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Sample records for al-doped zno nanorod

  1. Synthesis and conductivity enhancement of Al-doped ZnO nanorod array thin films.

    PubMed

    Hsu, Chih-Hsiung; Chen, Dong-Hwang

    2010-07-16

    Al-doped ZnO (AZO) nanorod array thin films with various Al/Zn molar ratios were synthesized by chemical bath deposition. The resultant AZO nanorods were well-aligned at the glass substrate, growing vertically along the c-axis [001] direction. In addition, they had an average diameter of 64.7 +/- 16.8 nm and an average length of about 1.0 microm with the structure of wurtzite-type ZnO. Analyses of energy dispersive x-ray spectra and x-ray photoelectron spectra indicated that Al atoms had been doped into the ZnO crystal lattice. The doping of Al atoms did not result in significant changes in the structure and crystal orientation, but the electrical resistivity was found to increase first and then decrease with increasing Al content owing to the increase of carrier concentration and the decrease of mobility. In addition, the transmission in the visible region increased but the increase was reduced at higher Al doping levels. After hydrogen treatment, the morphology of the AZO nanorod array thin films remained unchanged. However, the electrical resistivity decreased significantly due to the formation of oxygen vacancies and interstitial hydrogen atoms. When the real Al/Zn molar ratio was about 3.7%, the conductivity was enhanced about 1000 times and a minimum electrical resistivity of 6.4 x 10( - 4) Omega cm was obtained. In addition, the transmission of the ZnO nanorod array thin film in the visible region was significantly increased but the increase was less significant for the AZO nanorod array thin film, particularly at higher Al doping levels. In addition, the current-voltage curves of the thin film devices with ZnO or AZO nanorod arrays revealed that AZO had a higher current response than ZnO and hydrogen treatment led to a more significant enhancement of current responses (about 100-fold).

  2. Optical parameters of Al-doped ZnO nanorod array thin films grown via the hydrothermal method.

    PubMed

    Kim, Soaram; Kim, Min Su; Nam, Giwoong; Park, Hyunggil; Yoon, Hyunsik; Leem, Jae-Young

    2013-09-01

    ZnO seed layers were deposited onto a quartz substrate using the sol--gel method, and Al-doped ZnO (AZO) nanorod array thin films with different Al concentrations that ranged from 0 to 2.0 at. % were grown on the ZnO seed layers via the hydrothermal method. Optical parameters, including the optical band gap, the absorption coefficient, the Urbach energy, the refractive index, the dispersion parameter, and the optical conductivity, were studied to investigate the effects of Al doping on the optical properties of AZO nanorod array thin films. The optical band gaps of the ZnO and AZO nanorod array thin films were 3.206 at 0 at.%, 3.214 at 0.5 at.%, 3.226 at 1.5 at.%, and 3.268 at 2.0 at.%. The Urbach energy gradually decreased from 126 meV (0 at.%) to 70 meV (2.0 at.%) as the Al concentration was increased. The dispersion energy, the single-oscillator energy, the average oscillator wavelength, the average oscillator strength, the refractive index, and the optical conductivity of the AZO nanorod array thin films were all affected by Al doping.

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

    SciTech Connect

    Son, Hyo-Soo; Choi, Nak-Jung; Kim, Kyoung-Bo; Kim, Moojin; Lee, Sung-Nam

    2016-10-15

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

  4. Fabrication and characterization of silicon wire solar cells having ZnO nanorod antireflection coating on Al-doped ZnO seed layer

    PubMed Central

    2012-01-01

    In this study, we have fabricated and characterized the silicon [Si] wire solar cells with conformal ZnO nanorod antireflection coating [ARC] grown on a Al-doped ZnO [AZO] seed layer. Vertically aligned Si wire arrays were fabricated by electrochemical etching and, the p-n junction was prepared by spin-on dopant diffusion method. Hydrothermal growth of the ZnO nanorods was followed by AZO film deposition on high aspect ratio Si microwire arrays by atomic layer deposition [ALD]. The introduction of an ALD-deposited AZO film on Si wire arrays not only helps to create the ZnO nanorod arrays, but also has a strong impact on the reduction of surface recombination. The reflectance spectra show that ZnO nanorods were used as an efficient ARC to enhance light absorption by multiple scattering. Also, from the current-voltage results, we found that the combination of the AZO film and ZnO nanorods on Si wire solar cells leads to an increased power conversion efficiency by more than 27% compared to the cells without it. PMID:22222067

  5. Fabrication and characterization of silicon wire solar cells having ZnO nanorod antireflection coating on Al-doped ZnO seed layer.

    PubMed

    Baek, Seong-Ho; Noh, Bum-Young; Park, Il-Kyu; Kim, Jae Hyun

    2012-01-05

    In this study, we have fabricated and characterized the silicon [Si] wire solar cells with conformal ZnO nanorod antireflection coating [ARC] grown on a Al-doped ZnO [AZO] seed layer. Vertically aligned Si wire arrays were fabricated by electrochemical etching and, the p-n junction was prepared by spin-on dopant diffusion method. Hydrothermal growth of the ZnO nanorods was followed by AZO film deposition on high aspect ratio Si microwire arrays by atomic layer deposition [ALD]. The introduction of an ALD-deposited AZO film on Si wire arrays not only helps to create the ZnO nanorod arrays, but also has a strong impact on the reduction of surface recombination. The reflectance spectra show that ZnO nanorods were used as an efficient ARC to enhance light absorption by multiple scattering. Also, from the current-voltage results, we found that the combination of the AZO film and ZnO nanorods on Si wire solar cells leads to an increased power conversion efficiency by more than 27% compared to the cells without it.

  6. Efficiency enhancement of regular-type perovskite solar cells based on Al-doped ZnO nanorods as electron transporting layers

    NASA Astrophysics Data System (ADS)

    Huang, Zheng-Lun; Chen, Chih-Ming; Lin, Zheng-Kun; Yang, Sheng-Hsiung

    2017-02-01

    In this paper, we first incorporated Al(NO3)3·9H2O as the Al source into ZnO nanorods (NRs) lattice via the hydrothermal method to modify nature properties of ZnO NRs for the fabrication of perovskite solar cells (PSCs). The X-ray diffraction (XRD) pattern of Al-doped ZnO NRs exhibits higher 2θ values and stronger intensity of (002) plane. Larger optical band gap and higher electrical conductivity of Al-doped ZnO NRs are also observed relative to non-doped ZnO ones. The steady-state photoluminescence shows effective charge extraction and collection at the interface between Al-doped ZnO NRs and perovskite layer. The optimized PSC based on Al-doped ZnO NRs showed an open-circuit voltage of 0.84 V, a short-circuit current density of 21.93 mA/cm2, a fill factor of 57%, and a power conversion efficiency of 10.45% that was 23% higher than the non-doped ZnO ones.

  7. CdS nanoparticles sensitization of Al-doped ZnO nanorod array thin film with hydrogen treatment as an ITO/FTO-free photoanode for solar water splitting

    PubMed Central

    2012-01-01

    Aluminum-doped zinc oxide (AZO) nanorod array thin film with hydrogen treatment possesses the functions of transparent conducting oxide thin film and 1-D nanostructured semiconductor simultaneously. To enhance the absorption in the visible light region, it is sensitized by cadmium sulfide (CdS) nanoparticles which efficiently increase the absorption around 460 nm. The CdS nanoparticles-sensitized AZO nanorod array thin film with hydrogen treatment exhibits significantly improved photoelectrochemical property. After further heat treatment, a maximum short current density of 5.03 mA cm−2 is obtained under illumination. They not only are much higher than those without CdS nanoparticles sensitization and those without Al-doping and/or hydrogen treatment, but also comparable and even slightly superior to some earlier works for the CdS-sensitized zinc oxide nanorod array thin films with indium tin oxide (ITO) or fluorine-doped tin oxide (FTO) as substrates. This demonstrated successfully that the AZO nanorod array thin film with hydrogen treatment is quite suitable as an ITO/FTO-free photoanode and has great potentials in solar water splitting after sensitization by quantum dots capable of visible light absorption. PMID:23098050

  8. Semiconducting properties of Al doped ZnO thin films.

    PubMed

    Al-Ghamdi, Ahmed A; Al-Hartomy, Omar A; El Okr, M; Nawar, A M; El-Gazzar, S; El-Tantawy, Farid; Yakuphanoglu, F

    2014-10-15

    Aluminum doped ZnO (AZO) thin films were successfully deposited via spin coating technique onto glass substrates. Structural properties of the films were analyzed by X-ray diffraction, atomic force microscopy (AFM) and energy dispersive X-ray spectroscopy. X-ray diffraction results reveal that all the films are polycrystalline with a hexagonal wurtzite structure with a preferential orientation according to the direction (002) plane. The crystallite size of ZnO and AZO films was determined from Scherrer's formula and Williamson-Hall analysis. The lattice parameters of the AZO films were found to decrease with increasing Al content. Energy dispersive spectroscopy (EDX) results indicate that Zn, Al and O elements are present in the AZO thin films. The electrical conductivity, mobility carriers and carrier concentration of the films are increased with increasing Al doping concentration. The optical band gap (Eg) of the films is increased with increasing Al concentration. The AZO thin films indicate a high transparency in the visible region with an average value of 86%. These transparent AZO films may be open a new avenue for optoelectronic and photonic devices applications in near future.

  9. Structural, optical and electronic structure studies of Al doped ZnO thin films

    NASA Astrophysics Data System (ADS)

    Devi, Vanita; Kumar, Manish; Shukla, D. K.; Choudhary, R. J.; Phase, D. M.; Kumar, Ravindra; Joshi, B. C.

    2015-07-01

    Structural, optical and electronic structure of Al doped ZnO thin films grown using pulsed laser deposition on glass substrate are investigated. X-ray diffraction measurements reveal that all the films are textured along the c-axis and have wurtzite structure. Al doping in ZnO films leads to increase in grain size due to relaxation in compressive stress. Enhancement in band gap of ZnO films with the Al doping is also noticed which can be ascribed to the Brustein-Moss shift. The changes in the electronic structure caused by Al in the doped thin film samples are understood through X-ray absorption measurements.

  10. Atomic layer deposition of Al-doped ZnO thin films

    SciTech Connect

    Tynell, Tommi; Yamauchi, Hisao; Karppinen, Maarit; Okazaki, Ryuji; Terasaki, Ichiro

    2013-01-15

    Atomic layer deposition has been used to fabricate thin films of aluminum-doped ZnO by depositing interspersed layers of ZnO and Al{sub 2}O{sub 3} on borosilicate glass substrates. The growth characteristics of the films have been investigated through x-ray diffraction, x-ray reflection, and x-ray fluorescence measurements, and the efficacy of the Al doping has been evaluated through optical reflectivity and Seebeck coefficient measurements. The Al doping is found to affect the carrier density of ZnO up to a nominal Al dopant content of 5 at. %. At nominal Al doping levels of 10 at. % and higher, the structure of the films is found to be strongly affected by the Al{sub 2}O{sub 3} phase and no further carrier doping of ZnO is observed.

  11. Photoluminescence lifetime of Al-doped ZnO films in visible region

    NASA Astrophysics Data System (ADS)

    Sharma, Bhupendra K.; Khare, Neeraj; Haranath, D.

    2010-12-01

    ZnO and Al-doped ZnO films have been deposited on quartz substrates by ultrasonically assisted chemical vapor deposition technique. Photoluminescence (PL) spectra of the films reveal that Al doping leads to suppression of defect related visible band. Time resolved photoluminescence studies have been carried out for the measurement of lifetime of deep level luminescence. The decay of PL intensity with time has been found to follow biexponential behavior. The relative contributions of fast decay component (τ1) and slow decay component (τ2) in total decay process are found to be ˜99% and ˜1% respectively. The values of τ1 and τ2 are found to decrease with Al doping in ZnO film. The decrease of both τ1 and τ2 is attributed to increase in non-radiative recombination due to reduction in grain sizes and the decrease in radiative recombination due to suppression of defects.

  12. Gas sensing properties of Al-doped ZnO for UV-activated CO detection

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

    Al-doped ZnO (AZO) samples were prepared using a modified sol-gel route and charaterized by means of trasmission electron microscopy, x-ray diffraction and photoluminescence analysis. Resistive planar devices based on thick films of AZO deposited on interdigitated alumina substrates were fabricated and investigated as UV light activated CO sensors. CO sensing tests were performed in both dark and illumination condition by exposing the samples to UV radiation (λ  =  400 nm).Under UV light, Al-doped ZnO gas sensors operated at lower temperature than in dark. Furthermore, by photoactivation we also promoted CO sensitivity and made signal recovery of AZO sensors faster. Results demonstrate that Al-doped ZnO might be a promising sensing material for the detection of CO under UV illumination.

  13. Influence Al doped ZnO nanostructure on structural and optical properties

    NASA Astrophysics Data System (ADS)

    Ramelan, Ari Handono; Wahyuningsih, Sayekti; Chasanah, Uswatul; Munawaroh, Hanik

    2016-04-01

    The preparation of Al-doped ZnO (AZO) thin films prepared by the spin-coating method was reported. Preparation of AZO was conducted by annealing treatment at a temperature of 700°C. While the spin-coating process of AZO thin films were done at 2000 and 3000 rpm respectively. The structural properties of ZnO were determined by X- ray diffraction (XRD) analysis. ZnOnanostructure was formed after annealed at atemperature of 400°C.The morphology of ZnO was determined by Scanning Electron Microscopy (SEM) showed the irregular morphology about 30-50µm in size. Al doped on ZnO influenced the optical properties of those material. Increasing Al contain on ZnO cause of shifting to the lower wavelength. The optical properties of the ZnO as well as AZO films showed that higher reflectance on the ultraviolet region so those materials were used as anti-reflecting agent.Al addition significantly enhance the optical transparency and induce the blue-shift in optical bandgap of ZnO films.

  14. Thermoelectric properties of Al-doped ZnO: experiment and simulation

    NASA Astrophysics Data System (ADS)

    Jantrasee, S.; Moontragoon, P.; Pinitsoontorn, S.

    2016-09-01

    Advancement in doping other elements, such as Ce, Dy, Ni, Sb, In and Ga in ZnO[1], have stimulated great interest for high-temperature thermoelectric application. In this work, the effects of Al-doping in a ZnO system on the electronic structure and thermoelectric properties are presented, by experiment and calculation. Nanosized powders of Zn1-x Al x O (x = 0,0.01, 0.02, 0.03 and 0.06) were synthesized by hydrothermal method. From XRD results, all samples contain ZnO as the main phase and ZnAl2O4 (spinel phase) peaks were visible when Al additive concentrations were just 6 at%. The shape of the samples changed and the particle size decreased with increasing Al concentration. Seebeck coefficients, on the other hand, did not vary significantly. They were negative and the absolute values increased with temperature. However, the electrical resistivity decreased significantly for higher Al content. The electronic structure calculations were carried out using the open-source software package ABINIT[2], which is based on DFT. The energy band gap, density of states of Al-doped ZnO were investigated using PAW pseudopotential method within the LDA + U. The calculated density of states was then used in combination with the Boltzmann transport equation[3] to calculate the thermoelectric parameters of Al-doped ZnO. The electronic band structures showed that the position of the Fermi level of the doped sample was shifted upwards in comparison to the undoped one. After doping Al in ZnO, the energy band gap was decreased, Seebeck coefficient and electrical conductivity were increased. Finally, the calculated results were compared with the experimental results. The good agreement of thermoelectric properties between the calculation and the experimental results were obtained.

  15. Effects of Al Doping on the Properties of ZnO Thin Films Deposited by Atomic Layer Deposition

    NASA Astrophysics Data System (ADS)

    Zhai, Chen-Hui; Zhang, Rong-Jun; Chen, Xin; Zheng, Yu-Xiang; Wang, Song-You; Liu, Juan; Dai, Ning; Chen, Liang-Yao

    2016-09-01

    The tuning of structural, optical, and electrical properties of Al-doped ZnO films deposited by atomic layer deposition technique is reported in this work. With the increasing Al doping level, the evolution from (002) to (100) diffraction peaks indicates the change in growth mode of ZnO films. Spectroscopic ellipsometry has been applied to study the thickness, optical constants, and band gap of AZO films. Due to the increasing carrier concentration after Al doping, a blue shift of band gap and absorption edge can be observed, which can be interpreted by Burstein-Moss effect. The carrier concentration and resistivity are found to vary significantly among different doping concentration, and the optimum value is also discussed. The modulations and improvements of properties are important for Al-doped ZnO films to apply as transparent conductor in various applications.

  16. Effects of Al Doping on the Properties of ZnO Thin Films Deposited by Atomic Layer Deposition.

    PubMed

    Zhai, Chen-Hui; Zhang, Rong-Jun; Chen, Xin; Zheng, Yu-Xiang; Wang, Song-You; Liu, Juan; Dai, Ning; Chen, Liang-Yao

    2016-12-01

    The tuning of structural, optical, and electrical properties of Al-doped ZnO films deposited by atomic layer deposition technique is reported in this work. With the increasing Al doping level, the evolution from (002) to (100) diffraction peaks indicates the change in growth mode of ZnO films. Spectroscopic ellipsometry has been applied to study the thickness, optical constants, and band gap of AZO films. Due to the increasing carrier concentration after Al doping, a blue shift of band gap and absorption edge can be observed, which can be interpreted by Burstein-Moss effect. The carrier concentration and resistivity are found to vary significantly among different doping concentration, and the optimum value is also discussed. The modulations and improvements of properties are important for Al-doped ZnO films to apply as transparent conductor in various applications.

  17. Substrate temperature effects on the electrical properties of sputtered Al doped ZnO thin films

    NASA Astrophysics Data System (ADS)

    Kim, Deok-Kyu; Kim, Hong-Bae

    2015-09-01

    Al doped ZnO (AZO) thin films were deposited on glass substrate by RF magnetron sputtering system. The dependence of structural, electrical, and optical properties on the substrate temperature variations in the range of 0-400 °C was investigated. The structural results reveal that the AZO films are (0 0 2) oriented and at 400 °C a considerable crystallinity enhancement of the films is observed. With increasing the substrate temperature, the resistivity is increased by decreasing of the mobility and carrier concentration. X-ray photoelectron spectroscopy (XPS) results show that the mobility and the carrier concentration are decreased by increasing the surface bonding and decreasing the Al content, respectively. In our case, the increase in substrate temperature suppressed the incorporation of Al atoms together with the decrease of oxygen vacancy. The improvement of Al doping efficiency is a very important factor to obtain better electrical properties at high substrate temperatures.

  18. Synthesis and Characterization of Al doped ZnO (AZO) by Sol-gel Method

    NASA Astrophysics Data System (ADS)

    Munawaroh, H.; Wahyuningsih, S.; Ramelan, A. H.

    2017-02-01

    Al doped ZnO (AZO) nanoparticles have been successfully synthesized by the simple sol-gel method. The starting materials of Al doped ZnO were Zn(CH3COO)2·2H2O and Al(OH)(CH3COO)2. Preparation of AZO using polyethylene glycol as a surfactant. The solution of precursors was stirred at 60 °C for 2 hour in the conditions of Al contents are 0%, 2%, 3% and 4% (g/mL), respectivelly. In the last step reaction, gelation occurred from solution to sol gel. The sol gel then were dried at 60 °C following by annealing process for crystalization. By this simple sol gel method, the nanoparticles have been produced. The characterizations were conducted X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Fourrier Transform Infra-Red (FTIR) and X-Ray Fluorescence (XRF). XRD analysis reveals that all samples has crystallizes in polycrystalline nature and exhibit no other impurity phase. The variation of Al doped ZnO slighly affect the crystallinity and crystal size. Both crystallinity and crystal size decrease with increasing of Al content in AZO. Morphology of AZO shown the particle distribution more equitable with increased Al content. The synthesized AZO gaved shift peak absorption of asymetric and symetric vibrations of Zn-O-Zn around wavelengths of 680 cm-1 and 1630 cm-1 atributed of the uptake of the Al-O-Al bond instead Zn-O-Zn. XRF analysis shown that the increase ratio of Al entering into Zn influenced the Al dopant concentration.

  19. Structural and optical properties of pure and Al doped ZnO nanocrystals

    NASA Astrophysics Data System (ADS)

    Ghosh, A.; Kumari, N.; Tewari, S.; Bhattacharjee, A.

    2013-11-01

    Pure and Al doped zinc oxide (ZnO) were prepared by co-precipitation method. The dopant concentration [Al/Zn in atomic percentage (wt%)] was varied from 0 to 3 wt%. Structural characterisation of the samples performed with XRD and SEM-EDAX confirmed that polycrystalline nature of samples containing ZnO nanoparticles of size in the range of 97-47 nm. UV-Vis studies showed that the absorbance peaks, observed in the wavelength range of 800-250 nm, decreased with the increase in dopant concentration indicating widening of the band gap. The calculations of band gap (analyzed in terms of Burstein-Moss shift) from the reflectance showed an increase from 3.37 to 3.49 eV with increasing Al concentration.

  20. Temperature dependent dual hydrogen sensor response of Pd nanoparticle decorated Al doped ZnO surfaces

    SciTech Connect

    Gupta, D.; Barman, P. B.; Hazra, S. K.; Dutta, D.; Kumar, M.; Som, T.

    2015-10-28

    Sputter deposited Al doped ZnO (AZO) thin films exhibit a dual hydrogen sensing response in the temperature range 40 °C–150 °C after surface modifications with palladium nanoparticles. The unmodified AZO films showed no response in hydrogen in the temperature range 40 °C–150 °C. The operational temperature windows on the low and high temperature sides have been estimated by isolating the semiconductor-to-metal transition temperature zone of the sensor device. The gas response pattern was modeled by considering various adsorption isotherms, which revealed the dominance of heterogeneous adsorption characteristics. The Arrhenius adsorption barrier showed dual variation with change in hydrogen gas concentration on either side of the semiconductor-to-metal transition. A detailed analysis of the hydrogen gas response pattern by considering the changes in nano palladium due to hydrogen adsorption, and semiconductor-to-metal transition of nanocrystalline Al doped ZnO layer due to temperature, along with material characterization studies by glancing incidence X-ray diffraction, atomic force microscopy, and transmission electron microscopy, are presented.

  1. Temperature dependent dual hydrogen sensor response of Pd nanoparticle decorated Al doped ZnO surfaces

    NASA Astrophysics Data System (ADS)

    Gupta, D.; Dutta, D.; Kumar, M.; Barman, P. B.; Som, T.; Hazra, S. K.

    2015-10-01

    Sputter deposited Al doped ZnO (AZO) thin films exhibit a dual hydrogen sensing response in the temperature range 40 °C-150 °C after surface modifications with palladium nanoparticles. The unmodified AZO films showed no response in hydrogen in the temperature range 40 °C-150 °C. The operational temperature windows on the low and high temperature sides have been estimated by isolating the semiconductor-to-metal transition temperature zone of the sensor device. The gas response pattern was modeled by considering various adsorption isotherms, which revealed the dominance of heterogeneous adsorption characteristics. The Arrhenius adsorption barrier showed dual variation with change in hydrogen gas concentration on either side of the semiconductor-to-metal transition. A detailed analysis of the hydrogen gas response pattern by considering the changes in nano palladium due to hydrogen adsorption, and semiconductor-to-metal transition of nanocrystalline Al doped ZnO layer due to temperature, along with material characterization studies by glancing incidence X-ray diffraction, atomic force microscopy, and transmission electron microscopy, are presented.

