01

    Dy3+/Tm3+ co-doped oxyfluoride glass ceramics containing hexagonal β-NaGdF4 nanocrystals were prepared by the melt-quenching method and subsequent heat-treatment procedure. During the crystallization process, the structural evolution of glass network was systematically investigated using XRD, TEM and FTIR spectra. Experimental results provided new evidences that a silica-enriched layer around the precipitated fluoride nanocrystals was formed during the crystallization process. Strong white light emission was obtained in the oxyfluoride glass ceramics by modifying the relative concentration ratio of Tm3+ and Dy3+ ions.

  1. Photonic Band Gap Effect on Energy Transfer in Tb3+, Eu3+ CO-Doped TiO2 Inverse Opal Films

    Science.gov (United States)

    Liu, Zhendong; Zhou, Ji; Li, Bo

    2013-06-01

    The energy transfer from Tb3+ to Eu3+ co-doped TiO2(TiO2:Tb, Eu) inverse opal photonic crystals was investigated by photoluminescence. The results showed that the photonic band gap enhanced energy transfer from the donor Tb3+ to the acceptor Eu3+. When the fluorescence emission wavelength of Tb3+ overlaps with the photonic band gap, the fluorescence intensity of Tb3+ is suppressed, while the fluorescence intensity of Eu3+ is enhanced. Energy transfer efficiencies were attributed to the tuning effects of energy transfer in the photoluminescence process by photonic crystal structure.

  2. New fluorophosphate glasses co-doped with Eu{sup 3+} and Tb{sup 3+} as candidates for generating tunable visible light

    Energy Technology Data Exchange (ETDEWEB)

    Queiroz, T.B. de, E-mail: thiago.branquinho-de-queiroz@uni-bayreuth.de [Physics Institute of São Carlos, University of São Paulo, 13566-590 São Carlos, SP (Brazil); Theoretical Physics IV, University of Bayreuth, 95440 Bayreuth (Germany); Botelho, M.B.S. [Physics Institute of São Carlos, University of São Paulo, 13566-590 São Carlos, SP (Brazil); University of Brasilia, 70910-900 Brasilia, DF (Brazil); Gonçalves, T.S.; Dousti, M. Reza [Physics Institute of São Carlos, University of São Paulo, 13566-590 São Carlos, SP (Brazil); Camargo, A.S.S. de, E-mail: andreasc@ifsc.usp.br [Physics Institute of São Carlos, University of São Paulo, 13566-590 São Carlos, SP (Brazil)

    2015-10-25

    A series of optically active Eu{sup 3+} and Tb{sup 3+} doped fluorophosphate glasses with compositions (BaF{sub 2}){sub 0.25}(SrF{sub 2}){sub 0.25}(AlF{sub 3}){sub 0.10}[Al(PO{sub 3}){sub 3}]{sub 0.20}(YF{sub 3}){sub 0.20-x}(EuF{sub 3} and/or TbF{sub 3}){sub x} (x = 0 to 0.04) was prepared and characterized by optical spectroscopy. While embedded in the oxyfluoride host, the cited rare earth (RE) ions exhibit improved spectroscopic properties such as longer excited state lifetimes than in oxide glasses and intense emissions in the red ({sup 5}D{sub 0} → {sup 7}F{sub 2}, Eu{sup 3+}), green and blue ({sup 5}D{sub 4} → {sup 7}F{sub 5} and {sup 5}D{sub 3},{sup 5}G{sub 6} → {sup 7}F{sub 5},{sup 7}F{sub 4}, Tb{sup 3+}) spectral regions. Based on this fact, co-doped samples can be designed with appropriate concentrations of these two ions and generate tunable and white light upon excitation with suitable wavelengths, dispensing the need for a third blue emitting RE ion. Four co-doped samples with equal amounts of EuF{sub 3} and TbF{sub 3} and total concentration of 0.3, 0.5, 1.0 and 1.5 mol% were tested. Their CIE chromaticity coordinates were calculated for various excitation wavelengths in the region from 350 to 360 nm allowing tuned emission from blue to red. The long lifetime values of the emitting levels in these co-doped samples (τ ≈ 3.1 ms for Eu{sup 3+5}D{sub 0}, and τ ≈ 4.0 ms for Tb{sup 3+5}D{sub 4}), associated with fairly high quantum yields (Q.Y. = 5–12%) of the samples indicate that these materials could be efficiently pumped by high power LEDs around 355 nm. - Highlights: • Fluorophosphate glasses doped with Eu{sup 3+} and Tb{sup 3+} and excellent optical properties. • Tunable visible emission and white emission in co-doped samples. • Rare earth bonding preference to fluoride rather than phosphate ions.

  3. Effect of calcination temperature on the structure and visible-light photocatalytic activities of (N, S and C) co-doped TiO{sub 2} nano-materials

    Energy Technology Data Exchange (ETDEWEB)

    Lei, X.F., E-mail: leixuefei69@163.com [School of Resources and Materials, Northeastern University at Qinhuangdao, Qinhuangdao 066004 (China); Institute of Metallurgical Resource and Environmental Engineering, Northeastern University, Shenyang 110819 (China); Liaoning Key Laboratory of Metallurgical Resource Recycling Science, Shenyang 110819 (China); Liaoning Engineering and Technology Research Center of Boron Resource, Comprehensive Utilization, Shenyang 110819 (China); Liaoning Provincial Universities Key Laboratory of Boron Resource Ecological, Utilization Technology and Boron Materials, Shenyang 110819 (China); Xue, X.X.; Yang, H. [Institute of Metallurgical Resource and Environmental Engineering, Northeastern University, Shenyang 110819 (China); Liaoning Key Laboratory of Metallurgical Resource Recycling Science, Shenyang 110819 (China); Liaoning Engineering and Technology Research Center of Boron Resource, Comprehensive Utilization, Shenyang 110819 (China); Liaoning Provincial Universities Key Laboratory of Boron Resource Ecological, Utilization Technology and Boron Materials, Shenyang 110819 (China); Chen, C.; Li, X.; Niu, M.C.; Gao, X.Y.; Yang, Y.T. [School of Resources and Materials, Northeastern University at Qinhuangdao, Qinhuangdao 066004 (China)

    2015-03-30

    Graphical abstract: (N, S and C) co-doped TiO{sub 2} samples show good photocatalytic activity for Cr(VI) reduction under visible light irradiation. - Highlights: • (N, S and C) co-doping in TiO{sub 2} can preserve the anatase form to higher temperature. • (N, S and C) co-doped TiO{sub 2} samples can absorb both UV and visible light. • The band gap energy of the sample significantly reduced after (N, S and C) co-doping. • (N, S and C) co-doped TiO{sub 2} samples effective for visible light induced reduction of Cr(VI). - Abstract: The (N, S and C) co-doped TiO{sub 2} samples (NSC-TiO{sub 2}) were synthesized by the sol–gel method combining with the high energy ball milling method calcined at the different temperature (400–700 °C), employing butyl titanate as the titanium source and thiourea as the doping agent. The structures of NSC-TiO{sub 2} samples were characterized by X-ray diffraction (XRD), UV–vis diffuse reflectance spectra (DRS), X-ray photoluminescence (PL) spectroscopy, X-ray photoelectron spectroscopy (XPS), thermogravimetry and differential thermal analysis (TG–DTA), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscope (TEM), scanning electron microscopy (SEM) and nitrogen adsorption–desorption isotherms. The photocatalytic activities were checked through the photocatalytic reduction of Cr(VI) as a model compound under visible light irradiation. The results showed that the (N, S and C) co-doping and the calcination temperature played important role on the microstructure and photocatalytic activity of the samples. According to XPS spectra, sulfur was mainly attributed to the Ti−O−S bond; nitrogen was ascribed to the Ti−O−N and Ti−N bonds; carbon was assigned to the Ti−O−C bond in the NSC-TiO{sub 2} samples. (N, S and C) co-doped TiO{sub 2} samples calcinated at 500 °C exhibits higher photocatalytic activity than that of the other samples under visible light irradiation, which can be

  4. Dependence of the up-conversion emission of Li{sup +} co-doped Y{sub 2}O{sub 3}:Er{sup 3+} films with dopant concentration

    Energy Technology Data Exchange (ETDEWEB)

    Meza-Rocha, A.N., E-mail: ameza@fis.cinvestav.mx [Centro de Investigación y de Estudios Avanzados del IPN, Departamento de Física, Av. IPN 2508, Col. San Pedro Zacatenco, 07360 México, DF (Mexico); Huerta, E.F. [Programa de Doctorado en Nanociencias y Nanotecnología, CINVESTAV IPN, Av. IPN 2508, 07360 México, DF (Mexico); Caldiño, U. [Departamento de Física, Universidad Autónoma Metropolitana-Iztapalapa, P.O. Box 55-534, 09340 México, DF (Mexico); Carmona-Téllez, S. [Instituto de Física, UNAM, A.P. 20-364, Del. A. Obregón, 01000 México, DF (Mexico); Bettinelli, M. [Dipartimento Scientifico e Tecnologico, Università di Verona, and INSTM, UdR Verona, Strada Le Grazie 15, I-37314 Verona (Italy); Speghini, A. [Dipartimento Scientifico e Tecnologico, Università di Verona, and INSTM, UdR Verona, Strada Le Grazie 15, I-37314 Verona (Italy); Istituto di Fisica Applicata Nello Carrara, C.N.R., Via Madonna del Piano 10, 50019 Sesto Fiorentino, Firenze (Italy); Pelli, S. [Istituto di Fisica Applicata Nello Carrara, C.N.R., Via Madonna del Piano 10, 50019 Sesto Fiorentino, Firenze (Italy); Righini, G.C. [Istituto di Fisica Applicata Nello Carrara, C.N.R., Via Madonna del Piano 10, 50019 Sesto Fiorentino, Firenze (Italy); Museo Storico della Fisica e Centro Studi e Ricerche “Enrico Fermi”, Piazza del Viminale 2, 00184 Roma (Italy); and others

    2015-11-15

    The effect of dopant concentration on the up-conversion emission, and in particular on the Er{sup 3+} related green and red emissions of spray pyrolysis deposited films of Y{sub 2}O{sub 3}:Er{sup 3+} co-doped with Li{sup +}, is reported. Er{sup 3+} concentrations in the films in the range of 1.1–5.6 at% (1.5–14 at% Er{sup 3+} in the spraying solution) were studied, as well as the effect of co-doping them with Li{sup +}. Large concentrations of Er{sup 3+} favor the red emission, especially for contents higher than 10 at% in the spraying solution. Li{sup +} co-doping improves the green and red emissions up to 365 and 171 times, respectively, depending on the Er{sup 3+} and Li{sup +} concentrations. - Highlights: Up-converting Y{sub 2}O{sub 3}:Er{sup 3+} and Y{sub 2}O{sub 3}:Er{sup 3+}, Li{sup +} films were deposited by spray pyrolysis. The effect of Li{sup +} co-doping on the green and red UC Er{sup 3+} emission is reported. Li{sup +} co-doping improves the green and red emission up to 365 and 171 times.

  5. Synthesis and dissolution behavior of nanosized silicon and magnesium co-doped fluorapatite obtained by high energy ball milling

    NARCIS (Netherlands)

    Ahmadi, T.; Monshi, A.; Mortazavi, V.; Fathi, M. H.; Sharifi, S.; Beni, B. Hashemi; Abed, A. Moghare; Kheradmandfard, M.; Sharifnabi, A.

    Nanosized hydroxyapatite (HA) powders exhibit a greater surface area than coarser crystals and are expected to show an improved bioactivity. In addition, properties of HA can be tailored over a wide range by incorporating different ions into HA lattice. The aim of this study was to prepare and

  6. Hydro- and solvothermally-prepared ZnO and its catalytic effect on photodegradation of reactive orange 16 dye

    Directory of Open Access Journals (Sweden)

    Simović Bojana

    2014-01-01

    Full Text Available In this work, zinc oxide powders were obtained by two different techniques: hydro- and solvothermal synthesis starting from Zn(NO32 and Zn(CH3COO2, respectively. The influence of synthetic procedure on the structural, microstructural, thermal and photocatalytic properties of the prepared ZnO powders was investigated. Both ZnO samples were further annealed at moderate conditions (300°C to avoid grain growth and to remove traces of impurities. In all four cases a single-phase hexagonal ZnO was confirmed by X-ray powder diffraction. The morphology of prepared ZnO powders was different and it varied from rounded nanograins to microrods. All prepared samples showed higher photocatalytic efficiency in degradation of textile azo-dye Reactive Orange 16(RO16 than the commercial ZnO. In addition, the non-annealed samples had better photocatalytic properties than the commercial Degussa P25 TiO2 powder. [Projekat Ministarstva nauke Republike Srbije, br. III45007, br. ON171032 i br. ON172013

  7. Synthesis of C-N co-doped nano-CeO2 and dye degradation under compact fluorescent lamp irradiation.

    Science.gov (United States)

    Li, Ruixing; Li, Chengqiang; Yin, Shu; Fu, Cong; Sato, Tsugio

    2012-03-01

    Carbon and nitrogen (C-N) co-doped nano-CeO2 was synthesized by the solvothermal method using hexamethylenetetramine (HMT) as a precipitator at 140 degrees C for 24 h. We found that the degradation of acid orange 7 (AO7) was 94.4% and 98.8% with C-N co-doped nano-CeO2 upon irradiation with a 100-watt high-pressure mercury lamp (HML) and a 10-watt compact fluorescent lamp (CFL), respectively. By comparison, TiO2 degraded 68.4% and 43.0% of the AO7 irradiated by HML and CFL, respectively. We found that the degradation efficiencies of AO7 upon irradiation with the 10-watt CFL in the presence of the samples synthesized using different precipitators decreased as follows: CeO2(HMT)> CeO2-TiO2(HMT) > TiO2(HMT) > CeO2(NaHCO3) > CeO2(Na2CO3).

  8. Broadband near-infrared emission property in Er3+/Ce3+ co-doped silica-germanate glass for fiber amplifier.

    Science.gov (United States)

    Wei, Tao; Chen, Fangze; Tian, Ying; Xu, Shiqing

    2014-05-21

    Er(3+) doped and Er(3+)/Ce(3+) co-doped silica-germanate glasses were synthesized by high-temperature melt-quenching technique. A detailed study of the 1.53μm spectroscopic properties and thermal stability was presented in this work. The absorption spectra, 1.53μm emission spectra and fluorescence lifetimes were measured and investigated, along with the quantitative calculations and analyses of Judd-Ofelt intensity parameters, stimulated absorption and emission cross-sections and the product of FWHM×σem(p). It was found that the prepared samples have outstanding thermal stability (Tg=585°C), large FWHM (77nm and 108nm) and high stimulated emission cross-sections (9.55×10(-28)cm(3) and 8.72×10(-28)cm(3)) of Er(3+). The 1.53μm fluorescence intensity improved significantly with the introduction of Ce(3+). Furthermore, the wavelength dependent gain coefficient G(λ) of (4)I13/2→(4)I15/2 transition of Er(3+) was determined by means of the absorption and emission cross-sections. The results indicate that the developed glass co-doped with Er(3+)/Ce(3+) is a promising gain medium applied for broadband amplifier pumped with a 980nm laser diode. Copyright © 2014 Elsevier B.V. All rights reserved.

  9. Effective Construction of High-quality Iron Oxy-hydroxides and Co-doped Iron Oxy-hydroxides Nanostructures: Towards the Promising Oxygen Evolution Reaction Application

    Science.gov (United States)

    Zhang, Xinyu; An, Li; Yin, Jie; Xi, Pinxian; Zheng, Zhiping; Du, Yaping

    2017-01-01

    Rational design of high efficient and low cost electrocatalysts for oxygen evolution reaction (OER) plays an important role in water splitting. Herein, a general gelatin-assisted wet chemistry method is employed to fabricate well-defined iron oxy-hydroxides and transitional metal doped iron oxy-hydroxides nanomaterials, which show good catalytic performances for OER. Specifically, the Co-doped iron oxy-hydroxides (Co0.54Fe0.46OOH) show the excellent electrocatalytic performance for OER with an onset potential of 1.52 V, tafel slope of 47 mV/dec and outstanding stability. The ultrahigh oxygen evolution activity and strong durability, with superior performance in comparison to the pure iron oxy-hydroxide (FeOOH) catalysts, originate from the branch structure of Co0.54Fe0.46OOH on its surface so as to provide many active edge sites, enhanced mass/charge transport capability, easy release oxygen gas bubbles, and strong structural stability, which are advantageous for OER. Meanwhile, Co-doping in FeOOH nanostructures constitutes a desirable four-electron pathway for reversible oxygen evolution and reduction, which is potentially useful for rechargeable metal−air batteries, regenerative fuel cells, and other important clean energy devices. This work may provide a new insight into constructing the promising water oxidation catalysts for practical clean energy application. PMID:28272443

  10. Effective Construction of High-quality Iron Oxy-hydroxides and Co-doped Iron Oxy-hydroxides Nanostructures: Towards the Promising Oxygen Evolution Reaction Application

    Science.gov (United States)

    Zhang, Xinyu; An, Li; Yin, Jie; Xi, Pinxian; Zheng, Zhiping; Du, Yaping

    2017-03-01

    Rational design of high efficient and low cost electrocatalysts for oxygen evolution reaction (OER) plays an important role in water splitting. Herein, a general gelatin-assisted wet chemistry method is employed to fabricate well-defined iron oxy-hydroxides and transitional metal doped iron oxy-hydroxides nanomaterials, which show good catalytic performances for OER. Specifically, the Co-doped iron oxy-hydroxides (Co0.54Fe0.46OOH) show the excellent electrocatalytic performance for OER with an onset potential of 1.52 V, tafel slope of 47 mV/dec and outstanding stability. The ultrahigh oxygen evolution activity and strong durability, with superior performance in comparison to the pure iron oxy-hydroxide (FeOOH) catalysts, originate from the branch structure of Co0.54Fe0.46OOH on its surface so as to provide many active edge sites, enhanced mass/charge transport capability, easy release oxygen gas bubbles, and strong structural stability, which are advantageous for OER. Meanwhile, Co-doping in FeOOH nanostructures constitutes a desirable four-electron pathway for reversible oxygen evolution and reduction, which is potentially useful for rechargeable metal-air batteries, regenerative fuel cells, and other important clean energy devices. This work may provide a new insight into constructing the promising water oxidation catalysts for practical clean energy application.

  11. Hydrogenation temperature related inner structures and visible-light-driven photocatalysis of N–F co-doped TiO{sub 2} nanosheets

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Wei, E-mail: wangweinj0603@126.com; Ni, Yaru, E-mail: niyr2000@hotmail.com; Lu, Chunhua, E-mail: lchnjut@163.com; Xu, Zhongzi, E-mail: xzznjut@163.com

    2014-01-30

    A systematic study has been devoted to prepare N–F co-doped anatase TiO{sub 2} nanosheets with further hydrogenation treatment at different temperatures. The hydrogenation temperature plays a significant role in changing the inner structure of TiO{sub 2} from N–F co-doping to the truly hydrogenated characteristic, resulting in various bandgap structures with different light absorption ability and photogenerated electron–hole pair separation efficiency. Moreover, the visible-light-driven photocatalytic activity not only depend on the light absorption ability, but also affected by the amount of defect states significantly. Results indicate that isolated defect state will serve as photogenerated electron–hole pair recombination center, while a large amount of combined defect states will truly reduce the bandgap, enhance the light absorption and the photogenerated electron–hole pair separation efficiency. The photocatalyst hydrogenated at 500 °C, which has a specific bandgap structure, gives the highest ability in the degradation of phenol under the visible light irradiation. This simple investigation is of great significance for the design and preparation of anion modified TiO{sub 2}-based photocatalysts with specific crystal structures to make sufficient use of the visible light for environment protection.

  12. Fabrication of Ce/N co-doped TiO{sub 2}/diatomite granule catalyst and its improved visible-light-driven photoactivity

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Yan; Liu, Kuiren, E-mail: liukr@smm.neu.edu.cn

    2017-02-15

    Highlights: • Ce/N co-doped TiO{sub 2}/diatomite granule (CNTD-G) was prepared via sol-gel method. • The optimal doping amount of Ce was determined. • The effects of impurity ions on photodegradation process were studied. • The intermediates generated during photodegradation process were deduced. • The mechanism of photodegradation process was proposed. - Abstract: Eliminating antibiotic remnants in aquatic environment has become one of the hottest topics among current research works. Thus, we prepared Ce, N co-doped TiO{sub 2}/diatomite granule (CNTD-G) catalyst to provide a new method. As one typical antibiotics, oxytetracycline (OTC) was selected as the target pollutant to be degradated under visible light irradiation. The carrier diatomite helped the spread of TiO{sub 2} nanoparticles onto its surface, and inhibited their agglomeration. The synergy of Ce and N dopants highly improved the visible-light-driven photoactivity of TiO{sub 2}. The optimal doping amount and degradation conditions were determined. Besides, the effects of impurity ions were also investigated, including cations: Ca{sup 2+}, Mg{sup 2+}; or anions: NO{sub 3}{sup −}, SO{sub 4}{sup 2−} and PO{sub 4}{sup 3−}. The intermediates generated during degradation process were studied, and the mechanism of the photodegradation process was proposed. CNTD-G could be easily collected from the reactor, and showed excellent recyclability.

  13. High-performance colossal permittivity materials of (Nb + Er) co-doped TiO2 for large capacitors and high-energy-density storage devices.

    Science.gov (United States)

    Tse, Mei-Yan; Wei, Xianhua; Hao, Jianhua

    2016-09-21

    The search for colossal permittivity (CP) materials is imperative because of their potential for promising applications in the areas of device miniaturization and energy storage. High-performance CP materials require high dielectric permittivity, low dielectric loss and relatively weak dependence of frequency- and temperature. In this work, we first investigate the CP behavior of rutile TiO2 ceramics co-doped with niobium and erbium, i.e., (Er0.5Nb0.5)xTi1-xO2. Excellent dielectric properties were observed in the materials, including a CP of up to 10(4)-10(5) and a low dielectric loss (tan δ) down to 0.03, which are lower than that of the previously reported co-doped TiO2 CP materials when measured at 1 kHz. Stabilities of frequency and temperature were also accomplished via doping Er and Nb. Valence states of the elements in the material were analyzed using X-ray photoelectron spectroscopy. The Er induced secondary phases were observed using elemental mapping and energy-dispersive spectrometry. Consequently, this work may provide comprehensive guidance to develop high-performance CP materials for fully solid-state capacitor and energy storage applications.

  14. Magnetic multi-metal co-doped magnesium ferrite nanoparticles: An efficient visible light-assisted heterogeneous Fenton-like catalyst synthesized from saprolite laterite ore.

    Science.gov (United States)

    Diao, Yifei; Yan, Zhikai; Guo, Min; Wang, Xidong

    2018-02-15

    Magnetic nanoparticles of multi-metal co-doped magnesium ferrite (MgFe 2 O 4 ) were synthesized from saprolite laterite ore by a hydrothermal method, and firstly proposed as a heterogeneous photon-Fenton-like catalyst for degradation of Rhodamine B (RhB). The factors that influence the degradation reaction including pH value, the concentration of H 2 O 2 and the amount of catalyst, were systematically investigated. The doped MgFe 2 O 4 exhibited a degradation efficiency up to 96.8%, and the chemical oxygen demand (COD) and total organic carbon (TOC) removal efficiencies about 85.6% and 68.3%, respectively, under visible light illumination for 180min. The high activity is mainly attributed to the high specific surface area of the catalyst and the synergistic interaction between photo-catalytic oxidation and Fenton-like oxidation. Moreover, the catalyst also showed good stability and recycling performance for degrading RhB. After five consecutive degradation cycles, the activity decayed no more than 10%. Compared to other catalysts prepared from pure chemical agents, the multi-metal co-doped MgFe 2 O 4 is more competitive due to its high activity, good stability, ease of recollection, and especially the use of saprolite laterite ore as precursor. This work may provide a new avenue to synthesize efficient ferrite catalysts for degrading organic pollutants in wastewater by using natural minerals. Copyright © 2017 Elsevier B.V. All rights reserved.

  15. Compositional dependence of up-conversion emission and optical transition in Yb3+-Ho3+ co-doped tellurite-phosphate glasses

    Science.gov (United States)

    Yang, Yanmin; Zhang, Wei; Guo, Shuqing; Yang, Zhiping

    2010-07-01

    Optical absorption and photoluminescence properties of Yb3+-Ho3+ co-doped tellurite-phosphate glasses have been investigated. Up-conversion emissions have been observed at 540nm (green) and 650nm (red) at room temperature. The effect of host composition on up-conversion luminescence has been studied by analyzing the phenomenological Judd-Ofelt parameters Ωλ (λ = 2,4,6) as well as radiative transition probability and emission cross sections of 5F4 (5S2) and 5F5 levels in these glasses samples. Obtained data indicated that the green transition rapidly decreased relative to the red transition with increasing phosphate concentration, which can be attributed to increasing population of 5F4 (5S2) and 5F5 levels due to increasing host phonon energy. So, the color of up-conversion emission can be modulated by changed host composition. The effect of Ho3+ concentration on up-conversion emission was also studied in Yb3+-Ho3+ co-doped tellurite glasses. The red transition rapidly decreased relative to the green transition with increasing Ho3+ concentration. We attributed it to the lower phonon energy of tellurite glass host.

  16. Enhanced photoluminescence of Y{sub 2}O{sub 3}:Er{sup 3+} thin films by Li{sup +} co-doping

    Energy Technology Data Exchange (ETDEWEB)

    Meza-Rocha, A.N., E-mail: ameza@fis.cinvestav.mx [Centro de Investigación y de Estudios Avanzados del IPN, Departamento de Física, Av. IPN 2508, Col. San Pedro Zacatenco, CP 07360 México, DF (Mexico); Huerta, E.F. [Departamento de Física, Universidad Autónoma Metropolitana-Iztapalapa, Av. San Rafael Atlixco 186, CP 09340 México, DF (Mexico); Zaleta-Alejandre, E.; Rivera-Álvarez, Z.; Falcony, C. [Centro de Investigación y de Estudios Avanzados del IPN, Departamento de Física, Av. IPN 2508, Col. San Pedro Zacatenco, CP 07360 México, DF (Mexico)

    2013-09-15

    The enhancement of the photoluminescence from Y{sub 2}O{sub 3}:Er{sup 3+} thin films with Li{sup +} co-doping is reported. The characteristic Er{sup 3+} related emission spectra showed an intensity increase by a factor of ∼4–5 times with the addition of 2% of Li{sup +}. This behavior is attributed to the distortion of the local crystalline field induced by the incorporation of Li{sup +}. The films were deposited at 500 °C by ultrasonic spray pyrolysis technique on (1 0 0) silicon wafers. The films were the polycrystalline with a pure Y{sub 2}O{sub 3} cubic phase. The addition of Li{sup +} reduces the intensity of the diffraction peaks after 1%, and shifts the main diffraction peak toward large angles for Li{sup +} doping less than 3%. FTIR spectra were used to monitor the incorporation of Li-species in the films. -- Highlights: • We deposited Y{sub 2}O{sub 3}:Er thin films (100 nm) co-doped with lithium by the low cost ultrasonic spray pyrolysis technique. • The incorporation of lithium at 2% improves greatly the characteristic erbium related emission. • Lithium induces a distortion of the crystalline field which plays an important role in the photoluminescence characteristics.

  17. Hierarchical Cobalt Hydroxide and B/N Co-Doped Graphene Nanohybrids Derived from Metal-Organic Frameworks for High Energy Density Asymmetric Supercapacitors

    Science.gov (United States)

    Tabassum, Hassina; Mahmood, Asif; Wang, Qingfei; Xia, Wei; Liang, Zibin; Qiu, Bin; zhao, Ruo; Zou, Ruqiang

    2017-01-01

    To cater for the demands of electrochemical energy storage system, the development of cost effective, durable and highly efficient electrode materials is desired. Here, a novel electrode material based on redox active β-Co(OH)2 and B, N co-doped graphene nanohybrid is presented for electrochemical supercapacitor by employing a facile metal-organic frameworks (MOFs) route through pyrolysis and hydrothermal treatment. The Co(OH)2 could be firmly stabilized by dual protection of N-doped carbon polyhedron (CP) and B/N co-doped graphene (BCN) nanosheets. Interestingly, the porous carbon and BCN nanosheets greatly improve the charge storage, wettability, and redox activity of electrodes. Thus the hybrid delivers specific capacitance of 1263 F g−1 at a current density of 1A g−1 with 90% capacitance retention over 5000 cycles. Furthermore, the new aqueous asymmetric supercapacitor (ASC) was also designed by using Co(OH)2@CP@BCN nanohybrid and BCN nanosheets as positive and negative electrodes respectively, which leads to high energy density of 20.25 Whkg−1. This device also exhibits excellent rate capability with energy density of 15.55 Whkg−1 at power density of 9331 Wkg−1 coupled long termed stability up to 6000 cycles. PMID:28240224

  18. Energy transfer and color tunable emission in Tb3 +,Eu3 + co-doped Sr3LaNa(PO4)3F phosphors

    Science.gov (United States)

    Li, Shuo; Guo, Ning; Liang, Qimeng; Ding, Yu; Zhou, Huitao; Ouyang, Ruizhuo; Lü, Wei

    2018-02-01

    A group of color tunable Sr3LaNa(PO4)3F:Tb3 +,Eu3 + phosphors were prepared by conventional high temperature solid state method. The phase structures, luminescence properties, fluorescence lifetimes and energy transfer were investigated in detail. Under 369 nm excitation, owing to efficient energy transfer of Tb3 + → Eu3 +, the emission spectra both have green emission of Tb3 + and red emission of Eu3 +. An efficient energy transfer occur in Tb3 +, Eu3 + co-doped Sr3LaNa(PO4)3F phosphors. The most possible mechanism of energy transfer is dipole-dipole interaction by Dexter's theoretical model. The energy transfer of Tb3 + and Eu3 + was confirmed by the variations of emission and excitation spectra and Tb3 +/Eu3 + decay lifetimes in Sr3LaNa(PO4)3F:Tb3 +,Eu3 +. The color tone can tuned from yellowish-green through yellow and eventually to reddish-orange with fixed Tb3 + content by changing Eu3 + concentrations. The results show that the prepared Tb3 +, Eu3 + co-doped color tunable Sr3LaNa(PO4)3F phosphor can be used for white LED.

  19. Infrared optical characterization and energy transfer of Na5Lu9F32 single crystals co-doped with Er3+/Tm3+ grown by Bridgman method

    Science.gov (United States)

    Tang, Qingyang; Xia, Haiping; He, Shinan; Sheng, Qiguo; Chen, Baojiu

    2017-11-01

    This paper reported on successful preparation of Na5Lu9F32 single crystals co-doped with ∼2 mol% Er3+ and various Tm3+ concentrations from 0.7 mol% to 3.2 mol% by Bridgman method. The J-O intensity parameters of Er3+ were calculated and analyzed according to the absorption spectra. The fluorescence decay curve at Er3+:4I13/2 level was measured to investigate the luminescent properties of the Er3+/Tm3+ co-doped Na5Lu9F32, and the energy transfer process between Er3+ and Tm3+. An intense 2.7 μm emission was achieved with Tm3+ ions sensitizing Er3+ ions under the 800 nm LD pumping. The maximum emission intensity at 2.7 μm was obtained at about 3.2 mol% doping concentration of Tm3+ when the concentration of Er3+ ions was fixed at ∼2 mol% in the current research. The calculated maximum value of emission cross section at 2.7 μm was 2.22 × 10-20 cm2, and energy transfer efficiency from Er3+:4I13/2 to Tm3+:3F4 was 78%. The electric dipole-dipole interaction was dominant for the energy transfer from Er3+ to Tm3+ ions by using Inokuti-Hirayama's model.

  20. Li(Zn,Co,MnAs: A bulk form diluted magnetic semiconductor with Co and Mn co-doping at Zn sites

    Directory of Open Access Journals (Sweden)

    Bijuan Chen

    2016-11-01

    Full Text Available We report the synthesis and characterization of a series of bulk forms of diluted magnetic semiconductors Li(Zn1-x-yCoxMnyAs with a crystal structure close to that of III-V diluted magnetic semiconductor (Ga,MnAs. No ferromagnetic order occurs with single (Zn,Co or (Zn, Mn substitution in the parent compound LiZnAs. Only with co-doped Co and Mn ferromagnetic ordering can occur at the Curie temperature ∼40 K. The maximum saturation moment of the this system reached to 2.17μB/Mn, which is comparable to that of Li (Zn,MnAs. It is the first time that a diluted magnetic semiconductor with co-doping Co and Mn into Zn sites is achieved in “111” LiZnAs system, which could be utilized to investigate the basic science of ferromagnetism in diluted magnetic semiconductors. In addition, ferromagnetic Li(Zn,Co,MnAs, antiferromagnetic LiMnAs, and superconducting LiFeAs share square lattice at As layers, which may enable the development of novel heterojunction devices in the future.

  1. Tuning the opto-electrical properties of SnO{sub 2} thin films by Ag{sup +1} and In{sup +3} co-doping

    Energy Technology Data Exchange (ETDEWEB)

    Mouchaal, Younes [Laboratoire de Physique des Couches Minces et Matériaux pour l’Electronique (LPCMME) Université de Oran, BP 1524 EL M-Naouer 31000, Oran (Algeria); Enesca, Alexandru, E-mail: aenesca@unitbv.ro [Center for Renewable Energy Systems and Recycling, R& D Institute of the Transilvania University of Brasov, Eroilor 29 Street, 500036, Brasov (Romania); Mihoreanu, Ciprian [Center for Renewable Energy Systems and Recycling, R& D Institute of the Transilvania University of Brasov, Eroilor 29 Street, 500036, Brasov (Romania); Khelil, Abdelbacet [Laboratoire de Physique des Couches Minces et Matériaux pour l’Electronique (LPCMME) Université de Oran, BP 1524 EL M-Naouer 31000, Oran (Algeria); Duta, Anca [Center for Renewable Energy Systems and Recycling, R& D Institute of the Transilvania University of Brasov, Eroilor 29 Street, 500036, Brasov (Romania)

    2015-09-15

    Graphical abstract: - Highlights: • Polycrystalline SnO{sub 2} tetragonal structure with preferential (1 1 0) orientation. • Silver segregation and oxidation threshold. • Suitable diode-type behavior observed for the samples rich in silver. • Higher silver doping (8–12 at%) increases the grains’ size. - Abstract: In this work transparent thin films of Ag{sup +1}-In{sup +3} co-doped SnO{sub 2} were obtained using robotic spray pyrolysis. The effect of silver doping concentration on their optical, electrical and structural properties was investigated. Silver co-doping was varied between 0 and 12 at% in the precursor solution keeping the concentration of indium fixed at 2 at%. The optical transmittance has values between 90.3 and 82.7%, when the Ag{sup +1} doping ranges from 0 to 12 at%. The X-ray diffraction shows a single SnO{sub 2} phase, for silver doping between 0 and 8 at%, and a new silver oxide phase when the silver increases up to 12 at%. The current–voltage characteristics show diode-like behavior for low and high doping concentrations, corresponding to 2 and 12 at%. The films exhibit photocurrent which is affected by the silver amount in the structure. The highest and most stable generated photocurrent was achieved for samples with 12 at% Ag{sup +1}.

  2. A simple preparation method and characterization of B and N co-doped TiO2 nanotube arrays with enhanced photoelectrochemical performance

    Science.gov (United States)

    Georgieva, J.; Valova, E.; Armyanov, S.; Tatchev, D.; Sotiropoulos, S.; Avramova, I.; Dimitrova, N.; Hubin, A.; Steenhaut, O.

    2017-08-01

    Highly ordered TiO2 nanotube arrays (TNTA) have attracted much attention due to the excellent photocatalytic, optical and electrical properties. However, their absorption range is limited to ultraviolet (UV) spectrum only due to the wide band gap (3.2 eV). One of the strategies to overcome this problem is doping with boron and nitrogen. They are produced via titanium sheet anodization and subsequent electrochemical treatment of titania in an electrolyte containing boric acid. The as-prepared B-TNTA are annealed in N2 atmosphere at 500 °C for 2 h to obtain B,N-TNTA. The samples are characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), UV-vis diffuse reflectance spectroscopy (DRS) and X-ray photoelectron spectroscopy (XPS). The B,N-TNTA consist of uniform and well aligned nanotubes with an average inner diameter of 80-100 nm and a length not exceeding 1 μm. The photocurrent response measurements of undoped TNTA, N-doped and B,N-co-doped samples are performed under UV and visible light (Vis) illumination and a comparison is made. The obtained results show that the B,N-doping leads to remarkable photocurrent enhancement and better photocatalytic activity for methyl orange (MO) degradation due to the synergistic effects of B,N-co-doping and lower electron-hole recombination rates.

  3. The influence of material type and composition of TiO2- ZnO on manufacturing of paste for the application of DSSC

    Science.gov (United States)

    Retnaningsih, L.; Muliani, L.; Aggraini, P. N.; Hidayat, J.

    2016-11-01

    Research, fabrication and material selection for the application of Dye- sensitized solar cell (DSSC) has been performed on glass FTO (Flour Tin Oxide). The material is used in the form of TiO2 paste, TiO2 powder and ZnO powder. Dye-sensitized solar cell (DSSC), is a fotoelektrokimia-based solar cells where the absorption process light done by the dye molecules and the process of separation of inorganic semiconductor materials by charge of Titanium dioxide (TiO2) and Zinc oxide (ZnO). The purpose of this research is to know the exact composition of TiO2 and ZnO materials in order to produce the best efficiency with DSSC. On this research was done making prototype dye-sensitized solar cell using dye Z 907, and semiconductor nanoparticles TiO2 and ZnO powder that is made into a paste by mixing different composition in two variations of samples: A = ZnO (powder) + 40% TiO2 (powder) and B = 60% TiO2 (powder) (40%) + TiO2 (pasta) 60%. The second variation of this high efficiency is value at sample B i.e. TiO2 (powder) + 40% TiO2 (paste) of 60%.

  4. Antibacterial characteristics of heated zinc oxide powders on Escherichia coli and Staphylococcus aureus; Kanetsu shori sareta sanka aen funmatsu no daichokin oyobi oshoku budoukyukin ni taisuru kokin tokusei

    Energy Technology Data Exchange (ETDEWEB)

    Sawai, J.; Yamamoto, O.; Hotta, M.; Kojima, H.; Sasamoto, T. [Kanagawa Inst. of Tech., Kanagawa (Japan)

    1998-09-10

    Influence of heat treatment temperature of zinc oxide (ZnO) powders on antibacterial property against Escherichia coli and Staphylococcus aureus was studied. The values of the minimal inhibitory concentrations (MIC) were determined by the electric conductance method to examine the antibacterial property. MIC is defined as concentration at lowest temperature where no changes of the conductance are detected. MIC of ZnO powders increases with an increase in heating temperature. The variation of MIC against E. coli is larger than that against Staph. aureus. Concentration dependence of antibacterial effect by hydrogen peroxide is larger against E. coli than that against Staph. aureus and agrees to the variation tendency of MIC with ZnO powders. The difference in the sensitivity against E. coli and Staph. aureus is suggested to be due to the action of hydrogen peroxide generated from ZnO powders. 8 refs., 3 figs., 1 tab.

  5. ZnO Micro- and Nanostructures Obtained by Thermal Oxidation: Microstructure, Morphogenesis, Optical, and Photoluminescence Properties

    Directory of Open Access Journals (Sweden)

    Alejandro Escobedo-Morales

    2016-10-01

    Full Text Available ZnO micro- and nanostructures were obtained through thermal oxidation of Zn powders at high temperature under air atmosphere. A detailed study of the microstructure, morphology, optical, and photoluminescence properties of the generated products at different stages of thermal oxidation is presented. It was found that the exposure time has a strong influence on the resulting morphology. The morphogenesis of the different ZnO structures is discussed, and experimental parameters for fabricating ZnO tetrapods, hollow, core-shell, elongated, or rounded structures by thermal oxidation method are proposed on the basis on the obtained results. Notoriously, the crystal lattice of the ZnO structures has negligible residual strain, although, the density of point defects increases when the thermal treatment is extended; as consequence, their visible luminescence upon UV excitation enhances.

  6. ZnO whiskers and belts in chestnut husk-like structures: synthesis and proof of chemomechanical transduction.

    Science.gov (United States)

    Alessandri, Ivano; Bergese, Paolo; Depero, Laura E

    2009-02-01

    The preparation of chestnut husk-like ZnO starting from Zn powders is described, pointing out the role of ZnO(1-x) seeds in the self-catalytic liquid-solid growth process. The final architecture is made up of ZnO whiskers stemming from ZnO platelets which are self-assembled into spheroidal agglomerates. Whiskers can be converted into belts by using polyvinylpyrrolidone and configurations exhibiting whiskers and belts on the same husk are obtained through a sequential growth procedure. Polystyrene microspheres are employed in Raman microscopy proof of concept experiments to demonstrate the potential of ZnO whiskers in transduction of chemomechanical interactions, which opens promising perspectives for in-vivo bioapplications.

  7. Highly efficient inverted polymer solar cells using aqueous ammonia processed ZnO as an electron selective layer

    Science.gov (United States)

    Zhu, Xiao-Zhao; Zu, Feng-Shuo; Xu, Mei-Feng; Shi, Xiao-Bo; Jin, Zhi-Ming; Wang, Zhao-Kui; Liao, Liang-Sheng

    2014-09-01

    The authors demonstrate a simple method to deposit solution-processable ZnO thin film by directly dissolving the ZnO powder into aqueous ammonia. ZnO film casting from its aqueous ammonia solution ( a-ZnO) is used successfully as an electron selective layer in poly(3-hexylthiophene) and indene-C60 bisadduct (IC60BA) based heterojunction solar cells with improved power conversion efficiency (PCE) compared with that using conventional sol- gel based ZnO ( c-ZnO). The improved PCE is mainly attributed to an increase of short-circuit current density owing to the better transmittance of a-ZnO than that of c-ZnO in the absorption range of IC60BA, and efficient electron extraction at cathode. In addition, no additional by-products originated from the organic solvents are introduced as like in sol- gel based ZnO films.

  8. Photocatalytic degradation of Malachite Green dye by modified ZnO ...

    Indian Academy of Sciences (India)

    adverse effect on reproductive and immune system [1,2]. MG is used .... XRD technique. The powder XRD patterns of the ZnO sam- ples were recorded using a Rigako Ultima–IV Bruker X-ray diffractometer with CuKα radiation (λ = 0.15418 nm), at a. 2θ scan ..... photochemical-assisted formation of some reactive species is.

  9. Effects of morphology on the thermoelectric properties of Al-doped ZnO

    DEFF Research Database (Denmark)

    Han, Li; Van Nong, Ngo; Zhang, Wei

    2014-01-01

    The nanoparticles of Al-doped ZnO were successfully grown into rod-like and platelet-like morphologies by soft chemical routes. These powders were consolidated using spark plasma sintering (SPS) technique. The samples consolidated from rods and platelets exhibited characteristic structures...

  10. Nanoparticles of ZnO doped with Mn: structural and morphological characteristics

    Energy Technology Data Exchange (ETDEWEB)

    Bonifacio, Maria Aparecida Ribeiro; Lira, Helio de Lucena; Gama, Lucianna, E-mail: m_aparecidaribeiro@yahoo.com.br [Universidade Federal de Campina Grande (UFCG), PB (Brazil). Departamento de Engenharia de Materiais; Neiva, Laedna Souto [Universidade Federal do Cariri (UFCA), Juazeiro do Norte, CE (Brazil). Unidade Academica de Materiais; Kiminami, Ruth H. G. A. [Universidade Federal de Sao Carlos (USCar), SP (Brazil). Departamento de Engenharia de Materiais

    2017-07-15

    In this study, the effects of dopant concentrations on the structural and morphological characteristics of Zn{sub 1-x}Mn{sub x} O powders (x= 0.025, 0.05, 0.075, and 0.1 mole) synthesized by the Pechini method has been investigated. The powder was characterized by X-ray diffraction (XRD), Brunauer-Emmet-Teller (BET) specific surface, energy dispersive X-ray (EDX), scanning electron microscopy (SEM) and Spectroscopy with Fourier transform (FTIR). An XRD analysis of the powder showed the formation of ZnO phase with a typical single phase wurtzite structure. The EDX analysis revealed Mn incorporated in the ZnO structure. The particle size calculated by BET ranged from 24 to 63 nm, confirming the nanometric size of the powder particles. The SEM analysis revealed irregular shaped particle agglomerates and the presence of nanosheets. From FTIR it was confirmed the wurtzite structure in ZnO and ZnO nanoparticles doped with Mn. (author)

  11. Synthesis and optical study of heat-treated ZnO nanopowder for ...

    Indian Academy of Sciences (India)

    UV emitting ZnO nanopowder was chemically synthesized and subsequently subjected to heat treatment in oxygen atmosphere for ... toluminescence, SEM, FT-IR and XRD were performed to see the effect of high temperature heat treatment and subsequently oxygen ... The dry synthetic powders were weighed and the ...