  2. Electrical and optical properties of Al doped Zno film prepared by spray pyrolysis technique

    NASA Astrophysics Data System (ADS)

    Shrestha, Shankar Prasad; Basnet, Pradeep

    2008-04-01

    Transparent conducting thin films of zinc oxides and aluminum doped zinc oxide (AZO) were prepared by the spray pyrolysis technique using an aqueous solution of dehydrate zinc acetate (CH 3COOH. 2H IIO, pure- Merck A. R. grade) and hex hydrate aluminum chloride (AlCl 3 .6H IIO) on the micro glass slides. The prepared thin films are found to be highly adherent to the substrate and possess uniform conduction. The optical and electrical properties of the film were investigated in terms of different Al concentration in the starting solution and different substrate temperature. Four probe method in Van der pauw configuration was used for electrical resistivity measurements. The resistivity of Al doped film is observed to vary with doping concentration. The lowest resistivity is observed in the film doping with 2 at % [Al/Zn]. The Hall coefficient measurements show that both ZnO and AZO show the n-type conduction. The carrier concentration was observed to be highest at 2 at% of Al doping. The optical measurements of all the samples with aluminum concentrations was found to be >85 % showing the film to be highly transparent in nature. With increase in Al concentration, the optical band gap was observed increase from 3.27 eV to 3.41 eV.

  3. Work function increase of Al-doped ZnO thin films by B+ ion implantation.

    PubMed

    Hong, Sang-Jin; Heo, Gi-Seok; Park, Jong-Woon; Lee, In-Hwan; Choi, Bum-Ho; Lee, Jong-Ho; Park, Se-Yeon; Shin, Dong-Chan

    2007-11-01

    The work function of an Al-doped ZnO (AZO) thin film can be increased via B+ ion implantation from 3.92 eV up to 4.22 eV. The ion implantation has been carried out with the ion dose of 1 x 10(16) cm(-2) and ion energy of 5 keV. The resistance of the B+ implanted AZO films has been a bit raised, while their transmittance is slightly lowered, compared to those of un-implanted AZO films. These behaviors can be explained by the doping profile and the resultant band diagram. It is concluded that the coupling between the B+ ions and oxygen vacancies would be the main reason for an increase in the work function and a change in the other properties. We also address that the work function is more effectively alterable if the defect density of the top transparent conducting oxide layer can be controlled.

  4. Sputter deposition of Al-doped ZnO films with various incident angles

    SciTech Connect

    Sato, Yasushi; Yanagisawa, Kei; Oka, Nobuto; Nakamura, Shin-ichi; Shigesato, Yuzo

    2009-09-15

    Al-doped ZnO (AZO) films were sputter deposited on glass substrates heated at 200 degree sign C under incident angles of sputtered particles at 0 degree sign (incidence normal to substrate), 20 deg., 40 deg., 60 deg., and 80 deg. In the case of normal incidence, x-ray diffraction pole figures show a strong [001] preferred orientation normal to the film surface. In contrast, in the case wherein the incident angles were higher than 60 degree sign , the [001] orientation inclined by 25 deg. - 35 deg. toward the direction of sputtered particles. Transmission electron microscopy revealed that the tilt angle of the [001] orientation increased with increasing angle of the incident sputtered particles, whereas the columnar structure did not show any sign of inclination with respect to the substrate plane.

  5. Electron transport in Al-doped ZnO nanolayers obtained by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Blagoev, B. S.; Dimitrov, D. Z.; Mehandzhiev, V. B.; Kovacheva, D.; Terziyska, P.; Pavlic, J.; Lovchinov, K.; Mateev, E.; Leclercq, J.; Sveshtarov, P.

    2016-03-01

    Al-doped ZnO thin films with different Al content were prepared by atomic layer deposition (ALD). To carry out thermal ALD, diethyl zinc (DEZ) and tri-methyl aluminium (TMA) were used as Zn and Al precursors, respectively, and water vapor as oxidant. Various numbers n of DEZ and m TMA cycles was used to obtain different [ZnO] n [Al2O3] m films, where n = 100 - 95, m = 1 - 5. The X-ray diffraction analysis showed a predominantly (100) oriented polycrystalline phase for the ZnO:Al films with a low Al content (m = 1 - 3) and an amorphous structure for pure Al2O3. In ZnO:Al with a higher Al content (m = 4 - 6) the (100) reflection disappeared and the (002) peak increased. The resistivity of the films decreased with the increase in the Al content, reaching a minimum of 3.3×10-3 Ω cm at about 1.1 % Al2O3 for the [ZnO]99[Al2O3]2 sample; for higher dopant concentrations, the resistivity increased because of the increased crystal inhomogeneity due to axis reorientation.

  6. Structural defects and photoluminescence studies of sol-gel prepared ZnO and Al-doped ZnO films

    NASA Astrophysics Data System (ADS)

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

    2016-11-01

    ZnO and Al-doped ZnO (AZO) films were synthesized using sol-gel spin-coating method. The powder XRD analysis revealed the stress relaxation mechanism upon Al doping in ZnO film. The reduction in the imaginary part of the dielectric constant and suppression of deep level acceptor type octahedral oxygen interstitial defects account for the reduction in carrier concentration in AZO with respect to ZnO. Electrical conductivity measurements and grain boundary conduction model are used to quantify the carrier concentration. From the Commission Internationale d'Eclairge diagram of ZnO and AZO, color parameters like dominant wavelength, color purity and luminosity are determined and reported for the first time. The prepared ZnO and AZO films show considerable blue emission. These films can be used for white light generation.

  7. Sol-gel synthesis and characterization of undoped and Al-doped ZnO thin films for memristive application

    NASA Astrophysics Data System (ADS)

    Ayana, Dawit G.; Prusakova, Valentina; Collini, Cristian; Nardi, Marco V.; Tatti, Roberta; Bortolotti, Mauro; Lorenzelli, Leandro; Chiappini, Andrea; Chiasera, Alessandro; Ferrari, Maurizio; Lunelli, Lorenzo; Dirè, Sandra

    2016-11-01

    The Sol-gel route is a versatile method to fabricate multi-layer, dense and homogeneous ZnO thin films with a controlled thickness and defects for a memristive application. In this work, sol-gel derived multi-layer undoped and Al-doped ZnO thin films were prepared by a spin-coating technique on SiO2/Ti/Pt and silica glass substrates. The effect of both Al doping and curing conditions on the structural and morphological features of ZnO films was investigated by complementary techniques, including electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, micro-Raman spectroscopy, and X-ray diffraction analysis. Electrical measurements were performed on SiO2/Ti/Pt/ZnO/Pt(dishes) and SiO2/Ti/Pt/ZnO(Al)/Pt(dishes) fabricated memristive cells and preliminary current-voltage curves were acquired.

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

    NASA Astrophysics Data System (ADS)

    Ciccarino, Christopher; Sahiner, M. Alper

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

  9. Using the hydrothermal method to grow p-type ZnO nanowires on Al-doped ZnO thin film to fabricate a homojunction diode.

    PubMed

    Tseng, Yung-Kuan; Hung, Meng-Chun; Su, Shun-Lung; Li, Sheng-Kai

    2014-10-01

    In this study, the hydrothermal method is used to grow phosphorus-doped ZnO nanowires on Si/SiO2 substrates deposited with Al-doped ZnO thin film. This structure forms a homogeneous p-n junction. In this study, we are the pioneers to use ammonium hypophosphite (NH4H2PO2) as a source of phosphorus to prepare the precursor solution. Ammonium hypophosphite of different concentration levels is used to observe its effects on the growth of nanowires. The results show that the precursor solution prepared from ammonium hypophosphite can produce good crystalline ZnO nanowires while there is no linear relationship between the amounts and concentration levels of phosphorus doped into the nanowires. Whether the phosphorus-doped ZnO nanowires have the characteristics of a p-type semiconductor is indirectly verified by measuring whether the p-n junction made up of Al-doped ZnO thin film and phosphorus-doped ZnO nanowires shows rectifying behavior. I-V measurements are made on the specimens. The results show good rectifying behavior, proving that the phosphorus-doped ZnO nanowires and Al-doped AZO films have p-type and n-type semiconductor properties, constituting a good p-n junction. This result also proves that ammonium hypophosphite is a better source of phosphorus in the hydrothermal method to synthesize phosphorus-doped ZnO nanowires.

  10. Tailoring Energy Bandgap of Al Doped ZnO Thin Films Grown by Vacuum Thermal Evaporation Method.

    PubMed

    Vyas, Sumit; Singh, Shaivalini; Chakrabarti, P

    2015-12-01

    The paper presents the results of our experimental investigation pertaining to tailoring of energy bandgap and other associated characteristics of undoped and Al doped ZnO (AZO) thin film by varying the atomic concentration of Al in ZnO. Thin films of ZnO and ZnO doped with Al (1, 3, and 5 atomic percent (at.%)) were deposited on silicon substrate for structural characterization and on glass substrate for optical characterization. The dependence of structural and optical properties of Al doped ZnO on the atomic concentration of Al added to ZnO has been reported. On the basis of the experimental results an empirical formula has been proposed to calculate the energy bandgap of AZO theoretically in the range of 1 to 5 at.% of Al. The study revealed that AZO films are composed of smaller and larger number of grains as compared to pure ZnO counterpart and density of the grains was found to increase as the Al concentration increased (from 1 to 5 at.%). The transmittance in the visible region was greater than 90% and found to increase with increasing Al concentration up to 5 at.%. The optical bandgap was found to increase initially with increase in atomic concentration of Al concentration up to 3 at.% and decrease thereafter with increasing concentration of Al.

  11. Temperature-dependence on the structural, optical, and magnetic properties of Al-doped ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Lu, Xiaofei; Liu, Yongsheng; Si, Xiaodong; Shen, Yulong; Yu, Wenying; Wang, Wenli; Luo, Xiaojing; Zhou, Tao

    2016-12-01

    Al-doped ZnO nanoparticles synthesized by a hydrothermal method at relatively low temperature synthesis and anneal were reported in this paper. The XRD results reveal that all the samples have a hexagonal wurtzite structure. A higher synthesis temperature leads to a slight increase in the grain size and improvement of the crystal quality. Different morphologies evolved from acicular closely-packed morphology to dandelion-like 3D nanostructures can be obtained by controlling the synthesis temperatures. Moreover, the influence of synthesis temperature on optical property indicates that the absorption ability in ultraviolet region declines with increasing the synthesis temperature. In addition, the annealed nanoparticles have an enhancement of the room temperature ferromagnetism (RT-FM) and the saturation magnetization (MS). Those results suggest that Al-doped ZnO nanoparticles synthesized at relatively low temperature could be a promising candidate for photosensitive and room temperature nanolasers applications.

  12. Structural, electrical, and optical properties of atomic layer deposition Al-doped ZnO films

    SciTech Connect

    Banerjee, P; Lee, W. J.; Bae, K. R.; Lee, Sang Bok; Rubloff, Gary W

    2010-01-01

    Al-doped ZnO (AZO) films of ~100nm thickness with various Aldoping were prepared at 150°C by atomic layer deposition on quartz substrates. At low Aldoping, the films were strongly textured along the [100] direction, while at higher Aldoping the films remained amorphous. Atomic force microscopy results showed that Al–O cycles when inserted in a ZnOfilm, corresponding to a few atomic percent Al, could remarkably reduce the surface roughness of the films. Hall measurements revealed a maximum mobility of 17.7cm{sup 2} /Vs . Film resistivity reached a minima of 4.4×10{sup -3} Ωcm whereas the carrier concentration reached a maxima of 1.7×10{sup 20} cm{sup -3} , at 3 at.% Al. The band gap of AZO films varied from 3.23 eV for undoped ZnOfilms to 3.73 eV for AZO films with 24.6 at.% Al. Optical transmittance over 80% was obtained in the visible region. The detrimental impact of increased Al resulting in decreased conductivity due to doping past 3.0 at.% is evident in the x-ray diffraction data, as an abrupt increase in the optical band gap and as a deviation from the Burstein–Moss effect.

  13. Effects of annealing pressure and Ar+ sputtering cleaning on Al-doped ZnO films

    NASA Astrophysics Data System (ADS)

    Wang, Jiwei; Mei, Yong; Lu, Xuemei; Fan, Xiaoxing; Kang, Dawei; Xu, Panfeng; Tan, Tianya

    2016-11-01

    Post-treatments of Al-doped ZnO films fabricated by sol-gel method were studied in condition of annealing in air, vacuum and protective ambient, as well as the follow-up Ar+ sputtering cleaning. The effect of annealing pressure on resistivity of AZO films was investigated from 105 to 10-4 Pa, where the resistivity decreased four orders of magnitude as the pressure decreased and approached to its minimum at 10 Pa. It was observed that the main decreasing of resistivity occurred in a very narrow range of middle vacuum (between 100 and 10 Pa) and high vacuum was dispensable. The XRD and XPS characterizations demonstrated that the radical increasing of oxygen vacancy, Zn interstitial and substitution of Al3+ for Zn2+ under middle vacuum were responsible for the significant enhancement of conductivity. The follow-up Ar+ sputtering cleaning can further decrease the resistivity through removing the chemisorbed oxygen on film surface and grain boundaries, meanwhile fulfil the surface texture process, and thus improve both electrical and optical performances for applications.

  14. High carrier concentration ZnO nanowire arrays for binder-free conductive support of supercapacitors electrodes by Al doping.

    PubMed

    Zheng, Xin; Sun, Yihui; Yan, Xiaoqin; Sun, Xu; Zhang, Guangjie; Zhang, Qian; Jiang, Yaru; Gao, Wenchao; Zhang, Yue

    2016-12-15

    Doping semiconductor nanowires (NWs) for altering their electrical and optical properties is a critical strategy for tailoring the performance of nanodevices. Here, we prepared in situ Al-doped ZnO nanowire arrays by using continuous flow injection (CFI) hydrothermal method to promote the conductivity. This reasonable method offers highly stable precursor concentration for doping that effectively avoid the appearance of the low conductivity ZnO nanosheets. Benefit from this, three orders of magnitude rise of the carrier concentration from 10(16)cm(-3) to 10(19)cm(-3) can be achieved compared with the common hydrothermal (CH) mothed in Mott-Schottky measurement. Possible effect of Al-doping was discussed by first-principle theory. On this basis, Al-doped ZnO nanowire arrays was developed as a binder-free conductive support for supercapacitor electrodes and high capacitance was triggered. It is owing to the dramatically decreased transfer resistance induced by the growing free-moving electrons and holes. Our results have a profound significance not merely in the controlled synthesis of other doping nanomaterials by co-precipitation method but also in the application of binder-free energy materials or other materials.

  15. Enhanced photoluminescence and Raman properties of Al-Doped ZnO nanostructures prepared using thermal chemical vapor deposition of methanol assisted with heated brass.

    PubMed

    Thandavan, Tamil Many K; Gani, Siti Meriam Abdul; San Wong, Chiow; Md Nor, Roslan

    2015-01-01

    Vapor phase transport (VPT) assisted by mixture of methanol and acetone via thermal evaporation of brass (CuZn) was used to prepare un-doped and Al-doped zinc oxide (ZnO) nanostructures (NSs). The structure and morphology were characterized by field emission scanning electron microscopy (FESEM) and x-ray diffraction (XRD). Photoluminescence (PL) properties of un-doped and Al-doped ZnO showed significant changes in the optical properties providing evidence for several types of defects such as zinc interstitials (Zni), oxygen interstitials (Oi), zinc vacancy (Vzn), singly charged zinc vacancy (VZn-), oxygen vacancy (Vo), singly charged oxygen vacancy (Vo+) and oxygen anti-site defects (OZn) in the grown NSs. The Al-doped ZnO NSs have exhibited shifted PL peaks at near band edge (NBE) and red luminescence compared to the un-doped ZnO. The Raman scattering results provided evidence of Al doping into the ZnO NSs due to peak shift from 145 cm-1 to an anomalous peak at 138 cm-1. Presence of enhanced Raman signal at around 274 and 743 cm-1 further confirmed Al in ZnO NSs. The enhanced D and G band in all Al-doped ZnO NSs shows possible functionalization and doping process in ZnO NSs.

  16. Enhanced Photoluminescence and Raman Properties of Al-Doped ZnO Nanostructures Prepared Using Thermal Chemical Vapor Deposition of Methanol Assisted with Heated Brass

    PubMed Central

    Thandavan, Tamil Many K.; Gani, Siti Meriam Abdul; San Wong, Chiow; Md. Nor, Roslan

    2015-01-01

    Vapor phase transport (VPT) assisted by mixture of methanol and acetone via thermal evaporation of brass (CuZn) was used to prepare un-doped and Al-doped zinc oxide (ZnO) nanostructures (NSs). The structure and morphology were characterized by field emission scanning electron microscopy (FESEM) and x-ray diffraction (XRD). Photoluminescence (PL) properties of un-doped and Al-doped ZnO showed significant changes in the optical properties providing evidence for several types of defects such as zinc interstitials (Zni), oxygen interstitials (Oi), zinc vacancy (Vzn), singly charged zinc vacancy (VZn-), oxygen vacancy (Vo), singly charged oxygen vacancy (Vo+) and oxygen anti-site defects (OZn) in the grown NSs. The Al-doped ZnO NSs have exhibited shifted PL peaks at near band edge (NBE) and red luminescence compared to the un-doped ZnO. The Raman scattering results provided evidence of Al doping into the ZnO NSs due to peak shift from 145 cm-1 to an anomalous peak at 138 cm-1. Presence of enhanced Raman signal at around 274 and 743 cm-1 further confirmed Al in ZnO NSs. The enhanced D and G band in all Al-doped ZnO NSs shows possible functionalization and doping process in ZnO NSs. PMID:25756598

  17. Enhancement ZnO nanofiber as semiconductor for dye-sensitized solar cells by using Al doped

    NASA Astrophysics Data System (ADS)

    Sutanto, Bayu; Arifin, Zainal; Suyitno, Hadi, Syamsul; Pranoto, Lia Muliani; Agustia, Yuda Virgantara

    2016-03-01

    The purpose of this research is to produce Al-doped ZnO (AZO) nanofibers in order to enhance the performance of Dye-Sensitized Solar Cell (DSSC). AZO nanofiber semiconductor was manufactured by electrospinning process of Zinc Acetate Dehydrate (Zn(CH3COO)2) solution and precursor of Polyvinyl Acetate (PVA). The doping process of Al was built by dissolving 0-4 wt% in concentrations of AlCl3 to Zinc Acetate. AZO green fiber was sintered at temperature 500°C for an hour. The result shows that Al doped ZnO had capability to increase the electrical conductivity of semiconductor for doping 0, 1, 2, 3, and 4 wt% for 2,07×10-3; 3,71×10-3; 3,59 ×10-3; 3,10 ×10-3 and 2,74 ×10-3 S/m. The best performance of DSSC with 3 cm2 active area was obtained at 1 wt% Al-ZnO which the value of VOC, ISC, FF, and efficiency were 508,43 mV, 3,125 mA, 38,76%, and 0,411% respectively. These coincide with the electrical conductivity of semiconductor and the crystal size of XRD result that has the smallest size as compared to other doping variations.

  18. Genesis of flake-like morphology and dye-sensitized solar cell performance of Al-doped ZnO particles: a study

    NASA Astrophysics Data System (ADS)

    Sengupta, D.; Mondal, B.; Mukherjee, K.

    2017-03-01

    In dye-sensitized solar cell (DSSC) application, the particulate morphologies of photo-anode facilitate efficient dye loading and thus lead to better photo-conversion efficiency than their thin film counterpart. However, till date, the electronic and optical properties as well as the DSSC application of Al-doped ZnO (AZO) particles as photo-anode material is studied less than thin films. Herein, phase formation behavior, morphology evolution, optical properties, and dye-sensitized solar cell performance of wet chemically prepared ZnO and AZO (dopant level: 1-4 mol%) particles are studied. It is found that Al doping modulates significantly the ZnO morphology which in turn results the maximum dye adsorption as well as best photo-conversion efficiency at optimum dopant concentration. Specifically, the nanoparticle of ZnO turns predominantly to flake-like morphology with a higher surface area when 2 mol% Al is doped. Such morphology modulation is expected, since the crystallinity, lattice parameters, and lattice strain of ZnO changes appreciably with Al doping. The variations of optical properties (absorbance, diffused reflectance, and band gap) of AZO materials as compared to primitive ZnO are also identified through UV-vis studies. An attempt is made here to correlate the structural features with the photovoltaic performances of ZnO and AZO.

  19. Structure and thermoelectric properties of Al-doped ZnO films prepared by thermal oxidization under high magnetic field

    NASA Astrophysics Data System (ADS)

    Liu, Shiying; Peng, Sunjuan; Ma, Jun; Li, Guojian; Qin, Xuesi; Li, Mengmeng; Wang, Qiang

    2017-04-01

    This paper studies the effects of high magnetic field (HMF) on the structure, optical and thermoelectric properties of the doped ZnO thin films. The results show that both Al dopant and application of HMF can affect the crystal structure, surface morphology, elemental distribution and so on. The particles of the thin films become small and regular by doping Al. The ZnO films oxidized from the Au/Zn bilayer have needle structure. The ZnO films oxidized from the Au/Zn-Al bilayer transform to spherical from hexagonal due to the application of HMF. The transmittance decreases with doping Al because of the opaque of Al element and decreases with the application of HMF due to the dense structure obtained under HMF. Electrical resistivity (ρ) of the ZnO films without Al decreases with increasing measurement temperature (T) and is about 1.5 × 10-3 Ω·m at 210 °C. However, the ρ of the Al-doped ZnO films is less than 10-5 Ω·m. The Seebeck coefficient (S) of the films oxidized from the Au/Zn-Al films reduces with increasing T. The S values oxidized under 0 T and 12 T conditions are 2.439 μV/K and -3.415 μV/K at 210 °C, respectively. Power factor reaches the maximum value (3.198 × 10-4 W/m·K2) at 210 °C for the film oxidized under 12 T condition. These results indicate that the Al dopant and the application of HMF can be used to control structure and thermoelectric properties of doped ZnO films.

  20. Electrochemical Synthesis of Highly Oriented, Transparent, and Pinhole-Free ZnO and Al-Doped ZnO Films and Their Use in Heterojunction Solar Cells.

    PubMed

    Kang, Donghyeon; Lee, Dongho; Choi, Kyoung-Shin

    2016-10-04

    Electrochemical synthesis conditions using nonaqueous solutions were developed to prepare highly transparent (T > 90%) and crystalline ZnO and Al-doped ZnO (AZO) films for use in solar energy conversion devices. A focused effort was made to produce pinhole-free films in a reproducible manner by identifying a key condition to prevent the formation of cracks during deposition. The polycrystalline domains in the resulting films had a uniform orientation (i.e., the c-axis perpendicular to the substrate), which enhanced the electron transport properties of the films. Furthermore, electrochemical Al doping of ZnO using nonaqueous media, which was demonstrated for the first time in this study, effectively increased the carrier density and raised the Fermi level of ZnO. These films were coupled with an electrodeposited p-type Cu2O to construct p-n heterojunction solar cells to demonstrate the utilization of these films for solar energy conversion. The resulting n-ZnO/p-Cu2O and n-AZO/p-Cu2O cells showed excellent performance compared with previously reported n-ZnO/p-Cu2O cells prepared by electrodeposition. In particular, replacing ZnO with AZO resulted in simultaneous enhancements in short circuit current and open circuit potential, and the n-AZO/p-Cu2O cell achieved an average power conversion efficiency (η) of 0.92 ± 0.09%. The electrodeposition condition reported here will offer a practical and versatile way to produce ZnO or AZO films, which play key roles in various solar energy conversion devices, with qualities comparable to those prepared by vacuum-based techniques.