  12. In situ high temperature XRD studies of ZnO nanopowder prepared ...

    Indian Academy of Sciences (India)

    This is a promising method for large area deposition at low temperature inspite of being simple, inexpensive and safe. The particle size, lattice parameters and crystal structure of ZnO nanopowder are characterized by in situ high temperature X-ray diffraction (XRD). Surface morphology of powder was studied using ...

  13. Optical properties of pure and TM-doped single-walled ZnO nanotubes (8,0) (TM = V and Co) by first principles calculations

    Science.gov (United States)

    Mendi, R. Taghavi; Sarmazdeh, M. Majidiyan; Boochani, A.; Elahi, S. M.; Naderi, S.

    2016-01-01

    In this paper, some optical properties of pure and transition metal-doped (TM = Co and V) single-walled ZnO nanotubes (8,0) (SWZnONT(8,0)) such as, real and imaginary parts of the dielectric function, optical conductivity, refractive index and optical reflectivity, were investigated. The calculations have been performed within framework of the density functional theory (DFT) using the full potential linearized augmented plane wave (FP-LAPW) and the generalized gradient approximation (GGA). The results show that, optical properties of SWZnONT(8,0) are anisotropic, especially at low energies and this anisotropy at low energies increases with doping of V in SWZnONT(8,0) while the Co-doped SWZnONT(8,0) behaves like pure SWZnONT(8,0). Doping of ZnO nanotubes has a significant impact on the value of the dielectric constant, so that due to the presence of V atom, the dielectric constant is increased up to three times. Study of the imaginary part of the dielectric function and optical conductivity showed that the important energy range for absorption processes and optical transitions is low energy range to 15 eV. The optical transitions have been studied based on band structure and density of states. The results of the optical reflectivity showed that these nanotubes are transparent in a wide energy ranges which provide them for using in transparent coatings. In addition, due to the reported magnetic properties for V- and Co-doped ZnO nanotubes, these nanotubes are suitable for using in spintronics and magneto-optic devices.

  14. Inhibition of growth of S. epidermidis by hydrothermally synthesized ZnO nanoplates

    Science.gov (United States)

    Abinaya, C.; Mayandi, J.; Osborne, J.; Frost, M.; Ekstrum, C.; Pearce, J. M.

    2017-07-01

    The antibacterial effect of zinc oxide (ZnO#1) as prepared and annealed (ZnO#2) at 400 °C, Cu doped ZnO (CuZnO), and Ag doped ZnO (AgZnO) nanoplates on Staphylococcus epidermidis was investigated for the inhibition and inactivation of cell growth. The results shows that pure ZnO and doped ZnO samples exhibited antibacterial activity against Staphylococcus epidermidis (S. epidermidis) as compared to tryptic soy broth (TSB). Also it is observed that S. epidermidis was extremely sensitive to treatment with ZnO nanoplates and it is clear that the effect is not purely depend on Cu/Ag. Phase identification of a crystalline material and unit cell dimensions were studied by x-ray powder diffraction (XRD). The scanning electron microscopy (SEM) provides information on sample’s surface topography and the EDX confirms the presence of Zn, O, Cu and Ag. X-ray photo-electron spectroscopy (XPS) was used to analyze the elemental composition and electronic state of the elements that exist within the samples. These studies confirms the formation of nanoplates and the presence of Zn, O, Ag, Cu with the oxidation states  +2, -2, 0 and  +2 respectively. These results indicates promising antibacterial applications of these ZnO-based nanoparticles synthesized with low-cost hydrothermal methods.

  15. Synthesis of SiO2-Coated Core-Shell ZnO Composites for Preparing High-Voltage Varistors

    Science.gov (United States)

    Qu, Xiao; Yao, Da-Chuan; Liu, Jin-Ran; Wang, Mao-Hua; Zhang, Han-Ping

    2017-09-01

    Monodispersed ZnO composite microspheres were successfully prepared by a facile ultrasound irradiation method. Then, the uniform core-shell structured composites were synthesized through the hydrolysis of tetraethyl orthosilicate on the surface of the ZnO composite microspheres. Microstructural studies of the as-obtained powders were carried out using the techniques of the x-ray powder diffraction, field emission scanning electron microscopy and transmission electron microscopy with energy dispersive x-ray spectroscopy. The results show that the pink ZnO composite powders as the core were spherical structures with the size of approximately 100 nm, and the SiO2 shell was fully coated on the surface of the core. On the basis of these results, the effect of SiO2 content on the thickness of the synthesized composites and microstructure, as well as the electrical properties of the ZnO varistors sintered in air at 1150°C for 2 h, were fully studied. In particular, the ZnO varistor prepared with the appropriate amount of the SiO2 coating (˜40 nm) leads to a superior electrical performance with the high breakdown voltage of 418 V mm-1 and an excellent nonlinear coefficient of 70.7, compared with the varistors obtained without the SiO2 coating. The high performance is attributed to the smaller and more homogeneous ZnO grains obtained via the SiO2 coating.

  16. Synthesis of SiO2-Coated Core-Shell ZnO Composites for Preparing High-Voltage Varistors

    Science.gov (United States)

    Qu, Xiao; Yao, Da-Chuan; Liu, Jin-Ran; Wang, Mao-Hua; Zhang, Han-Ping

    2018-01-01

    Monodispersed ZnO composite microspheres were successfully prepared by a facile ultrasound irradiation method. Then, the uniform core-shell structured composites were synthesized through the hydrolysis of tetraethyl orthosilicate on the surface of the ZnO composite microspheres. Microstructural studies of the as-obtained powders were carried out using the techniques of the x-ray powder diffraction, field emission scanning electron microscopy and transmission electron microscopy with energy dispersive x-ray spectroscopy. The results show that the pink ZnO composite powders as the core were spherical structures with the size of approximately 100 nm, and the SiO2 shell was fully coated on the surface of the core. On the basis of these results, the effect of SiO2 content on the thickness of the synthesized composites and microstructure, as well as the electrical properties of the ZnO varistors sintered in air at 1150°C for 2 h, were fully studied. In particular, the ZnO varistor prepared with the appropriate amount of the SiO2 coating (˜40 nm) leads to a superior electrical performance with the high breakdown voltage of 418 V mm-1 and an excellent nonlinear coefficient of 70.7, compared with the varistors obtained without the SiO2 coating. The high performance is attributed to the smaller and more homogeneous ZnO grains obtained via the SiO2 coating.

  17. Talcum powder poisoning

    Science.gov (United States)

    ... better the chance for recovery. Breathing in talcum powder can lead to very serious lung problems, even death. Use caution when using talcum powder on babies. Talc-free baby powder products are ...

  18. Effects of post-annealing and cobalt co-doping on superconducting properties of (Ca,Pr)Fe{sub 2}As{sub 2} single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Okada, T., E-mail: 8781303601@mail.ecc.u-tokyo.ac.jp; Ogino, H.; Yakita, H.; Yamamoto, A.; Kishio, K.; Shimoyama, J.

    2014-10-15

    Highlights: • Post-annealing at 400 °C killed superconductivity for Co-free sample. • Pr,Co co-doped samples maintained superconductivity even after annealing. • Two-step superconducting transition was observed via magnetization measurement. • Bulk superconductivity of low-T{sub c} component was confirmed. • Superconducting volume fraction of high-T{sub c} component was always small. - Abstract: In order to clarify the origin of anomalous superconductivity in (Ca,RE)Fe{sub 2}As{sub 2} system, Pr doped and Pr,Co co-doped CaFe{sub 2}As{sub 2} single crystals were grown by the FeAs flux method. These samples showed two-step superconducting transition with T{sub c1} = 25–42 K, and T{sub c2} < 16 K, suggesting that (Ca,RE)Fe{sub 2}As{sub 2} system has two superconducting components. Post-annealing performed for these crystals in evacuated quartz ampoules at various temperatures revealed that post-annealing at ∼400 °C increased the c-axis length for all samples. This indicates that as-grown crystals have a certain level of strain, which is released by post-annealing at ∼400 °C. Superconducting properties also changed dramatically by post-annealing. After annealing at 400 °C, some of the co-doped samples showed large superconducting volume fraction corresponding to the perfect diamagnetism below T{sub c2} and high J{sub c} values of 10{sup 4}–10{sup 5} A cm{sup −2} at 2 K in low field, indicating the bulk superconductivity of (Ca,RE)Fe{sub 2}As{sub 2} phase occurred below T{sub c2}. On the contrary, the superconducting volume fraction above T{sub c2} was always very small, suggesting that 40 K-class superconductivity observed in this system is originating in the local superconductivity in the crystal.

  19. Effects of synthesis method on cation distribution and optical properties of Co/Cr co-doped MgGa{sub 2}O{sub 4} nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Jian; Duan, Xiulan, E-mail: xlduan@sdu.edu.cn; Li, Nannan; Jiang, Huaidong

    2015-08-15

    Highlights: • Co{sup 2+}/Cr{sup 3+} co-doped MgGa{sub 2}O{sub 4} nanoparticles were prepared by three different methods. • The effect of synthesis method on the distribution of the cations was studied by XPS. • The samples prepared by sol–gel method have the largest inversion degree. • The synthesis method has also effect on the optical absorption and emission properties. • Optical properties of the nanoparticles are discussed on the basis of the structural results. - Abstract: Co{sup 2+}/Cr{sup 3+} co-doped MgGa{sub 2}O{sub 4} nanoparticles were prepared by three different methods (sol–gel, co-precipitation and solid state reaction). The effect of synthesis method on distribution of cations (Ga{sup 3+}, Mg{sup 2+} and Cr{sup 3+} ions) was studied using X-ray photoelectron spectroscopy (XPS). These cations occupied octahedral sites as well as tetrahedral sites of the spinel structure in all samples. However, the inversion degree of these samples is greatly influenced by the synthesis method. The Co{sup 2+}/Cr{sup 3+} co-doped MgGa{sub 2}O{sub 4} nanoparticles prepared by the sol–gel method a larger inversion degree than those prepared by other methods. The effect of the synthesis method on absorption spectra and emission spectra was also studied. Samples obtained by sol–gel and co-precipitation methods exhibit broad absorption bands in two wavelength ranges: 300–500 nm and 500–700 nm, while the sample synthesized by solid state reaction only has an absorption peak at 430 nm in the range 300–500 nm. The difference in absorption spectra can be related to the distribution of Co{sup 2+} and Cr{sup 3+} ions. Emission spectra for samples prepared by sol–gel and co-precipitation methods show a broad emission band peaking at 700 and 680 nm, combining the emission characteristic of octahedral Cr{sup 3+} and tetrahedral Co{sup 2+} ions.

  20. Tm3+/Yb3+ co-doped tellurite glass with silver nanoparticles for 1.85 μm band laser material

    Science.gov (United States)

    Huang, Bo; Zhou, Yaxun; Cheng, Pan; Zhou, Zizhong; Li, Jun; Jin, Wei

    2016-10-01

    Tm3+/Yb3+ co-doped tellurite glasses with different silver nanoparticles (Ag NPs) concentrations were prepared using the conventional melt-quenching technique and characterized by the UV/Vis/NIR absorption spectra, 1.85 μm band fluorescence emission spectra, transmission electron microscopy (TEM) images, differential scanning calorimeter (DSC) curves and X-ray diffraction (XRD) patterns to investigate the effects of Ag NPs on the 1.85 μm band spectroscopic properties of Tm3+ ions, thermal stability and structural nature of glass hosts. Under the excitation of 980 nm laser diode (LD), the 1.85 μm band fluorescence emission of Tm3+ ions enhances significantly in the presence of Ag NPs with average diameter of ∼8 nm and local surface Plasmon resonance (LSPR) band of ∼590 nm, which is mainly attributed to the increased local electric field induced by Ag NPs at the proximity of doped rare-earth ions on the basis of energy transfer from Yb3+ to Tm3+ ions. An improvement by about 110% of fluorescence intensity is observed in the Tm3+/Yb3+ co-doped tellurite glass containing 0.5 mol% amount of AgNO3 while the prepared glass samples possess good thermal stability and amorphous structural nature. Meanwhile, the Judd-Ofelt intensity parameters Ωt (t = 2,4,6), spontaneous radiative transition probabilities, fluorescence branching ratios and radiative lifetimes of relevant excited levels of Tm3+ ions were determined based on the Judd-Ofelt theory to reveal the enhanced effects of Ag NPs on the 1.85 μm band spectroscopic properties, and the energy transfer micro-parameters and phonon contribution ratios were calculated based on the non-resonant energy transfer theory to elucidate the energy transfer mechanism between Yb3+ and Tm3+ ions. The present results indicate that the prepared Tm3+/Yb3+ co-doped tellurite glass with an appropriate amount of Ag NPs is a promising lasing media applied for 1.85 μm band solid-state lasers and amplifiers.

  1. Preparation, Characterization, and Biotoxicity of Nanosized Doped ZnO Photocatalyst

    Directory of Open Access Journals (Sweden)

    Lingling Liu

    2014-01-01

    Full Text Available Metal-doped nanosized ZnO (nZnO photocatalyst has been widely used for its typical properties and has thus gained considerable attention. In this study, five types of nZnO (nondoped nZnO, iron- (Fe- doped nZnO, cobalt- (Co- doped nZnO, nickel- (Ni- doped nZnO, and manganese- (Mn- doped nZnO materials were prepared through a wet chemical method and then exposed to Daphnia magna (D. magna at low and high concentrations (50 and 250 μg L−1. Results showed that the different metal-doped nZnOs had a variety of shapes and sizes and exhibited diverse dissolubility. After exposure tests, Zn accumulation, metallothionein (MT, and malondialdehyde (MDA contents in D. magna under 250 μg L−1 were significantly higher than those in the 50 μg L−1 groups. Compared with nondoped nZnO, Co-doped and Ni-doped nZnO enhanced Zn accumulation in D. magna whereas Mn-doped nZnO reduced such accumulation. MT and MDA contents in metal-doped nZnO (except Ni-nZnO treatments were lower than those in nondoped nZnO. Zn accumulation showed a negative relationship with dissolved Zn percentage, which can be explained by the swallowing of nZnO particles as an important pathway of D. magna ingestion. Sizes, dissolubility, and physiological functions of doping metals were the influencing factors on metal-doped nZnO biotoxicity to D. magna.

  2. Synthesis and Sintering of ZnO Nanopowders

    Directory of Open Access Journals (Sweden)

    Anne Aimable

    2017-05-01

    Full Text Available Nanopowders are continuously under investigation as they open new perspectives in numerous fields. There are two main challenges to stimulating their development: sufficient low-cost, high throughput synthesis methods which lead to a production with well-defined and reproducible properties; and for ceramics specifically, the conservation of the powders’ nanostructure after sintering. In this context, this paper presents the synthesis of a pure nanosized powder of ZnO (dv50~60 nm, easily redispersable by using a continuous Segmented Flow Tubular Reactor (SFTR, which has previously shown its versatility and its robustness, ensuring a high powder quality and reproducibility over time. A higher scale of production can be achieved based on a “scale-out” concept by replicating the tubular reactors. The sinterability of ZnO nanopowders synthesized by the SFTR was studied, by natural sintering at 900 °C and 1100 °C, and Spark Plasma Sintering (SPS at 900 °C. The performance of the synthesized nanopowder was compared to a commercial ZnO nanopowder of high quality. The samples obtained from the synthesized nanopowder could not be densified at low temperature by traditional sintering, whereas SPS led to a fully dense material after only 5 min at 900 °C, while also limiting the grain growth, thus leading to a nanostructured material.

  3. Preparation, characterization and photocatalytic activity of Fe2O3/ZnO and Fe3O4/ZnO

    Directory of Open Access Journals (Sweden)

    Patij Shah

    2014-03-01

    Full Text Available Composite Iron oxide-Zinc oxide (α-Fe2O3/ZnO and Fe3O4/ZnO was synthesized by two step method. In the first step, uniform α-Fe2O3 and Fe3O4 particles were prepared through a hydrolysis process of ferric chloride at 80°C. In the second step, the ZnO particles were included in the α-Fe2O3 and Fe3O4 particles by a zinc acetate [Zn(Ac2·2H2O] assisted hydrothermal method at low temperature (90 °C. X-ray Powder Diffraction (XRD, Scanning Electron microscopy (SEM, Energy-dispersive X-ray spectroscopy (EDAX was used to study its structural properties. The α-Fe2O3 and ZnO phases were identified by XRD, energy dispersive X-ray analysis (EDAX. The photoactivities of α-Fe2O3/ZnO and Fe3O4/ZnO nanoparticles under UV irradiation were quantified by the degradation of formaldehyde. The determination of magnetic property was also carried out by Gouy balance method.

  4. Exchange Bias and Inverse Magnetocaloric Effect in Co and Mn Co-Doped Ni2MnGa Shape Memory Alloy

    Directory of Open Access Journals (Sweden)

    Yong Liu

    2013-01-01

    Full Text Available Exchange bias effect observed in the Ni1.68Co0.32Mn1.20Ga0.80 alloy confirms the coexistence of antiferromagnetic and ferromagnetic phases in the martensite phase. A large inverse magnetocaloric effect has been observed within the martensitic transformation temperature range, which is originated from modified magnetic order through magnetic-field-induced phase transformation from partially antiferromagnetic martensite to ferromagnetic austenite. The magnetic entropy change is 16.2 J kg−1 K−1 at 232 K under ΔH = 60 kOe, with the net refrigerant capacity of 68 J kg−1. These properties indicate Co and Mn co-doped Ni2MnGa alloy is a multifunctional material potentially suitable for magnetic refrigeration and spintronics applications.

  5. Effect of lithium halide on glass network structure and upconversion luminescence in Er3+ co-doped oxyfluoride glass ceramics containing NaGdF4 nanocrystals

    Science.gov (United States)

    Ren, Peng; Yang, Yong; Zhou, Dacheng; Li, Zhencai; Qiu, Jianbei

    2017-10-01

    LiR(R = Br, Cl, F) co-doped oxyfluoride glass ceramics containing NaGdF4 nanocrystals were prepared. The effect on glass network structure by dopants was investigated through the Raman spectra. The crystallization temperature and integrity of the glass network structure was gradually reduced by introducing halogen ions. The types and distribution of nanocrystals were determined by X-ray diffraction and transmission electron microscope. The size of nanocrystals were shown in column type distribution map. The mean size of nanocrystals was bigger from SABr to SAF. The upconversion luminescence of Er3+ in SABr, SACl and SAF were study. The intensity ratio of red and green light was reduced in glass ceramics when the content from LiBr turn to LiF.

  6. Investigation of phase evolution and control over phase transformation temperature and thermal hysteresis using stoichiometry and co-doping in VO2 thin films

    Science.gov (United States)

    Jaffari, G. Hassnain; Mahmood, Wardah

    2017-11-01

    Structural phase transition temperature and its associated hysteresis in VO2 have been controlled by high valent dopant induced local structural modification which acts as phase nucleation site during phase transformation. Monoclinic phase intensity loops plotted against temperature has been observed to exhibit thermal hysteresis. It is shown that the size, shape and central position of hysteresis loop depend on stoichiometry and doping concentration. Highest reduction in phase transformation temperature and thermal hysteresis width has been observed in case of W+6-Mo+6 co-doping and W+6 doping, respectively. Hence energy barrier associated with the structural phase transition has been successfully manipulated to vary Tc and hysteresis width. These findings have implications for designing the phase switching devices and smart window applications.

  7. Highly efficient Yb3+/Tm3+ co-doped NaYF4 nanotubes: Synthesis and intense ultraviolet to infrared up-conversion luminescence

    Science.gov (United States)

    Zhang, Y. Y.; Wang, Y.; Deng, J. Q.; Wang, J.; Ni, S. C.

    2014-02-01

    Nanocrystals of up-conversion (UC) phosphor Yb3+/Tm3+ co-doped NaYF4 are prepared by a facile hydrothermal method using oleic acid as a stabilizing agent. The as-prepared nanocrystals are of hexagonal phase, and have tube-like morphology and strong ultraviolet (UV) and blue UC fluorescence intensity, which have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and luminescence spectroscopy. The effect of Yb3+ concentration on the UC emission properties is also analyzed. Our results reveal that the intensity of emission peaks can be controlled by varying the Yb3+ concentration and these NaYF4 nanotubes are highly efficient host material. The as-prepared NaYF4 nanotubes show potential applications in UV compact solid state lasers and multi-channel fluorescent label.

  8. Rich stochastic dynamics of co-doped Er:Yb fluorescence upconversion nanoparticles in the presence of thermal, non-conservative, harmonic and optical forces

    Science.gov (United States)

    Nome, Rene A.; Sorbello, Cecilia; Jobbágy, Matías; Barja, Beatriz C.; Sanches, Vitor; Cruz, Joyce S.; Aguiar, Vinicius F.

    2017-03-01

    The stochastic dynamics of individual co-doped Er:Yb upconversion nanoparticles (UCNP) were investigated from experiments and simulations. The UCNP were characterized by high-resolution scanning electron microscopy, dynamic light scattering, and zeta potential measurements. Single UCNP measurements were performed by fluorescence upconversion micro-spectroscopy and optical trapping. The mean-square displacement (MSD) from single UCNP exhibited a time-dependent diffusion coefficient which was compared with Brownian dynamics simulations of a viscoelastic model of harmonically bound spheres. Experimental time-dependent two-dimensional trajectories of individual UCNP revealed correlated two-dimensional nanoparticle motion. The measurements were compared with stochastic trajectories calculated in the presence of a non-conservative rotational force field. Overall, the complex interplay of UCNP adhesion, thermal fluctuations and optical forces led to a rich stochastic behavior of these nanoparticles.

  9. Resistive switching properties of Ce and Mn co-doped BiFeO3 thin films for nonvolatile memory application

    Directory of Open Access Journals (Sweden)

    Zhenhua Tang

    2013-12-01

    Full Text Available The Ce and Mn co-doped BiFeO3 (BCFMO thin films were synthesized on Pt/Ti/SiO2/Si substrates using a sol-gel method. The unipolar resistive switching (URS and bipolar resistive switching (BRS behaviors were observed in the Pt/BCFMO/Pt device structure, which was attributed to the formation/rupture of metal filaments. The fabricated device exhibits a large ROFF/RON ratio (>80, long retention time (>105 s and low programming voltages (<1.5 V. Analysis of linear fitting current-voltage curves suggests that the space charge limited leakage current (SCLC and Schottky emission were observed as the conduction mechanisms of the devices.

  10. Highly luminescent S,N co-doped carbon quantum dots-sensitized chemiluminescence on luminol-H2 O2 system for the determination of ranitidine.

    Science.gov (United States)

    Chen, Jianqiu; Shu, Juan; Chen, Jiao; Cao, Zhiran; Xiao, An; Yan, Zhengyu

    2017-05-01

    S,N co-doped carbon quantum dots (N,S-CQDs) with super high quantum yield (79%) were prepared by the hydrothermal method and characterized by transmission electron microscopy, photoluminescence, UV-Vis spectroscopy and Fourier transformed infrared spectroscopy. N,S-CQDs can enhance the chemiluminescence intensity of a luminol-H2 O2 system. The possible mechanism of the luminol-H2 O2 -(N,S-CQDs) was illustrated by using chemiluminescence, photoluminescence and ultraviolet analysis. Ranitidine can quench the chemiluminescence intensity of a luminol-H2 O2 -N,S-CQDs system. So, a novel flow-injection chemiluminescence method was designed to determine ranitidine within a linear range of 0.5-50 μg ml(-1) and a detection limit of 0.12 μg ml(-1) . The method shows promising application prospects. Copyright © 2016 John Wiley & Sons, Ltd.

  11. Investigation of crystal structure, dielectric and magnetic properties in La and Nd co-doped BiFeO{sub 3} multiferroics

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Ompal [Department of Physics, Guru Jambheshwar University of Science & Technology, Hisar 125001, Haryana (India); Agarwal, Ashish, E-mail: aagju@yahoo.com [Department of Physics, Guru Jambheshwar University of Science & Technology, Hisar 125001, Haryana (India); Sanghi, Sujata [Department of Physics, Guru Jambheshwar University of Science & Technology, Hisar 125001, Haryana (India); Das, Amitabh [Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Anju [Department of Physics, Chaudhary Devi Lal University, Sirsa 125025, Haryana (India)

    2017-03-15

    For the investigation of the crystal structure, dielectric properties and magnetic properties of La and Nd co-doped BiFeO{sub 3} multiferroics; Bi{sub 0.8}La{sub 0.2−x}Nd{sub x}FeO{sub 3} (x=0.075, 0.1, 0.125) samples were prepared through solid state reaction method. Rietveld refinement of the obtained XRD patterns shows that there is change in crystal structure in these samples. At higher concentration of La (at x=0.075), the crystal structure was found to have mixed symmetry with rhombohedral and triclinic phases, while with equal concentration of both the dopants (at x=0.1), the structure changes to mixed symmetry having rhombohedral and orthorhombic phases. At higher concentration of Nd (at x=0.125), again mixed symmetry was established having both phases of the previous composition but approximately in reverse fraction. In dielectric analysis, x=0.1 sample showed the highest values of dielectric constant (ε′) and dielectric loss (tan δ). For x=0.125 sample, it was observed that the dielectric constant and dielectric loss response are improved. The magnetic characterization (M–H loops) indicates the significant enhancement in magnetisation with increasing concentration of Nd. Nd doping leads to the destruction of spiral modulation, forming the antiferromagnets, and visualisation of improved magnetisation via canting of spins. - Highlights: • La and Nd co-doped BiFeO{sub 3} were synthesized. • Change in crystal structure is observed. • Significant enhancement in magnetisation is observed.

  12. Microwave hydrothermal synthesis and infrared to visible upconversion luminescence of Er{sup 3+}/Yb{sup 3+} co-doped bismuth molybdate nanopowder

    Energy Technology Data Exchange (ETDEWEB)

    Adhikari, Rajesh; Joshi, Bhupendra [Research Center for Eco-Multifunctional Nanomaterials, Sun Moon University (Korea, Republic of); Narro-García, R.; De la Rosa, E. [Centro de Investigaciones en Óptica, A.P. 1-948, León, Gto. 37150 (Mexico); Lee, Soo Wohn, E-mail: swlee@sunmoon.ac.kr [Department of Environmental Engineering, Sun Moon University (Korea, Republic of)

    2014-01-15

    This paper reports the microwave hydrothermal synthesis and infrared to visible upconversion luminescence of Er{sup 3+/}Yb{sup 3+} co-doped Bi{sub 2}MoO{sub 6} nanopowder. Crystal structure, morphology and chemical composition were analyzed by means of X-ray Diffraction, Transmission Electron Microscopy and Raman Spectroscopy. Upconversion luminescence properties were studied in detail. The infrared to visible upconversion luminescence has been investigated in Er{sup 3+}/Yb{sup 3+} doped Bi{sub 2}MoO{sub 6} with different Yb{sup 3+} concentrations. Intense green and red upconversion emissions around 532, 545, and 655 nm corresponding to the {sup 2}H{sub 11/2}, {sup 4}S{sub 3/2}, and {sup 4}F{sub 9/2} transitions, respectively, to the {sup 4}I{sub 15/2} ground state were observed when excited by CW laser radiation at 980 nm. The effect of Yb{sup 3+} on the upconversion luminescence intensity was analyzed and the upconversion luminescence mechanism was explained in terms of the energy transfer process. From this study, it confirms that the like fluorides, and germinate glasses, metal oxide nanoparticles could also be a potential host to achieve desired upconversion luminescence. -- Highlights: • Er{sup 3+}/Yb{sup 3+} co-doped bismuth molybdate nanopowder was successfully synthesized. • Infrared to visible upconversion luminescence was observed at 980 nm excitation. • Green and red emissions at 532 nm, 546 nm and 656 nm were investigated. • Bismuth molybdate could be a potential host material for upconversion luminescence.

  13. Microwave-Assisted Synthesis of Boron and Nitrogen co-doped Reduced Graphene Oxide for the Protection of Electromagnetic Radiation in Ku-Band.

    Science.gov (United States)

    Umrao, Sima; Gupta, Tejendra K; Kumar, Shiv; Singh, Vijay K; Sultania, Manish K; Jung, Jung Hwan; Oh, Il-Kwon; Srivastava, Anchal

    2015-09-09

    The electromagnetic interference (EMI) shielding of reduced graphene oxide (MRG), B-doped MRG (B-MRG), N-doped MRG (N-MRG), and B-N co-doped MRG (B-N-MRG) have been studied in the Ku-band frequency range (12.8-18 GHz). We have developed a green, fast, and cost-effective microwave assisted route for synthesis of doped MRG. B-N-MRG shows high electrical conductivity in comparison to MRG, B-MRG and N-MRG, which results better electromagnetic interference (EMI) shielding ability. The co-doping of B and N significantly enhances the electrical conductivity of MRG from 21.4 to 124.4 Sm(-1) because N introduces electrons and B provides holes in the system and may form a nanojunction inside the material. Their temperature-dependent electrical conductivity follows 2D-variable range hopping (2D-VRH) and Efros-Shklovskii-VRH (ES-VRH) conduction model in a low temperature range (T<50 K). The spatial configuration of MRG after doping of B and N enhances the space charge polarization, natural resonance, dielectric polarization, and trapping of EM waves by internal reflection leading to a high EMI shielding of -42 dB (∼99.99% attenuation) compared to undoped MRG (-28 dB) at a critical thickness of 1.2 mm. Results suggest that the B-N-MRG has great potential as a candidate for a new type of EMI shielding material useful in aircraft, defense industries, communication systems, and stealth technology.

  14. Effect of bismuth oxide introduction on spectroscopic properties of Er{sup 3+}/Yb{sup 3+} co-doped aluminophosphate glasses

    Energy Technology Data Exchange (ETDEWEB)

    Fang Yongzheng [Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Graduate School of Chinese Academy of Sciences, 390 Qinghe Road, Jiading District, Shanghai 201800 (China); Shanghai Institute of Technology, Shanghai 200235 (China)], E-mail: fangyzh@yahoo.com.cn; Hu Lili; Liao Meisong; Wen Lei [Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Graduate School of Chinese Academy of Sciences, 390 Qinghe Road, Jiading District, Shanghai 201800 (China)

    2008-06-12

    The absorption spectra, emission spectra and infrared spectra of Er{sup 3+}/Yb{sup 3+} co-doped xBi{sub 2}O{sub 3}-(65 - x)P{sub 2}O{sub 5}-4Yb{sub 2}O{sub 3}-11Al{sub 2}O{sub 3}-5BaO-15Na{sub 2}O were measured and investigated. Spontaneous emission probability, radiative lifetime and branching ratios of Er{sup 3+} were calculated according to the Judd-Ofelt theory. The role of substitution of Bi{sub 2}O{sub 3} for P{sub 2}O{sub 5} on luminescence of Er{sup 3+}/Yb{sup 3+} co-doped aluminophosphate glasses has been investigated. The calculated radiative lifetimes ({tau}{sub rad}) for {sup 4}I{sub 13/2} and {sup 4}I{sub 11/2} were decreasing with Bi{sub 2}O{sub 3} content increases, whereas the measured total lifetime ({tau}{sub meas}) for {sup 4}I{sub 13/2} showed linearly increasing trends. The effect of Bi{sub 2}O{sub 3} introduction on OH{sup -} groups was also discussed according to the IR transmittance spectra of glasses. It was found that FWHM of glasses were not affected with the substitution of Bi{sub 2}O{sub 3} for P{sub 2}O{sub 5}. The emission spectra intensity increased with Bi{sub 2}O{sub 3} content due to the decreases of phonon energy and OH{sup -} content in glasses.

  15. Enhanced ethanol gas sensing performance of the networked Pd, In2O3-codecorated ZnO nanorod sensor

    Science.gov (United States)

    Lee, Sangmin; Sun, Gun-Joo; Lee, Jae Kyung; Hyun, Soong Keun; Lee, Chongmu

    2017-10-01

    ZnO nanorods codecorated with Pd and In2O3 nanoparticles were synthesized by thermal evaporation of a mixture of ZnO and graphite powders in an oxidizing atmosphere and followed by solvothermal deposition of Pd and In2O3 and their ethanol gas sensing properties were examined. Pristine ZnO nanorods, Pd-decorated ZnO nanorods and In2O3-decorated ZnO nanorods were also prepared in a similar manner. The codecorated ZnO nanorod sensor showed significantly stronger response to ethanol than the other three sensors, suggesting a synergistic effect of Pd and In2O3 codecoration. The former also showed faster response and recovery than the latter. The pristine and codecorated ZnO nanorod sensors exhibited selectivity toward ethanol over other gases such as acetone, CO, benzene, and toluene. The underlying mechanism for the enhanced sensing performance of the Pd, In2O3-codecorated ZnO nanorod sensor toward ethanol is discussed.

  16. Resin-Powder Dispenser

    Science.gov (United States)

    Standfield, Clarence E.

    1994-01-01

    Resin-powder dispenser used at NASA's Langley Research Center for processing of composite-material prepregs. Dispenser evenly distributes powder (resin polymer and other matrix materials in powder form) onto wet uncured prepregs. Provides versatility in distribution of solid resin in prepreg operation. Used wherever there is requirement for even, continuous distribution of small amount of powder.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2017-02-15

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

  18. EGCG assisted green synthesis of ZnO nanopowders: Photodegradative, antimicrobial and antioxidant activities

    Science.gov (United States)

    Suresh, D.; Udayabhanu; Nethravathi, P. C.; Lingaraju, K.; Rajanaika, H.; Sharma, S. C.; Nagabhushana, H.

    2015-02-01

    Zinc oxide nanopowders were synthesized by solution combustion method using Epigallocatechin gallate (EGCG) a tea catechin as fuel. The structure and morphology of the product was characterized by Powder X-ray Diffraction, Scanning Electron Microscopy, photoluminescence and UV-Visible spectroscopy. The nanopowders (Nps) were subjected to photocatalytic and biological activities such as antimicrobial and antioxidant studies. PXRD patterns demonstrate that the formed product belongs to hexagonal wurtzite system. SEM images show that the particles are agglomerated to form sponge like structure and the average crystallite sizes were found to be ∼10-20 nm. PL spectra exhibit broad and strong peak at 590 nm due to the Zn-vacancies, and O-vacancies. The prepared ZnO Nps exhibit excellent photocatalytic activity for the photodegradation of malachite green (MG) and methylene blue (MB) indicating that the ZnO NPs are potential photocatalytic semiconductor materials. ZnO NPs exhibit significant bactericidal activity against Klebsiella aerogenes, Pseudomonas aeruginosa, Escherichia coli and Staphylococcus aureus using the agar well diffusion method. Furthermore, the ZnO nano powders show good antioxidant activity by potentially scavenging DPPH radicals. The study successfully demonstrates synthesis of ZnO NPs by simple ecofriendly route employing EGCG as fuel that exhibit superior photodegradative, antibacterial and antioxidant activities.

  19. ZnO nanocoral reef grown on porous silicon substrates without catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Abdulgafour, H.I., E-mail: hind_alshaikh@yahoo.com [School of Physics, University Sains Malaysia 11800 Penang (Malaysia); Yam, F.K.; Hassan, Z.; AL-Heuseen, K.; Jawad, M.J. [School of Physics, University Sains Malaysia 11800 Penang (Malaysia)

    2011-05-05

    Research highlights: > Porous silicon (PS) technology is utilized to grow coral reef-like ZnO nanostructures on the surface of Si substrates. > Flower-like aligned ZnO nanorods are fabricated directly onto the silicon substrates through zinc powder evaporation using a simple thermal evaporation method without a catalyst for comparison. > The PL spectra show that for ZnO nanocoral reefs the UV emission shifts slightly towards lower frequency. > This non-catalyst growth technique on the rough surface of substrates may have potential applications in the fabrication of nanoelectronic and nanooptical devices. - Abstract: Porous silicon (PS) technology is utilized to grow coral reef-like ZnO nanostructures on the surface of Si substrates with rough morphology. Flower-like aligned ZnO nanorods are also fabricated directly onto the silicon substrates through zinc powder evaporation using a simple thermal evaporation method without a catalyst for comparison. The characteristics of these nanostructures are investigated using field-emission scanning electron microscopy, grazing-angle X-ray diffraction (XRD), and photoluminescence (PL) measurements of structures grown on both Si and porous Si substrates. The texture coefficient obtained from the XRD spectra indicates that the coral reef-like nanostructures are highly oriented on the porous silicon substrate with decreasing nanorods length and diameter from 800-900 nm to 3.5-5.5 {mu}m and from 217-229 nm to 0.6-0.7 {mu}m, respectively. The PL spectra show that for ZnO nanocoral reefs the UV emission shifts slightly towards lower frequency and the intensity increase with the improvement of ZnO crystallization. This non-catalyst growth technique on the rough surface of substrates may have potential applications in the fabrication of nanoelectronic and nanooptical devices.

  20. Ethyl Cellulose and Cetrimonium Bromide Assisted Synthesis of Mesoporous, Hexagon Shaped ZnO Nanodisks with Exposed ±{0001} Polar Facets for Enhanced Photovoltaic Performance in Quantum Dot Sensitized Solar Cells.

    Science.gov (United States)

    Chetia, Tridip Ranjan; Ansari, Mohammad Shaad; Qureshi, Mohammad

    2015-06-24

    Hexagon shaped mesoporous zinc oxide nanodisks (ZnO NDs) with exposed ±{0001} polar facets have been synthesized by using ethyl cellulose (EC) and cetrimonium bromide (CTAB) as the capping and structure directing agents. We have characterized ZnO NDs using analytical techniques, such as powder X-ray diffraction (PXRD), diffuse reflectance UV-visible (UV-vis) spectroscopy, photoluminescence (PL) spectroscopy, field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and Brunauer-Emmett-Teller (BET) surface area analysis and proposed a plausible mechanism for the formation of ZnO NDs. EC molecules form a colloidal solution in a 1-butanol:water (3:1) solvent system having a negative zeta potential (ζ ≈ -32 mV) value which can inhibit CTAB assisted c-axis growth of ZnO crystal and encourage the formation of ZnO NDs. In the control reactions carried out in presence of only CTAB and only EC, formation of hexagonal ZnO nanorods (NRs) and ZnO nanosheets (NSs) composed of numerous ZnO nanoparticles are observed, respectively. Photovoltaic properties of ZnO NDs as compared to ZnO NRs, ZnO NSs, and conventional ZnO nanoparticles (NPs) are investigated by co-sensitizing with CdS/CdSe quantum dots (QDs). An ∼35% increase in power conversion efficiency (PCE, η) is observed in ZnO NDs (η ≈ 4.86%) as compared to ZnO NPs (η ≈ 3.14%) while the values of PCE for ZnO NR and ZnO NS based devices are found to be ∼2.52% and ∼1.64%, respectively. Enhanced photovoltaic performance of the ZnO NDs based solar cell is attributed to an efficient charge separation and collection, boosted by the exposed ±(0001) facets apart from the single crystalline nature, better light-scattering effects, and high BET surface area for sensitizer particle adsorption. Electrochemical impedance spectroscopy (EIS) analysis further reveals that the charge recombination resistance and photoinduced electron lifetime are substantially higher in the ZnO ND based

  1. Controlled fabrication of ordered structure-based ZnO films by electrochemical deposition

    Energy Technology Data Exchange (ETDEWEB)

    Lei, J.F., E-mail: leijianfei9966@163.com [School of Physics and Engineering, Henan University of Science and Technology, Luoyang 471023 (China); Wang, Z.W. [School of Physics and Engineering, Henan University of Science and Technology, Luoyang 471023 (China); Li, W.S. [School of Chemistry and Environment, South China Normal University, Guangzhou 510006 (China)

    2014-12-31

    Orderly structured ZnO films were fabricated by electrochemical deposition combined with a templating method. The floating-transfer technique was used to assemble polystyrene sphere (PS) templates. Hierarchical structures containing two-diameter PS were easily assembled on the surface of F–SnO{sub 2} conductive glass (FTO). When used as a working electrode, the FTO glass coated with PS templates provided arrayed cavities to accommodate ZnO crystals under potentiostatic deposition and was ultimately covered by ordered, porous ZnO films after removal of PS templates. The morphologies of the samples were examined by field-emission scanning electron microscopy and crystallographic information for the samples was obtained from X-ray powder diffraction measurements. The results indicate that ZnO films fabricated by electrochemical deposition show excellent template replication over large areas and exhibit the typical wurtzite structure. - Highlights: • PS templates with tunable layers assembled by a floating-transfer technique are presented. • ZnO films with controllable morphologies are prepared by using electrochemical deposition. • With a binary PS template, hierarchical ZnO films are obtained.

  2. Synthesis of ZnO nanopencils using wet chemical method and its investigation as LPG sensor

    Energy Technology Data Exchange (ETDEWEB)

    Shimpi, Navinchandra G., E-mail: navin_shimpi@rediffmail.com [Department of Chemistry, University of Mumbai, Santacruz (East), Mumbai-400098 (India); Jain, Shilpa [Department of Chemistry, University of Mumbai, Santacruz (East), Mumbai-400098 (India); Karmakar, Narayan [Department of Physics, University of Mumbai, Santacruz (East), Mumbai-400098 (India); Shah, Akshara [Department of Chemistry, University of Mumbai, Santacruz (East), Mumbai-400098 (India); Kothari, D.C. [Department of Physics, University of Mumbai, Santacruz (East), Mumbai-400098 (India); National Centre for Nanosciences & Nanotechnology, University of Mumbai, Santacruz (East), Mumbai-400098 (India); Mishra, Satyendra [University Institute of Chemical Technology, North Maharashtra University, Jalgaon (India)

    2016-12-30

    Highlights: • Synthesis using a simple and cost-effective wet chemical process. • Uniform, monodispersed and pure nanoparticles. • Pencil shaped rods with sharp tips. • Understanding of Growth mechanism. • Efficient LPG sensing with high response. • Morphology dependent sensing. - Abstract: ZnO nanopencils (NPCs) were prepared by a novel wet chemical process, using triethanolamine (TEA) as a mild base, which is relatively simple and cost effective method as compared to hydrothermal method. ZnO NPCs were characterized using powder X-ray diffraction (XRD), Fourier Transform Infra-Red (FTIR) spectroscopy in mid-IR and far-IR regions, X-ray Photoelectron Spectroscopy (XPS), UV–vis (UV–vis) absorption spectroscopy, room temperature Photoluminescence (PL) spectroscopy and Field Emission Scanning Electron Microscopy (FESEM). ZnO NPCs obtained, were highly pure, uniform and monodispersed.XRD pattern indicated hexagonal unit cell structure with preferred orientation along the c-axis. Sensing behaviour of ZnO NPCs was studied towards Liquefied Petroleum Gas (LPG) at different operating temperatures. The study shows that ZnO NPCs were most sensitive and promising candidate for detection of LPG at 250 °C with gas sensitivity > 60%. The high response towards LPG is due to high surface area of ZnO NPCs and their parallel alignment.

  3. ZnO Film Photocatalysts

    Directory of Open Access Journals (Sweden)

    Bosi Yin

    2014-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Nayak, Sanjeev Kumar

    2012-04-24

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

  5. Structural, electrical and optical properties of Al-Sn codoped ZnO transparent conducting layer deposited by spray pyrolysis technique

    Science.gov (United States)

    Bedia, A.; Bedia, F. Z.; Aillerie, M.; Maloufi, N.

    2017-11-01

    Low cost Al-Sn codoped ZnO (ATZO) Transparent Conductive Oxide films were deposited by spray pyrolysis on glass substrate. The influence of Al-Sn codoping on the structural, optical and electrical properties of ZnO thin films was studied by comparing the same properties obtained in undoped ZnO, Al doped ZnO (AZO) and Sn doped ZnO (TZO) thin films. The so-obtained films crystallized in hexagonal wurtzite structure. The morphology and structural defects have been investigated by both High resolution Field Effect Scanning Electron Microscopy (FE-SEM) and Raman spectroscopy at 532 nm excitation source. In the visible region, the undoped and doped films show an average transmittance of the order of 85%, while for ATZO thin film, it is of the order of 72%, which points out a degradation of the optical properties due to the co-doping. The optical band gap of ATZO thin film achieves 3.31eV and this shift, compared to the referred samples is attributed to the Burstein-Moss (BM) and band gap narrowing (BGN) opposite effects which is due to the increase of the carrier concentration in degenerate semiconductors. Within all the samples, the ATZO thin film exhibits the lowest electrical resistivity of 4.56 × 10-3 Ωcm with a Hall mobility equal to 2.13 cm2 V-1s-1, and the highest carrier concentration of 6.41 × 1020 cm-3. The performance of ATZO transparent conductive oxide film are determined by its figure of merit (φTC), found equal to 1.69 10-4 Ω-1, which is a suitable value for potentially high-performance solar cell applications.

  6. The origin of room temperature ferromagnetism mediated by Co–VZn complexes in the ZnO grain boundary

    KAUST Repository

    Devi, Assa Aravindh Sasikala

    2016-05-20

    Ferromagnetism in polycrystalline ZnO doped with Co has been observed to be sustainable in recent experiments. We use first-principle calculations to show that Co impurities favorably substitute at the grain boundary (GB) rather than in the bulk. We reveal that room-temperature ferromagnetism (RTFM) at the Co-doped ZnO GB in the presence of Zn vacancies is due to ferromagnetic exchange coupling of a pair of closely associated Co atoms in the GB, with a ferromagnetic exchange coupling energy of ∼300 meV, which is in contrast to a previous study that suggested the O vacancy-Co complex induced ferromagnetism. Electronic structure analysis was used to predict the exchange coupling mechanism, showing that the hybridization of O p states with Co and Zn d states enhances the magnetic polarization originating from the GB. Our results indicate that RTFM originates from Co clusters at interfaces or in GBs. © 2016 The Royal Society of Chemistry.