  1. Dopant-induced bandgap shift in Al-doped ZnO thin films prepared by spray pyrolysis

    NASA Astrophysics Data System (ADS)

    Hung-Chun Lai, Henry; Basheer, Tahseen; Kuznetsov, Vladimir L.; Egdell, Russell G.; Jacobs, Robert M. J.; Pepper, Michael; Edwards, Peter P.

    2012-10-01

    A series of 1 at. % Al-doped ZnO (AZO) films were deposited onto glass substrates by a spray pyrolysis technique. We find that the observed blue shift in the optical bandgap of 1% AZO films is dominated by the Burstein Moss effect. The Fermi level for an 807 nm thick AZO film rose by some 0.16 eV with respect to the edge of the conduction band. By controlling the film thickness, all AZO films exhibit the same lattice strain values. The influence of strain-induced bandgap shift was excluded by selecting films with nearly the same level of bandgap volume-deformation potentials, and the differences in out-plain strain and in-plain stress remained effectively constant.

  2. High rate reactive magnetron sputter deposition of Al-doped ZnO with unipolar pulsing and impedance control system

    SciTech Connect

    Nishi, Yasutaka; Hirohata, Kento; Tsukamoto, Naoki; Sato, Yasushi; Oka, Nobuto; Shigesato, Yuzo

    2010-07-15

    Al-doped ZnO (AZO) films were deposited on quartz glass substrates, unheated and heated to 200 deg. C, using reactive sputtering with a special feedback system of discharge impedance combined with midfrequency pulsing. A planar Zn-Al alloy target was connected to the switching unit, which was operated in a unipolar pulse mode. The oxidation of the target surface was precisely controlled by a feedback system for the entire O{sub 2} flow ratio including ''the transition region''. The deposition rate was about 10-20 times higher than that for films deposited by conventional sputtering using an oxide target. A deposition rate of AZO films of 390 nm/min with a resistivity of 3.8x10{sup -4} {Omega} cm and a transmittance in the visible region of 85% was obtained when the films were deposited on glass substrates heated to 200 deg. C with a discharge power of 4 kW.

  3. Enhance the light-harvesting capability of the ITO-free inverted small molecule solar cell by ZnO nanorods.

    PubMed

    Lin, Ming-Yi; Wu, Shang-Hsuan; Hsiao, Li-Jen; Budiawan, Widhya; Boopathi, Karunakara Moorthy; Tu, Wei-Chen; Chang, Yia-Chung; Chu, Chih-Wei

    2016-08-08

    The ITO-free inverted SMPV1:PC71BM solar cells with an Al doped ZnO (AZO) transparent electrodes are fabricated. The AZO thin film prepared by pulsed laser deposition (PLD) technique exhibits high transmission (>85%) and low sheet resistance (~30 Ω/sq) and the power conversion efficiency (PCE) of devices based on AZO electrode can reach around 4%. To further enhance the light harvesting of the absorption layer of solar cells, ZnO nanorods interlayer is grown on the AZO layer before the deposition the active layer. The absorption spectrums of devices under various conditions are also simulated by RCWA method to identify the optical saturation length of the ZnO nanorods. The PCE of ITO-free inverted small molecule solar cell improved with ZnO nanorods can reach 6.6%.

  4. Al-doped ZnO contact to CdZnTe for x- and gamma-ray detector applications

    NASA Astrophysics Data System (ADS)

    Roy, U. N.; Camarda, G. S.; Cui, Y.; Gul, R.; Hossain, A.; Yang, G.; Mundle, R. M.; Pradhan, A. K.; James, R. B.

    2016-06-01

    The poor adhesion of common metals to CdZnTe (CZT)/CdTe surfaces has been a long-standing challenge for radiation detector applications. In this present work, we explored the use of an alternative electrode, viz., Al-doped ZnO (AZO) as a replacement to common metallic contacts. ZnO offers several advantages over the latter, such as having a higher hardness, a close match of the coefficients of thermal expansion for CZT and ZnO, and better adhesion to the surface of CZT due to the contact layer being an oxide. The AZO/CZT contact was investigated via high spatial-resolution X-ray response mapping for a planar detector at the micron level. The durability of the device was investigated by acquiring I-V measurements over an 18-month period, and good long-term stability was observed. We have demonstrated that the AZO/CZT/AZO virtual-Frisch-grid device performs fairly well, with comparable or better characteristics than that for the same detector fabricated with gold contacts.

  5. Transparent conducting Si-codoped Al-doped ZnO thin films prepared by magnetron sputtering using Al-doped ZnO powder targets containing SiC

    SciTech Connect

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

    2009-07-15

    Transparent conducting Al-doped ZnO (AZO) thin films codoped with Si, or Si-codoped AZO (AZO:Si), were prepared by radio-frequency magnetron sputtering using a powder mixture of ZnO, Al{sub 2}O{sub 3}, and SiC as the target; the Si content (Si/[Si+Zn] atomic ratio) was varied from 0 to 1 at. %, but the Al content (Al/[Al+Zn] atomic ratio) was held constant. To investigate the effect of carbon on the electrical properties of AZO:Si thin films prepared using the powder targets containing SiC, the authors also prepared thin films using a mixture of ZnO, Al{sub 2}O{sub 3}, and SiO{sub 2} or SiO powders as the target. They found that when AZO:Si thin films were deposited on glass substrates at about 200 degree sign C, both Al and Si doped into ZnO acted as effective donors and the atomic carbon originating from the sputtered target acted as a reducing agent. As a result, sufficient improvement was obtained in the spatial distribution of resistivity on the substrate surface in AZO:Si thin films prepared with a Si content (Si/[Si+Zn] atomic ratio) of 0.75 at. % using powder targets containing SiC. The improvement in resistivity distribution was mainly attributed to increases in both carrier concentration and Hall mobility at locations on the substrate corresponding to the target erosion region. In addition, the resistivity stability of AZO: Si thin films exposed to air for 30 min at a high temperature was found to improve with increasing Si content.

  6. Evolution of Metallic Conductivity in Epitaxial ZnO Thin Films on Systematic Al Doping

    NASA Astrophysics Data System (ADS)

    Chinta, P. V.; Lozano, O.; Wadekar, P. V.; Hsieh, W. C.; Seo, H. W.; Yeh, S. W.; Liao, C. H.; Tu, L. W.; Ho, N. J.; Zhang, Y. S.; Pang, W. Y.; Lo, Ikai; Chen, Q. Y.; Chu, W. K.

    2017-04-01

    The metal-like behaviors and metal-semiconductor transition (MST) of highly conducting Zn1- x Al x O ( x = 1 at.% to 10 at.%) thin films deposited by cosputtering on a-Al2O3 have been investigated. The temperature-dependent transport properties reveal that the Zn1- x Al x O films were highly degenerate. The MST temperature ( T MST) varied from 190 K to 260 K with Al doping from x = 2 at.% to 10 at.%. A simple degenerate band model is used to explain the observed shift in the metal-like behaviors upon Al doping. An empirical approach is used to analyze the resistivity functional below TMST, taking into account the contributions from both the weak localization and Coulomb interactions in explaining the MST. Analysis by least-square fittings of measured data shows excellent agreement. The optical bandgap increases with carrier concentration as n Hall 2/3 , which is interpreted as the Burstein-Moss shift for a nonparabolic effective mass. Such nonparabolicity is scrutinized by quantitative comparisons of the plasma edge values n optical versus the n Hall values.

  7. Evolution of Metallic Conductivity in Epitaxial ZnO Thin Films on Systematic Al Doping

    NASA Astrophysics Data System (ADS)

    Chinta, P. V.; Lozano, O.; Wadekar, P. V.; Hsieh, W. C.; Seo, H. W.; Yeh, S. W.; Liao, C. H.; Tu, L. W.; Ho, N. J.; Zhang, Y. S.; Pang, W. Y.; Lo, Ikai; Chen, Q. Y.; Chu, W. K.

    2016-11-01

    The metal-like behaviors and metal-semiconductor transition (MST) of highly conducting Zn1-x Al x O (x = 1 at.% to 10 at.%) thin films deposited by cosputtering on a-Al2O3 have been investigated. The temperature-dependent transport properties reveal that the Zn1-x Al x O films were highly degenerate. The MST temperature (T MST) varied from 190 K to 260 K with Al doping from x = 2 at.% to 10 at.%. A simple degenerate band model is used to explain the observed shift in the metal-like behaviors upon Al doping. An empirical approach is used to analyze the resistivity functional below TMST, taking into account the contributions from both the weak localization and Coulomb interactions in explaining the MST. Analysis by least-square fittings of measured data shows excellent agreement. The optical bandgap increases with carrier concentration as n {Hall/2/3}, which is interpreted as the Burstein-Moss shift for a nonparabolic effective mass. Such nonparabolicity is scrutinized by quantitative comparisons of the plasma edge values n optical versus the n Hall values.

  8. Plasma versus thermal annealing for the Au-catalyst growth of ZnO nanocones and nanowires on Al-doped ZnO buffer layers

    NASA Astrophysics Data System (ADS)

    Güell, Frank; Martínez-Alanis, Paulina R.; Roso, Sergio; Salas-Pérez, Carlos I.; García-Sánchez, Mario F.; Santana, Guillermo; Marel Monroy, B.

    2016-06-01

    We successfully synthesized ZnO nanocones and nanowires over polycrystalline Al-doped ZnO (AZO) buffer layers on fused silica substrates by a vapor-transport process using Au-catalyst thin films. Different Au film thicknesses were thermal or plasma annealed in order to analyze their influence on the ZnO nanostructure growth morphology. Striking differences have been observed. Thermal annealing generates a distribution of Au nanoclusters and plasma annealing induces a fragmentation of the Au thin films. While ZnO nanowires are found in the thermal-annealed samples, ZnO nanocones and nanowires have been obtained on the plasma-annealed samples. Enhancement of the preferred c-axis (0001) growth orientation was demonstrated by x-ray diffraction when the ZnO nanocones and nanowires have been grown over the AZO buffer layer. The transmittance spectra of the ZnO nanocones and nanowires show a gradual increase from 375 to 900 nm, and photoluminescence characterization pointed out high concentration of defects leading to observation of a broad emission band in the visible range from 420 to 800 nm. The maximum emission intensity peak position of the broad visible band is related to the thickness of the Au-catalyst for the thermal-annealed samples and to the plasma power for the plasma-annealed samples. Finally, we proposed a model for the plasma versus thermal annealing of the Au-catalyst for the growth of the ZnO nanocones and nanowires. These results are promising for renewable energy applications, in particular for its potential application in solar cells.

  9. Fabrication of nanostructured Al-doped ZnO thin film for methane sensing applications

    NASA Astrophysics Data System (ADS)

    Shafura, A. K.; Sin, N. D. Md.; Azhar, N. E. I.; Saurdi, I.; Uzer, M.; Mamat, M. H.; Shuhaimi, A.; Alrokayan, Salman A. H.; Khan, Haseeb A.; Rusop, M.

    2016-07-01

    CH4 gas sensor was fabricated using spin-coating method of the nanostructured ZnO thin film. Effect of annealing temperature on the electrical and structural properties of the film was investigated. Dense nanostructured ZnO film are obtained at higher annealing temperature. The optimal condition of annealing temperature is 500°C which has conductivity and sensitivity value of 3.3 × 10-3 S/cm and 11.5%, respectively.

  10. Investigation of the interrelation between the chemical state and the electric properties in Al-doped ZnO films

    NASA Astrophysics Data System (ADS)

    Wang, Jinzhao; Ni, Dongfang; Zhang, Tianjin; Wang, Duofa; Liang, Kun

    2015-09-01

    Transparent conducting Al-doped ZnO (AZO) thin films were prepared on glass substrates by radio frequency magnetron sputtering in pure Ar. The influence of the annealing atmosphere on the microstructure, chemical state, electric and optical properties of the AZO films was investigated with X-ray diffraction, field-emission scanning electron microscopy, X-ray photoelectron spectroscopy and Hall measurements. The AZO thin films annealed under vacuum had the highest carrier concentration of 2.488 × 1020 cm-3 and a Hall mobility of 16.35 cm2 V-1 s-1, while the AZO thin films annealed in air had the lowest carrier concentration of 4.182 × 1017 cm-3 and a Hall mobility of 2.375 cm2 V-1 s-1. The fitted narrow-scan O1 s spectra revealed that O1 s was composed of three components. The AZO thin films annealed under vacuum appeared to have a higher proportion of medium binding energy which correspond to O2- ions in the oxygen-deficient regions within the ZnO matrix, and have a lower proportion of high binding energy component which correspond to loosely bound chemisorbed oxygen. It believed that the oxygen vacancies and chemisorbed oxygen of the films played an important role in the electrical conductance. The carrier concentration increased with the formation of oxygen vacancies. The Hall mobility increased with desorption of the loosely bound oxygen.

  11. Spectroscopic characterization of the plasmas formed during the deposition of ZnO and Al-doped ZnO films by plasma-assisted pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Liang, Peipei; Cai, Hua; Yang, Xu; Li, Hui; Zhang, Wu; Xu, Ning; Sun, Jian; Wu, Jiada

    2016-11-01

    An oxygen-zinc plasma and an oxygen-zinc-aluminum plasma are formed by pulsed laser ablation of a Zn target or pulsed laser co-ablation of a Zn target and an Al target in an electron cyclotron resonance (ECR) discharge-generated oxygen plasma for the deposition of ZnO and Al-doped ZnO (AZO) films. The plasmas are characterized spectroscopically by time-integrated and time-resolved optical emission spectroscopy. Both the oxygen-zinc plasma and the oxygen-zinc-aluminum plasma contain excited species originally present in the working O2 gas and energetic species ablated from the targets. The optical emission of the oxygen-zinc-aluminum plasma is abundant in the emission bands of oxygen molecular ions and the emission lines of mono-atomic oxygen, zinc and aluminum atoms and atomic ions. The time-integrated spectra as well as the time-resolved spectra of the plasma emission indicate that the oxygen species in the ECR oxygen plasma experience additional excitation by the expanding ablation plumes, and the ablated species are excited frequently when traveling accompanying the plume expansion in the oxygen plasma, making the formed plasma highly excited and very reactive, which plays an important role in the reactive growth of ZnO matrix and the in-situ doping of Al into the growing ZnO matrix. The deposited ZnO and AZO films were evaluated for composition analysis by energy dispersive X-ray spectroscopy, structure characterization by X-ray diffraction and optical transmission measurement. The deposited ZnO is slightly rich in O. The Al concentration of the AZO films can be controlled and varied simply by changing the repetition rate of the laser used for Al target ablation. Both the ZnO and the AZO films are featured with hexagonal wurtzite crystal structure and exhibit high optical transparency in a wide spectral region. Al doping results in an improvement in the ultraviolet transparency, a blue shift in the absorption edge and a widening of the band gap.

  12. Effect of the H2 plasma treatment of a seed layer on the synthesis of ZnO nanorods using a microwave hydrothermal method

    NASA Astrophysics Data System (ADS)

    Koo, Horng-Show; Lin, Ching-Cheng; Chen, Yao-Ju; Peng, Cheng-Hsiung; Chen, Mi

    2014-01-01

    The effect of H2 plasma treatment of a seed layer on the synthesis and characterization of zinc oxide (ZnO) nanorods is determined. Using an Al-doped ZnO (AZO) thin film as a seed layer, well-aligned ZnO nanorods are rapidly grown on an indium tin oxide (ITO)-coated glass substrate using a microwave hydrothermal method. The deposited AZO substrate was previously treated with H2 plasma. The effect of H2 plasma treatment of the seed layer on the alignment, growth rate, and crystallinity of the ZnO nanorods is determined. It is shown that the alignment and growth rate of the ZnO nanorods depend on the characteristics and roughness of the seed layer, which are improved by H2 plasma treatment. Various characterization methods such as X-ray diffraction (XRD), cathodoluminescence (CL), transmission electron microscopy (TEM), and X-ray photoemission spectroscopy (XPS) are used to determine the characteristic quality of the ZnO nanorods. A fundamental model of the effect of H2 plasma treatment on the seed layer and ZnO growth using a microwave hydrothermal process is also presented.

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

    PubMed Central

    2011-01-01

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

  14. Effect of aging under ambient conditions on the optical properties of Al-doped ZnO thin films deposited by direct current sputtering

    NASA Astrophysics Data System (ADS)

    Barhoumi, A.; Leroy, G.; Duponchel, B.; Gest, J.; Guermazi, S.

    2017-01-01

    Transparent and conductive Al-doped ZnO (AZO) thin films were deposited on a glass substrate by direct current sputtering. In a previous study, we noted the influence of time on structural and electrical characteristics of films. In the present paper, the effect of a two-year aging under ambient conditions on the optical properties was investigated. A global improvement of the optical properties of AZO thin films was observed. The optical transmittance spectra revealed a high transmittance more than 90% in the Vis-NIR regions and a high absorption in the ultraviolet range. It is assumed that the crystallinity segregation leads to the decrease of optical scattering. The results from the optical measurements showed a reorganization of the structure leading to the degradation of the structural homogeneity. Nevertheless, the evolution of the figure of merit shows that Al-doped ZnO is a good candidate for the manufacturing and the commercialization of transparent conducting oxide devices.

  15. Near infrared ray annealing effects on the properties of Al-doped ZnO thin films prepared by spin-coating method.

    PubMed

    Jun, Min-Chul; Park, Sang-Uk; Chae, Moon-Soon; Shin, Dong-Jin; Ha, Jae-Geun; Koo, Sang-Mo; Lee, Kyung-Ju; Moon, Byung-Moo; Song, Chi-Young; Koh, Jung-Hyuk

    2013-09-01

    In this research, we will present Al doped ZnO thin films for transparent conducting oxide applications. Aluminum doped zinc oxide (AZO) thin films have been deposited on the glass substrates by sol-gel spin-coating method using zinc acetate dehydrate (Zn(CH3COO)2 2H2O) and aluminum chloride hexahydrate (AlCl3 x 6H2O) as cation sources. In this study, we investigated the effects of near infrared ray (NIR) annealing on the structural, optical and electrical characteristics of the AZO thin films. The experimental results showed that AZO thin films have a hexagonal wurtzite crystal structure and had a good transmittance higher than 85% within the visible wavelength region. It was also found that the additional energy of NIR helps to improve the electrical properties of Al doped ZnO transparent conducting oxides.

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

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

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

  17. Nonequilibrium-Plasma-Synthesized ZnO Nanocrystals with Plasmon Resonance Tunable via Al Doping and Quantum Confinement.

    PubMed

    Greenberg, Benjamin L; Ganguly, Shreyashi; Held, Jacob T; Kramer, Nicolaas J; Mkhoyan, K Andre; Aydil, Eray S; Kortshagen, Uwe R

    2015-12-09

    Metal oxide semiconductor nanocrystals (NCs) exhibit localized surface plasmon resonances (LSPRs) tunable within the infrared (IR) region of the electromagnetic spectrum by vacancy or impurity doping. Although a variety of these NCs have been produced using colloidal synthesis methods, incorporation and activation of dopants in the liquid phase has often been challenging. Herein, using Al-doped ZnO (AZO) NCs as an example, we demonstrate the potential of nonthermal plasma synthesis as an alternative strategy for the production of doped metal oxide NCs. Exploiting unique, thoroughly nonequilibrium synthesis conditions, we obtain NCs in which dopants are not segregated to the NC surfaces and local doping levels are high near the NC centers. Thus, we achieve overall doping levels as high as 2 × 10(20) cm(-3) in NCs with diameters ranging from 12.6 to 3.6 nm, and for the first time experimentally demonstrate a clear quantum confinement blue shift of the LSPR energy in vacancy- and impurity-doped semiconductor NCs. We propose that doping of central cores and heavy doping of small NCs are achievable via nonthermal plasma synthesis, because chemical potential differences between dopant and host atoms-which hinder dopant incorporation in colloidal synthesis-are irrelevant when NC nucleation and growth proceed via irreversible interactions among highly reactive gas-phase ions and radicals and ligand-free NC surfaces. We explore how the distinctive nucleation and growth kinetics occurring in the plasma influences dopant distribution and activation, defect structure, and impurity phase formation.

  18. Local probe microscopic studies on Al-doped ZnO: Pseudoferroelectricity and band bending at grain boundaries

    SciTech Connect

    Kumar, Mohit; Basu, Tanmoy; Som, Tapobrata

    2016-01-07

    In this paper, based on piezoforce measurements, we show the presence of opposite polarization at grains and grain boundaries of Al-doped ZnO (AZO). The polarization can be flipped by 180° in phase by switching the polarity of the applied electric field, revealing the existence of nanoscale pseudoferroelectricity in AZO grown on Pt/TiO{sub 2}/SiO{sub 2}/Si substrate. We also demonstrate an experimental evidence on local band bending at grain boundaries of AZO films using conductive atomic force microscopy and Kelvin probe force microscopy. The presence of an opposite polarization at grains and grain boundaries gives rise to a polarization-driven barrier formation at grain boundaries. With the help of conductive atomic force microscopy, we show that the polarization-driven barrier along with the defect-induced electrostatic potential barrier account for the measured local band bending at grain boundaries. The present study opens a new avenue to understand the charge transport in light of both polarization and electrostatic effects.

  19. Fabrication of deep-profile Al-doped ZnO one- and two-dimensional lattices as plasmonic elements

    NASA Astrophysics Data System (ADS)

    Jensen, Flemming; Shkondin, Evgeniy; Takayama, Osamu; Larsen, Pernille V.; Mar, Mikkel D.; Malureanu, Radu; Lavrinenko, Andrei V.

    2016-09-01

    In this work, we report on fabrication of deep-profile one- and two-dimensional lattices made from Al-doped ZnO (AZO). AZO is considered as an alternative plasmonic material having the real part of the permittivity negative in the near infrared range. The exact position of the plasma frequency of AZO is doping concentration dependent, allowing for tuning possibilities. In addition, the thickness of the AZO film also affects its material properties. Physical vapor deposition techniques typically applied for AZO coating do not enable deep profiling of a plasmonic structure. Using the atomic layer deposition technique, a highly conformal deposition method, allows us to fabricate high-aspect ratio structures such as one-dimensional lattices with a period of 400 nm and size of the lamina of 200 nm in width and 3 μm in depth. Thus, our structures have an aspect ratio of 1:15 and are homogeneous on areas of 2×2 cm2 and more. We also produce two-dimensional arrays of circular nanopillars with similar dimensions. Instead of nanopillars hollow tubes with a wall thickness on demand from 20 nm up to a complete fill can be fabricated.