  7. Visible and near infrared up-conversion luminescence in Yb{sup 3+}/Tm{sup 3+} co-doped yttria-alumino-silicate glass based optical fibers

    Energy Technology Data Exchange (ETDEWEB)

    Halder, Arindam [Fiber Optics and Photonics Division, Central Glass and Ceramic Research Institute (CGCRI), Council of Scientific and Industrial Research (CSIR), Jadavpur, Kolkata-700032 (India); Chandra Paul, Mukul, E-mail: mcpal1266@gmail.com [Fiber Optics and Photonics Division, Central Glass and Ceramic Research Institute (CGCRI), Council of Scientific and Industrial Research (CSIR), Jadavpur, Kolkata-700032 (India); Wadi Harun, Sulaiman [Depertment of Electrical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur (Malaysia); Kumar Bhadra, Shyamal, E-mail: skbhadra@cgcri.res.in [Fiber Optics and Photonics Division, Central Glass and Ceramic Research Institute (CGCRI), Council of Scientific and Industrial Research (CSIR), Jadavpur, Kolkata-700032 (India); Bysakh, Sandip [Electron Microscopy Section, Central Glass and Ceramic Research Institute (CGCRI), Council of Scientific and Industrial Research (CSIR), Jadavpur, Kolkata-700032 (India); Das, Shyamal; Pal, Mrinmay [Fiber Optics and Photonics Division, Central Glass and Ceramic Research Institute (CGCRI), Council of Scientific and Industrial Research (CSIR), Jadavpur, Kolkata-700032 (India)

    2013-11-15

    We report blue light up-conversion (UC) emission in Yb–Tm co-doped nano-phase separated yttria-alumino-silicate (YAS) glass based D-shaped with low-index cladding optical fibers. Y{sub 2}O{sub 3} creates an environment of nano structured YAS glass phases with Yb and Tm rich zone into the core glass which confirmed from TEM analyses. This kind of glass host assists in distributing of Yb and Tm rich zone uniformly throughout the core region. Yb and Tm doped regions exist mainly into nano YAS phases, defined as RE rich nano YAS-RE phases. All samples exhibit UC luminescence peaks at 483 nm, 650 nm and 817 nm for Tm{sup 3+} and 1044 nm for Yb{sup 3+} under excitation by 975 nm laser light. In such type of nano-engineered glass–ceramic based host, almost all the Yb ions transferred its energy to the nearer Tm ions. In particular 483 nm emission is attributed to {sup 1}G{sub 4}→{sup 3}H{sub 6} transition through a three step resonance energy transfer (ET) from excited Yb{sup 3+}. The highest emission intensity is obtained with a concentration of 0.5 wt% Tm{sup 3+} and 2.0 wt% Yb{sup 3+}. The ET between Yb{sup 3+} and Tm{sup 3+} is increased with increase of Yb{sup 3+} concentration with respect to Tm{sup 3+}. The experimental fluorescence life-times of Tm{sup 3+} upconversion emission at visible wavelengths into such kind of fiber is reported under 975 nm pump excitation. The present study is important for development of an efficient tunable 483 nm fluorescence light source. -- Highlights: • We report nano-phase separated YAS glass host based Yb–Tm co-doped optical fibers. • Almost all the Yb transferred its energy to the neighboring Tm ions. • We report strong UC luminescence peaks at 483 nm and 817 nm wavelengths. • We report third ET coefficient as 1.6723 Hz for such kind of Yb–Tm codoped fiber. • We report suitable fiber as an efficient tunable 483 nm fluorescence light source.

  8. Microstructure and property of diamond-like carbon films with Al and Cr co-doping deposited using a hybrid beams system

    Energy Technology Data Exchange (ETDEWEB)

    Dai, Wei, E-mail: popdw@126.com [School of Electromechanical Engineering, Guangdong University of Technology, Guangzhou 510006 (China); Liu, Jingmao; Geng, Dongsen [School of Electromechanical Engineering, Guangdong University of Technology, Guangzhou 510006 (China); Guo, Peng [Key Laboratory of Marine Materials and Related Technologies, Zhejiang Key Laboratory of Marine Materials and Protective Technologies, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Zheng, Jun [Science and Technology on Surface Engineering Laboratory, Lanzhou Institute of Physics, Lanzhou 730000 (China); Wang, Qimin, E-mail: qmwang@gdut.edu.cn [School of Electromechanical Engineering, Guangdong University of Technology, Guangzhou 510006 (China)

    2016-12-01

    Highlights: • Diamond-like carbon films with Al and Cr doping were deposited. • Alternate multilayered structure consisted of Al-poor layer and Al-rich layer was formed. • The periodic Al-rich layers can greatly improve the residual stress and elastic resilience of the films. - Abstract: DLC films with weak carbide former Al and carbide former Cr co-doping (Al:Cr-DLC) were deposited by a hybrid beams system comprising an anode-layer linear ion beam source (LIS) and high power impulse magnetron sputtering using a gas mixture of C{sub 2}H{sub 2} and Ar as the precursor. The doped Al and Cr contents were controlled via adjusting the C{sub 2}H{sub 2} fraction in the gas mixture. The composition, microstructure, compressive stress, mechanical properties and tribological behaviors of the Al:Cr-DLC films were researched carefully using X-ray photoelectron spectroscopy, transmission electron microscopy, Raman spectroscopy, stress-tester, nanoindentation and ball-on-plate tribometer as function of the C{sub 2}H{sub 2} fraction. The results show that the Al and Cr contents in the films increased continuously as the C{sub 2}H{sub 2} fraction decreased. The doped Cr atoms preferred to bond with the carbon while the Al atoms mainly existed in metallic state. Structure modulation with alternate multilayer consisted of Al-poor DLC layer and Al-rich DLC layer was found in the films. Those periodic Al-rich DLC layers can effectively release the residual stress of the films. On the other hand, the formation of the carbide component due to Cr incorporation can help to increase the film hardness. Accordingly, the residual stress of the DLC films can be reduced without sacrificing the film hardness though co-doping Al and Cr atoms. Furthermore, it was found that the periodic Al-rich layer can greatly improve the elastic resilience of the DLC films and thus decreases the film friction coefficient and wear rate significantly. However, the existence of the carbide component would

  9. Nd and Sc co-doped BiFeO{sub 3} nanopowders displaying enhanced ferromagnetism at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Hernández, N., E-mail: netzahualpille.hernandeznv@uanl.edu.mx [Centro de Innovación, Investigación y Desarrollo en Ingeniería y Tecnología, Km. 10 Nueva carretera al Aeropuerto Internacional de Monterrey, PIIT Monterrey, CP 66600 Apodaca, Nuevo León (Mexico); González-González, V.A. [Centro de Innovación, Investigación y Desarrollo en Ingeniería y Tecnología, Km. 10 Nueva carretera al Aeropuerto Internacional de Monterrey, PIIT Monterrey, CP 66600 Apodaca, Nuevo León (Mexico); Facultad de Ingeniería Mecánica y Eléctrica, Universidad Autónoma de Nuevo León, Pedro de Alba S/N, San Nicolás de los Garza, Nuevo León 66450 (Mexico); Dzul-Bautista, I.B. [Centro de Innovación, Investigación y Desarrollo en Ingeniería y Tecnología, Km. 10 Nueva carretera al Aeropuerto Internacional de Monterrey, PIIT Monterrey, CP 66600 Apodaca, Nuevo León (Mexico); Gutiérrez, J.; Barandiarán, J.M. [Basque Center for Materials, Applications and Nanostructures (BCMaterials), Universidad del País Vasco (UPV/EHU), Parque Tecnológico de Bizkaia, Ed. 500, Derio 48160 (Spain); and others

    2015-07-25

    Highlights: • Will study the structure of materials obtained. • A well crystallized BiFeO{sub 3} doped material was obtained without further annealing. • The obtained nanoparticles have sizes less than 60 nm. • Enhanced ferromagnetic materials was obtained. - Abstract: We have developed a novel synthetic route for the preparation of single phase Nd{sub x}Bi{sub 1−x}Fe{sub 0.95}Sc{sub 0.05}O{sub 3} (NBFSO) nanopowder materials by a surfactant-assisted combustion-derived method. Rietveld fitting of the Powder X-ray diffraction data showed the nanopowder structure evolves from a distorted rhombohedral BiFeO{sub 3} crystalline structure (R3c, x = 0) to a orthorhombic structure (Pbnm, x = 0.10). Differential thermal analysis and thermogravimetric analysis (DTA/TGA) showed a crystallization temperature of 200 °C. Transmission electron microscopy (TEM) images revealed the presence of clusters formed by fine nanoparticles less than 60 nm in diameter. From Raman spectroscopy, the change from rhombohedral structure to cubic structure was observed by a drastic intensity reduction of the A{sub 1}{sup −2} and A{sub 1}{sup −3} Raman modes, with the A{sub 1}{sup −1} and A{sub 1}{sup −2} modes gradually merging together, indicating the merge of the orthorhombic phase. Despite the antiferromagnetic nature of bulk BiFeO{sub 3}, the NBFSO nanopowders obtained displayed a ferromagnetic hysteresis loop, with coercivities of 0.08 T and remanent magnetizations of 0.65–4.05 Am{sup 2}/kg when measured at room temperature. The increasing and uncompensated spins at the surface of nanoparticles and the canted internal spin by the tilt of FeO{sub 6} octahedral units and the structure transition appear to be the main reason for observed this ferromagnetic behavior.

  10. SOVIET ABSTRACTS ON POWDER METALLURGY

    Science.gov (United States)

    CERMETS, * POWDER METALLURGY , ABSTRACTS, CERAMIC MATERIALS, HEAT RESISTANT ALLOYS, INDUSTRIAL PRODUCTION, MECHANICAL PROPERTIES, PIEZOELECTRIC CRYSTALS, POLARIZATION, POROUS METALS, POWDER ALLOYS, POWDER METALS, SINTERING.

  11. Comparative studies on the structural and luminescent properties of ZnO micro and nanostructures prepared by different hydrothermal growth

    Science.gov (United States)

    Sun, Qi; Wang, Yongqian; Yuan, Ximing; Li, Yinchang; Yang, Jun; Jin, Hongyun; Li, Fei

    2013-12-01

    In the present work, various ZnO micro and nanostructures were successively prepared under a certain pH value at the temperature of 180 °C by non-surfactant and surfactant-assisted hydrothermal growth. The crystalline structure and morphology of the as-obtained products were characterized by powder X-ray diffraction, Raman spectroscopy, scanning electron microscopy and transmission electron microscopy. The results of characterization indicated that all ZnO micro and nanostructures were high quality, hexagonal wurtzite crystal, exhibiting different morphology, such as flower-like and cabbage-like micro and nanostructures. Photoluminescence measurement of the ZnO micro and nanostructures was conducted and it showed that all products showed similar emission peaks. In addition, the growth mechanism of these ZnO micro and nanostructures by different hydrothermal growth was preliminarily discussed.

  12. Optical and structural properties of ZnO hexagonal rods prepared by thermal chemical vapor deposition technique

    Directory of Open Access Journals (Sweden)

    A Reyhani

    2014-11-01

    Full Text Available In this research, ZnO nanostructure hexagonal pyramid rods with high optical and structural quality were synthesized by the simple thermal chemical vapor deposition of Zn powder without a metal catalyst. Surface morphologies were characterized by scanning electron microscopy (SEM. XRD analyses demonstrated that ZnO hexagonal pyramid rods had a wurtzite structure with the orientation of (002. Investigation of optical properties of samples by photoluminescence spectrum exhibited a sharp UV emission peak at 380nm. The quality and composition of the ZnO pyramid rods were characterized using the Fourier transform infrared spectrum (FTIR at room temperature. In addition, the growth mechanism of ZnO hexagonal rods is also briefly discussed.

  13. Mesoporous ZnO microcube derived from a metal-organic framework as photocatalyst for the degradation of organic dyes

    Science.gov (United States)

    Ban, Jin-jin; Xu, Guan-cheng; Zhang, Li; Lin, He; Sun, Zhi-peng; Lv, Yan; Jia, Dian-zeng

    2017-12-01

    A cube-like porous ZnO architecture was synthesized by direct two-step thermolysis of a zinc-based metal-organic framework [(CH3)2NH2][Zn(HCOO)3]. The obtained ZnO microcube was characterized by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy and nitrogen adsorption and desorption isotherms. The mesoporous ZnO microcube was comprised by many nanoparticles, and inherited the cube shape from [(CH3)2NH2][Zn(HCOO)3] precursor. With large surface area and mesoporous structure, the ZnO microcube exhibits excellent photocatalytic activities against methyl orange (MO) and rhodamine B (RhB) under UV irradiation, and the degradation rates reached 99.7% and 98.1% within 120 min, respectively.

  14. Encapsulation of ZnO particles by metal fluorides: Towards an application as transparent insulating coatings for windows

    Science.gov (United States)

    Trenque, Isabelle; Mornet, Stéphane; Duguet, Etienne; Majimel, Jérôme; Brüll, Annelise; Teinz, Katharina; Kemnitz, Erhard; Gaudon, Manuel

    2013-01-01

    Because ZnO is a promising candidate for getting efficient films or varnishes with thermal insulating abilities for windows applications, the effect of the encapsulation of ZnO particles in shells of low refractive index material on the improvement of the visible light transmission was investigated. ZnO-MgF2 core-shell particles were synthesized by deposition of fluoride sols on ZnO particles through a vacuum slip casting process like. The transmission behaviours were first indirectly studied by diffuse reflexion measurements on powder beds. Then, particle films were elaborated by a screen printing process which ensured direct transmission measurements. The encapsulation of ZnO particles with a coating shell of 1.3 wt.% of MgF2 improves the visible light transmission of 32%.

  15. Aluminum powder metallurgy processing

    Energy Technology Data Exchange (ETDEWEB)

    Flumerfelt, J.F.

    1999-02-12

    The objective of this dissertation is to explore the hypothesis that there is a strong linkage between gas atomization processing conditions, as-atomized aluminum powder characteristics, and the consolidation methodology required to make components from aluminum powder. The hypothesis was tested with pure aluminum powders produced by commercial air atomization, commercial inert gas atomization, and gas atomization reaction synthesis (GARS). A comparison of the GARS aluminum powders with the commercial aluminum powders showed the former to exhibit superior powder characteristics. The powders were compared in terms of size and shape, bulk chemistry, surface oxide chemistry and structure, and oxide film thickness. Minimum explosive concentration measurements assessed the dependence of explosibility hazard on surface area, oxide film thickness, and gas atomization processing conditions. The GARS aluminum powders were exposed to different relative humidity levels, demonstrating the effect of atmospheric conditions on post-atomization processing conditions. The GARS aluminum powders were exposed to different relative humidity levels, demonstrating the effect of atmospheric conditions on post-atomization oxidation of aluminum powder. An Al-Ti-Y GARS alloy exposed in ambient air at different temperatures revealed the effect of reactive alloy elements on post-atomization powder oxidation. The pure aluminum powders were consolidated by two different routes, a conventional consolidation process for fabricating aerospace components with aluminum powder and a proposed alternative. The consolidation procedures were compared by evaluating the consolidated microstructures and the corresponding mechanical properties. A low temperature solid state sintering experiment demonstrated that tap densified GARS aluminum powders can form sintering necks between contacting powder particles, unlike the total resistance to sintering of commercial air atomization aluminum powder.

  16. The synthesis of nitrogen/sulfur co-doped TiO2 nanocrystals with a high specific surface area and a high percentage of {001} facets and their enhanced visible-light photocatalytic performance

    Science.gov (United States)

    2012-01-01

    Nitrogen/sulfur co-doped anatase TiO2 nanocrystals with a high specific surface area and a high percentage of {001} facets were synthesized by a solvent-thermal process followed by the calcination with thiourea at an optimum heat treatment temperature. Under current experimental conditions, the optimum heat treatment temperature was found at 300°C, which successfully introduced nitrogen and sulfur dopants into the anatase lattice to replace a small portion of oxygen atoms while preserving the geometry of these anatase TiO2 nanocrystals to maintain a high percentage of {001} facets. These nitrogen/sulfur co-doped anatase TiO2 nanocrystals demonstrated a largely enhanced light absorption in the whole visible-light range and exhibited much higher photocatalytic performance than both P25 TiO2 nanoparticles and anatase TiO2 nanocrystals with a high percentage of {001} facets under visible-light illumination. PMID:23095371

  17. Influence of the preparation method on the structure, optical and photocatalytic properties of nanosized ZnO

    Energy Technology Data Exchange (ETDEWEB)

    Gancheva, M., E-mail: mancheva@svr.igic.bas.bg [Institute of General and Inorganic Chemistry, Bulgarian Academy of Science, Acad. G. Bonchev Str., bl.11, 1113, Sofia (Bulgaria); Uzunov, I.; Iordanova, R. [Institute of General and Inorganic Chemistry, Bulgarian Academy of Science, Acad. G. Bonchev Str., bl.11, 1113, Sofia (Bulgaria); Papazova, K. [University of Sofia, Faculty of Chemistry and Pharmacy, James Bourchier 1 Blvd., 1164, Sofia (Bulgaria)

    2015-08-15

    Mechanochemical activation is the most commonly applied approach for improving the photocatalytic properties of commercial zinc oxide. Here we show that ZnO obtained by two-pathway decomposition of basic zinc carbonate also possesses a very good photocatalytic activity. Nanosized ZnO powders were successfully prepared by thermal and mechanochemical decomposition of Zn{sub 5}(CO{sub 3}){sub 2}(OH){sub 6}, precipitated under soft conditions. The precursor and final products were characterized by X-ray diffraction (XRD), thermal analysis (TG/DTA), infrared spectroscopy (IR) and B.E.T method. The morphology of the ZnO was observed by SEM analysis. The optical and photocatalytic properties of the prepared zinc oxides were also investigated and compared with commercial ZnO. The band gaps of the thermal and mechanochemical obtained ZnO nanopowders are 3.22 and 3.04 eV, respectively. The degree of decomposition of Malachite Green under UV and visible irradiations in the presence of ZnO prepared by both methods reached levels above 90%. Better catalytic activity was found for the visible region. It was established that the process follows second order kinetics. - Graphical abstract: Display Omitted - Highlights: • Synthesis of nanosized ZnO from hydrozincite by thermal and mechanochemical route. • ZnO powders possess high photocatalytic activity under UV and visible irradiation. • The degree of decomposition of Malachite Green is more than 90% for the both ZnO's. • The photodecomposition of MG under UV/Vis irradiation follows second order kinetics.

  18. Synthesis and characterization of surfactants assisted Cu(2+) doped ZnO nanocrystals.

    Science.gov (United States)

    Dhamodharan, P; Gobi, R; Shanmugam, N; Kannadasan, N; Poonguzhali, R; Ramya, S

    2014-10-15

    In the present work, we report a simple chemical precipitation method to synthesize precursors of different levels of Cu(2+) ions doped crystalline zinc oxide (ZnO) nanoparticles in the presence of capping agents namely cetyltrimethyl ammonium bromide (CTAB) and sodium hexametaphosphate (SHMP). Thermal analysis result suggests that 300°C could be the optimum level of annealing for the harvest of pure phase of ZnO from the as prepared particles. The structural, optical and chemical features of undoped and surfactants assisted ZnO: Cu(2+) nanoparticles were studied by X-ray powder diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), Ultraviolet-Visible (UV-Vis) absorption spectroscopy and photoluminescence (PL) measurements. Among the two surfactants used SHMP is an effective one in controlling the size and morphology of the particles. Copyright © 2014 Elsevier B.V. All rights reserved.

  19. Synthesis and characterization of surfactants assisted Cu2+ doped ZnO nanocrystals

    Science.gov (United States)

    Dhamodharan, P.; Gobi, R.; Shanmugam, N.; Kannadasan, N.; Poonguzhali, R.; Ramya, S.

    2014-10-01

    In the present work, we report a simple chemical precipitation method to synthesize precursors of different levels of Cu2+ ions doped crystalline zinc oxide (ZnO) nanoparticles in the presence of capping agents namely cetyltrimethyl ammonium bromide (CTAB) and sodium hexametaphosphate (SHMP). Thermal analysis result suggests that 300 °C could be the optimum level of annealing for the harvest of pure phase of ZnO from the as prepared particles. The structural, optical and chemical features of undoped and surfactants assisted ZnO: Cu2+ nanoparticles were studied by X-ray powder diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), Ultraviolet-Visible (UV-Vis) absorption spectroscopy and photoluminescence (PL) measurements. Among the two surfactants used SHMP is an effective one in controlling the size and morphology of the particles.

  20. "High Quantum Efficiency of Band-Edge Emission from ZnO Nanowires"

    Energy Technology Data Exchange (ETDEWEB)

    GARGAS, DANIEL; GAO, HANWEI; WANG, HUNGTA; PEIDONG, YANG

    2010-12-01

    External quantum efficiency (EQE) of photoluminescence as high as 20 percent from isolated ZnO nanowires were measured at room temperature. The EQE was found to be highly dependent on photoexcitation density, which underscores the importance of uniform optical excitation during the EQE measurement. An integrating sphere coupled to a microscopic imaging system was used in this work, which enabled the EQE measurement on isolated ZnO nanowires. The EQE values obtained here are significantly higher than those reported for ZnO materials in forms of bulk, thin films or powders. Additional insight on the radiative extraction factor of one-dimensional nanostructures was gained by measuring the internal quantum efficiency of individual nanowires. Such quantitative EQE measurements provide a sensitive, noninvasive method to characterize the optical properties of low-dimensional nanostructures and allow tuning of synthesis parameters for optimization of nanoscale materials.

  1. Low-cost adsorbent derived and in situ nitrogen/iron co-doped carbon as efficient oxygen reduction catalyst in microbial fuel cells.

    Science.gov (United States)

    Cao, Chun; Wei, Liling; Su, Min; Wang, Gang; Shen, Jianquan

    2016-08-01

    A novel low-cost adsorbent derived and in situ nitrogen/iron co-doped carbon (N/Fe-C) with three-dimensional porous structure is employed as efficient oxygen reduction catalyst in microbial fuel cells (MFCs). The electrochemical active area is significantly improved to 617.19m(2)g(-1) in N/Fe-C by Fe-doping. And N/Fe-C (4.21at.% N, 0.11at.% Fe) exhibits excellent electrocatalytic activity with the oxygen reduction potential of -0.07V (vs. Ag/AgCl) which is comparable to commercial Pt/C. In MFCs tests, the maximum power density and output voltage with N/Fe-C are enhanced to 745mWm(-2) and 562mV (external resistance 1kΩ), which are 11% and 0.72% higher than Pt/C (0.5mgPtcm(-2)), respectively. Besides, the long-term stability of N/Fe-C retains better for more than one week. Moreover, the charge transfer resistance (Rct) values are recorded by the impedance measurements, and the low Rct of N/Fe-C is also result in better catalytic activity. Copyright © 2016 Elsevier Ltd. All rights reserved.

  2. Combined up conversion, down conversion and down shifting photo-luminescence of low cost erbium-ytterbium co-doped porous silicon produced by stain etching

    Energy Technology Data Exchange (ETDEWEB)

    Diaz-Herrera, B. [Departamento de Fisica Basica, Universidad de La Laguna (ULL), Avenida Astrofisico Francisco Sanchez, 2, 38206 La Laguna, S/C de Tenerife (Spain); Linsun Power Technology (Quanzhou) Corp. Ltd. Co., Economic Development Zone, Jinjiang 362200, Fujian (China); Jimenez-Rodriguez, E. [Departamento de Fisica Basica, Universidad de La Laguna (ULL), Avenida Astrofisico Francisco Sanchez, 2, 38206 La Laguna, S/C de Tenerife (Spain); Gonzalez-Diaz, B. [Departamento de Fisica Basica, Universidad de La Laguna (ULL), Avenida Astrofisico Francisco Sanchez, 2, 38206 La Laguna, S/C de Tenerife (Spain); Instituto Tecnologico y de Energias Renovables, S.A. (ITER), Poligono Industrial de Granadilla, S/N, E38600, Granadilla de Abona (Spain); Montesdeoca-Santana, A. [Departamento de Fisica Basica, Universidad de La Laguna (ULL), Avenida Astrofisico Francisco Sanchez, 2, 38206 La Laguna, S/C de Tenerife (Spain); Velazquez, J.J. [Departamento de Fisica Fundamental y Experimental, Electronica y Sistemas, Avenida Astrofisico Francisco Sanchez, 2, 38206 La Laguna, S/C de Tenerife (Spain); Guerrero-Lemus, R., E-mail: rglemus@ull.es [Departamento de Fisica Basica, Universidad de La Laguna (ULL), Avenida Astrofisico Francisco Sanchez, 2, 38206 La Laguna, S/C de Tenerife (Spain); Fundacion de Estudios de Economia Aplicada, Programa Focus-Abengoa de Energia y Cambio Climaticoi, Jorge Juan 46, 28001 Madrid (Spain)

    2011-07-01

    In this work, erbium and ytterbium have been incorporated into luminescent porous silicon (PS) layers by simple impregnation of the PS substrate with a saturated nitrate solution of erbium and ytterbium. The photoluminescence of the co-doped rare earth layers have been evaluated. The doping process has been designed for its potential in silicon-based solar cell production, with the aim to improve the Shockley-Queisser limit with a reasonable cost effective method for the industry, which implies a significant enhancement of the efficiency under non-concentrated sunlight irradiation. The temperature and annealing time of the doping process were selected according to industry standards in order to ease a trial adoption. The composition was analyzed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy in order to characterize the doping profile. Different up-conversion and down-conversion contributions from the rare earths in the visible and IR were detected, together with the down shifting effect of the stain etched PS. There is no evidence of energy transference between the PS matrix and the rare earths.

  3. Chromium–niobium co-doped vanadium dioxide films: Large temperature coefficient of resistance and practically no thermal hysteresis of the metal–insulator transition

    Directory of Open Access Journals (Sweden)

    Kenichi Miyazaki

    2016-05-01

    Full Text Available We investigated the effects of chromium (Cr and niobium (Nb co-doping on the temperature coefficient of resistance (TCR and the thermal hysteresis of the metal–insulator transition of vanadium dioxide (VO2 films. We determined the TCR and thermal-hysteresis-width diagram of the V1−x−yCrxNbyO2 films by electrical-transport measurements and we found that the doping conditions x ≳ y and x + y ≥ 0.1 are appropriate for simultaneously realizing a large TCR value and an absence of thermal hysteresis in the films. By using these findings, we developed a V0.90Cr0.06Nb0.04O2 film grown on a TiO2-buffered SiO2/Si substrate that showed practically no thermal hysteresis while retaining a large TCR of 11.9%/K. This study has potential applications in the development of VO2-based uncooled bolometers.

  4. Chromium–niobium co-doped vanadium dioxide films: Large temperature coefficient of resistance and practically no thermal hysteresis of the metal–insulator transition

    Energy Technology Data Exchange (ETDEWEB)

    Miyazaki, Kenichi, E-mail: kenichi-miyazaki@denso.co.jp, E-mail: k.shibuya@aist.go.jp [Denso Corporation, Aichi 470-0111 (Japan); University of Tsukuba, Tsukuba 305-8571 (Japan); Shibuya, Keisuke, E-mail: kenichi-miyazaki@denso.co.jp, E-mail: k.shibuya@aist.go.jp; Sawa, Akihito [National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8565 (Japan); Suzuki, Megumi; Sakai, Kenichi [Denso Corporation, Aichi 470-0111 (Japan); Fujita, Jun-ichi [University of Tsukuba, Tsukuba 305-8571 (Japan)

    2016-05-15

    We investigated the effects of chromium (Cr) and niobium (Nb) co-doping on the temperature coefficient of resistance (TCR) and the thermal hysteresis of the metal–insulator transition of vanadium dioxide (VO{sub 2}) films. We determined the TCR and thermal-hysteresis-width diagram of the V{sub 1−x−y}Cr{sub x}Nb{sub y}O{sub 2} films by electrical-transport measurements and we found that the doping conditions x ≳ y and x + y ≥ 0.1 are appropriate for simultaneously realizing a large TCR value and an absence of thermal hysteresis in the films. By using these findings, we developed a V{sub 0.90}Cr{sub 0.06}Nb{sub 0.04}O{sub 2} film grown on a TiO{sub 2}-buffered SiO{sub 2}/Si substrate that showed practically no thermal hysteresis while retaining a large TCR of 11.9%/K. This study has potential applications in the development of VO{sub 2}-based uncooled bolometers.

  5. B, N co-doped carbon from cross-linking induced self-organization of boronate polymer for supercapacitor and oxygen reduction reaction

    Science.gov (United States)

    Chang, Ying; Yuan, Conghui; Liu, Cheng; Mao, Jie; Li, Yuntong; Wu, Haiyang; Wu, Yuzhe; Xu, Yiting; Zeng, Birong; Dai, Lizong

    2017-10-01

    A novel strategy has been developed to generate B, N co-doped carbon materials (CNBs) through the pyrolysis of boronate polymer nanoparticles (BPNs) derived from the condensation reaction between catechol and boronic monomers. The morphology, surface area and heteroatom (viz. B and N) content of the CNBs can be easily adjusted by altering the molar ratio between catechol and boronic monomers. The supercapacitor and oxygen reduction reaction (ORR) performance of the CNBs are optimized. CNBs derived from equal molar ratio of catechol and boronic monomers exhibit favorable performance for supercapacitor, featuring a specific capacitance of up to 299.4 F/g at 0.2 A/g, an improved rate capability and excellent cycle stability. Notably, CNBs prepared using 1/2 molar ratio of catechol to boronic monomers show excellent ORR performance, as they demonstrate good electrocatalytic activity, high tolerance for methanol and long durability. Our findings may be of interest in the design of carbon materials with optimized electrochemical properties through the control over surface area and the content of heteroatom.

  6. N, S co-doped carbon spheres with highly dispersed CoO as non-precious metal catalyst for oxygen reduction reaction

    Science.gov (United States)

    Chen, Linlin; Guo, Xingpeng; Zhang, Guoan

    2017-08-01

    It is still a great challenge in preparing non-precious metal catalysts with high activity and long-term stability to substitute for precious metal catalysts for oxygen reduction reaction (ORR) in fuel cells. Herein, we report a novel and facile catalyst-N, S co-doped carbon spheres with highly dispersed CoO (CoO@NS-CSs), where biomass glucose spheres act as carbon precursor and H2S, NH3 derived from the decomposition of thiourea not only provide N, S sources but also can etch carbon spheres to produce nanoporous structure. CoO@NS-CSs catalyst exhibits excellent ORR activity with a high onset potential of 0.946 V vs. RHE (reversible hydrogen electrode) and a half-wave potential of 0.821 V vs. RHE through a four-electron pathway in alkaline solution, which is comparable to commercial Pt/C catalyst (onset potential: 0.926 V vs. RHE, half-wave potential: 0.827 V vs. RHE). Furthermore, both the long-term stability and methanol-tolerance of CoO@NS-CSs catalyst are superior to those of commercial Pt/C catalyst. The excellent ORR performance of CoO@NS-CSs catalyst can be attributed to its micro-mesopore structure, high specific surface area (667 m2 g-1), and highly dispersed CoO. This work manifests that the obtained CoO@NS-CSs catalyst is promising to be applied to fuel cells.

  7. Photophysical and energy transfer processes in Ce{sup 3+} co-doped ZrO{sub 2}: Eu{sup 3+} nanorods

    Energy Technology Data Exchange (ETDEWEB)

    Ahemen, I.; Dejene, F.B. [University of the Free State-Qwaqwa Campus, Department of Physics, Phuthaditjhaba (South Africa)

    2017-02-15

    Cerium (III) ion co-doped ZrO{sub 2}: Eu{sup 3+} nanorods at varying Ce{sup 3+} ion concentrations were synthesized by a simple chemical dehydration route. Their structural, morphological and optical properties were investigated. Structural studies revealed a tetragonal phase with CeO{sub 2} phase grafted onto its surface. Field emission scanning electron microscopy images show nanorods of different dimensions. Diffraction peaks shifted towards smaller angles indicating the incorporation of the rare earth ions. Both Ce{sup 3+} (donor) and Eu{sup 3+} (activator) emission peaks were obtained when the samples were excited via the Ce{sup 3+} excitation band indicating energy transfer from the donor to activator. The process of energy transfer is both multipolar and exchange interactions. However, no significant enhancement of the activator's emission intensity, because concentration quenching process dominated the energy transfer process. The internal quantum efficiency, though low (20-25%), increased with increasing Ce{sup 3+} concentration. (orig.)

  8. Structural and optical properties of Tb and Na–Tb co-doped Ca3V2O8 phosphors prepared by sol–gel process

    Science.gov (United States)

    Parab, Shambhu S.; Salker, A. V.

    2018-01-01

    A malic acid assisted sol–gel route was successfully employed to prepare two distinct series of green emitting Ca3V2O8 phosphors. In the first series, Tb was solely doped whereas in the second series Na and Tb were doped simultaneously in the Ca3V2O8 crystal lattice. X-ray diffraction studies proved the utility of adopted preparative method by confirming the monophasic formation of all compounds from both the series. Spectral analysis like Raman spectroscopy, UV-DRS were undertaken to analyse the local structure, crystallinity and absorptive characteristics. XPS validated the presence of desired oxidation states of all the elements present. Finally, photoluminescence studies were done to elucidate the scope of prepared compounds as green emitting phosphors and also to understand the effect of both doping schemes on the luminescence. Intense green emission was observed in both the cases. Tb concentration of 0.08 was found to be optimum in case of Tb singly doped compounds whereas Tb = 0.12 showed highest intensity among the Na–Tb co-doped samples. Moreover, a red shift in the excitation wavelength was observed after Na doping signifying a change in the local electronic environment which in turn has affected the luminescence pattern. Local crystallinity and vacancy concentrations were found to have a major say on the emission intensities.

  9. The role of air annealing on the optical and scintillation properties of Mg co-doped Pr:LuAG transparent ceramics

    Science.gov (United States)

    Hu, Zewang; Cao, Maoqing; Chen, Haohong; Shi, Yun; Kou, Huamin; Xie, Tengfei; Wu, Lexiang; Pan, Yubai; Feng, Xiqi; Vedda, Anna; Beitlerova, A.; Nikl, M.; Li, Jiang

    2017-10-01

    Polycrystalline 0.2at%Pr:Lu3Al5O12 (Pr:LuAG) transparent ceramics were fabricated by solid-state reaction using 0.01 wt% MgO as sintering aid. The as-sintered ceramics were annealed in air at different temperatures. Optical absorption, photoluminescence, X-ray excited luminescence and pulse height spectra obtained after different annealing were compared. Modifications of the oxygen vacancy concentrations are found to govern the changes of the optical and scintillation response for annealing temperatures lower than 1000 °C, while the oxidation of Pr3+ to Pr4+ plays a more important role for higher temperatures. Air annealing up to 700 °C is an effective tool to improve the 5d-4f emission efficiency of MgO co-doped Pr:LuAG transparent ceramics. The highest radioluminescence intensity is obtained for the 700 °C annealed sample. At variance, higher temperature annealing leads to the deterioration of 5d-4f photoluminescence and scintillation properties because of the self-absorption of Pr4+ and energy transfer from Pr3+ to Pr4+. In addition, we find that the 4f-4f slow emission of ceramics shows different response characteristics under different irradiation sources.

  10. Fabrication and characterization of Tm3+-Ho3+ co-doped tellurite glass microsphere lasers operating at ∼2.1 μm

    Science.gov (United States)

    Yang, Zhengsheng; Wu, Yuehao; Yang, Kun; Xu, Peipeng; Zhang, Wei; Dai, Shixun; Xu, Tiefeng

    2017-10-01

    We used a Tm3+-Ho3+ co-doped tellurite glass as the laser medium to build active microsphere laser resonators. A droplet method is implemented and hundreds of high quality microspheres can be fabricated simultaneously. Typical Quality factors (Q-factors) of microspheres fabricated in this work reach 106. Silica fiber tapers are used as the coupling mechanism and a commercial 808 nm laser diode is used as the pump source. Laser lines at ∼2.1 μm can be observed in the emission spectrum of these active microsphere resonators. Pump thresholds for generating single mode laser lines in a 59.52 μm diameter microsphere is measured to be 0.887 mW and as the pump power is increased to 1.413 mW, multi-mode laser lines can be generated. We also demonstrate microsphere lasers fabricated in this work can be thermally tuned with a temperature sensitivity of 32 pm/°C, implying these microspheres can be used as highly compact temperature sensors in various mid-infrared applications.

  11. In vitro characterisation of a sol-gel derived in situ silica-coated silicate and carbonate co-doped hydroxyapatite nanopowder for bone grafting.

    Science.gov (United States)

    Latifi, Seyed Mohsen; Fathi, Mohammadhossein; Sharifnabi, Ali; Varshosaz, Jaleh

    2017-06-01

    Design and synthesis of materials with better properties and performance are essential requirements in the field of biomaterials science that would directly improve patient quality of life. For this purpose, in situ silica-coated silicate and carbonate co-doped hydroxyapatite (Sc/S.C.HA) nanopowder was synthesized via the sol-gel method. Characterisation of the prepared nanopowder was carried out by XRD, FTIR, TEM, SEM, EDX, ICP, zeta potential, acid dissolution test, and cell culture test. The substitution of the silicate and carbonate ions into hydroxyapatite structure was confirmed by FTIR analysis. XRD analysis showed that silica is an amorphous phase, which played a role in covering the surface of the S.C.HA nanoparticles as confirmed by acid dissolution test. Low thickness and low integrity of the amorphous silica surface layer facilitated ions release from S.C.HA nanoparticles into physiological saline solution. Zeta potential of the prepared nanopowder suspended in physiological saline solution was -27.3±0.2mV at pH7.4. This negatively charged surface, due to the presence of amorphous silica layer upon the S.C.HA nanoparticles, not only had an accelerating effect on in vitro biomineralization of apatite, but also had a positive effect on cell attachment. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. The simultaneous enhancement of photorefraction and optical damage resistance in MgO and Bi2O3 co-doped LiNbO3 crystals

    Science.gov (United States)

    Zheng, Dahuai; Kong, Yongfa; Liu, Shiguo; Chen, Muling; Chen, Shaolin; Zhang, Ling; Rupp, Romano; Xu, Jingjun

    2016-02-01

    For a long time that optical damage was renamed as photorefraction, here we find that the optical damage resistance and photorefraction can be simultaneously enhanced in MgO and Bi2O3 co-doped LiNbO3 (LN:Bi,Mg). The photorefractive response time of LN:Bi,Mg was shortened to 170 ms while the photorefractive sensitivity reached up to 21 cm2/J. Meanwhile, LN:Bi,Mg crystals could withstand a light intensity higher than 106  W/cm2 without apparent optical damage. Our experimental results indicate that photorefraction doesn’t equal to optical damage. The underground mechanism was analyzed and attributed to that diffusion dominates the transport process of charge carriers, that is to say photorefraction causes only slight optical damage under diffusion mechanism, which is very important for the practical applications of photorefractive crystals, such as in holographic storage, integrated optics and 3D display.

  13. White photoluminescence emission from ZrO{sub 2} co-doped with Eu{sup 3+}, Tb{sup 3+} and Tm{sup 3+}

    Energy Technology Data Exchange (ETDEWEB)

    Lovisa, L.X., E-mail: lovisaengmat@ig.com.br [Departamento de Engenharia de Materiais, Universidade Federal do Rio Grande do Norte, 59072-970, Natal, RN (Brazil); Araújo, V.D. [UACSA, Universidade Federal Rural de Pernambuco, 54510-000, Cabo de Santo Agostinho, PE (Brazil); Tranquilin, R.L.; Longo, E. [LIEC, Universidade Federal de São Carlos, 13565-905, São Carlos, SP (Brazil); Li, M.S. [Instituto de Física de São Carlos, Universidade de São Paulo, 13566-590, São Carlos, SP (Brazil); Paskocimas, C.A.; Bomio, M.R.D.; Motta, F.V. [Departamento de Engenharia de Materiais, Universidade Federal do Rio Grande do Norte, 59072-970, Natal, RN (Brazil)

    2016-07-25

    The search for high efficiency, reliable, low power consumption and environmental friendly materials for white light-emitting diodes has become a proficient field. Single-phase doped materials have been made to solve some of these challenges. Particles with color-tunable emission can be obtained by a combination of some lanthanide ions in the host material. The luminescence properties and crystalline structure of ZrO{sub 2} particles co-doped with rare earth ions (RE{sup 3+} = Tb{sup 3+}, Eu{sup 3+} and Tm{sup 3+}) calcined at different temperatures were studied. We aimed to investigate the emission spectrum of the particles in the red, green, and blue regions under UV excitation. The x and y coordination chromaticity - (x = 0.34, y = 0.34) and (x = 0.31, y = 0.34) - presented values close to those of the white color (x = y = 0.33). In conclusion, the ZrO{sub 2}:RE{sup 3+} powers were successfully obtained by the complex polymerization method and are promising candidates for white light-emitting applications. - Highlights: The ZrO{sub 2}:RE materials presented here are promising photoluminescent materials. The CIE coordinates calculated are disposed in the blank region in the CIE diagram. The results for the Raman confirm the response obtained by XRD: stabilization of cubic phase.

  14. A portable luminescent thermometer based on green up-conversion emission of Er3+/Yb3+ co-doped tellurite glass

    Science.gov (United States)

    Manzani, Danilo; Petruci, João Flávio Da Silveira; Nigoghossian, Karina; Cardoso, Arnaldo Alves; Ribeiro, Sidney J. L.

    2017-01-01

    The determination of temperature is essential in many applications in the biomedical, technological, and industrial fields. Optical thermometry appears to be an excellent alternative for conventional electric temperature sensors because it is a non-contact method that offers a fast response, electromagnetic passivity, and high temperature sensitivity. In this paper, we propose an optical thermometer probe comprising an Er3+/Yb3+ co-doped tellurite glass attached to the tip of an optical fibre and optically coupled to a laser source and a portable USB spectrometer. The ratio of the up-conversion green emission integrated peak areas when excited at 980 nm was temperature dependent, and it was used to calibrate the thermometer. The thermometer was operated in the range of 5-50 °C and 50-200 °C, and it revealed excellent linearity (r2 > 0.99), suitable accuracy, and precisions of ±0.5 and ±1.1 °C, respectively. By optimizing Er3+ concentration, we could obtain the high green emission intensity, and in turn, high thermal sensitivity for the probe. The probe fabricated in the study exhibited suitable properties for its application as a temperature sensor and superior performance compared to other Er3+ -based optical thermometers in terms of thermal sensitivity.

  15. Effect of WO{sub 3} on the spectroscopic properties in Er{sup 3+}/Yb{sup 3+} co-doped bismuth-borate glasses

    Energy Technology Data Exchange (ETDEWEB)

    Wang Jun [Faculty of Information Science and Engineering, State Key Laboratory Base of Novel Functional Materials and Preparation Science, Ningbo University, Zhejiang 315211 (China)], E-mail: wjun_nbu@126.com; Zhou Yaxun [Faculty of Information Science and Engineering, State Key Laboratory Base of Novel Functional Materials and Preparation Science, Ningbo University, Zhejiang 315211 (China); College of Optoelectronic Engineering, Chongqing University, Chongqing 400044 (China); Dai Shixun; Xu Tiefeng; Nie Qiuhua [Faculty of Information Science and Engineering, State Key Laboratory Base of Novel Functional Materials and Preparation Science, Ningbo University, Zhejiang 315211 (China)

    2007-11-15

    The spectroscopic properties of Er{sup 3+}/Yb{sup 3+} co-doped Bi{sub 2}O{sub 3}-B{sub 2}O{sub 3}-WO{sub 3} (BBW) glasses were analyzed and discussed. The effect of WO{sub 3} content on the absorption spectra, the Judd-Ofelt parameters {omega}{sub t} (t=2, 4, 6), emission spectra and the lifetime of the {sup 4}I{sub 13/2} level and the quantum efficiency of Er{sup 3+}:{sup 4}I{sub 13/2}{yields}{sup 4}I{sub 15/2} transition were also investigated. With the substitution of WO{sub 3} for B{sub 2}O{sub 3}, the measured lifetime of the {sup 4}I{sub 13/2} level and the quantum efficiency of Er{sup 3+}:{sup 4}I{sub 13/2}{yields}{sup 4}I{sub 15/2} transition increase from 0.98 to 1.31 ms and from 38.2% to 49.2%, respectively. The effective width of emission band and the emission cross-section both decrease slightly. And the emission spectra is analyzed via the different curve ({sigma}{sub e}-{sigma}{sub a}) of BBW glasses, the influence of OH{sup -} is also discussed.

  16. Effective visible light-active boron and europium co-doped BiVO4 synthesized by sol-gel method for photodegradion of methyl orange.