  20. Local probe microscopic studies on Al-doped ZnO: Pseudoferroelectricity and band bending at grain boundaries

    NASA Astrophysics Data System (ADS)

    Kumar, Mohit; Basu, Tanmoy; Som, Tapobrata

    2016-01-01

    In this paper, based on piezoforce measurements, we show the presence of opposite polarization at grains and grain boundaries of Al-doped ZnO (AZO). The polarization can be flipped by 180° in phase by switching the polarity of the applied electric field, revealing the existence of nanoscale pseudoferroelectricity in AZO grown on Pt/TiO2/SiO2/Si substrate. We also demonstrate an experimental evidence on local band bending at grain boundaries of AZO films using conductive atomic force microscopy and Kelvin probe force microscopy. The presence of an opposite polarization at grains and grain boundaries gives rise to a polarization-driven barrier formation at grain boundaries. With the help of conductive atomic force microscopy, we show that the polarization-driven barrier along with the defect-induced electrostatic potential barrier account for the measured local band bending at grain boundaries. The present study opens a new avenue to understand the charge transport in light of both polarization and electrostatic effects.

  1. Highly transparent and conductive Al-doped ZnO nanoparticulate thin films using direct write processing.

    PubMed

    Vunnam, S; Ankireddy, K; Kellar, J; Cross, W

    2014-05-16

    Solution processable Al-doped ZnO (AZO) thin films are attractive candidates for low cost transparent electrodes. We demonstrate here an optimized nanoparticulate ink for the fabrication of AZO thin films using scalable, low-cost direct write processing (ultrasonic spray deposition) in air at atmospheric pressure. The thin films were made via thermal processing of as-deposited films. AZO films deposited using the proposed nanoparticulate ink with further reducing in vacuum and rf plasma of forming gas exhibited optical transparency greater than 95% across the visible spectrum, and electrical resistivity of 0.5 Ω cm and it drops down to 7.0 × 10(-2) Ω cm after illuminating with UV light, which is comparable to commercially available tin doped indium oxide colloidal coatings. Various structural analyses were performed to investigate the influence of ink chemistry, deposition parameters, and annealing temperatures on the structural, optical, and electrical characteristics of the spray deposited AZO thin films. Optical micrographs confirmed the presence of surface defects and cracks using the AZO NPs ink without any additives. After adding N-(2-Aminoethyl)-3-aminopropylmethyldimethoxy silane to the ink, AZO films exhibited an optical transparency which was virtually identical to that of the plain glass substrate.

  2. Characteristics of Al-doped ZnO films grown by atomic layer deposition for silicon nanowire photovoltaic device.

    PubMed

    Oh, Byeong-Yun; Han, Jin-Woo; Seo, Dae-Shik; Kim, Kwang-Young; Baek, Seong-Ho; Jang, Hwan Soo; Kim, Jae Hyun

    2012-07-01

    We report the structural, electrical, and optical characteristics of Al-doped ZnO (ZnO:Al) films deposited on glass by atomic layer deposition (ALD) with various Al2O3 film contents for use as transparent electrodes. Unlike films fabricated by a sputtering method, the diffraction peak position of the films deposited by ALD progressively moved to a higher angle with increasing Al2O3 film content. This indicates that Zn sites were effectively replaced by Al, due to layer-by-layer growth mechanism of ALD process which is based on alternate self-limiting surface chemical reactions. By adjusting the Al2O3 film content, a ZnO:Al film with low electrical resistivity (9.84 x 10(-4) Omega cm) was obtained at an Al2O3 film content of 3.17%, where the Al concentration, carrier mobility, optical transmittance, and bandgap energy were 2.8 wt%, 11.20 cm2 V(-1) s(-1), 94.23%, and 3.6 eV, respectively. Moreover, the estimated figure of merit value of our best sample was 8.2 m7Omega(-1). These results suggest that ZnO:Al films deposited by ALD could be useful for electronic devices in which especially require 3-dimensional conformal deposition of the transparent electrode and surface passivation.

  3. Effects of Al concentration on microstructural characteristics and electrical properties of Al-doped ZnO thin films on Si substrates by atomic layer deposition.

    PubMed

    Lee, Ju Ho; Lee, Jae-Won; Hwang, Sooyeon; Kim, Sang Yun; Cho, Hyung Koun; Lee, Jeong Yong; Park, Jin-Seong

    2012-07-01

    Al-doped ZnO (AZO) thin films with various Al concentrations were synthesized on Si(001) substrates with native oxide layers by atomic layer deposition process. The effects of the Al concentration on the microstructural characteristics of the AZO thin films grown at 250 degrees C and the correlation between their microstructural characteristics and electrical properties of the AZO thin films were investigated by AFM, XRD, HRTEM and Hall measurements. The XRD and HRTEM results revealed that the crystallinity and electrical properties of the undoped ZnO thin films were enhanced by 2.48 at% Al doping. However, 12.62 at% Al doping induced the deterioration of their crystallinity and electrical properties due to the formation of nano-sized metallic Al clusters and randomly oriented ZnO-based nano-crystals. To enhance the electrical properties of the AZO thin films while maintaining their crystallinity and electrical properties, a moderate Al concentration has to be chosen under the solubility limit of Al in ZnO.

  4. Memristive switching of ZnO nanorod mesh

    NASA Astrophysics Data System (ADS)

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

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

  5. Transparent conductive Al-doped ZnO thin films grown at room temperature

    SciTech Connect

    Wang Yuping; Lu Jianguo; Bie Xun; Gong Li; Li Xiang; Song Da; Zhao Xuyang; Ye Wenyi; Ye Zhizhen

    2011-05-15

    Aluminum-doped ZnO (ZnO:Al, AZO) thin films were prepared on glass substrates by dc reactive magnetron sputtering from a Zn-Al alloy target at room temperature. The effects of the Ar-to-O{sub 2} partial pressure ratios on the structural, electrical, and optical properties of AZO films were studied in detail. AZO films grown using 100:4 to 100:8 Ar-to-O{sub 2} ratio result in acceptable quality films with c-axis orientated crystals, uniform grains, 10{sup -3} {Omega} cm resistivity, greater than 10{sup 20} cm{sup -3} electron concentration, and high transmittance, 90%, in the visible region. The lowest resistivity of 4.11x10{sup -3} {Omega} cm was obtained under the Ar-to-O{sub 2} partial pressure ratio of 100:4. A relatively strong UV emission at {approx}3.26 eV was observed in the room-temperature photoluminescence spectrum. X-ray photoelectron spectroscopy analysis confirmed that Al was introduced into ZnO and substitutes for Zn and doped the film n-type.

  6. Electrical and optical properties of Al-doped ZnO and ZnAl2O4 films prepared by atomic layer deposition

    PubMed Central

    2013-01-01

    ZnO/Al2O3 multilayers were prepared by alternating atomic layer deposition (ALD) at 150°C using diethylzinc, trimethylaluminum, and water. The growth process, crystallinity, and electrical and optical properties of the multilayers were studied with a variety of the cycle ratios of ZnO and Al2O3 sublayers. Transparent conductive Al-doped ZnO films were prepared with the minimum resistivity of 2.4 × 10−3 Ω·cm at a low Al doping concentration of 2.26%. Photoluminescence spectroscopy in conjunction with X-ray diffraction analysis revealed that the thickness of ZnO sublayers plays an important role on the priority for selective crystallization of ZnAl2O4 and ZnO phases during high-temperature annealing ZnO/Al2O3 multilayers. It was found that pure ZnAl2O4 film was synthesized by annealing the specific composite film containing alternative monocycle of ZnO and Al2O3 sublayers, which could only be deposited precisely by utilizing ALD technology. PMID:23537274

  7. Ferromagnetic behavior due to Al3+ doping into ZnO nanorods

    NASA Astrophysics Data System (ADS)

    Yingsamphancharoen, T.; Nakarungsee, P.; Herng, T. S.; Ding, J.; Tang, I. M.; Thongmee, S.

    2016-12-01

    Al doped ZnO nanorods (NR's) having Al concentration up to 10 mol% were grown by the hydrothermal method. XRD measurements showed that the Al substituted ZnO NR's maintained the hexagonal wurtzite structure for all levels of Al substitution. EDX measurements of the ZnO:Al NR's indicated that the Al substitution created additional Zn vacancies in the wurtzite structure which is reflected in the enhanced photoluminescence emission in the visible light spectra between 450 and 550 nm of the more heavily doped ZnO:Al NR's. SEM images of the heavier doped ZnO:Al nanorods showed nano nodules being formed on the surface of the hexagonal shaped NR's. The saturation magnetizations of the ZnO:Al NR's as measured by a SQUID magnetometer increased to 10.66×10-4 emu/g as more Al was substituted in. The hysteresis loops for the ZnO:Al NR's began to exhibit novel effects, such as horizontal shift (exchange bias field 0.0382 kOe for the 9 mol% NR) and butterfly shapes.

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

    NASA Astrophysics Data System (ADS)

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

    2017-02-01

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

  9. On the variations of optical property and electronic structure in heavily Al-doped ZnO films during double-step growth process

    SciTech Connect

    Hu, Q. C.; Ding, K. Zhang, J. Y.; Yan, F. P.; Pan, D. M.; Huang, F.; Chiou, J. W.

    2014-01-13

    We have investigated the variations of optical property and electronic structure in heavily Al-doped ZnO (AZO) films during the growth process, which were formed by first creating Zn vacancies in O{sub 2}-rich atmosphere and second filling the vacancies with Zn atoms in Zn-vapor atmosphere. After the first step, the high-resistance AZO films have the same optical bandgap with nominally undoped ZnO, indicating that negligible variations in the fundamental bandgap happened to the AZO films although Al atom was incorporated into the ZnO lattice. After the second step, once free electrons were brought into the lattice by Zn-filling, the optical transition energy blueshifts due to the band-filling effect. X-ray absorption fine structure measurements suggest that Zn-filling process decreased the unoccupied states of the conduction band, but not raised the conduction band minimum.

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

    SciTech Connect

    Shirahata, Yasuhiro; Tanaike, Kohei; Akiyama, Tsuyoshi; Fujimoto, Kazuya; Suzuki, Atsushi; Balachandran, Jeyadevan; Oku, Takeo

    2016-02-01

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

  11. Interfacially Al-doped ZnO nanowires: greatly enhanced near band edge emission through suppressed electron-phonon coupling and confined optical field.

    PubMed

    Wu, Yiming; Dai, Yanmeng; Jiang, Shenlong; Ma, Chao; Lin, Yue; Du, Dongxue; Wu, Yukun; Ding, Huaiyi; Zhang, Qun; Pan, Nan; Wang, Xiaoping

    2017-04-05

    Aluminium (Al)-doped zinc oxide (ZnO) nanowires (NWs) with a unique core-shell structure and a Δ-doping profile at the interface were successfully grown using a combination of chemical vapor deposition re-growth and few-layer AlxOy atomic layer deposition. Unlike the conventional heavy doping which degrades the near-band-edge (NBE) luminescence and increases the electron-phonon coupling (EPC), it was found that there was an over 20-fold enhanced NBE emission and a notably-weakened EPC in this type of interfacially Al-doped ZnO NWs. Further experiments revealed a greatly suppressed nonradiative decay process and a much enhanced radiative recombination rate. By comparing the finite-difference time-domain simulation with the experimental results from intentionally designed different NWs, this enhanced radiative decay rate was attributed to the Purcell effect induced by the confined and intensified optical field within the interfacial layer. The ability to manipulate the confinement, transport and relaxation dynamics of ZnO excitons can be naturally guaranteed with this unique interfacial Δ-doping strategy, which is certainly desirable for the applications using ZnO-based nano-photonic and nano-optoelectronic devices.

  12. CdS/CdSe-sensitized solar cell based on Al-doped ZnO nanoparticles prepared by the decomposition of zinc acetate solid solution

    NASA Astrophysics Data System (ADS)

    Deng, Jianping; Wang, Minqiang; Ye, Wei; Fang, Junfei; Zhang, Pengchao; Yang, Yongping; Yang, Zhi

    2017-01-01

    In the study, Al-doped ZnO nanoparticles (Al-ZnO NPs) were prepared by the decomposition of zinc acetate solid solution. The X-ray diffraction results showed that Al3+ was successfully doped without the formation of Al and Al2O3 impurity phases. The less Al-doping did not change the hexagonal wurtzite crystal structure of ZnO. The ratio of Al to Al + Zn (9.05%) measured by the energy dispersive X-ray also confirmed the formation of Al-ZnO. The Al-ZnO NPs were used as the photoanode material to prepare CdS/CdSe-sensitized solar cell. Compared with the cell based on commercial ZnO NPs (C-ZnO), the short-circuit current density and the fill factor of the cell were increased from 5.8 mA/cm2 and 34.1% (C-ZnO) to 7.78 mA/cm2 and 48.7% (Al-ZnO), respectively. The cell efficiency was increased from 1.01% (C-ZnO) to (1.9%) (Al-ZnO) and the increase percentage reached 88.1%. The results of electrochemical impedance spectroscopy and open-circuit voltage-decay suggested the lower carrier transport resistance and the longer electron lifetime of Al-ZnO-based cell.

  13. Field-induced doping-mediated tunability in work function of Al-doped ZnO: Kelvin probe force microscopy and first-principle theory

    NASA Astrophysics Data System (ADS)

    Kumar, Mohit; Mookerjee, Sumit; Som, Tapobrata

    2016-09-01

    We demonstrate that the work function of Al-doped ZnO (AZO) can be tuned externally by applying an electric field. Our experimental investigations using Kelvin probe force microscopy show that by applying a positive or negative tip bias, the work function of AZO film can be enhanced or reduced, which corroborates well with the observed charge transport using conductive atomic force microscopy. These findings are further confirmed by calculations based on first-principles theory. Tuning the work function of AZO by applying an external electric field is not only important to control the charge transport across it, but also to design an Ohmic contact for advanced functional devices.

  14. Evolution of dielectric function of Al-doped ZnO thin films with thermal annealing: effect of band gap expansion and free-electron absorption.

    PubMed

    Li, X D; Chen, T P; Liu, Y; Leong, K C

    2014-09-22

    Evolution of dielectric function of Al-doped ZnO (AZO) thin films with annealing temperature is observed. It is shown that the evolution is due to the changes in both the band gap and the free-electron absorption as a result of the change of free-electron concentration of the AZO thin films. The change of the electron concentration could be attributed to the activation of Al dopant and the creation/annihilation of the donor-like defects like oxygen vacancy in the thin films caused by annealing.

  15. Improved optical and electrical properties of rf sputtered Al doped ZnO films on polymer substrates by low-damage processes

    SciTech Connect

    Min, Hyung Seob; Yang, Min Kyu; Lee, Jeon-Kook

    2009-03-15

    Three types of low-damage radio-frequency (rf) magnetron sputtering processes--an interruptive process, a rotating cylindrical holder method, and an off-axis sputtering method--were designed and studied to reduce the film surface temperature during deposition. Low-damage sputtering processes were investigated to improve the resistivity and optical transmittance in the visible range of Al doped ZnO (AZO) thin films deposited on polymer substrates. In the case of the polyethersulfone substrate, AZO films with a resistivity of 1.0x10{sup -3} {omega} cm and an optical transmittance of 75% were obtained by the rotating repeat holder method during rf sputtering.

  16. Field-induced doping-mediated tunability in work function of Al-doped ZnO: Kelvin probe force microscopy and first-principle theory.

    PubMed

    Kumar, Mohit; Mookerjee, Sumit; Som, Tapobrata

    2016-09-16

    We demonstrate that the work function of Al-doped ZnO (AZO) can be tuned externally by applying an electric field. Our experimental investigations using Kelvin probe force microscopy show that by applying a positive or negative tip bias, the work function of AZO film can be enhanced or reduced, which corroborates well with the observed charge transport using conductive atomic force microscopy. These findings are further confirmed by calculations based on first-principles theory. Tuning the work function of AZO by applying an external electric field is not only important to control the charge transport across it, but also to design an Ohmic contact for advanced functional devices.

  17. Synthesis of flower-like Al doped ZnO microstructures by hydrothermal process and analysis of their gas sensing properties

    NASA Astrophysics Data System (ADS)

    Li, Zan; Qin, Wei; Zhao, Wenjie; Wu, Xiaohong

    2014-04-01

    Al-doped ZnO (AZO) powders with flower-like microstructures were successfully synthesized through a simple and efficient hydrothermal approach, and were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy diffraction spectrum (EDS). All the samples presented high crystallinity with a hexagonal wurtzite structure. The heater gas sensors based on AZO were fabricated and investigation of gas sensing properties was conducted. The sensors showed high response values and reproducible response-recovery for 50-1800 ppm ethanol at 332°C, comparing with NH3, SO2, CO, and HCHO. The underlying mechanism was discussed.

  18. Arrays of ZnO/AZO (Al-doped ZnO) nanocables: a higher open circuit voltage and remarkable improvement of efficiency for CdS-sensitized solar cells.

    PubMed

    Deng, Jianping; Wang, Minqiang; Liu, Jing; Song, Xiaohui; Yang, Zhi

    2014-03-15

    Photoelectrode of nanocables (NCs) structure of ZnO nanowires (NWs) coated with Al-doped ZnO (AZO) shells was investigated for CdS quantum dots sensitized solar cells (QDSSCs). ZnO NWs serve as the frame for the preparation of AZO shells, in which electron transport more rapidly due to the more higher electron mobility of AZO (n-ZnO) than that of i-ZnO. AZO shells were assembled onto the surface of ZnO NWs via a spin-coating method. Optical band-gap of the ZnO/AZO films varies from 3.19 eV for pure ZnO to 3.25 eV for AZO (15%) depending on the Al-doping concentration. The PL intensity of AZO/ZnO, V(oc), J(sc) and η of the cells first increased and then decreased with the increase in the Al-doping (from 0% to 20%) and post-annealed temperature. Remarkably, the value of V(oc) can achieve above 0.8 V after Al-doping. The dark current and absorption spectrum provided direct evidence of the increase in J(sc) and V(oc), respectively. Moreover, we discussed the effect of Al-doping on optical band-gap of the samples and the transfer of electron.

  19. Competition between (001) and (111) MgO thin film growth on Al-doped ZnO by oxygen plasma assisted pulsed laser deposition

    SciTech Connect

    Xiao, Bo; Yang, Qiguang; Walker, Brandon; Gonder, Casey A.; Romain, Gari C.; Mundle, Rajeh; Bahoura, Messaoud; Pradhan, A. K.

    2013-06-07

    We report on the study of epitaxial MgO thin films on (0001) Al-doped ZnO (Al: ZnO) underlayers, grown by oxygen plasma assisted pulsed laser deposition technique. A systematic investigation of the MgO thin films was performed by X-ray diffraction and atomic force microscopy, along with the current-voltage characteristics. A distinguished behavior was observed that the preferred MgO orientation changes from (111) to (001) in the films as the growth temperature increases. Two completely different in-plane epitaxial relationships were also determined from X-ray diffraction as: [110]MgO//[1120]Al: ZnO and [110]MgO//[1100]Al: ZnO for (001) MgO with 60 Degree-Sign rotated triplet domains, and [110]MgO//[1120]Al: ZnO for (111) MgO with 180 Degree-Sign rotated twin. The pronounced temperature dependence indicates a reconciliation of the nucleation driving forces among surface, interfacial, and strain energy for heteroepitaxy of cubic MgO on hexagonal Al: ZnO. The related interfacial atomic registry is considered to be important to the formation of unusual (001) MgO on hexagonal crystals. In addition, the electrical characterization revealed a dramatic reduction of the leakage current in (001) MgO thin films, whereas the small grain size of (111) MgO is identified by atomic force microscopy as a main cause of large leakage current.

  20. Size-controllable growth of ZnO nanorods on Si substrate

    NASA Astrophysics Data System (ADS)

    Yu, Zhentao; Li, Hui; Qiu, Yining; Yang, Xu; Zhang, Wu; Xu, Ning; Sun, Jian; Wu, Jiada

    2017-01-01

    Here we report a simple two-step chemical-solution-based method to grow highly oriented and size-controllable ZnO nanorods on ZnO-seeded Si substrate. The morphology of the grown ZnO nanorods was examined by field emission scanning electron microscopy. The structure was characterized by X-ray diffraction and Raman scattering spectrum. Photoluminescence spectra were measured at room temperature and low temperatures to evaluate the photoluminescence properties of the ZnO nanorods. The grown ZnO nanorods are structured with hexagonal wurtzite. The diameter and length of ZnO nanorods can be controlled by varying the crystal quality of the underlying ZnO seed layers. The crystal quality of the seed layers gets improved as the deposition time and annealing temperature for ZnO seed layers are increased. The effects of annealing on the ZnO nanorods were also studied.

  1. Optimizing performance of Cu2O/ZnO nanorods heterojunction based self-powered photodetector with ZnO seed layer

    NASA Astrophysics Data System (ADS)

    Wang, Chang; Xu, Jianping; Shi, Shaobo; Zhang, Yuzhu; Gao, Yanyan; Liu, Zeming; Zhang, Xuguang; Li, Lan

    2017-04-01

    The Cu2O films were electrodeposited on ZnO nanorod arrays (NRs) and the Cu2O/ZnO NRs heterojunctions were formed. The optical-electronic response of the heterojunctions was investigated. The diameter size and crystal quality of ZnO NRs were modified by the seed layer. ZnO NRs with good crystal quality were obtained on the 0.5% Al doped ZnO seed layer film (named as AZO (0.5%)). The devices based on the Cu2O/ZnO NRs heterojunction exhibit excellent stability and reproducibility of the self-powered photoresponse properties. The device with AZO (0.5%) seed layer demonstrates the high photoresponsivity of 60-70 mA/W in the violet and blue light with a fast response speed at zero applied bias.

  2. Structural, optical, morphological and electrical properties of undoped and Al-doped ZnO thin films prepared using sol—gel dip coating process

    NASA Astrophysics Data System (ADS)

    Boukhenoufa, N.; Mahamdi, R.; Rechem, D.

    2016-11-01

    In this work, sol—gel dip-coating technique was used to elaborate ZnO pure and ZnO/Al films. The impact of Al-doped concentration on the structural, optical, surface morphological and electrical properties of the elaborated samples was investigated. It was found that better electrical and optical performances have been obtained for an Al concentration equal to 5%, where the ZnO thin films exhibit a resistivity value equal to 1.64104 Ω·cm. Moreover, highest transparency has been recorded for the same Al concentration value. The obtained results from this investigation make the developed thin film structure a potential candidate for high optoelectronic performance applications.

  3. Electronic structure of Al-doped ZnO transparent conductive thin films studied by x-ray absorption and emission spectroscopies

    SciTech Connect

    Huang, W. H.; Sun, S. J.; Chiou, J. W.; Chou, H.; Chan, T. S.; Lin, H.-J.; Kumar, Krishna; Guo, J.-H.