    Science.gov (United States)

    Wang, Min; Che, Yinsheng; Niu, Chao; Dang, Mingyan; Dong, Duo

    2013-11-15

    Eu-B co-doped BiVO4 visible-light-driven photocatalysts have been synthesized using the sol-gel method. The resulting materials were characterized by a series of joint techniques, including XPS, XRD, SEM, BET, and UV-vis DRS analyses. Compared with BiVO4 and B-BiVO4 photocatalysts, the Eu-B-BiVO4 photocatalysts exhibited much higher photocatalytic activity for methyl orange (MO) degradation under visible light irradiation. The optimal Eu doping content is 0.8 mol%. It was revealed that boron and europium were doped into the lattice of BiVO4 and this led to more surface oxygen vacancies, high specific surface areas, small crystallite size, a narrower band gap and intense light absorbance in the visible region. The doped Eu(III) cations can help in the separation of photogenerated electrons. The synergistic effects of boron and europium in doped BiVO4 were the main reason for improving visible light photocatalytic activity. Copyright © 2013 Elsevier B.V. All rights reserved.

  17. Synthesis and characterization of Ce3+/Tb3+ co-doped CaLa4Si3O13 phosphors for application in white LED

    Science.gov (United States)

    Khan, Sayed Ali; Ji, Weiwei; Hao, Luyuan; Xu, Xin; Agathopoulos, Simeon; Khan, Noor Zamin

    2017-10-01

    Phosphors of CaLa4Si3O13 singly- and co-doped with Ce3+ and Tb3+, which are suitable for application in white LEDs, were successfully produced by using a high temperature solid state reaction method. Their apatite crystalline structure as well as their photoluminescent properties both at room temperature and at higher temperatures (up to 150 °C) were experimentally determined, which also allowed the determination of the energy transfer efficiency and mechanism in the host lattice from the sensitizer Ce3+ ions to the activator Tb3+ ions. The excitation spectra of the doped phosphors exhibited an intense, broad band from 200 to 420 nm, which is a good match for the UV and near-UV chip (350-420 nm). Under excitation with UV light, two distinct luminescence bands were recorded; a blue one centered at 433 nm, which is typical for Ce3+ emission, and a green one, which peaks at 552 nm, originated from 5D4 → 7F5 transition in Tb3+.

  18. One-pot synthesis of nitrogen and sulfur co-doped carbon dots and its application for sensor and multicolor cellular imaging.

    Science.gov (United States)

    Chen, Jiucun; Liu, Jianhua; Li, Junzhi; Xu, Liqun; Qiao, Yajuan

    2017-01-01

    Nitrogen and sulfur co-doped carbon dots (N, S/C-dots) were prepared via one-pot hydrothermal treatment of citric acid and cystamine dihydrochloride. The as-prepared N, S/C-dots exhibited excellent excitation-wavelength-independent photoluminescence property and higher fluorescence quantum yield (QY) of 39.7% compared to C,N-dots (QY=2.6%) prepared using citric acid and 1,6-diaminohexane dihydrochloride as the precursor. The N, S/C-dots were well-dispersed in aqueous solution and showed good photoluminescence stabilities in different pH and temperature without any surface modification. Additionally, the fluorescence of N, S/C-dots can be quenched based on inner filter effect (IFE) upon the addition of Cr(VI) and showed good selectivity and sensitivity to Cr(VI). The detection for Cr(VI) exhibited a good linear correlation ranging from 1 to 80μM with a detection limit of 0.86μM. What's more, in comparison with other quantum dots and organic dyes, these N, S/C-dots were much more eco-friendly and can be used for multicolor bioimaging. Copyright © 2016 Elsevier Inc. All rights reserved.

  19. Growth of Ca, Zr co-doped BaTiO3 lead-free ferroelectric single crystal and its room-temperature piezoelectricity

    Science.gov (United States)

    Liu, Donglin; Shim, Jaeshik; Sun, Yue; Li, Qiang; Yan, Qingfen

    2017-09-01

    Lead-free Ca, Zr co-doped BaTiO3 (BCZT) single crystal with a dimension up to 2mm×2mm×2mm was grown by a spontaneous nucleation technique using KF as the flux. The composition of the studied single crystal was defined to be Ba0.798Ca0.202Zr0.006Ti0.994O3, corresponding to a tetragonal phase at room temperature. The oriented single crystal exhibited a quasi-static piezoelectric constant of approximately 232 pC/N. The effective piezoelectric coefficient d33* of the single domain crystal obtained under a unipolar electric field of 35 kV/cm was 179 pm/V. Rayleigh analysis was used to identify the intrinsic and extrinsic contributions to the room-temperature piezoelectricity of BCZT single crystal. The extrinsic contribution was estimated up to 40% due to the irreversible domain wall movement. Furthermore a sixth-order polynomial of Landau expansion was employed to analyze the intrinsic contribution to piezoelectricity of BCZT single crystal. The large energy barriers inhibited polarization rotations, leading to the relatively low piezoelectricity.

  20. Photocatalytic degradation of organic dyes with Er{sup 3+}:YAlO{sub 3}/ZnO composite under solar light

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jun [Department of Chemistry, Liaoning University, Shenyang 110036 (China)]|[Department of Pharmacy, Liaoning University, Shenyang 110036 (China); Xie, Yingpeng; Li, Jia; Chen, Xia; Xu, Rui; Zhang, Xiangdong [Department of Chemistry, Liaoning University, Shenyang 110036 (China); Zhang, Zhaohong [Department of Environment, Liaoning University, Shenyang 110036 (China); Zhang, Liquan [Department of Pharmacy, Liaoning University, Shenyang 110036 (China)

    2009-03-15

    The Er{sup 3+}:YAlO{sub 3}/ZnO composite, a new photocatalyst that could effectively utilize visible light, was prepared by ultrasonic dispersion and liquids boiling method in this work. In succession, the Er{sup 3+}:YAlO{sub 3}/ZnO composite, Er{sup 3+}:YAlO{sub 3} particle and pure ZnO powder were characterized by X-ray diffraction (XRD). The Acid Red B dye as a model compound was degraded under solar light irradiation to evaluate the photocatalytic activity of the Er{sup 3+}:YAlO{sub 3}/ZnO composite. In addition, the effects of Er{sup 3+}:YAlO{sub 3} content, heat-treated temperature and heat-treated time on photocatalytic activity of Er{sup 3+}:YAlO{sub 3}/ZnO composite were reviewed through the degradation of Acid Red B dye under solar light. Otherwise, the effects of initial concentration, Er{sup 3+}:YAlO{sub 3}/ZnO amount, solution acidity and solar light irradiation time on the photocatalytic degradation of Acid Red B dye were investigated in detail. It was found that the photocatalytic activity of Er{sup 3+}:YAlO{sub 3}/ZnO composite is much higher than that of pure ZnO powder for the similar system. Perhaps, the use of this Er{sup 3+}:YAlO{sub 3}/ZnO composite may provide a new way to take advantage of ZnO in sewage treatment aspects using solar energy. (author)

  1. Nanoscale α-MnS crystallites grown on N-S co-doped rGO as a long-life and high-capacity anode material of Li-ion batteries

    Science.gov (United States)

    Liu, Boli; Liu, Zhengjiao; Li, Dan; Guo, Pengqian; Liu, Dequan; Shang, Xiaonan; Lv, Mingzhi; He, Deyan

    2017-09-01

    The rock-salt structural manganous sulfide (α-MnS) is of higher lithium storage capacity. To improve the cyclability of α-MnS anode in lithium-ion batteries, we prepared a composite of α-MnS nanocrystallites grown on nitrogen and sulfur co-doped reduced graphene oxide (rGO) honeycomb framework. N and S atoms have been co-doped into rGO along with the growth of the α-MnS nanocystallites by a one-pot hydrothermal synthesis using thiourea as dopant and reactant. The typical α-MnS/Nsbnd S co-doped rGO (NSG) composite electrode exhibits a reversible capacity as high as 763.5 mAh g-1 after 100 cycles at 100 mA g-1, and a reversible capacity of 576.7 mAh g-1 even after 2000 cycles at 1000 mA g-1. More importantly, the α-MnS/NSG composite electrodes show superior cycle performance at asymmetric discharge/charge current densities. The excellent electrochemical performance can be attributed to that the α-MnS nanocrystallites shorten lithium ion transmission distance, N-S co-doping improves the electronic conductivity of rGO, and the formation of chemical bonds combination between α-MnS and NSG enhances the electrode structural stability and the electron transport. In addition, more stable architecture of NSG-supported ultrafine α-MnS particles is formed upon cycling, which greatly enhances the electrical contact and further improves the electrochemical performance.

  2. Thermoluminescence response of K{sub 2}Ca{sub 2}(SO{sub 4}){sub 3} nanophosphor Co-doped with Eu and Ce for gamma ray dosimetry

    Energy Technology Data Exchange (ETDEWEB)

    Patil, B. J. [Dept. of Physics, Abasaheb Garware College, Pune-411004 (India); Bhadane, Mahesh S.; Dahiwale, S. S.; Bhoraskar, V. N.; Dhole, S. D., E-mail: sanjay@physics.unipune.ac.in [Department of Physics, University of Pune, Pune 411007 (India); Mandlik, N. T. [Dept. of Physics, Fergusson College, Pune-411004 (India); Kulkarni, M. S. [Radiation Safety Systems Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Bhatt, B. C. [Radiological Physics and Advisory Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India)

    2015-06-24

    K{sub 2}Ca{sub 2}(SO{sub 4}){sub 3} nanophosphors co-doped with Eu and Ce were synthesized by the chemical co-precipitation method. These samples were further annealed at 700 °C structural reformation. The structural and morphological characteristics were studied using XRD and TEM techniques. The particle size calculated from XRD spectra was around 35 nm. The as synthesized sample shows cubic structure annealed at 700 °C. The as synthesized and annealed sample of K{sub 2}Ca{sub 2}(SO{sub 4}){sub 3}: EuCe were irradiated with Co{sup 60} gamma rays for the doses from 2Gy to 1kGy. The TL characteristic sample of co-doped were studied for the dosimetric application by gamma radiation. The TL spectrum of annealed sample has single peaked at 160 °C. The Eu doped sample has a high TL sensitivity than Ce doped sample. But after co-doping with Eu and Ce, TL intensity observed to be decreased. The decrees in TL peak intensity of the phosphor on co-doping of Eu and Ce gives an insight into the emission mechanism of the phosphor which involves energy transfer from Eu to Ce. The TL response of all the samples were found to be linear for the dose from 2 Gy to 1 KGy. Therefore, K{sub 2}Ca{sub 2}(SO{sub 4}){sub 3}: EuCe nanophosphor can be used for the measurement of high dose of gamma radiation.

  3. ZnO UV Detectors Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Radiation-hard UV detectors will be developed with ZnO in Phase I efforts by MOXtronics, Inc. (MOX). ZnO is a very suitable material for fabrication of high-speed,...

  4. An Improved Metal-Packaged Strain Sensor Based on A Regenerated Fiber Bragg Grating in Hydrogen-Loaded Boron–Germanium Co-Doped Photosensitive Fiber for High-Temperature Applications

    Directory of Open Access Journals (Sweden)

    Yun Tu

    2017-02-01

    Full Text Available Local strain measurements are considered as an effective method for structural health monitoring of high-temperature components, which require accurate, reliable and durable sensors. To develop strain sensors that can be used in higher temperature environments, an improved metal-packaged strain sensor based on a regenerated fiber Bragg grating (RFBG fabricated in hydrogen (H2-loaded boron–germanium (B–Ge co-doped photosensitive fiber is developed using the process of combining magnetron sputtering and electroplating, addressing the limitation of mechanical strength degradation of silica optical fibers after annealing at a high temperature for regeneration. The regeneration characteristics of the RFBGs and the strain characteristics of the sensor are evaluated. Numerical simulation of the sensor is conducted using a three-dimensional finite element model. Anomalous decay behavior of two regeneration regimes is observed for the FBGs written in H2-loaded B–Ge co-doped fiber. The strain sensor exhibits good linearity, stability and repeatability when exposed to constant high temperatures of up to 540 °C. A satisfactory agreement is obtained between the experimental and numerical results in strain sensitivity. The results demonstrate that the improved metal-packaged strain sensors based on RFBGs in H2-loaded B–Ge co-doped fiber provide great potential for high-temperature applications by addressing the issues of mechanical integrity and packaging.

  5. Room temperature ferromagnetism and gas sensing in ZnO nanostructures: Influence of intrinsic defects and Mn, Co, Cu doping

    Energy Technology Data Exchange (ETDEWEB)

    Mhlongo, Gugu H., E-mail: gmhlongo@csir.co.za [DST/CSIR National Centre for Nanostructured Materials, Council for Scientific and Industrial Research, Pretoria 0001 (South Africa); Shingange, Katekani; Tshabalala, Zamaswazi P.; Dhonge, Baban P. [DST/CSIR National Centre for Nanostructured Materials, Council for Scientific and Industrial Research, Pretoria 0001 (South Africa); Mahmoud, Fawzy A. [Solid State Physics Dept., National Research Centre, P.O. 12622, Dokki, Giza (Egypt); Mwakikunga, Bonex W.; Motaung, David E. [DST/CSIR National Centre for Nanostructured Materials, Council for Scientific and Industrial Research, Pretoria 0001 (South Africa)

    2016-12-30

    Highlights: • Preparation of Mn, Co, Cu doped ZnO via microwave-assisted method. • Doping alters the morphology of ZnO nanostructures. • Concentration of zinc and oxygen related defects vary with doping. • Correlation between PL and EPR was established. • Both undoped and doped ZnO nanostructures showed selectivity towards NH{sub 3}. - Abstract: Undoped and transition metal (Cu, Co and Mn) doped ZnO nanostructures were successfully prepared via a microwave-assisted hydrothermal method followed by annealing at 500 °C. Numerous characterization facilities such as X-ray powder diffraction (XRD), field emission scanning electron microscopy (FESEM), and high-resolution transmission electron microscopy (HRTEM) were employed to acquire the structural and morphological information of the prepared ZnO based products. Combination of defect structure analysis based on photoluminescence (PL) and electron paramagnetic resonance (EPR) indicated that co-existing oxygen vacancies (V{sub O}) and zinc interstitials (Zn{sub i}) defects are responsible for the observed ferromagnetism in undoped and transition metal (TM) doped ZnO systems. PL analysis demonstrated that undoped ZnO has more donor defects (V{sub O} and Zn{sub i}) which are beneficial for gas response enhancement. Undoped ZnO based sensor exhibited a higher sensor response to NH{sub 3} gas compared to its counterparts owing to high content of donor defects while transition metal doped sensors showed short response and recovery times compared to undoped ZnO.

  6. Hydrothermal fabrication of selectively doped organic assisted advanced ZnO nanomaterial for solar driven photocatalysis.

    Science.gov (United States)

    Namratha, K; Byrappa, K; Byrappa, S; Venkateswarlu, P; Rajasekhar, D; Deepthi, B K

    2015-08-01

    Hydrothermal fabrication of selectively doped (Ag(+)+Pd(3+)) advanced ZnO nanomaterial has been carried out under mild pressure temperature conditions (autogeneous; 150°C). Gluconic acid has been used as a surface modifier to effectively control the particle size and morphology of these ZnO nanoparticles. The experimental parameters were tuned to achieve optimum conditions for the synthesis of selectively doped ZnO nanomaterials with an experimental duration of 4 hr. These selectively doped ZnO nanoparticles were characterized using powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), UV-Vis spectroscopy and scanning electron microscopy (SEM). The solar driven photocatalytic studies have been carried out for organic dyes, i.e., Procion MX-5B dye, Cibacron Brilliant Yellow dye, Indigo Carmine dye, separately and all three mixed, by using gluconic acid modified selectively doped advanced ZnO nanomaterial. The influence of catalyst, its concentration and initial dye concentration resulted in the photocatalytic efficiency of 89% under daylight. Copyright © 2015. Published by Elsevier B.V.

  7. Evaluation of gas-sensing properties of ZnO nanostructures electrochemically doped with Au nanophases

    Directory of Open Access Journals (Sweden)

    Elena Dilonardo

    2016-01-01

    Full Text Available A one-step electrochemical method based on sacrificial anode electrolysis (SAE was used to deposit stabilized gold nanoparticles (Au NPs directly on the surface of nanostructured ZnO powders, previously synthesized through a sol–gel process. The effect of thermal annealing temperatures (300 and 550 °C on chemical, morphological, and structural properties of pristine and Au-doped ZnO nancomposites (Au@ZnO was investigated. Transmission and scanning electron microscopy (TEM and SEM, as well as X-ray photoelectron spectroscopy (XPS, revealed the successful deposition of nanoscale gold on the surface of spherical and rod-like ZnO nanostructures, obtained after annealing at 300 and 550 °C, respectively. The pristine ZnO and Au@ZnO nanocomposites are proposed as active layer in chemiresistive gas sensors for low-cost processing. Gas-sensing measurements towards NO2 were collected at 300 °C, evaluating not only the Au-doping effect, but also the influence of the different ZnO nanostructures on the gas-sensing properties.

  8. Study on the Optoelectronic Properties of UV Luminescent Polymer: ZnO Nanoparticles Dispersed PANI

    Directory of Open Access Journals (Sweden)

    J. Kayathri

    2013-01-01

    Full Text Available The present work is focused on the synthesis and characterization of a new polymer thin film material suitable for emissive layer in polymer light-emitting diodes. Thin films of polyaniline and ZnO nanoparticles dispersed polyaniline have been prepared and investigated for the suitability of emissive layer in polymer light emitting diodes. ZnO nanoparticles have been synthesized using wet chemical method and characterized using powder X-ray diffraction. Diffraction pattern reveals that the ZnO nanoparticles are grown in hexagonal wurtzite structure with the preferential orientation of (001 plane. Polyaniline was synthesized using potassium persulphate (initiator at room temperature. ZnO nanoparticles are then dispersed in different doping level (5%, 10%, 15% 20% and 50% with polyaniline. Thin films of ZnO dispersed polyaniline (PANI/ZnO were prepared and characterized using scanning electron microscopy in order to investigate the surface morphology of the film. The optical characteristics and the suitability of film as emissive layer were analyzed using UV-visible absorption and fluorescence spectroscopy.

  9. Sorption Profile of Phosphorus Ions onto ZnO Nanorods Synthesized via Sonic Technique

    Directory of Open Access Journals (Sweden)

    M. F. Elkady

    2016-01-01

    Full Text Available High surface area zinc oxide material in nanorod morphological structure was synthesized using an ultrasonic technique in the presence of polyvinyl pyrrolidone as stabilizing agent. The crystallite, morphology, and surface area of the prepared white powder material were identified using XRD, SEM, and BET techniques, respectively. X-ray analysis confirms the high purity of synthesized ZnO. The evaluated specific surface area of prepared ZnO was 16.7 m2/g; this value guarantees high efficiency for water purification. The feasibility of synthesized ZnO nanorods for phosphorus sorption from aqueous solution was established using batch technique. Nano-zinc oxide exhibits high efficiency for phosphorus removal; the equilibrium state was recorded within 90 minutes. The most effective hydrogen ion concentration of the polluted solution was recorded at pH = 1 for phosphorus decontamination. The equilibrium of phosphorus sorption onto ZnO nanorods was well explained using both Langmuir and Temkin isotherm models. The calculated maximum monolayer sorption capacity was 89 mg/g according to Langmuir isotherm at 27°C. In order to explain the phosphorus sorption mechanism onto the prepared ZnO nanorods, three simplified kinetic models of pseudo-first order, pseudo-second order, and intraparticle diffusion rate models were tested. Kinetics was well fitted by pseudo-second order kinetic model with a contribution of intraparticle diffusion.

  10. Controllable microwave and ultrasonic wave combined synthesis of ZnO micro-/nanostructures in HEPES solution and their shape-dependent photocatalytic activities

    Energy Technology Data Exchange (ETDEWEB)

    Li, Qin; Li, Hui; Wang, Runming; Li, Guangfang; Yang, Hao [Key Laboratory for Green Chemical Process of Ministry of Education and Hubei Novel Reactor and Green Chemical Technology Key Laboratory, Wuhan Institute of Technology, Xiongchu Street, Wuhan 430073 (China); Chen, Rong, E-mail: rchenhku@hotmail.com [Key Laboratory for Green Chemical Process of Ministry of Education and Hubei Novel Reactor and Green Chemical Technology Key Laboratory, Wuhan Institute of Technology, Xiongchu Street, Wuhan 430073 (China); Engineering Research Center of Nano-Geomaterials of Ministry of Education, China University of Geosciences, Lumo Road, Wuhan 430074 (China)

    2013-08-05

    Grahpical abstract: ZnO micro-/nanostructures with controllable size and morphology were successfully synthesized by microwave and ultrasonic wave combined method in HEPES solution, and exhibit shape-dependent photocatalytic activity for MB degradation under UV light irradiation. Highlights: •ZnO micro-/nanostructures were synthesized by combined microwave-ultrasonic wave method. •Morphologies of ZnO micro-/nanostructures could be modulated by varying reaction conditions. •HEPES plays a crucial role in the controllable synthesis of ZnO micro-/nanostructures. •ZnO micro-/nanostructures exhibit shape-dependent photocatalytic activity. •Spindle-like ZnO microstructures show superior photocatalytic activity. -- Abstract: Size- and morphology-controlled zinc oxide (ZnO) micro-/nanostructures have been successfully synthesized via a facile and rapid microwave and ultrasonic wave combined method in HEPES solution (HEPES = 2-[4-(2-hydroxyethyl)-1-piperazinyl]ethanesulfonic acid). The as-prepared ZnO products are characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and UV–vis diffuse reflection spectroscopy (DRS). Various morphologies of ZnO products, including grenade-like, column-like, spindle-like, rod-like, shuttle-like and flower-like micro-/nanostructures are obtained, which are strongly dependent on Zn/HEPES moral ratio, pH value and Zn precursor. It is found that HEPES plays a crucial role in the formation of ZnO micro-/nanostructures with controllable size and morphology. The photocatalytic activities of the prepared ZnO micro-/nanostructures are evaluated by degradation of methylene blue (MB) under UV light irradiation, among which spindle-like ZnO microstructures exhibit superior photocatalytic activity compared with other ZnO products.

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

    Science.gov (United States)

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

    2017-03-01

    Here, we present the microwave-assisted synthesis of In2S3/ZnS core/shell quantum dots (QDs) co-doped with Ag+ and Mn2+ (referred to as AgMn:In2S3/ZnS). Ag+ altered the optical properties of the host QDs, whereas the spin magnetic moment (S=5/2) of Mn2+ efficiently induced the longitudinal relaxation of water protons. To the best of our knowledge, this is the first report of the aqueous synthesis of color-tunable AgMn:In2S3/ZnS core/shell QDs with magnetic properties. The synthetic procedure is rapid, facile, reproducible, and scalable. The obtained QDs offered a satisfactory quantum yield (45%), high longitudinal relaxivity (6.84s-1mM-1), and robust photostability. In addition, they exhibited excellent stability over a wide pH range (5-12) and high ionic strength (0.15-2.0M NaCl). As seen by confocal microscopy and magnetic resonance imaging, AgMn:In2S3/ZnS conjugated to hyaluronic acid (referred to as AgMn:In2S3/ZnS@HA) efficiently and specifically targeted cluster determinant 44, a receptor overexpressed on cancer cells. Moreover, AgMn:In2S3/ZnS@HA showed negligible cytotoxicity in vitro and in vivo, rendering it a promising diagnostic probe for dual-modal imaging in clinical applications. In this manuscript, we reported a facial and rapid method to prepare In2S3/ZnS core/shell quantum dots (QDs) co-doped with Ag+ and Mn2+ (referred to as AgMn:In2S3/ZnS). Ag+ dopants were used to alter the optical properties of the In2S3 host, whereas Mn2+ co-dopants with their unpaired electrons provided paramagnetic properties. The emission wavelength of the core/shell QDs could be tuned from 550 to 743nm with a maximum PL quantum yield of 45%. The resulting core/shell QDs also maintained a stable emission in aqueous solution at broad ranges of pH (5-12) and ionic strength (0.15-2.0M NaCl), as well as a high photostability under continuous irradiation. In vivo cytotoxicity experiments showed that up to 500μg/mL AgMn:In2S3/ZnS@HA did not cause obvious toxicity to zebrafish

  12. One-pot solvothermal preparation and enhanced photocatalytic activity of metallic silver and graphene co-doped BiVO{sub 4} ternary systems

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Lei; Wei, Yongge [School of Chemistry and Environmental Engineering, Changchun University of Science and Technology, Changchun 130022 (China); Guo, Wan [School of Chemistry, Northeast Normal University, Changchun 130024 (China); Guo, Yihang, E-mail: guoyh@nenu.edu.cn [School of Environment, Northeast Normal University, Changchun 130117 (China); Guo, Yingna [School of Chemistry, Northeast Normal University, Changchun 130024 (China)

    2015-03-30

    Graphical abstract: - Highlights: • We have obtained Ag/GR/BiVO{sub 4} ternary system by one-pot solvothermal route. • The best photocatalytic activity to RhB has been attained for 3%Ag/5%GR/BiVO{sub 4}. • Silver nanoparticles and graphene nanosheets doping clearly favor the photocarriers separation. • The Ag/GR/BiVO{sub 4} heterojunction photocatalyst can be reused five times without obvious loss of the reactivity. - Abstract: A series of metallic silver and graphene (GR) co-doped monoclinic BiVO{sub 4} ternary systems (Ag/GR/BiVO{sub 4}) are demonstrated by a single-step solvothermal method. The phase and chemical structure, morphology, textural and optical absorption properties of the Ag/GR/BiVO{sub 4} ternary systems are well characterized, and then their simulated sunlight and visible-light photocatalytic activity were evaluated by the degradation of a typical dye pollutant, rhodamine B (RhB). For comparison, binary systems of Ag/BiVO{sub 4} and GR/BiVO{sub 4} as well as solitary BiVO{sub 4} are also tested under the same conditions. Meanwhile, the separation and transportation of the photogenerated carriers in the simulated sunlight-irradiating Ag/GR/BiVO{sub 4} ternary systems are studied by photoelectrochemistry experiments, and the active species generated during the process of photodegradation are investigated by free radical and hole scavenging experiments. On the basis of the above results, mechanism of photocatalytic degradation of RhB over the Ag/GR/BiVO{sub 4} ternary system is revealed. Finally, the reusability of the catalyst was evaluated by five consecutive catalytic runs.

  13. Synthesis, characterization and visible light photocatalytic activity of Cr 3+ , Ce 3+ and N co-doped TiO 2 for the degradation of humic acid

    KAUST Repository

    Rashid, S. G.

    2015-01-01

    The synthesis, characterization and photocatalytic activity of Cr3+ and Ce3+ co-doped TiON (N-doped TiO2) for the degradation of humic acid with exposure to visible light is reported. The synthesized bimetal (Cr3+ + Ce3+) modified TiON (Cr-Ce/TiON), with an evaluated bandgap of 2.1 eV, exhibited an enhanced spectral response in the visible region as compared to pure and Ce3+ doped TiON (Ce/TiON). The XRD analysis revealed the insertion of Cr3+ and Ce3+ in the crystal lattice along with Ti4+ and N that resulted in the formation of a strained TiON anatase structure with an average crystallite size of ∼10 nm. Raman analysis also supported the formation of stressed rigid structures after bimetal doping. HRTEM confirmed the homogeneous distribution of both the doped metallic components in the crystal lattice of TiON without the formation of surface oxides of either Cr3+ or Ce3+. Electron energy loss spectroscopy (EELS) analysis revealed no change in the oxidation of either Cr or Ce during the synthesis. The synthesized Cr-Ce/TiON catalyst exhibited appreciable photocatalytic activity for the degradation of humic acid on exposure to visible light. Additionally, a noticeable mineralization of carbon rich humic acid was also witnessed. The photocatalytic activity of the synthesized catalyst was compared with pristine and Ce3+ doped TiON. © The Royal Society of Chemistry 2015.

  14. Synthesis, characterization, and photocatalytic activity of porous La-N-co-doped TiO2 nanotubes for gaseous chlorobenzene oxidation.

    Science.gov (United States)

    Cheng, Zhuowei; Gu, Zhiqi; Chen, Jianmeng; Yu, Jianming; Zhou, Lingjun

    2016-08-01

    The photocatalytic oxidation of gaseous chlorobenzene (CB) by the 365nm-induced photocatalyst La/N-TiO2, synthesized via a sol-gel and hydrothermal method, was evaluated. Response surface methodology (RSM) was used to model and optimize the conditions for synthesis of the photocatalyst. The optimal photocatalyst was 1.2La/0.5N-TiO2 (0.5) and the effects of La/N on crystalline structure, particle morphology, surface element content, and other structural characteristics were investigated by XRD (X-ray diffraction), TEM (Transmission Electron Microscopy), FTIR (Fourier transform infrared spectroscopy), UV-vis (Ultraviolet-visible spectroscopy), and BET (Brunauer Emmett Teller). Greater surface area and smaller particle size were produced with the co-doped TiO2 nanotubes than with reference TiO2. The removal of CB was effective when performed using the synthesized photocatalyst, though it was less efficient at higher initial CB concentrations. Various modified Langmuir-Hinshelwood kinetic models involving the adsorption of chlorobenzene and water on different active sites were evaluated. Fitting results suggested that competitive adsorption caused by water molecules could not be neglected, especially for environments with high relative humidity. The reaction intermediates found after GC-MS (Gas chromatography-mass spectrometry) analysis indicated that most were soluble, low-toxicity, or both. The results demonstrated that the prepared photocatalyst had high activity for VOC (volatile organic compounds) conversion and may be used as a pretreatment prior to biopurification. Copyright © 2016. Published by Elsevier B.V.

  15. Titanium Powder Metallurgy Forgings.

    Science.gov (United States)

    TITANIUM ALLOYS, *FORGING), (* POWDER METALLURGY , TITANIUM ALLOYS), ENGINE COMPONENTS, INLET GUIDE VANES, JET ENGINES, RINGS, AIRFRAMES, ANCHORS(STRUCTURAL), COLD WORKING, SINTERING, MECHANICAL PROPERTIES

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

    OpenAIRE

    Meléndrez Manuel; Martínez Eduardo; Solís-Pomar Francisco; Pérez-Tijerina Eduardo

    2011-01-01

    Abstract A hydrothermal method to grow vertical-aligned ZnO nanorod arrays on ZnO films obtained by atomic layer deposition (ALD) is presented. The growth of ZnO nanorods is studied as function of the crystallographic orientation of the ZnO films deposited on silicon (100) substrates. Different thicknesses of ZnO films around 40 to 180 nm were obtained and characterized before carrying out the growth process by hydrothermal methods. A textured ZnO layer with preferential direction in the norm...

  17. Room temperature ferromagnetism and gas sensing in ZnO nanostructures: Influence of intrinsic defects and Mn, Co, Cu doping

    Science.gov (United States)

    Mhlongo, Gugu H.; Shingange, Katekani; Tshabalala, Zamaswazi P.; Dhonge, Baban P.; Mahmoud, Fawzy A.; Mwakikunga, Bonex W.; Motaung, David E.

    2016-12-01

    Undoped and transition metal (Cu, Co and Mn) doped ZnO nanostructures were successfully prepared via a microwave-assisted hydrothermal method followed by annealing at 500 °C. Numerous characterization facilities such as X-ray powder diffraction (XRD), field emission scanning electron microscopy (FESEM), and high-resolution transmission electron microscopy (HRTEM) were employed to acquire the structural and morphological information of the prepared ZnO based products. Combination of defect structure analysis based on photoluminescence (PL) and electron paramagnetic resonance (EPR) indicated that co-existing oxygen vacancies (VO) and zinc interstitials (Zni) defects are responsible for the observed ferromagnetism in undoped and transition metal (TM) doped ZnO systems. PL analysis demonstrated that undoped ZnO has more donor defects (VO and Zni) which are beneficial for gas response enhancement. Undoped ZnO based sensor exhibited a higher sensor response to NH3 gas compared to its counterparts owing to high content of donor defects while transition metal doped sensors showed short response and recovery times compared to undoped ZnO.

  18. Nonquenching of charge carriers by Fe3O4 core in Fe3O4/ZnO nanosheet photocatalyst.

    Science.gov (United States)

    Karunakaran, Chockalingam; Vinayagamoorthy, Pazhamalai; Jayabharathi, Jayaraman

    2014-12-16

    Fe3O4-implanted ZnO and pristine ZnO nanosheets have been synthesized hydrothermally. High-resolution scanning electron microscopy, high-resolution transmission electron microscopy, energy dispersive X-ray spectroscopy, elemental mapping, selected area electron diffractometry, powder X-ray diffractometry, Raman spectroscopy, vibrating sample magnetometry, solid state impedance spectroscopy, UV-visible diffuse reflectance spectroscopy, and photoluminescence spectroscopy show implantation of Fe3O4 in ZnO nanosheets. Fe3O4 core with ZnO shell is of type I core/shell heterostructure which is to quench charge carriers and suppress photocatalysis. But the photocatalytic activity is not suppressed on implantation of Fe3O4 in ZnO nanosheets, and time controlled single photon counting lifetime spectroscopy shows that the photogenerated charge carriers are not quenched by the Fe3O4 core in the ZnO nanosheets. The composite nanosheets are photostable, reusable, and magnetically recoverable, revealing potential application in mineralization of organic pollutants.

  19. Dispersion effect of sodium hexametaphosphate on the photocatalytic efficiency of a solution-combusted ZnO nanopowder

    Science.gov (United States)

    Park, Sung; Choi, Gil Rak; Kim, Ji Hye; Lee, Jae Chun; Kim, Sun-Jae

    2012-11-01

    ZnO nanopowder was synthesized by using a unique method combusting a mixed water solution that contained an oxidant and a fuel. Zn(OH)2 powder was used as an oxidant (source material). Three kinds of fuels, glycine, carbohydrazide and urea, were respectively used to synthesize the ZnO nanopowder. Sodium hexametaphosphate was used as a dispersant to avoid aggregation of the ZnO nanoparticles in the solution. The zeta potential and the ion mobility of the dispersed ZnO nanoparticles were measured to evaluate the dispersion properties. The ZnO nanopowder synthesized with glycine showed highest zeta potential and ion mobility. A photocatalytic reaction was performed to evaluate the photocatalytic efficiency. The dispersion of the ZnO nanoparticles in waste water enhanced the Cu++ ion removal from the waste water. The Cu++ ions were completely removed in 15 h with dispersion. Without dispersion, however, they were not completely removed, not even in 35 h. This means that the dispersant changed even the extreme performance limit of the photocatalyst.

  20. Biosynthesis and characterization of ZnO nanoparticles using the aqueous leaf extract of Imperata cylindrica L.

    Science.gov (United States)

    Saputra, I. S.; Yulizar, Y.

    2017-04-01

    ZnO nanoparticles (ZnO NPs) were biosynthesized.The growth was observed by a sol-gel method. ZnO were successfully formed through the reaction of zinc nitrate tetrahydrate Zn(NO3)2.4H2O precursor with aqueous leaf extract of Imperata cylindrica L (ICL). The structural and optical properties of ZnO were investigated. The as-synthesized products were characterized by UV-Visible (UV-Vis), UV diffuse reflectance spectroscopy (UV-DRS), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). UV-Vis absorption data showed hydrolysis and characteristic of absorption peak at 300 nm of Zn(OH)2. UV-DRS confirmed that ZnO NPs has the indirect band gap at 3.13 eV. FTIR spectrum revealed the functional groups and indicated the presence of protein as the capping and stabilizing agent on the ZnO surface. Powder XRD studies indicated the formation of pure wurtzite hexagonal structure with particle size of 11.9 nm. The detailed morphological and structural characterizations revealed that the synthesized products were hexagonal nanochip.

  1. Reduced graphene oxide/ZnO nanohybrids: Metallic Zn powder induced one-step synthesis for enhanced photocurrent and photocatalytic response

    Energy Technology Data Exchange (ETDEWEB)

    Song, Na, E-mail: beijing2008songna@163.com; Fan, Huiqing, E-mail: hqfan3@163.com; Tian, Hailin, E-mail: erictian8687@163.com

    2015-10-30

    Graphical abstract: - Highlights: • A one-spot, additives-free aqueous solution access to RGO/ZnO nanohybrids. • Metallic Zn powder is a reducing agent of GO and a morphology controller of ZnO. • Nanohybrids show enhanced photocurrent and photocatalytic response than pure ZnO. • C−O−Zn bonds and electronic interactions form at interface of two components. - Abstract: Reduced graphene oxide hybridized hierarchical ZnO nanorods (RGO/ZnO) were fabricated through thermal treatment of aqueous solution containing metallic Zn powder, Zn(NO{sub 3}){sub 2}·6H{sub 2}O, graphene oxide (GO), and NaOH at 110 °C. This one-spot, additives-free method successfully made metallic Zn powder a reducing agent of GO, a precursor of ZnO, and also a morphology controller of RGO/ZnO. RGO/ZnO nanohybrids with 4 wt-% of RGO displayed optimal photocurrent and photocatalytic response under UV irradiation with 10 times and 2.2 times that of pure ZnO nanoflowers, respectively. Strong coupling and electronic interaction between GO and ZnO were verified by using XPS measurement and photoelectrochemical technique. The combination of supreme absorption (of UV light and dye), suppressed photogenerated carriers recombination, and decreased solid interlayer resistance of nanohybrids contributed to their superior photochemical properties.

  2. Red emission enhancement in Ce3+/Mn2+ co-doping suited garnet host MgY2Al4SiO12 for tunable warm white LED

    Science.gov (United States)

    Pan, Zaifa; Chen, Jiacheng; Wu, Haiqin; Li, Weiqiang

    2017-10-01

    To enhance the red emission of YAG:Ce3+ system, co-doping a second activator is one of the attractive approaches and Mn2+ is a priority candidate for red emission. However, the doping of Mn2+ in YAG will result in the multi-occupancy in different crystallographic sites, due to the mismatch of crystal radius and charge. Thus, a suited aluminate silicate garnet phosphor host MgY2Al4SiO12 with ideal crystallographic sites for the co-doping of Ce3+ and Mn2+ ions, was adopted to be the host. The local coordination of Mn2+ ions, occupying only the dodecahedral Mg2+ sites in our suited garnet phosphor, was confirmed by XRD, XPS and photoluminescence results. A color tunable emission of the Ce3+/Mn2+ co-doping phosphor MgY2Al4SiO12 can be realized by combining the yellow emission (565 nm) originating from Ce3+ with the red emission (620 nm) from Mn2+, under 460 nm excitation. The energy transfer efficiency from Ce3+ to Mn2+ via adipole-quadrupole mechanism was demonstrated to be high and reach 79.7%, which is quite higher than 45% in YAG:Ce3+,Mn2+,Si4+. More importantly, the enhancement of red emission makes the emitting colors be able to be adjusted from yellow to orange-red, which would be beneficial to the colorpoint tuning of WLED. The excellent photoluminescence characterizes with high quantum yields (up to 89.0%) indicates that the designed MgY2Al4SiO12:Ce3+,Mn2+ phosphor is a good candidate to obtain warm white LED.

  3. Spectroscopic studies and downconversion luminescence in OH{sup −}-free Pr{sup 3+}–Yb{sup 3+} co-doped low-silica calcium aluminosilicate glasses

    Energy Technology Data Exchange (ETDEWEB)

    Borrero-González, L.J., E-mail: borrero.luis@gmail.com [Instituto de Física de São Carlos, Universidade de São Paulo, CP 369, 13560-970, São Carlos, SP (Brazil); Nunes, L.A.O. [Instituto de Física de São Carlos, Universidade de São Paulo, CP 369, 13560-970, São Carlos, SP (Brazil); Carmo, J.L.; Astrath, F.B.G.; Baesso, M.L. [Departamento de Física, Universidade Estadual de Maringá, Av. Colombo, 5790, 87020-900 Maringá, PR (Brazil)

    2014-01-15

    We report on spectroscopic studies and downconversion luminescence in OH{sup −}-free Pr{sup 3+}–Yb{sup 3+} co-doped low-silica calcium aluminosilicate glasses (LSCAS). The dependencies of the visible to near-infrared emissions, photoacoustic signals, luminescence decay times and energy transfer efficiencies from Pr{sup 3+}→Yb{sup 3+} on the doped Yb{sub 2}O{sub 3} concentration were investigated. The results confirmed the occurrence of downconversion processes in the examined samples, followed by a back-energy transfer mechanism from the Yb{sup 3+}:{sup 2}F{sub 5/2} level to the Pr{sup 3+}:{sup 1}G{sub 4} level, from where the multiphonon relaxations through the {sup 1}G{sub 4},{sup 3}F{sub 4}→{sup 3}H{sub 4} transitions occurred. The photoacoustic data provided evidence of the energy transfer that resulted in heat generation in the sample, confirming the observations provided by the luminescence data. The energy transfer mechanisms that are involved in the Pr{sup 3+}:Yb{sup 3+} co-doped LSCAS glasses are discussed. -- Highlights: • We report on spectroscopic studies and downconversion luminescence in OH{sup −}-free Pr{sup 3+}–Yb{sup 3+} co-doped low-silica calcium aluminosilicate glasses. • The dependencies of downconversion properties and photoacoustic signals on the Yb{sub 2}O{sub 3} concentration provided new insights on energy transfer Pr{sup 3+}→Yb{sup 3+}. • The results confirmed the occurrence of downconversion, followed by a back-energy transfer mechanism Yb{sup 3+}→Pr{sup 3+} and multiphonon relaxations in Pr{sup 3+}.

  4. Investigating the effect of Cd-Mn co-doped nano-sized BiFeO3 on its physical properties

    Science.gov (United States)

    Ishaq, B.; Murtaza, G.; Sharif, S.; Azhar Khan, M.; Akhtar, Naeem; Will, I. G.; Saleem, Murtaza; Ramay, Shahid M.

    This work deals with the investigation of different effects on the structural, magnetic, electronic and dielectric properties of Cd and Mn doped Bi0.75Cd0.25Fe1-xMnxO3 multiferroic samples by taking fixed ratios of Cd and varying the Mn ratio with values of x = 0.0, 0.5, 0.10 and 0.15. Cd-Mn doped samples were synthesized chemically using a microemulsion method. All the samples were finally sintered at 700 °C for 2 h to obtain the single phase perovskites structure of BiFeO3 materials. The synthesized samples were characterized by different techniques, such as X-ray diffractometry (XRD), Scanning Electron Microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), LCR meter and magnetic properties using VSM. XRD results confirm BFO is a perovskite structure having crystallite size in the range of 24-54 nm. XRD results also reveal observed structural distortion due to doping of Cd at the A-site and Mn at the B-site of BFO. SEM results depict that, as the substitution of Cd-Mn increases in BFO, grain size decreases up to 30 nm. FTIR spectra showed prominent absorption bands at 555 cm-1 and 445 cm-1 corresponding to the stretching vibrations of the metal ions complexes at site A and site B, respectively. Variation of dielectric constant (ɛ‧) and loss tangent (tan δ) at room temperature in the range of 1 MHz to 3 GHz have been investigated. Results reveal that with Cd-Mn co doping a slight decrease in dielectric constant have been observed. Magnetic properties of Cd-Mn doped pure BFO samples have been studied at 300 K. Results reveal that undoped BiFeO3 exhibits weak ferromagnetic ordering due to the canting of its spin. Increase in magnetization and decrease in coercivity is a clear indication that a material can be used in high density recording media and memory devices.

  5. Preparation of Ho3+/Tm3+ Co-doped Lanthanum Tungsten Germanium Tellurite Glass Fiber and Its Laser Performance for 2.0 μm

    Science.gov (United States)

    Zhou, Dechun; Bai, Xuemei; Zhou, Hang

    2017-03-01

    Ho3+/Tm3+ co-doped 50TeO2-25GeO2-3WO3-5La2O3-3Nb2O5-5Li2O-9BaF2 glass fiber is prepared with the rod-tube drawing method of 15 μm core diameter and 125 μm inner cladding diameter applied in the 2.0 μm-infrared laser. The 2.0 μm luminescence properties of the core glass are researched and the fluorescence intensity variation for different Tm3+ doping concentration is systematically analyzed. The results show that the 2.0 μm luminescence of Ho3+ is greatly influenced by the doping concentration ratio of Ho3+ to Tm3+ and that the maximum fluorescence intensity of the core glass can be obtained and its emission cross section can reach 0.933 × 10-21 cm2 when the sensitized proportion of holmium to thulium is 0.3 to 0.7 (mol%). Simultaneously, the maximum phonon energy of the core glass sample is 753 cm-1, which is significantly lower than that of silicate, gallate and germanate glass and the smaller matrix phonon energy can be conductive to the increase 2.0 μm-band emission intensity. The continuous laser with the maximum laser output power of 0.993 W and 2051 nm -wavelength of 31.9%-slope efficiency is output within the 0.5 m glass fiber and the experiment adopts 1560 nm erbium-doped fiber laser(EDFL) as the pump source and the self-built all-fiber laser. Therefore, the glass fiber has excellent laser characteristics and it is suitable for the 2.0 μm-band laser.

  6. Yb{sup 3+}/Tb{sup 3+} co-doped GdPO{sub 4} transparent magnetic glass-ceramics for spectral conversion

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Fangfang [Department of Physics, University of Science and Technology of Ch