    2011-11-15

    This study used O K-, Zn L{sub 3}-, Zn K-, and Al K-edges x-ray absorption near-edge structure (XANES) and O K-edge x-ray emission spectroscopy (XES) measurements to investigate the electronic structure of transparent Al-doped ZnO (AZO) thin film conductors. The samples were prepared on glass substrates at a low temperature near 77 K by using a standard RF sputtering method. High-purity Ne (5N) was used as the sputtering gas. The crystallography of AZO thin films gradually transformed from the ZnO wurtize structure to an amorphous structure during sample deposition, which suggests the suitability to grow on flexible substrates, eliminating the severe degradation due to fragmentation by repeated bending. The O K- and Zn L{sub 3}-edges XANES spectra of AZO thin films revealed a decrease in the number of both O 2p and Zn 3d unoccupied states when the pressure of Ne was increased from 5 to 100 mTorr. In contrast, Al K-edges XANES spectra showed that the number of unoccupied states of Al 3p increased in conjunction with the pressure of Ne, indicating an electron transfer from Al to O atoms, and suggesting that Al doping increases the negative effective charge of oxygen ions. XES and XANES spectra of O 2p states at the O K-edge also revealed that Al doping not only raised the conduction-band-minimum, but also increased the valence-band-maximum and the band-gap. The results indicate that the reduction in conductivity of AZO thin films is due to the generation of ionic characters, the increase in band-gap, and the decrease in density of unoccupied states of oxygen.

  4. Development of Solution-Processed ZnO Nanorod Arrays Based Photodetectors and the Improvement of UV Photoresponse via AZO Seed Layers.

    PubMed

    Zhang, Yuzhu; Xu, Jianping; Shi, Shaobo; Gao, Yanyan; Wang, Chang; Zhang, Xiaosong; Yin, Shougen; Li, Lan

    2016-08-31

    Designing a rational structure and developing an efficient fabrication technique for bottom-up devices offer a promising opportunity for achieving high-performance devices. In this work, we studied how Al-doped ZnO (AZO) seed layer films influence the morphology and optical and electrical properties for ZnO aligned nanorod arrays (NRs) and then the performance of ZnO NRs based ultraviolet photodetectors (UV PDs) with Au/ZnO NRs Schottky junctions and p-CuSCN/n-ZnO NRs heterojunctions. The PD with AZO thin film with 0.5 at. % Al doping (named as AZO (0.5%)) exhibited more excellent photoresponse properties than that with pristine ZnO and AZO (1%) thin films. This phenomenon can be ascribed to the good light transmission of the AZO layer, increased density of the NRs, and improved crystallinity of ZnO NRs. The PDs based on CuSCN/ZnO NRs heterojunctions showed good rectification characteristics in the dark and self-powered UV photoresponse properties with excellent stability and reproducibility under low-intensity illumination conditions. A large responsivity located at 365 nm of 22.5 mA/W was achieved for the PD with AZO (0.5%) thin film without applied bias. The internal electric field originated from p-CuSCN/n-ZnO NRs heterojunctions can separate photogenerated carriers in ZnO NRs and drift toward the corresponding electrode.

  5. Free-standing ZnO nanorods and nanowalls by aqueous solution method.

    PubMed

    Kim, Dae-Hee; Lee, Sam-Dong; Kim, Kyoung-Kook; Park, Gyeong-Su; Lee, Ji-Myon; Kim, Sang-Woo

    2008-09-01

    Large quantity of free-standing ZnO nanorods and nanowalls were synthesized at low temperature of below 100 degrees C using zinc acetate, zinc nitrate hexahydrate, and hexamethylenetetramine by using a simple aqueous solution method. The general morphology of the grown ZnO nanostructures which include nanorods and nanowalls was strongly influenced by growth conditions. It was found that the grown ZnO nanorods are of a single-crystalline hexagonal structure and preferred c-axis growth orientation. ZnO nanorods were of better crystallinity than ZnO nanowalls, due to the higher growth temperature used to grow ZnO nanorods. Strong free exciton emission bands with relatively weak deep level emission were clearly observed from ZnO nanorods and nanowalls, indicating their good optical properties.

  6. Recombination luminescence and trap levels in undoped and Al-doped ZnO thin films on quartz and GaSe (0 0 0 1) substrates

    SciTech Connect

    Evtodiev, I.; Caraman, I.; Leontie, L.; Rusu, D.-I.; Dafinei, A.; Nedeff, V.; Lazar, G.

    2012-03-15

    Highlights: Black-Right-Pointing-Pointer ZnO films on GaSe create electron trapping states and PL recombination levels. Black-Right-Pointing-Pointer Zn and Al diffusion in GaSe produces low-energy widening of its PL emission. Black-Right-Pointing-Pointer ZnO:Al films on GaSe lamellas are suitable for gas-discharge lamp applications. -- Abstract: Photoluminescence spectra of ZnO and ZnO:Al (1.00, 2.00 and 5.00 at.%) films on GaSe (0 0 0 1) lamellas and amorphous quartz substrates, obtained by annealing, at 700 K, of undoped and Al-doped metal films, are investigated. For all samples, the nonequilibrium charge carriers recombine by radiative band-to-band transitions with energy of 3.27 eV, via recombination levels created by the monoionized oxygen atoms, forming the impurity band laying in the region 2.00 - 2.70 eV. Al doping induces an additional recombination level at 1.13 eV above the top of the valence band of ZnO films on GaSe substrates. As a result of thermal diffusion of Zn and Al into the GaSe interface layer from ZnO:Al/GaSe heterojunction, electron trap levels located at 0.22 eV and 0.26 eV below the conduction band edge of GaSe, as well as a deep recombination level, responsible for the luminescent emission in the region 1.10 - 1.40 eV, are created.

  7. Seed-mediated growth of ZnO nanorods on multiwalled carbon nanotubes.

    PubMed

    Li, Changqing; Jin, Zhong; Chu, Haibin; Li, Yan

    2008-09-01

    The heterostructures of ZnO nanorods on multiwalled carbon nanotubes (MWNTs) were fabricated by a seed-mediated growth method. First, the surfaces of the carbon nanotubes (CNTs) were coated in situ with mono-dispersed ZnO nanocrystals of about 7 nm by the reaction of zinc acetate and sodium hydroxide. These nanocrystals were then served as the seeds for further growth of ZnO nanorods. In the second step, ZnO nanorods were grown on MWNTs coated with ZnO nanocrystals in an aqueous solution of zinc nitrate and equimolar hexamethylenetetramine at 85 degrees C. Typically, the ZnO nanorods had the length of 300-600 nm and the diameter of 40-140 nm and took a random direction on the outside walls of MWNTs. The morphology of the ZnO nanorods was dependent on pH, reactant concentration, and growing time.

  8. Micro/Nano hierarchical peony-like Al doped ZnO superhydrophobic film: The guiding effect of (100) preferred seed layer

    PubMed Central

    Li, Yang; Wang, Jingfeng; Kong, Yi; Zhou, Jia; Wu, Jinzhu; Wang, Gang; Bi, Hai; Wu, Xiaohong; Qin, Wei; Li, Qingkun

    2016-01-01

    In this communication, we present a versatile and controllable strategy for formation of superhydrophobic micro/nano hierarchical Al doped ZnO (AZO) films with a water contact angle (CA) of 170 ± 4°. This strategy involves a two-step layer-by-layer process employing an atomic layer deposition (ALD) technique followed by a hydrothermal method, and the resulting novel AZO surface layer consists of (100) dominant nano-rice-like AZO seed layer (the water CA of 110 ± 4°) covered with micro-peony-like AZO top. The growth mechanisms and superhydrophobic properties of the hierarchical AZO layer are discussed. It is believed that the present route holds promise for future success in the design and development of practical superhydrophobic materials. PMID:26753877

  9. Investigation of the biaxial stress of Al-doped ZnO thin films on a flexible substrate with RF magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Huang, Kuo-Ting; Chen, Hsi-Chao; Cheng, Po-Wei; Chang, Jhe-Ming

    2016-01-01

    Transparent conductive Al-doped ZnO (AZO) thin films were deposited onto poly(ethylene terephthalate) (PET) substrate, using the radio frequency (RF) magnetron sputtering method. The residual stress of flexible electronics was investigated by a double beam shadow moiré interferometer with phase shifting interferometry (PSI). Moreover, the biaxial stress of AZO thin films can be graphically represented by using Mohr’s circle of stress. The residual stress of AZO thin films becomes more compressive with the increase in sputtering power. The maximum residual stress is -1115.74 MPa, and the shearing stress is 490.57 MPa at a sputtering power of 200 W. The trends of residual stress were evidenced by the X-ray diffraction (XRD) patterns and optical properties of AZO thin films. According to the evaluation results of the refractive index and the extinction coefficient, the AZO thin films have better quality when the sputtering power less than 100 W.

  10. Spatial distribution of electrical properties for Al-doped ZnO films deposited by dc magnetron sputtering using various inert gases

    SciTech Connect

    Sato, Yasushi; Ishihara, Keita; Oka, Nobuto; Shigesato, Yuzo

    2010-07-15

    Spatial distribution of electrical properties of Al-doped ZnO (AZO) films deposited by magnetron sputtering was investigated. To adjust the intensity of bombardment by high-energy particles, the AZO films were deposited using Ar, Kr, or Xe gas with varying plasma impedance. The spatial distribution of the electrical properties clearly depends on the sputtering gas. In the case of using Kr or Xe, the resistivity of the films in front of the target center and erosion areas was significantly enhanced, in contrast with Ar. This was attributed to an enhancement in bombardment damage due to the increased sputtering voltages required for Kr or Xe discharges. The increase in plasma impedance was due to the smaller coefficients for secondary-electron emission of the target surface by Kr or Xe impingements, which leads to the larger sputtering voltage.

  11. Micro/Nano hierarchical peony-like Al doped ZnO superhydrophobic film: The guiding effect of (100) preferred seed layer

    NASA Astrophysics Data System (ADS)

    Li, Yang; Wang, Jingfeng; Kong, Yi; Zhou, Jia; Wu, Jinzhu; Wang, Gang; Bi, Hai; Wu, Xiaohong; Qin, Wei; Li, Qingkun

    2016-01-01

    In this communication, we present a versatile and controllable strategy for formation of superhydrophobic micro/nano hierarchical Al doped ZnO (AZO) films with a water contact angle (CA) of 170 ± 4°. This strategy involves a two-step layer-by-layer process employing an atomic layer deposition (ALD) technique followed by a hydrothermal method, and the resulting novel AZO surface layer consists of (100) dominant nano-rice-like AZO seed layer (the water CA of 110 ± 4°) covered with micro-peony-like AZO top. The growth mechanisms and superhydrophobic properties of the hierarchical AZO layer are discussed. It is believed that the present route holds promise for future success in the design and development of practical superhydrophobic materials.

  12. Mechanisms of lighting enhancement of Al nanoclusters-embedded Al-doped ZnO film in GaN-based light-emitting diodes

    SciTech Connect

    Lee, Hsin-Ying; Chou, Ying-Hung; Lee, Ching-Ting

    2010-01-15

    Aluminum (Al)-doped ZnO (AZO) films with embedded Al nanoclusters were proposed and utilized to enhance the light output power and maximum operation current of GaN-based light-emitting diodes (LEDs). The AZO films were sputtered using ZnO and Al targets in a magnetron cosputtering system. With Al dc power of 7 W and ZnO 100 W ac power, the electron concentration of 4.1x10{sup 20} cm{sup -3}, electron mobility of 16.2 cm{sup 2}/V s, and resistivity of 7.2x10{sup -4} {Omega} cm were obtained for the deposited AZO film annealed at 600 deg. C for 1 min in a N{sub 2} ambient. As verified by a high resolution transmission electron microscopy, the deposited AZO films with embedded Al nanoclusters were clearly observed. A 35% increase in light output power of the GaN-based LEDs with Al nanoclusters-embedded AZO films was realized compared with the conventional LEDs operated at 500 mA. It was verified experimentally that the various characteristics of GaN-based LEDs including the antireflection, light scattering, current spreading, and the light extraction efficiency in light emission could be significantly enhanced with the use of Al nanoclusters-embedded AZO films.

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

    PubMed

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

    2009-06-17

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

  14. Diameter Control and Photoluminescence of ZnO Nanorods from Trialkylamines

    DOE PAGES

    Andelman, Tamar; Gong, Yinyan; Neumark, Gertrude; ...

    2007-01-01

    A novel solution method to control the diameter of ZnO nanorods is reported. Small diameter (2-3 nm) nanorods were synthesized from trihexylamine, and large diameter (50–80 nm) nanorods were synthesized by increasing the alkyl chain length to tridodecylamine. The defect (green) emission of the photoluminescence (PL) spectra of the nanorods varies with diameter, and can thus be controlled by the diameter control. The small ZnO nanorods have strong green emission, while the large diameter nanorods exhibit a remarkably suppressed green band. We show that this observation supports surface oxygen vacancies as the defect that gives rise to the green emission.

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

    PubMed

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

    2016-06-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

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

  17. Electrical stability of Al-doped ZnO transparent electrode prepared by sol-gel method

    NASA Astrophysics Data System (ADS)

    Tabassum, Samia; Yamasue, Eiji; Okumura, Hideyuki; Ishihara, Keiichi N.

    2016-07-01

    Al-doped zinc oxide (AZO) thin films have been considered as a promising alternative to tin doped indium oxide (ITO), which is currently used in various optoelectronic applications. However, the environmental stability of AZO film is not satisfactory, in that the resistivity is significantly increases in air. Here, we investigate the resistivity stability of AZO thin films prepared by sol-gel method using various annealing temperatures and durations. The degradation of resistivity property was observed for AZO films stored in ambient or damp heat environment, where the degradation rate was influenced by annealing temperature. A significant improvement of electrical stability was attained in AZO films that were prepared at high annealing temperature. The films, which showed the highest and the lowest increasing rate of resistivity, were further characterized in detail to shed light on the possible mechanisms explaining the improved stability through crystallinity, surface morphology and elemental state of the thin film.

  18. Photoluminescence of spray pyrolysis deposited ZnO nanorods

    PubMed Central

    2011-01-01

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

  19. Photoluminescence of spray pyrolysis deposited ZnO nanorods

    NASA Astrophysics Data System (ADS)

    Kärber, Erki; Raadik, Taavi; Dedova, Tatjana; Krustok, Jüri; Mere, Arvo; Mikli, Valdek; Krunks, Malle

    2011-04-01

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

  20. Photoluminescence of spray pyrolysis deposited ZnO nanorods.

    PubMed

    Kärber, Erki; Raadik, Taavi; Dedova, Tatjana; Krustok, Jüri; Mere, Arvo; Mikli, Valdek; Krunks, Malle

    2011-04-21

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

  1. Thickness Effect of Al-Doped ZnO Window Layer on Damp Heat Stability of CuInGaSe2 Solar Cells: Preprint

    SciTech Connect

    Pern, F. J.; Mansfield, L.; DeHart, C.; Glick, S. H.; Yan, F.; Noufi, R.

    2011-07-01

    We investigated the damp heat (DH) stability of CuInGaSe2 (CIGS) solar cells as a function of thickness of the Al-doped ZnO (AZO) window layer from the 'standard' 0.12 μm to a modest 0.50 μm over an underlying 0.10-μm intrinsic ZnO buffer layer. The CIGS cells were prepared with external electrical contact using fine Au wire to the tiny 'standard' Ni/Al (0.05 μm/3 μm) metal grid contact pads. Bare cell coupons and sample sets encapsulated in a specially designed, Al-frame test structure with an opening for moisture ingress control using a TPT backsheet were exposed to DH at 85oC and 85% relative humidity, and characterized by current-voltage (I-V), quantum efficiency (QE), and (electrochemical) impedance spectroscopy (ECIS). The results show that bare cells exhibited rapid degradation within 50-100 h, accompanied by film wrinkling and delamination and corrosion of Mo and AlNi grid, regardless of AZO thickness. In contrast, the encapsulated cells did not show film wrinkling, delamination, and Mo corrosion after 168 h DH exposure; but the trend of efficiency degradation rate showed a weak correlation to the AZO thickness.

  2. Polymer solar cells with efficiency >10% enabled via a facile solution-processed Al-doped ZnO electron transporting layer (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Jagadamma, Lethy K.; Al-Senani, Mohammed; Amassian, Aram

    2015-10-01

    The present work details a facile and low-temperature (125C) solution-processed Al-doped ZnO (AZO) buffer layer functioning very effectively as electron accepting/hole blocking layer for a wide range of polymer:fullerene bulk heterojunction systems, and yielding power conversion efficiency in excess of 10% (8%) on glass (plastic) substrates. We show that ammonia addition to the aqueous AZO nanoparticle solution is a critically important step toward producing compact and smooth thin films which partially retain the aluminum doping and crystalline order of the starting AZO nanocrystals. The ammonia treatment appears to reduce the native defects via nitrogen incorporation, making the AZO film a very good electron transporter and energetically matched with the fullerene acceptor. Importantly, highly efficient solar cells are achieved without the need for additional surface chemical passivation or modification, which has become an increasingly common route to improving the performance of evaporated or solution-processed ZnO ETLs in solar cells.

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

    PubMed

    Nomoto, Junichi; Makino, Hisao; Yamamoto, Tetsuya

    2016-12-01

    Five hundred-nanometer-thick ZnO-based textured polycrystalline films consisting of 490-nm-thick Al-doped ZnO (AZO) films deposited on 10-nm-thick Ga-doped ZnO (GZO) films exhibited a high Hall mobility (μ H) of 50.1 cm(2)/Vs with a carrier concentration (N) of 2.55 × 10(20) cm(-3). Firstly, the GZO films were prepared on glass substrates by ion plating with dc arc discharge, and the AZO films were then deposited on the GZO films by direct current magnetron sputtering (DC-MS). The GZO interface layers with a preferential c-axis orientation play a critical role in producing AZO films with texture development of a well-defined (0001) orientation, whereas 500-nm-thick AZO films deposited by only DC-MS showed a mixture of the c-plane and the other plane orientation, to exhibit a μ H of 38.7 cm(2)/Vs with an N of 2.22 × 10(20) cm(-3).

  4. Biaxial stress and optoelectronic properties of Al-doped ZnO thin films deposited on flexible substrates by radio frequency magnetron sputtering.

    PubMed

    Chen, Hsi-Chao; Cheng, Po-Wei; Huang, Kuo-Ting

    2017-02-01

    Transparent conductive Al-doped ZnO (AZO) thin films were deposited on polyethylene terephthalate (PET) and polycarbonate (PC) substrates using radio frequency (RF) magnetron sputtering. The biaxial stress was measured with a double beam shadow moiré interferometer, and x-ray diffraction (XRD) was used to investigate the crystal orientation of ZnO. The substrate temperature was varied from room temperature to 150°C in steps of 25°C. The experimental results showed that the residual and shearing stresses increased with the increase in substrate temperature. The residual stress can be separated into principle and shearing stresses by Mohr's circle rule, and the shearing stress (tensile stress) was different from the compressive stress of the residual stress. However, the optimal substrate temperatures for PET and PC were 75°C and 100°C, and the shearing stresses were 424.82 and 543.68 MPa, respectively. AZO/PET and AZO/PC thin films cracked at substrate temperatures of 75°C and 100°C, respectively. AZO/PET thin film at a substrate temperature of 100°C had a resistivity low to the order of 10-3  Ω-cm.

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

    NASA Astrophysics Data System (ADS)

    Nomoto, Junichi; Makino, Hisao; Yamamoto, Tetsuya

    2016-06-01

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

  6. Enhanced Photoluminescence in Acetylene-Treated ZnO Nanorods.

    PubMed

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

    2016-12-01

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

  7. UV light sensing properties of Sm doped vertically aligned ZnO nanorod arrays

    SciTech Connect

    Kumar, D. Ranjith; Ranjith, K. S.; Rajendrakumar, R. T.

    2015-06-24

    Samarium doped ZnO nanorods were grown on silicon substrate by using vapor phase transport method (VPT) with the growth temperature of 950°C. The synthesized nanorods were characterized by XRD, field emission scanning electron microscopy, Raman spectra, and photocurrent measurements. The XRD result revealed that Sm was successfully doped into lattice plane of hexagonal ZnO nanorods. The FESEM result confirms the pure ZnO has nanorod like morphology with an average diameter and length of 130nm and 10µm respectively. The above observation is supported by the Micro-Raman spectroscopy result. The photocurrent in the visible region has been significantly enhanced due to deposition of Sm on the surface of the ZnO nanorods. Sm acts as a visible sensitizer because of its lower band gap compared to ZnO.

  8. Highly efficient yttrium-doped ZnO nanorods for quantum dot-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Kim, Soo-Kyoung; Gopi, Chandu V. V. M.; Srinivasa Rao, S.; Punnoose, Dinah; Kim, Hee-Je

    2016-03-01

    Yttrium-doped ZnO nanorod arrays were applied to photoanodes of quantum dot-sensitized solar cells (QDSCs). The introduction of yttrium to ZnO nanostructures facilitates the growth of ZnO nanorods and increases the amount of QD deposition with a large surface area. Furthermore, lower electrical resistance and longer electron lifetime were achieved with yttrium-doping owing to fewer defects and trap sites on the surface of yttrium-doped ZnO nanorods. As a result, the conversion efficiency of 3.3% was achieved with the optimized concentration of yttrium.

  9. Catalytic effects of ZnO nanorods grown by sonochemical decomposition of zinc acetate dihydrate.

    PubMed

    Cho, Seok Cheol; Lee, Ho Suk; Sohn, Sang Ho

    2012-07-01

    In this study, we prepared ZnO nanorods by a sonochemical method using a zinc acetate dihydrate as a new precursor. Well-aligned high-quality ZnO nanorods were synthesized on FTO glass by the sonochemical decomposition of zinc acetate dihydrate using a ZnO thin-film as the catalytic layer. The ZnO thin-films were deposited on the FTO glass by a sputtering method. To investigate their catalytic effects on the ZnO nanorods, catalytic ZnO thin-films of 20 nm, 40 nm, and 60 nm thickness were prepared by adjusting the sputtering time. The ZnO nanorods grown on catalytic layers with different thicknesses were characterized by SEM, XRD, and PL. The ZnO nanorods grown on the catalytic layer of 40 nm thickness show the best crystal and spatial orientation and as a result display the best optical properties. It was found that a catalytic ZnO thin-film of 40 nm in thickness yields well-aligned high-quality ZnO nanorods, due to its small surface roughness and structural strain.

  10. Catalyst free growth of ZnO nanorods by thermal evaporation method

    SciTech Connect

    Somvanshi, Divya; Jit, S.

    2013-06-03

    In this work, we report catalyst free growth of ZnO nanorods on n-Si substrate by a low cost thermal evaporation method. The surface morphology, chemical composition and crystalline structure of ZnO nanorods have been determined by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) spectroscopy respectively. It is found that, the as -deposited ZnO seed layer reduces lattice mismatching between ZnO and Si from 40.3 to 0.28%, therefore enhances the subsequent growth and crystalline quality of ZnO nanorods on Si substrate. The present methodology is simple, cost effective and highly applicable for synthesis of ZnO nanorods for optoelectronics applications.

  11. Optical characterization of pure and Al-doped ZnO prepared by sol-gel method

    NASA Astrophysics Data System (ADS)

    Belka, Radosław; Keczkowska, Justyna; Kasińska, Justyna

    2016-09-01

    In this paper the preparation process and optical characterization of pure and Al3+ doped zinc oxide (Al:ZnO) coatings will be presented. ZnO based materials have been studied extensively due to their potential applications in optoelectronic devices as conductive gas sensors, transparent conductive, electrodes, solar cell windows, varistors, UVfilters or photovoltaic cells. It is II-VI semiconductor with wide-band gap of 3.37 eV and large exciton binding energy of 60meV. It is possible to improve the conductivity of ZnO coating by intentionally doping ZnO with aluminium ions during preparation process. Such transparent and conducting thin films, known as AZO (Aluminium Zinc Oxide) films, are very good candidate for application as transparent conducting materials in many optoelectronic devices. The well-known sol-gel method is used for preparation of solution, coated on glass substrates by dip coating process. Prepared samples were investigated by Raman and UV-VIS spectroscopy. Transmittance as well as specular and diffuse reflectance spectroscopy methods were used for studies of optical parameters. We found that Al admixture influences on optical bandgap of ZnO.

  12. Electronic structure of Co-doped ZnO nanorods

    NASA Astrophysics Data System (ADS)

    Neffati, Ahmed; Souissi, Hajer; Kammoun, Souha

    2012-10-01

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

  13. Controllable growth of ZnO nanorod arrays with different densities and their photoelectric properties

    PubMed Central

    2012-01-01

    Since the photoelectric response and charge carriers transport can be influenced greatly by the density and spacing of the ZnO nanorod arrays, controlling of these geometric parameters precisely is highly desirable but rather challenging in practice. Here, we fabricated patterned ZnO nanorod arrays with different densities and spacing distances on silicon (Si) substrate by electron beam lithography (EBL) method combined with the subsequent hydrothermal reaction process. By using the EBL method, patterned ZnO seed layers with different areas and spacing distances were obtained firstly. ZnO nanorod arrays with different densities and various morphologies were obtained by the subsequent hydrothermal growth process. The combination of EBL and hydrothermal growth process was very attractive and could make us control the geometric parameters of ZnO nanorod arrays expediently. Finally, the vertical transport properties of the patterned ZnO nanorod arrays were investigated through the microprobe station equipment, and the I-V measurement results indicated that the back-to-back Schottky contacts with different barrier heights were formed in dark conditions. Under UV light illumination, the patterned ZnO nanorod arrays showed a high UV light sensitivity, and the response ratio was about 104. The controllable fabrication of patterned ZnO nanorod arrays and understanding their photoelectric transport properties were helpful to improve the performance of nanodevices based on them. PMID:22559262

  14. Bi-layer channel structure-based oxide thin-film transistors consisting of ZnO and Al-doped ZnO with different Al compositions and stacking sequences

    NASA Astrophysics Data System (ADS)

    Cho, Sung Woon; Yun, Myeong Gu; Ahn, Cheol Hyoun; Kim, So Hee; Cho, Hyung Koun

    2015-03-01

    Zinc oxide (ZnO)-based bi-layers, consisting of ZnO and Al-doped ZnO (AZO) layers grown by atomic layer deposition, were utilized as the channels of oxide thin-film transistors (TFTs). Thin AZO layers (5 nm) with different Al compositions (5 and 14 at. %) were deposited on top of and beneath the ZnO layers in a bi-layer channel structure. All of the bi-layer channel TFTs that included the AZO layers showed enhanced stability (Δ V Th ≤ 3.2 V) under a positive bias stress compared to the ZnO single-layer channel TFT (Δ V Th = 4.0 V). However, the AZO/ZnO bi-layer channel TFTs with an AZO interlayer between the gate dielectric and the ZnO showed a degraded field effect mobility (0.3 cm2/V·s for 5 at. % and 1.8 cm2/V·s for 14 at. %) compared to the ZnO single-layer channel TFT (5.5 cm2/V·s) due to increased scattering caused by Al-related impurities near the gate dielectric/channel interface. In contrast, the ZnO/AZO bi-layer channel TFTs with an AZO layer on top of the ZnO layer exhibited an improved field effect mobility (7.8 cm2/V·s for 14 at. %) and better stability. [Figure not available: see fulltext.

  15. Hydrothermal synthesis of ZnO nanorod arrays for photocatalytic inactivation of bacteria

    NASA Astrophysics Data System (ADS)

    Akhavan, O.; Mehrabian, M.; Mirabbaszadeh, K.; Azimirad, R.

    2009-11-01

    Arrays of ZnO nanorods were synthesized on ZnO seed layer/glass substrates by a hydrothermal method at a low temperature of 70 °C. The effect of pH > 7 of the hydrated zinc nitrate-NaOH precursor on the morphology and topography (e.g. size, surface area and roughness), the optical characteristics (e.g. optical transmission and band-gap energy), hydrophilicity and antibacterial activity of the grown ZnO nanostructure and nanorod coatings were investigated. For pH = 11.33 of the precursor (NaOH concentration of 0.10M), a fast growth of ZnO nanorods on the seed layer (length of ~1 µm in 1.5 h) was observed. The fast growth of the ZnO nanorods resulted in a significant reduction in the optical band-gap energy of the nanorod coating, which was attributed to the formation of more defects in the nanorods during their fast growth. The surface of the ZnO nanorod arrays was relatively hydrophilic (with a water contact angle of 16°) even after the subtraction of their surface roughness effect (with a contact angle of ca 27°). This hydrophilicity of the ZnO nanorods was assigned to the observed surface OH bonds. These characteristics caused the ZnO nanorod arrays to show an excellent UV-induced photocatalytic degradation of Escherichia coli bacteria. Furthermore, the synthesized ZnO nanorods were found to be strong photo-induced antibacterial material, even without considering their high surface area ratio.

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

    NASA Astrophysics Data System (ADS)

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

    2012-11-01

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

  17. Growth of well-aligned ZnO nanorods using auge catalyst by vapor phase transportation.

    PubMed

    Ha, S Y; Jung, M N; Park, S H; Ko, H J; Ko, H; Oh, D C; Yao, T; Chang, J H

    2006-11-01

    Well-aligned ZnO nanorods have been achieved using new alloy (AuGe) catalyst. Zn powder was used as a source material and it was transported in a horizontal tube furnace onto an AuGe deposited Si substrates. The structural and optical properties of ZnO nanorods were characterized by scanning electron microscopy, high resolution X-ray diffraction, and photoluminescence. ZnO nanorods grown at 650 degrees C on 53 nm thick AuGe layer show uniform shape with the length of 8 +/- 0.5 microm and the diameter of 150 +/- 5 nm. Also, the tilting angle of ZnO nanorods (+/- 5.5 degrees) is confirmed by HRXRD. High structural quality of the nanorods is conformed by the photoluminescence measurement. All samples show strong UV emission without considerable deep level emission. However, weak deep level emission appears at high (700 degrees C) temperature due to the increase of oxygen desertion.

  18. Characteristics of Ga-Al doped ZnO thin films with plasma treatment prepared by using facing target sputtering method.

    PubMed

    Kim, Ki Hyun; Choi, Hyung Wook; Kim, Kyung Hwan

    2013-09-01

    Ga-Al-doped ZnO (GAZO) thin films were prepared on glass substrates using facing targets sputtering at room temperature. GAZO thin films have been treated in O2 plasma to modify surface roughness in order to enhance the efficiency of OLED anodes made from the films. After deposition of the thin films, the substrate was subjected to plasma surface treatment. The electrical, optical, and surface properties of the deposited thin films were investigated by hall-effect measurement, UV/Vis spectrometry, and atomic force microscopy (AFM), respectively. As a result of increasing the plasma treatment time from 0 to 45 sec, the surface roughness of films after plasma treatment was improved, but their electrical, optical, and structural properties were slightly changed. The lowest values of the surface roughness were 1.409 nm for the as-deposited GAZO thin films for an O2 plasma treatment time of 40 sec. All GAZO thin films have an average transmittance of 90% in the visible range (400-800 nm).

  19. Transparent conducting Al-doped ZnO thin films prepared by magnetron sputtering with dc and rf powers applied in combination

    SciTech Connect

    Minami, Tadatsugu; Ohtani, Yuusuke; Miyata, Toshihiro; Kuboi, Takeshi

    2007-07-15

    A newly developed Al-doped ZnO (AZO) thin-film magnetron-sputtering deposition technique that decreases resistivity, improves resistivity distribution, and produces high-rate depositions has been demonstrated by dc magnetron-sputtering depositions that incorporate rf power (dc+rf-MS), either with or without the introduction of H{sub 2} gas into the deposition chamber. The dc+rf-MS preparations were carried out in a pure Ar or an Ar+H{sub 2} (0%-2%) gas atmosphere at a pressure of 0.4 Pa by adding a rf component (13.56 MHz) to a constant dc power of 80 W. The deposition rate in a dc+rf-MS deposition incorporating a rf power of 150 W was approximately 62 nm/min, an increase from the approximately 35 nm/min observed in dc magnetron sputtering with a dc power of 80 W. A resistivity as low as 3x10{sup -4} {omega} cm and an improved resistivity distribution could be obtained in AZO thin films deposited on substrates at a low temperature of 150 deg. C by dc+rf-MS with the introduction of hydrogen gas with a content of 1.5%. This article describes the effects of adding a rf power component (i.e., dc+rf-MS deposition) as well as introducing H{sub 2} gas into dc magnetron-sputtering preparations of transparent conducting AZO thin films.

  20. In situ spectroscopic ellipsometry growth studies on the Al-doped ZnO films deposited by remote plasma-enhanced metalorganic chemical vapor deposition

    SciTech Connect

    Volintiru, I.; Creatore, M.; Sanden, M. C. M. van de

    2008-02-01

    In situ spectroscopic ellipsometry (SE) was applied to study the pyramidlike and pillarlike growth of Al doped ZnO (AZO) films deposited by means of remote plasma-enhanced metalorganic chemical vapor deposition for transparent conductive oxide applications. Real time SE studies in the visible region allowed discerning between the two growth modes by addressing the time evolution of the bulk and surface roughness layer thickness. While the pillarlike mode is characterized by a constant growth rate, a slower rate in the initial stage (up to 150-200 nm film thickness), compared to the bulk, is observed for the growth of pyramidlike AZO films. The two modes differ also in terms of surface roughness development: a saturation behavior is observed for film thickness above 150-200 nm in the case of the pyramidlike films, while a slow linear increase with film thickness characterizes the pillarlike mode. By extending the SE analysis of the AZO films to the near infrared region, valuable information about the in grain properties could be extracted: excellent in grain mobility values, i.e., larger than 100 and 50 cm{sup 2}/V s, are determined for the pyramidlike and pillarlike AZO layers, respectively. The comparison between the outcome of the in situ real time SE studies and the ex situ electrical and chemical characterization highlights the limitations in the electron transport occurring in both types of films and allows one to address routes toward further improvement in AZO conductivity.

  1. Band alignment at the interface between Ni-doped Cr2O3 and Al-doped ZnO: implications for transparent p-n junctions

    NASA Astrophysics Data System (ADS)

    Arca, Elisabetta; McInerney, Michael A.; Shvets, Igor V.

    2016-06-01

    The realization of transparent electronic and optoelectronic devices requires the use of transparent p-n junctions. In this context, understanding the band alignment at the interface between the p- and n-components represents a fundamental step towards the realization of high performance devices. In this work, the band alignment at the interface between Al-doped ZnO (AZO) and Ni-doped Cr2O3 has been analysed. The formation and evolution of the core levels as the interface progressively forms have been followed by means of x-ray Photoelectron Spectroscopy, x-ray diffraction and x-ray reflectivity. A type two (staggered) band alignment was identified, with the valence band offset and conduction band offset found to be 2.6 eV and 2.5 eV, respectively. The electrical behaviour will be discussed in terms of the position of the bands, the presence of band bending and the expected built-in potential and how these can be engineered in order to achieve the maximum performance for this hetero-structure.

  2. Correlations between 1/f noise and thermal treatment of Al-doped ZnO thin films deposited by direct current sputtering

    SciTech Connect

    Barhoumi, A. Guermazi, S.; Leroy, G.; Gest, J.; Carru, J. C.; Yang, L.; Boughzala, H.; Duponchel, B.

    2014-05-28

    Al-doped ZnO thin films (AZO) have been deposited on amorphous glass substrates by DC sputtering at different substrate temperatures T{sub s}. X-Ray diffraction results reveal that AZO thin films have a hexagonal wurtzite structure with (002) preferred orientation. (002) peaks indicate that the crystalline structure of the films is oriented with c-axis perpendicular to the substrate. Three-dimensional (3D) atomic force microscopy images of AZO thin films deposited on glass substrate at 200 °C, 300 °C, and 400 °C, respectively, shows the improvement of the crystallinity and the homogeneity of AZO thin films with T{sub s} which is in agreement with the noise measurements. The noise was characterized between 1 Hz and 100 kHz and we have obtained 1/f spectra. The noise is very sensitive to the crystal structure especially to the orientation of the crystallites which is perpendicular to the substrate and to the grain boundaries which generate a high current flow and a sharp increase in noise. Through time, R{sub sh} and [αμ]{sub eff} increase with the modification of the crystallinity of AZO thin films. Study of noise aging shows that the noise is more sensitive than resistivity for all AZO thin films.

  3. Photoelectrochemical and photosensing behaviors of hydrothermally grown ZnO nanorods

    SciTech Connect

    Majumder, T.; Hmar, J. J. L.; Roy, J. N.; Mondal, S. P. E-mail: suvra.phy@nita.ac.in; Debnath, K.; Gogurla, N.; Ray, S. K.

    2014-07-21

    ZnO nanorods have been grown on indium-tin-oxide coated glass substrates by a low cost chemical process. Current-voltage characteristics have been studied using ZnO nanorods as photoanode in an electrochemical cell. The flat band voltage shift and depletion width of ZnO nanorods/electrolyte interface have been estimated from Mott-Schottky (MS) characteristics. The electrochemical impedance measurements have been carried out to study the charge transport mechanism at the semiconductor-electrolyte interface under dark and white light (100 mW/cm{sup 2}) illumination. The doping concentration of nanorods has been extracted from MS plot. Photoresponse behavior of ZnO nanorods is found to be enhanced than seed layers with the incident of white light. Spectral dependent photovoltage of ZnO nanorods has been carried out using monochromatic light of wavelength 250–600 nm. The photopotential recovery time has been estimated for nanorods and seed layers. The stability of ZnO nanorods as a photoanode has been investigated.

  4. Photoluminescence and field emission of 1D ZnO nanorods fabricated by thermal evaporation

    NASA Astrophysics Data System (ADS)

    Wang, B.; Jin, X.; Ouyang, Z. B.; Xu, P.

    2012-07-01

    Four kinds of new one-dimensional nanostructures, celery-shaped nanorods, needle-shaped nanorods, twist fold-shaped nanorods, and awl-shaped nanorods of ZnO, have been grown on single silicon substrates by an Au catalyst assisted thermal evaporation of ZnO and active carbon powders. The morphology and structure of the prepared nanorods are determined on the basis of field-emission scanning electron microscopy (FESEM) and x-ray diffraction (XRD). The photoluminescence spectra (PL) analysis noted that UV emission band is the band-to-band emission peak and the emission bands in the visible range are attributed to the oxygen vacancies, Zn interstitials, or impurities. The field-emission properties of four kinds of ZnO nanorods have been invested and the awl-shaped nanorods of ZnO have preferable characteristics due to the smallest emitter radius on the nanoscale in the tip in comparison with other nanorods. The growth mechanism of the ZnO nanorods can be explained on the basis of the vapor-liquid-solid (VLS) processes.

  5. Effects of Polyethyleneimine on the Sonochemical Synthesis of Gadolinium Ion-Modified ZnO Nanorods.

    PubMed

    Choi, Seok Cheol; Yun, Won Suk; Sohn, Sang Ho

    2015-01-01

    We prepared gadolinium (Gd) ion-modified ZnO nanorods by a sonochemical decomposition of zinc acetate dehydrate and gadolinium acetate hydrate precursor solutions with and without polyethyleneimine (PEI). We investigated the effects of PEI on the sonochemical synthesis of ZnO nanorods with and without Gd ion modifications. In the case of nascent ZnO nanorods, PEI in the precursor solutions can prohibit radial growth but allow axial growth, resulting in changes in the degree of preferred crystal orientations, and in the PL properties of the resulting nanorods. In the case of Gd ion-modified ZnO nanorods, we observed that the ZnO nanorods, fabricated sonochemically in the precursor solutions with PEI, exhibited a peak broadening of the ZnO(002) crystal plane and decreasing crystal orientation with respect to the c plane. We note that PEI can negatively affect the crystal orientation and crystallinity of Gd ion-modified ZnO nanorods, even though it cannot affect the lattice constant.

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

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

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

  7. Atom probe microscopy of zinc isotopic enrichment in ZnO nanorods

    NASA Astrophysics Data System (ADS)

    Ironside, C. N.; Saxey, D. W.; Rickard, W. D. A.; Gray, C.; McGlynn, E.; Reddy, S. M.; Marks, N. A.

    2017-02-01

    We report on atomic probe microscopy (APM) of isotopically enriched ZnO nanorods that measures the spatial distribution of zinc isotopes in sections of ZnO nanorods for natural abundance natZnO and 64Zn and 66Zn enriched ZnO nanorods. The results demonstrate that APM can accurately quantify isotopic abundances within these nanoscale structures. Therefore the atom probe microscope is a useful tool for characterizing Zn isotopic heterostructures in ZnO. Isotopic heterostructures have been proposed for controlling thermal conductivity and also, combined with neutron transmutation doping, they could be key to a novel technology for producing p-n junctions in ZnO thin films and nanorods.

  8. The Effect of the Oxygen Plasma Treatment for ITO and ZnO Nanorods on the Electroluminescence of ZnO Nanorod/MEH-PPV Heterostructure Devices

    NASA Astrophysics Data System (ADS)

    Zhao, Su-Ling; Wang, Yong-Sheng; Gao, Song; Yang, Yi-Fan; Xu, Zheng

    2013-03-01

    Series devices of ITO/ZnO/ZnO nanorods/MEH-PPV/Al have been fabricated. ITO and ZnO nanorods of some devices are treated by O2 plasma. The electroluminescence of different devices is detected under different biases. UV electroluminescence of ZnO nanorods at 380nm is observed in all the devices. The intensity of 380nm increases when both ITO and ZnO nanorods are treated. The turn-on voltage of the treated device is lower than that of the non-treated device, and the EL power is enhanced. When the thickness of MEH-PPV is sufficiently thin, only 380 nm electroluminescence, besides a weak defect emission at 760 nm, is detected. The enhancement mechanism of the electroluminescence of the treated devices is discussed.

  9. Electronic nose based on multipatterns of ZnO nanorods on a quartz resonator with remote electrodes.

    PubMed

    Ko, Wooree; Jung, Namchul; Lee, Moonchan; Yun, Minhyuk; Jeon, Sangmin

    2013-08-27

    An electrodeless monolithic multichannel quartz crystal microbalance (MQCM) sensor was developed via the direct growth of ZnO nanorod patterns of various sizes onto an electrodeless quartz crystal plate. The patterned ZnO nanorods acted as independent resonators with different frequencies upon exposure to an electric field. The added mass of ZnO nanostructures was found to significantly enhance the quality factor (QF) of the resonator in electrodeless QCM configuration. The QF increased with the length of the ZnO nanorods; ZnO nanorods 5 μm in length yielded a 7-fold higher QF compared to the QF of a quartz plate without ZnO nanorods. In addition, the ZnO nanorods offered enhanced sensitivity due to the enlarged sensing area. The developed sensor was used as an electronic nose for detection of vapor mixtures with impurities.

  10. Reversible Change in Electrical and Optical Properties in Epitaxially Grown Al-Doped ZnO Thin Films

    SciTech Connect

    Noh, J. H.; Jung, H. S.; Lee, J. K.; Kim, J. Y; Cho, C. M.; An, J.; Hong, K. S.

    2008-01-01

    Aluminum-doped ZnO (AZO) films were epitaxially grown on sapphire (0001) substrates using pulsed laser deposition. As-deposited AZO films had a low resistivity of 8.01 x 10{sup -4} {Omega} cm. However, after annealing at 450 C in air, the electrical resistivity of the AZO films increased to 1.97 x 10{sup -1} {Omega} cm because of a decrease in the carrier concentration. Subsequent annealing of the air-annealed AZO films in H{sub 2} recovered the electrical conductivity of the AZO films. In addition, the conductivity change was reversible upon repeated air and H{sub 2} annealing. A photoluminescence study showed that oxygen interstitial (O{sub i}) is a critical material parameter allowing for the reversible control of the electrical conducting properties of AZO films.

  11. Enhanced Performance in Al-Doped ZnO Based Transparent Flexible Transparent Thin-Film Transistors Due to Oxygen Vacancy in ZnO Film with Zn-Al-O Interfaces Fabricated by Atomic Layer Deposition.

    PubMed

    Li, Yang; Yao, Rui; Wang, Huanhuan; Wu, Xiaoming; Wu, Jinzhu; Wu, Xiaohong; Qin, Wei

    2017-04-05

    Highly conductive and optical transparent Al-doped ZnO (AZO) thin film composed of ZnO with a Zn-Al-O interface was fabricated by thermal atomic layer deposition (ALD) method. The as-prepared AZO thin film exhibits excellent electrical and optical properties with high stability and compatibility with temperature-sensitive flexible photoelectronic devices; film resistivity is as low as 5.7 × 10(-4) Ω·cm, the carrier concentration is high up to 2.2 × 10(21) cm(-3). optical transparency is greater than 80% in a visible range, and the growth temperature is below 150 °C on the PEN substrate. Compared with the conventional AZO film containing by a ZnO-Al2O3 interface, we propose that the underlying mechanism of the enhanced electrical conductivity for the current AZO thin film is attributed to the oxygen vacancies deficiency derived from the free competitive growth mode of Zn-O and Al-O bonds in the Zn-Al-O interface. The flexible transparent transistor based on this AZO electrode exhibits a favorable threshold voltage and Ion/Ioff ratio, showing promising for use in high-resolution, fully transparent, and flexible display applications.

  12. Tuning the emission of ZnO nanorods based light emitting diodes using Ag doping

    NASA Astrophysics Data System (ADS)

    Echresh, Ahmad; Chey, Chan Oeurn; Shoushtari, Morteza Zargar; Nur, Omer; Willander, Magnus

    2014-11-01

    We have fabricated, characterized, and compared ZnO nanorods/p-GaN and n-Zn0.94Ag0.06O nanorods/p-GaN light emitting diodes (LEDs). Current-voltage measurement showed an obvious rectifying behaviour of both LEDs. A reduction of the optical band gap of the Zn0.94Ag0.06O nanorods compared to pure ZnO nanorods was observed. This reduction leads to decrease the valence band offset at n-Zn0.94Ag0.06O nanorods/p-GaN interface compared to n-ZnO nanorods/p-GaN heterojunction. Consequently, this reduction leads to increase the hole injection from the GaN to the ZnO. From electroluminescence measurement, white light was observed for the n-Zn0.94Ag0.06O nanorods/p-GaN heterojunction LEDs under forward bias, while for the reverse bias, blue light was observed. While for the n-ZnO nanorods/p-GaN blue light dominated the emission in both forward and reverse biases. Further, the LEDs exhibited a high sensitivity in responding to UV illumination. The results presented here indicate that doping ZnO nanorods might pave the way to tune the light emission from n-ZnO/p-GaN LEDs.

  13. Novel Biomimatic Synthesis of ZnO Nanorods Using Egg White (Albumen) and Their Antibacterial Studies.

    PubMed

    Ahmed, Faheem; Arshi, Nishat; Jeong, Yeong Seung; Anwar, M S; Dwivedi, Saurabh; Alsharaeh, Edreese; Koo, B H

    2016-06-01

    Zinc oxide (ZnO) is well-recognized as a biocompatible multifunctional material with outstanding properties as well as low toxicity and biodegradability. In this work, a simple and versatile technique was developed to prepare highly crystalline ZnO nanorods by introducing egg white to a bio-inspired approach. X-ray diffraction (XRD) and selected area electron diffraction (SAED) pattern results indicated that the ZnO nanorods have single phase nature with the wurtzite structure. Field emission scanning electron microscopy (FESEM) and Transmission electron microscopy (TEM) results showed the nanometer dimension of the nanorods. Raman, FTIR, and TGA/DTA analyses revealed the formation of wurtzite ZnO. The antibacterial properties of ZnO nanorods were investigated using both Gram-positive and Gram-negative microorganisms. These studies demonstrate that ZnO nanorods have a wide range of antibacterial activities toward various microorganisms that are commonly found in environmental settings. Survival ratio of bacteria decreased with increasing powder concentration, i.e., increase in antibacterial activity. The antibacterial activity of the ZnO nanorods toward Pseudomonas aeruginosa was stronger than that of Escherichia coli and Staphylococcus aureus. Surprisingly, the antibacterial activity did not require specific UV activation using artificial lamps, rather activation was achieved under ambient lighting conditions. Overall, the experimental results suggest that ZnO nanorods could be developed as antibacterial agents against a wide range of microorganisms to control and prevent the spreading and persistence of bacterial infections. This research introduces a new concept to synthesize ZnO nanorods by using egg white as a biological template for various applications including food science, animal science, biochemistry, microbiology and medicine.

  14. Hexagonal ZnO nanorods assembled flowers for photocatalytic dye degradation: Growth, structural and optical properties

    NASA Astrophysics Data System (ADS)

    Rahman, Qazi Inamur; Ahmad, Musheer; Misra, Sunil Kumar; Lohani, Minaxi B.

    2013-12-01

    A facile hydrothermal method was used to synthesize highly crystalline hexagonal ZnO nanorods assembled flowers by the reaction of zinc acetate and hexamethylenetetraamine (HMTA) at 105 °C. The morphological characterizations revealed that well defined ZnO nanorods were assembled into flowers morphology. X-rays diffraction patterns showed the highly crystalline nature of ZnO with hexagonal wurtzite structure. The structural and optical properties of hexagonal ZnO nanorods assembled flowers were measured by Fourier transform infra-red (FT-IR) and ultraviolet-visible (UV-Vis) measurements. The as-synthesized hexagonal ZnO nanorods assembled flowers were applied as an efficient photocatalyst for the photodegradation of organic dyes under UV-light irradiation. The methylene blue (MB) and rhodamine B (RhB) over the surface of hexagonal ZnO nanorods assembled flowers considerably degraded by ∼91% and ∼80% within 140 min respectively. The degradation rate constants were found to be kapp (0.01313 mint-1) and kapp(0.0104 mint-1) for MB and RhB dye respectively. The enhanced dye degradation might be attributed to the efficient charge separation and the large number of oxyradicals generation on the surface of the hexagonal ZnO nanorods assembled flowers.

  15. Room Temperature Growth of Al-Doped ZnO Thin Films by Reactive DC Sputtering Technique with Metallic Target

    NASA Astrophysics Data System (ADS)

    Hasuike, Noriyuki; Nishio, Koji; Kisoda, Kenji; Harima, Hiroshi

    2013-01-01

    We prepared Al-deopd ZnO (AZO) films by reactive DC sputtering method using metallic target at room temperature. All the tested AZO films (0<[Al]<8.9%) with the transmittance above 85% in visible region were successfully grown on quartz substrate. All the AZO films have wurtzite structure with no impurity phase. The AZO films with [Al]<2.9% have the preferential orientation in c-axis direction, and the orientation became indistinct as increasing in Al content. In the optical measurement, the absorption edge was shifted from 3.30 to 3.66 eV due to Burstein-Moss effect, and the electron densities were roughly estimated at 2.5×1019 to 1.5×1021 cm-3, respectively. On the other hand, the high transmittance in infrared region suggested low electron mobility. Since this gives rise to the high electric resistivity, the further improvements and optimization of the growth conditions are required for the realization of AZO based transparent conductive.

  16. Electrodeposition of ZnO Nanorods in the Presence of Metal Ions

    SciTech Connect

    Seipel, Bjoern; Athavan, Nadarajah; Wutzke, Ben; Koenenkamp, Rolf F.

    2009-04-15

    We report on structural and optical changes induced by impurity incorporation in ZnO nanorods grown via electrodeposition. We find the lattice parameters of the hexagonal ZnO rods to be larger than in defect-free single-crystalline ZnO. SIMS measurements indicate impurity incorporation and doping in the bulk of the nanorods. The impurity content correlates with changes in the electroluminescence spectra. The maximum of the defect luminescence band around 600 nm shifts towards longer wavelengths with metal incorporation. Aluminum incorporation leads to a narrow luminescence band close by the bandgap of ZnO around 390 nm.

  17. Room temperature ferromagnetism in undoped and Fe doped ZnO nanorods: Microwave-assisted synthesis

    SciTech Connect

    Limaye, Mukta V.; Singh, Shashi B.; Das, Raja; Poddar, Pankaj; Kulkarni, Sulabha K.

    2011-02-15

    One-dimensional (1D) undoped and Fe doped ZnO nanorods of average length {approx}1 {mu}m and diameter {approx}50 nm have been obtained using a microwave-assisted synthesis. The magnetization (M) and coercivity (H{sub c}) value obtained for undoped ZnO nanorods at room temperature is {approx}5x10{sup -3} emu/g and {approx}150 Oe, respectively. The Fe doped ZnO samples show significant changes in M -H loop with increasing doping concentration. Both undoped and Fe doped ZnO nanorods exhibit a Curie transition temperature (T{sub c}) above 390 K. Electron spin resonance and Moessbauer spectra indicate the presence of ferric ions. The origin of ferromagnetism in undoped ZnO nanorods is attributed to localized electron spin moments resulting from surface defects/vacancies, where as in Fe doped samples is explained by F center exchange mechanism. -- Graphical abstract: Room temperature ferromagnetism has been reported in undoped and Fe doped ZnO nanorods of average length {approx}1 {mu}m and diameter {approx}50 nm. Display Omitted Research Highlights: {yields} Microwave-assisted synthesis of undoped and Fe doped ZnO nanorods. {yields} Observation of room temperature ferromagnetism in undoped and Fe doped ZnO nanorods. {yields} Transition temperature (T{sub c}) obtained in undoped and doped samples is above 390 K. {yields} In undoped ZnO origin of ferromagnetism is explained in terms of defects/vacancies. {yields} Ferromagnetism in Fe doped ZnO is explained by F-center exchange mechanism.

  18. Hydrothermally grown ZnO nanorods on self-source substrate and their field emission

    NASA Astrophysics Data System (ADS)

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

    2007-04-01

    Vertically aligned zinc oxide nanorod arrays were grown directly using a zinc foil as both source and substrate in pure water at low temperature by a simple hydrothermal reaction. The morphology and crystal structure of the ZnO nanorod arrays were examined by scanning electron microscopy, transmission electron microscopy and x-ray diffraction, respectively. The nanorods grew along the [0 0 0 1] direction and were 80 nm in diameter and almost 2 µm in length. Directly employing the zinc foil substrate as cathode, the field emission (FE) of the ZnO nanorods presented a two-stage slope behaviour in a ln(J/E2)-1/E plot according to the Fowler-Nordheim equation. The FE behaviour was investigated by considering the action of the defects in ZnO nanorods based on the measurement of the photoluminescence.

  19. Selective growth of ZnO nanorods on hydrophobic Si nanorod arrays.

    PubMed

    Lu, Ming-Yen; Wang, Ying-Jhe; Hong, Meng-Hsiang; Chiu, Cheng-Yao; You, Shuen-Jium; Lu, Ming-Pei

    2015-02-06

    In this paper we describe the selective growth of ZnO nanorods (NRs) on top of hydrophobic Si NR arrays. The periodic Si NR arrays, prepared through electroless chemical etching and HF treatment, functioned as hydrophobic substrates. Droplets containing ZnO seeds could be positioned on the Si NR arrays, causing the ZnO seeds to deposit selectively upon them, with n-ZnO NR/p-Si NR array heterojunctions ultimately forming after hydrothermal growth of ZnO NRs. Because of compensation for the difference in refractive index between air and the Si substrate, the n-ZnO NR/p-Si NR arrays exhibited excellent absorption ability in the visible range. Devices based on these n-ZnO NR/p-Si NR array heterojunctions displayed not only rectifying behavior but also photovoltaic effects when illuminated with UV light. The low temperature and low cost of this fabrication process suggest that the selective growth of n-ZnO NRs on p-Si NR arrays might allow such structures to have diverse applications in optoelectronics.

  20. Stable and high-quality Al-doped ZnO films with ICP-assisted facing targets sputtering at low temperature

    NASA Astrophysics Data System (ADS)

    Choi, Yoon S.; Kim, Hye R.; Han, Jeon G.

    2014-04-01

    FTS (facing targets sputtering) has been studied intensively for high-quality TCO films in low-temperature processes. In this study, we designed ICP-assisted FTS process for high-quality Al-doped ZnO film synthesis in a low temperature process. A one-turn ICP coil was installed a few cm above the upper target edge through which hydrogen was introduced and fully dissociated to the atomic radicals. The increase of ICP power caused heating and rarefaction of Ar gas and generated abundant hydrogen atoms and hydrogenated molecules. In FESEM analysis, the films synthesized with high ICP power showed high crystallinity. XPS was used to analyze the film structure. In O1s spectra, the low binding energy component located at ˜530.3 ± 0.4 eV corresponding to O2- ions on the wurtzite structure of the hexagonal Zn2+ ion array increased with the ICP power, indicating good crystal quality. With increasing ICP power fixing while fixing the RF power at the cathode, the resistivity was observed to decrease to 5 × 10-4 Ω-cm. For thermal reliability tests, films were stored in an air-based chamber at 200 °C. The films synthesized without ICP showed rapid degradation in the electrical properties, while the films synthesized with high ICP power showed good stabilities with little change in the electrical properties after 30 h of storage in an oven. By adding hydrogen, the carrier concentration of the films increased, while the mobility did not change much. From these results, it is expected that hydrogen was incorporated into the film as a stable n-dopant by using an auxiliary ICP plasma source.

  1. Effect of sputtering power on crystallinity, intrinsic defects, and optical and electrical properties of Al-doped ZnO transparent conducting thin films for optoelectronic devices

    NASA Astrophysics Data System (ADS)

    Hu, Yu Min; Li, Jung Yu; Chen, Nai Yun; Chen, Chih Yu; Han, Tai Chun; Yu, Chin Chung

    2017-02-01

    The crystallinity and intrinsic defects of transparent conducting oxide (TCO) films have a high impact on their optical and electrical properties and therefore on the performance of devices incorporating such films, including flat panel displays, electro-optical devices, and solar cells. The optical and electrical properties of TCO films can be modified by tailoring their deposition parameters, which makes proper understanding of these parameters crucial. Magnetron sputtering is the most adaptable method for preparing TCO films used in industrial applications. In this study, we investigate the direct and inter-property correlation effects of sputtering power (PW) on the crystallinity, intrinsic defects, and optical and electrical properties of Al-doped ZnO (AZO) TCO films. All of the films were preferentially c-axis-oriented with a wurtzite structure and had an average transmittance of over 80% in the visible wavelength region. Scanning electron microscopy images revealed significantly increased AZO film grain sizes for PW ≥ 150 W, which may lead to increased conductivity, carrier concentration, and optical band gaps but decreased carrier mobility and in-plane compressive stress in AZO films. Photoluminescence results showed that, with increasing PW, the near band edge emission gradually dominates the defect-related emissions in which zinc interstitial (Zni), oxygen vacancy (VO), and oxygen interstitial (Oi) are possibly responsible for emissions at 3.08, 2.8, and 2.0 eV, respectively. The presence of Zni- and Oi-related emissions at PW ≥ 150 W indicates a slight increase in the presence of Al atoms substituted at Zn sites (AlZn). The presence of Oi at PW ≥ 150 W was also confirmed by X-ray photoelectron spectroscopy results. These results clearly show that the crystallinity and intrinsic-defect type of AZO films, which dominate their optical and electrical properties, may be controlled by PW. This understanding may facilitate the development of TCO

  2. Fabrication of tunable hydrophobic surface of ZnO nanorods with Cu doping

    SciTech Connect

    Chakraborty, Mohua; Thangavel, R.

    2015-08-28

    In this work, tunable wettability of the Zinc Oxide (ZnO) nanorod surface with Cu doping prepared by a hydrothermal method. These grown samples were characterized by XRD, FESEM, AFM and water contact angle measurements. The wettability of the ZnO nanorods surface area was controlled and tuned by different concentration of copper doping. It was found that the hydrophobic surface of doped ZnO Nanorods shows a maximum and minimum contact angle of about 156.60° and 136.36° was achieved with doping concentration of 10 and 20 M % respectively. Further, the surface properties such as surface energy and work of adhesion were calculated for undoped and Cu doped ZnO nanostructure surfaces. These nanosructures can be potentially applicable to enlarge time honoured application of ZnO based electronic devices.

  3. Effect of Metallic Au Seed Layer Annealing on the Properties of Electrodeposited ZnO Nanorods.

    PubMed

    Park, Youngbin; Nam, Giwoong; Kim, Byunggu; Leem, Jae-Young

    2015-11-01

    This study focuses on the effect of annealing the Au seed layer (ASL) on the structural and optical properties of electrodeposited ZnO nanorods. ZnO nanorods were fabricated in a three-step approach. In the first step, ASLs were deposited using an ion sputter technique. In the second step, layers were annealed in air at various temperatures ranging from 400 degrees C to 600 degrees C. Finally, ZnO nanorods were grown using an electrodeposition method. The field-emission scanning electron microscopy analysis showed that better aligned ZnO nanorods are fabricated on the annealed ASL compared with non-annealed ASL The X-ray diffraction analysis showed a notable improvement in directional growth along the (002) crystallographic plane when ZnO nanorods were grown on the annealed ASL. The photoluminescence analysis showed that the UV emission peak of ZnO nanorods on the annealed ASL at 400 degrees C was blue-shifted and increased.

  4. Constructing MnO{sub 2}/single crystalline ZnO nanorod hybrids with enhanced photocatalytic and antibacterial activity

    SciTech Connect

    Yu, Weiwei; Liu, Tiangui; Cao, Shiyi; Wang, Chen; Chen, Chuansheng

    2016-07-15

    In order to improve the photocatalytic and antibacterial activity of ZnO nanorods, ZnO nanorods decorated with MnO{sub 2} nanoparticles (MnO{sub 2}/ZnO nanorod hybrids) were prepared by using microwave assisted coprecipitation method under the influence of hydrogen peroxide, and the structure, photocatalytic activity and antibacterial property of the products were studied. Experimental results indicated that MnO{sub 2} nanoparticles are decorated on the surface of single crystalline ZnO nanorods. Moreover, the resultant MnO{sub 2}/ZnO nanorod hybrids have been proven to possess good photocatalytic and antibacterial activity, which their degradated efficiency for Rhodamin B (RhB) is twice as the pure ZnO nanorods. Enhancement for photocatalytic and antibacterial activity is mainly attributed to the low band gap energy and excellent electrochemical properties of MnO{sub 2} nanoparticles. - Graphical abstract: The MnO{sub 2}/single crystalline ZnO nanorods hybrids, which MnO{sub 2} nanoparticles are loaded on the surface of ZnO nanorods, were prepared by the step-by-step precipitation method under the assistance of ammonia and hydrogen peroxide. Display Omitted - Highlights: • MnO{sub 2}/ZnO nanorod hybrids were prepared by the step-by-step assembly method. • Single crystalline ZnO nanorods can be decorated by MnO{sub 2} nanoparticles. • MnO{sub 2}/ZnO nanorod hybrids possess good photocatalytic and antibacterial activity. • MnO{sub 2} can improve the photocatalytic activity of ZnO nanorods under visible light.

  5. Selective growth of hierarchical ZnO nanorod arrays on the graphene nanosheets

    NASA Astrophysics Data System (ADS)

    Yang, Hui; Li, Lan; Li, Jinliang; Mo, Zhaojun

    2016-01-01

    We report directly selective-area grown (SAG) high-quality hierarchical ZnO nanorod arrays on the graphene nanosheets without invoking damage or introducing a catalyst. The SAG behavior in the non-catalytic growth mechanism is attributed to dangling bonds on the boundary edges of graphene nanosheets, which serve as the preferential adsorption and nucleation sites of ZnO nanorod. High densities of hierarchical ZnO nanorods show single-crystalline hexagonal wurtzite structure and are vertically well-aligned on the graphene nanosheets, with the diameter and the density strongly dependent on the growth temperature. Furthermore, no carbon impurity can be seen in the tips of the ZnO nanorods and also no carbon-related defect peak in the 10 K PL spectrum of ZnO nanorods. Our approach using a graphene-nanosheet substrate provides an efficient route for the growth of high-quality ZnO with a one-dimensional (1D) hierarchical nanostructure, which is highly desirable for fabricating 1D ZnO hybrid optoelectronic devices, particularly for a fast-response UV photodetector and highly-sensitive gas sensor.

  6. ZnO nanorods decorated with ZnS nanoparticles

    SciTech Connect

    Joicy, S.; Sivakumar, P.; Thangadurai, P.; Ponpandian, N.

    2015-06-24

    In this study, ZnO nanorods (NRs) and ZnS nanoparticles decorated ZnO-NRs were prepared by a combination of hydrothermal and hydrolysis method. Structural and optical properties of the samples were studied by XRD, FE-SEM, UV-Vis DRS and photoluminescence spectroscopy. Microscopy analysis revealed that the diameter of ZnO-NRs was ∼500 nm and the length was ranging from a few hundred nm to several micrometers and their surface was decorated with ZnS nanoparticles. UV-Vis DRS showed the absorption of ZnS decorated ZnO-NRs was blue shifted with respect to pure ZnO-NRs which enhanced the separation of electron-hole pairs. PL spectrum of ZnS decorated ZnO-NRs showed a decrease in intensity of UV and green emissions with the appearance of blue emission at 436 nm.

  7. Surface modification of ZnO nanorods with Hamilton receptors.

    PubMed

    Zeininger, Lukas; Klaumünzer, Martin; Peukert, Wolfgang; Hirsch, Andreas

    2015-04-13

    A new prototype of a Hamilton receptor suitable for the functionalization of inorganic nanoparticles was synthesized and characterized. The hydrogen bonding receptor was coupled to a catechol moiety, which served as anchor group for the functionalization of metal oxides, in particular zinc oxide. Synthesized zinc oxide nanorods [ZnO] were used for surface functionalization. The wet-chemical functionalization procedure towards monolayer-grafted particles [ZnO-HR] is described and a detailed characterization study is presented. In addition, the detection of specific cyanurate molecules is demonstrated. The hybrid structures [ZnO-HR-CA] were stable towards agglomeration and exhibited enhanced dispersability in apolar solvents. This observation, in combination with several spectroscopic experiments gave evidence of the highly directional supramolecular recognition at the surface of nanoparticles.

  8. g-C3N4 decorated ZnO nanorod arrays for enhanced photoelectrocatalytic performance

    NASA Astrophysics Data System (ADS)

    Kuang, Pan-Yong; Su, Yu-Zhi; Chen, Gao-Feng; Luo, Zhuo; Xing, Shu-Yang; Li, Nan; Liu, Zhao-Qing

    2015-12-01

    Heterojunction can not only offer a wide range of solar light absorption but also facilitate the separation of photoinduced charge carriers, and thereby lead to enhanced photoelectrochemical efficiency. Herein, we report the heterostructured g-C3N4/ZnO nanorod arrays (NRAs) for enhanced photoelectrocatalytic performance. The g-C3N4 shell layer of about 20-30 nm was coated on the surface of ZnO nanorod uniformly through thermal annealing the melamine precursor. Compared to the pristine ZnO and g-C3N4, the as-prepared g-C3N4/ZnO NRAs exhibit enhanced photoelectrocatalytic activity for methylene blue (MB) decolorization under visible light illumination. This enhancement of photoelectrocatalytic performance may be mainly attributed to improved separation efficiency of charge carriers from photoexcited g-C3N4 to ZnO across the g-C3N4/ZnO interfaces.

  9. Patterned fabrication of single ZnO nanorods and measurement of their optoelectrical characteristics.

    PubMed

    Yu, Chun-Wei; Lai, Shang-Hung; Wang, Teng-Yi; Lan, Ming-Der; Ho, Mon-Shu

    2008-09-01

    This work develops a new process of growing well ordered ZnO nanorods in large scale on the Si(111) substrate. Nanosphere lithography (NSL) was adopted to produce a matrix in an extensive area. A pattern with a controlled amount of gold was formed through the nanosphere mask. The ZnO nanorods were then grown on a patterned Au/Si substrate through a metal catalytic vapor-liquid-solid (VLS) process. The structure and characteristics of ZnO nanorods were investigated by XRD, SEM and TEM. The hexagonal nanorods were dominated at (0002) direction with a lattice constant of approximately 5.03 A. The optoelectronical properties were studied by PL emission spectroscopy. A strong UV emission at 380 nm was observed. The band gap of the single ZnO nanorod was directly measured to be 3.36 eV using a conductive AFM. The superiority of patterned ZnO nanorods indicates their great potential in field emission display arrays.

  10. Cu-doped ZnO nanorod arrays: the effects of copper precursor and concentration

    PubMed Central

    2014-01-01

    Cu-doped ZnO nanorods have been grown at 90°C for 90 min onto a quartz substrate pre-coated with a ZnO seed layer using a hydrothermal method. The influence of copper (Cu) precursor and concentration on the structural, morphological, and optical properties of ZnO nanorods was investigated. X-ray diffraction analysis revealed that the nanorods grown are highly crystalline with a hexagonal wurtzite crystal structure grown along the c-axis. The lattice strain is found to be compressive for all samples, where a minimum compressive strain of −0.114% was obtained when 1 at.% Cu was added from Cu(NO3)2. Scanning electron microscopy was used to investigate morphologies and the diameters of the grown nanorods. The morphological properties of the Cu-doped ZnO nanorods were influenced significantly by the presence of Cu impurities. Near-band edge (NBE) and a broad blue-green emission bands at around 378 and 545 nm, respectively, were observed in the photoluminescence spectra for all samples. The transmittance characteristics showed a slight increase in the visible range, where the total transmittance increased from approximately 80% for the nanorods doped with Cu(CH3COO)2 to approximately 90% for the nanorods that were doped with Cu(NO3)2. PMID:24855460

  11. Photoelectrochemical water splitting properties of hydrothermally-grown ZnO nanorods with controlled diameters

    NASA Astrophysics Data System (ADS)

    Babu, Eadi Sunil; Hong, Soon-Ku; Vo, Thanh Son; Jeong, Jong-Ryul; Cho, Hyung Koun

    2015-01-01

    The effect of diameter change on photoelectrochemical water splitting was investigated in depth for ZnO nanorods. ZnO nanorods were grown on SiO2/Si and indium tin-oxide substrates by the hydrothermal growth method. By controlling the concentration ratio between zinc nitrate hexahydrate (ZNT) and hexamethylenetetramine (HMTA) nanorod diameters were changed from 45 to 275 nm, in which the diameter decreased with decreasing the ratio. Photoelectrochemical properties of ZnO nanorods with diameters from 45 to 255 nm were investigated under ultraviolet (UV) and visible light illumination. The maximum photoconversion efficiency of 45.3% was obtained from ZnO nanorods with 45 nm diameter under 365 nm UV light illumination. The photoconversion efficiency of 0.42% was obtained under Air Mass 1.5 Global simulated solar light illumination. Higher photoconversion efficiency for smaller diameter nanorods is attributed to the increase in the light absorption with decreasing the diameter that is confirmed by our simulation using finite-difference time domain. The length change of nanorods showed relatively negligible effects compared to the diameter change in our system.

  12. Effect of aspect ratio and surface defects on the photocatalytic activity of ZnO nanorods

    PubMed Central

    Zhang, Xinyu; Qin, Jiaqian; Xue, Yanan; Yu, Pengfei; Zhang, Bing; Wang, Limin; Liu, Riping

    2014-01-01

    ZnO, aside from TiO2, has been considered as a promising material for purification and disinfection of water and air, and remediation of hazardous waste, owing to its high activity, environment-friendly feature and lower cost. However, their poor visible light utilization greatly limited their practical applications. Herein, we demonstrate the fabrication of different aspect ratios of the ZnO nanorods with surface defects by mechanical-assisted thermal decomposition method. The experiments revealed that ZnO nanorods with higher aspect ratio and surface defects show significantly higher photocatalytic performances. PMID:24699790

  13. ZnO Nanorods Grown Electrochemically on Different Metal Oxide Underlays

    NASA Astrophysics Data System (ADS)

    Gromyko, I.; Dedova, T.; Krunks, M.; Syritski, V.; Mere, A.; Mikli, V.; Unt, T.; Oja Acik, I.

    2015-03-01

    In this study we present results on electrochemically grown ZnO nanorods on different metal oxide underlays, such as ZnO seed layers with different morphologies, ZnS and TiO2 compact thin films produced by spray pyrolysis on transparent conductive oxide (TCO) substrates. Also in this work we present results on ZnO nanorods directly deposited on some chosen TCO substrates. The relationship between nanorod formation and substrate properties were studied. All ZnO nanorod layers were grown electrochemically using ZnCl2 aqueous solutions (c=0.2 mmol/L) at the bath temperature of 80 °C during one hour. The structural properties and morphology of metal oxide underlays and ZnO nanorods grown on them were studied by scanning electron microscopy (SEM), x-ray diffraction spectroscopy (XRD). Depending on the substrate morphology, ZnO rods with different dimension, orientation, shape and density were obtained. For instance, larger rods (d~200 nm, l~700 nm) were obtained on substrates, such as ITO/glass, FTO/glass and ZnO:In/ITO/glass. Smaller rods (d~60 nm, l~350 nm) were obtained on smooth, uniform and fine-grained underlays, such as ZnS and TiO2.

  14. Intracellular ZnO Nanorods Conjugated with Protoporphyrin for Local Mediated Photochemistry and Efficient Treatment of Single Cancer Cell

    PubMed Central

    2010-01-01

    ZnO nanorods (NRs) with high surface area to volume ratio and biocompatibility is used as an efficient photosensitizer carrier system and at the same time providing intrinsic white light needed to achieve cancer cell necrosis. In this letter, ZnO nanorods used for the treatment of breast cancer cell (T47D) are presented. To adjust the sample for intracellular experiments, we have grown the ZnO nanorods on the tip of borosilicate glass capillaries (0.5 μm diameter) by aqueous chemical growth technique. The grown ZnO nanorods were conjugated using protoporphyrin dimethyl ester (PPDME), which absorbs the light emitted by the ZnO nanorods. Mechanism of cytotoxicity appears to involve the generation of singlet oxygen inside the cell. The novel findings of cell-localized toxicity indicate a potential application of PPDME-conjugated ZnO NRs in the necrosis of breast cancer cell within few minutes. PMID:21076704

  15. Growth of 18O isotopically enriched ZnO nanorods by two novel VPT methods

    NASA Astrophysics Data System (ADS)

    Gray, Ciarán; Trefflich, Lukas; Röder, Robert; Ronning, Carsten; Henry, Martin O.; McGlynn, Enda

    2017-02-01

    We have developed two novel vapour phase transport methods to grow ZnO nanorod arrays isotopically enriched with 18O. Firstly, a three-step process used to grow natural and Zn-enriched ZnO nanorods has been further modified, by replacing the atmospheric O2 with enriched 18O2, in order to grow 18O-enriched ZnO nanorods using this vapour-solid method on chemical bath deposited buffer layers. In addition, 18O-enriched ZnO nanorods were successfully grown using 18O isotopically enriched ZnO source powders in a vapour-liquid-solid growth method. Scanning electron microscopy studies confirmed the success of both growth methods in terms of nanorod morphology, although in the case of the vapour-liquid-solid samples, the nanorods' c-axes were not vertically aligned due to the use of a non-epitaxial substrate. Raman and PL studies indicated clearly that O-enrichment was successful in both cases, although the results indicate that the enrichment is at a lower level in our samples compared to previous reports with the same nominal enrichment levels. The results of our studies also allow us to comment on both levels of enrichment achieved and on novel effects of the high temperature growth environment on the nanorod growth, as well as suggesting possible mechanisms for such effects. Very narrow photoluminescence line widths, far narrower than those reported previously in the literature for isotopically enriched bulk ZnO, are seen in both the vapour-solid and vapour-liquid-solid nanorod samples demonstrating their excellent optical quality and their potential for use in detailed optical studies of defects and impurities using low temperature photoluminescence.

  16. Photoluminescence studies of ZnO nanorods grown by plasma-assisted molecular beam epitaxy.

    PubMed

    Kim, Min Su; Nam, Giwoong; Leem, Jae-Young

    2013-05-01

    Metal catalyst-free ZnO nanorods were grown on PS with buffer layers grown at 450 degrees C by plasma-assisted molecular beam epitaxy. Room temperature and temperature-dependent photoluminescence were carried out to investigate the optical properties of the ZnO nanorods with the average diameter of 120 nm and length of 300 nm. Three emission peaks, free excition, neutral-donor exciton, and free electron-to-neutral acceptor, were observed at 10 K. Huang-Rhys factor S of the ZnO nanorods was 0.978, which is much higher than that of ZnO thin films. The values of Varshni's empirical equation fitting parameters were alpha = 4 x 10(-3) eV/K, beta = 4.1 x 10(4) K, and E9(0) = 3.388 eV and the activation energy was about 96 meV.

  17. Poole-Frenkel effect on electrical characterization of Al-doped ZnO films deposited on p-type GaN

    SciTech Connect

    Huang, Bohr-Ran; Liao, Chung-Chi; Ke, Wen-Cheng Chang, Yuan-Ching; Huang, Hao-Ping; Chen, Nai-Chuan

    2014-03-21

    This paper presents the electrical properties of Al-doped ZnO (AZO) films directly grown on two types of p-type GaN thin films. The low-pressure p-GaN thin films (LP-p-GaN) exhibited structural properties of high-density edge-type threading dislocations (TDs) and compensated defects (i.e., nitrogen vacancy). Compared with high-pressure p-GaN thin films (HP-p-GaN), X-ray photoemission spectroscopy of Ga 3d core levels indicated that the surface Fermi-level shifted toward the higher binding-energy side by approximately 0.7 eV. The high-density edge-type TDs and compensated defects enabled surface Fermi-level shifting above the intrinsic Fermi-level, causing the surface of LP-p-GaN thin films to invert to n-type semiconductor. A highly nonlinear increase in leakage current regarding reverse-bias voltage was observed for AZO/LP-p-GaN. The theoretical fits for the reverse-bias voltage region indicated that the field-assisted thermal ionization of carriers from defect associated traps, which is known as the Poole-Frenkel effect, dominated the I-V behavior of AZO/LP-p-GaN. The fitting result estimated the trap energy level at 0.62 eV below the conduction band edge. In addition, the optical band gap increased from 3.50 eV for as-deposited AZO films to 3.62 eV for 300 °C annealed AZO films because of the increased carrier concentration. The increasing Fermi-level of the 300 °C annealed AZO films enabled the carrier transport to move across the interface into the LP-p-GaN thin films without any thermal activated energy. Thus, the Ohmic behavior of AZO contact can be achieved directly on the low-pressure p-GaN films at room temperature.

  18. Characteristics of Al-doped ZnO thin films prepared in Ar + H{sub 2} atmosphere and their vacuum annealing behavior

    SciTech Connect

    Zhu, Bailin; Lü, Kun; Wang, Jun; Li, Taotao; Wu, Jun; Zeng, Dawen; Xie, Changsheng

    2013-11-15

    The microstructure and electrical–optical properties of Al-doped ZnO (AZO) films have been studied as a function of H{sub 2} flux in the magnetron sputtering process at 150 °C and postannealing temperature in vacuum. As H{sub 2} flux increases in the sputtering gas, the AZO films deposited have a (002) preferred orientation rather than the mixed (100) and (002) orientations, the grain size shows a tendency to first increase then decrease, and (002) diffraction peak position is inclined to shift to higher angles first then to lower angles. The resistivity of the films first decreases then increases with H{sub 2} flux, and the lowest resistivity of 4.02 × 10{sup −4}Ω cm is obtained at a H{sub 2} flux of 10 sccm. The average transmittance in the visible region shows little dependence on H{sub 2} flux. As a whole, the AZO films with higher values of figure of merit are obtained when the H{sub 2} flux is in the range of 6–12 sccm. The AZO films deposited in Ar and Ar + H{sub 2} exhibit different annealing behaviors. For the AZO film deposited in Ar, the grain size gradually increases, the stresses are relaxed, the resistivity first decreases then increases, and the average transmittance in the visible region is unchanged initially then somewhat decreased as annealing temperature is increased. The optimum annealing temperature for improving properties of AZO films deposited in Ar is 300 °C. For the AZO films deposited in Ar + H{sub 2}, annealing does not significantly change the microstructure but increases the resistivity of the films; the average transmittance in the visible region remains unchanged initially but greatly reduced with further increase in annealing temperature. The carrier transport in the as-deposited and annealed films appears to be controlled by a mechanism of grain boundary scattering, and the value of E{sub g} increases with the increase in carrier concentration due to Burstein–Moss effect.

  19. The mechanism of growth of ZnO nanorods by reactive sputtering

    NASA Astrophysics Data System (ADS)

    Nandi, R.; Major, S. S.

    2017-03-01

    DC reactive magnetron sputtering of zinc target in argon-oxygen sputtering atmosphere has been used to grow ZnO thin films/nanorods on Si in a wide substrate temperature range of 300-750 °C and under different sputtering conditions, namely, DC power, sputtering pressure and oxygen percentage in the sputtering atmosphere. Powder X-ray diffraction, Raman spectroscopy and a combination of top-down and cross-sectional scanning electron microscopy studies of ZnO films and nanorods grown under different conditions, have shown that substrate temperature critically controls their growth behavior and morphology, eventually resulting in the growth of vertically c-axis oriented, highly aligned and separated ZnO nanorods at substrate temperatures of 700-750 °C. The strongly substrate temperature dependent growth of nanorods is explained by considering that the growth above 600 °C, takes place in the 'desorption regime', in which, the surface diffusion length decreases exponentially with temperature. The diameter of nanorods increases with increase of DC power or decrease of sputtering pressure, which is attributed to the increase of surface diffusion length at higher deposition flux. The morphology of ZnO nanorods is not significantly affected by oxygen percentage in the sputtering atmosphere, since it does not influence the deposition flux.

  20. Preparation, characterization and electroluminescence studies of ZnO nanorods for optoelectronic device applications

    NASA Astrophysics Data System (ADS)

    Singh, Anju; Vishwakarma, H. L.

    2015-07-01

    In this work, ZnO nanorods were achieved by a simple chemical precipitation method in the presence of capping agent Poly Vinyl Pyrrolidone (PVP) at room temperature. X-Ray Diffraction (XRD) result indicates that the synthesized undoped ZnO nanorods have wurtzite hexagonal structure without any impurities. It has been seen that the growth orientation of the prepared ZnO nanorods were (101). XRD analysis revealed that the nanorods having the crystallite size 49 nm. The Scanning Electron Microscopy (SEM) image confirmed the size and shape of these nanorods. The diameter of nanorods has been found that 1.52 µm to 1.61 µm and the length of about 4.89 µm. It has also been found that at room temperature Ultra Violet Visible (UV-VIS) absorption band is around 355 nm (blue shifted as compared to bulk). Electroluminescence (EL) studies show that emission of light is possible at very small threshold voltage and increases rapidly with increasing applied voltage. It is seen that smaller ZnO nanoparticles give higher electroluminescence brightness starting at lower threshold voltage. The brightness is also affected by increasing the frequency of AC signal.

  1. Preparation, characterization and electroluminescence studies of ZnO nanorods for optoelectronic device applications

    SciTech Connect

    Singh, Anju; Vishwakarma, H. L.

    2015-07-31

    In this work, ZnO nanorods were achieved by a simple chemical precipitation method in the presence of capping agent Poly Vinyl Pyrrolidone (PVP) at room temperature. X-Ray Diffraction (XRD) result indicates that the synthesized undoped ZnO nanorods have wurtzite hexagonal structure without any impurities. It has been seen that the growth orientation of the prepared ZnO nanorods were (101). XRD analysis revealed that the nanorods having the crystallite size 49 nm. The Scanning Electron Microscopy (SEM) image confirmed the size and shape of these nanorods. The diameter of nanorods has been found that 1.52 µm to 1.61 µm and the length of about 4.89 µm. It has also been found that at room temperature Ultra Violet Visible (UV-VIS) absorption band is around 355 nm (blue shifted as compared to bulk). Electroluminescence (EL) studies show that emission of light is possible at very small threshold voltage and increases rapidly with increasing applied voltage. It is seen that smaller ZnO nanoparticles give higher electroluminescence brightness starting at lower threshold voltage. The brightness is also affected by increasing the frequency of AC signal.

  2. High-Sensitive Ultraviolet Photodetectors Based on ZnO Nanorods/CdS Heterostructures

    NASA Astrophysics Data System (ADS)

    Lam, Kin-Tak; Hsiao, Yu-Jen; Ji, Liang-Wen; Fang, Te-Hua; Hsiao, Kai-Hua; Chu, Tung-Te

    2017-01-01

    The ultraviolet (UV) photodetectors with ZnO nanorods (NRs)/CdS thin film heterostructures on glass substrates have been fabricated and characterized. It can be seen that the UV photoresponsivity of such a device became higher as the ZnO NR length was increased in the investigation. With an incident wavelength of 350 nm and 5 V applied bias, the responsivity of photodetectors based on ZnO NR/CdS heterostructures with the ZnO NR length at 500, 350, and 200 nm and traditional CdS film were at 12.86, 3.83, 0.91, and 0.75 A/W, respectively. The measurement results of the fabricated photodetectors based on ZnO nanorods (NRs)/CdS heterostructures have shown a significant high sensitivity in the range of UV light, which can be useful for the application of UV detection.

  3. Bioanalytical system for detection of cancer cells with photoluminescent ZnO nanorods

    NASA Astrophysics Data System (ADS)

    Viter, R.; Jekabsons, K.; Kalnina, Z.; Poletaev, N.; Hsu, S. H.; Riekstina, U.

    2016-11-01

    Using photoluminescent ZnO nanorods and carbohydrate marker SSEA-4, a novel cancer cell recognition system was developed. Immobilization of SSEA-4 antibodies (αSSEA-4) on ZnO nanorods was performed in buffer solution (pH = 7.1) over 2 h. The cancer cell line probes were fixed on the glass slide. One hundred microliters of ZnO-αSSEA-4 conjugates were deposited on the cell probe and exposed for 30 min. After washing photoluminescence spectra were recorded. Based on the developed methodology, ZnO-αSSEA-4 probes were tested on patient-derived breast and colorectal carcinoma cells. Our data clearly show that the carbohydrate SSEA-4 molecule is expressed on cancer cell lines and patient-derived cancer cells. Moreover, SSEA-4 targeted ZnO nanorods bind to the patient-derived cancer cells with high selectivity and the photoluminescence signal increased tremendously compared to the signal from the control samples. Furthermore, the photoluminescence intensity increase correlated with the extent of malignancy in the target cell population. A novel portable bioanalytical system, based on optical ZnO nanorods and fiber optic detection system was developed. We propose that carbohydrate SSEA-4 specific ZnO nanorods could be used for the development of cancer diagnostic biosensors and for targeted therapy.

  4. Low-temperature photoluminescence behaviour of Ag decorated ZnO Nanorods

    NASA Astrophysics Data System (ADS)

    Amutha, A.; Amirthapandian, S.; Sundaravel, B.; Panigrahi, B. K.; Saravanan, K.; Thangadurai, P.

    2016-11-01

    The Ag nanoparticles decorated ZnO nanorods (Ag:ZnO) were prepared by irradiating the precursor solution with ultra-violet radiation for two irradiation times (6 and 17 h). Structural and microstructural studies were done by X-ray diffraction and transmission electron microscopy, respectively. Optical properties were studied by UV-Vis spectroscopy at room temperature (300 K) and photoluminescence (PL) spectroscopy at low-temperature in the temperature range from 5 to 300 K. The Ag:ZnO nanorods possessed the wurtzite structure of ZnO along with the cubic fcc phase of Ag nanoparticles. Average size of Ag nanoparticles in Ag:ZnO nanorods prepared with 6 and 17 h of UV irradiation time was 4 and 16 nm, respectively. The 4 nm Ag nanoparticles had played a crucial role for enhanced PL emission (in the UV region) in the Ag:ZnO nanorods at 60 K. In the case of 16 nm sized Ag nanoparticles, violet emission has been enhanced about 3.5 times compared to that of pure ZnO nanorods and 4 nm-Ag:ZnO nanorods at 5 K. Thermal activation energy of 4 nm-Ag:ZnO and 16 nm-Ag:ZnO nanorods was found to be 0.6 and 0.7 meV, respectively, at low temperature region (5 to 60 K).

  5. Synthesis of highly efficient antibacterial agent Ag doped ZnO nanorods: Structural, Raman and optical properties

    SciTech Connect

    Jan, Tariq; Iqbal, Javed; Ismail, Muhammad; Mahmood, Arshad

    2014-04-21

    Here, synthesis, structural, morphological, Raman, optical properties and antibacterial activity of undoped and Ag doped ZnO nanorods by chemical co-precipitation technique have been reported. Structural analysis has revealed that Ag doping cannot deteriorate the structure of ZnO and wurtzite phase is maintained. Lattice constants are found to be decreased with the Ag doping. Fourier transform infrared and Raman spectroscopy also confirm the X-ray diffraction results. Scanning electron microscopy results have demonstrated the formation of ZnO nanorods with average diameter and length of 96 nm and 700 nm, respectively. Raman spectroscopy results suggest that the Ag doping enhances the number of defects in ZnO crystal. It has been found from optical study that Ag doping results in positional shift of band edge absorption peak. This is attributed to the successful incorporation of Ag dopant into ZnO host matrix. The antibacterial activity of prepared nanorods has been determined by two different methods and compared to that of undoped ZnO nanorods. Ag doped ZnO nanorods exhibit excellent antibacterial activity as compared to that of undoped ZnO nanorods. This excellent antibacterial activity may be attributed to the presence of oxygen vacancies and Zn{sup 2+} interstitial defects. Our preliminary findings suggest that Ag doped ZnO nanorods can be used externally to control the spreading of infections related with tested bacterial strains.

  6. Synthesis of highly efficient antibacterial agent Ag doped ZnO nanorods: Structural, Raman and optical properties

    NASA Astrophysics Data System (ADS)

    Jan, Tariq; Iqbal, Javed; Ismail, Muhammad; Mahmood, Arshad

    2014-04-01

    Here, synthesis, structural, morphological, Raman, optical properties and antibacterial activity of undoped and Ag doped ZnO nanorods by chemical co-precipitation technique have been reported. Structural analysis has revealed that Ag doping cannot deteriorate the structure of ZnO and wurtzite phase is maintained. Lattice constants are found to be decreased with the Ag doping. Fourier transform infrared and Raman spectroscopy also confirm the X-ray diffraction results. Scanning electron microscopy results have demonstrated the formation of ZnO nanorods with average diameter and length of 96 nm and 700 nm, respectively. Raman spectroscopy results suggest that the Ag doping enhances the number of defects in ZnO crystal. It has been found from optical study that Ag doping results in positional shift of band edge absorption peak. This is attributed to the successful incorporation of Ag dopant into ZnO host matrix. The antibacterial activity of prepared nanorods has been determined by two different methods and compared to that of undoped ZnO nanorods. Ag doped ZnO nanorods exhibit excellent antibacterial activity as compared to that of undoped ZnO nanorods. This excellent antibacterial activity may be attributed to the presence of oxygen vacancies and Zn2+ interstitial defects. Our preliminary findings suggest that Ag doped ZnO nanorods can be used externally to control the spreading of infections related with tested bacterial strains.

  7. Solid-state dye-sensitized solar cells based on ZnO nanoparticle and nanorod array hybrid photoanodes

    PubMed Central

    2011-01-01

    The effect of ZnO photoanode morphology on the performance of solid-state dye-sensitized solar cells (DSSCs) is reported. Four different structures of dye-loaded ZnO layers have been fabricated in conjunction with poly(3-hexylthiophene). A significant improvement in device efficiency with ZnO nanorod arrays as photoanodes has been achieved by filling the interstitial voids of the nanorod arrays with ZnO nanoparticles. The overall power conversion efficiency increases from 0.13% for a nanorod-only device to 0.34% for a device with combined nanoparticles and nanorod arrays. The higher device efficiency in solid-state DSSCs with hybrid nanorod/nanoparticle photoanodes is originated from both large surface area provided by nanoparticles for dye adsorption and efficient charge transport provided by the nanorod arrays to reduce the recombinations of photogenerated carriers. PMID:21884596

  8. Effect of growth time on ZnO nanorod arrays by a facile sonicated sol-gel immersion technique

    NASA Astrophysics Data System (ADS)

    Malek, M. F.; Mamat, M. H.; Musa, M. Z.; Ishak, A.; Saurdi, I.; Alrokayan, Salman A. H.; Khan, Haseeb A.; Rusop, M.

    2016-07-01

    A facile sonicated sol-gel immersion technique has been presented for synthesizing ZnO nanorod arrays with controllable diameter and lengths on glass substrates. A sol-gel dip-coating deposition was first used to grow a thin layer of ZAO nanocrystals on substrate serving as seeds for the subsequent growth of the nanorod arrays. The effect of growth time of the ZnO nanorod arrays on the ZAO seed layer were investigated. The optical transmission properties of the ZnO nanorods has been investigated. The thickness of the nanorods can be controlled by the growth time. These highly oriented ZnO nanorod arrays are potential for the creation of functional materials, such as the electrode of the solar cells, optoelectronic devices and etc.

  9. Controlled growth of well-aligned ZnO nanorod arrays by hydrothermal method

    NASA Astrophysics Data System (ADS)

    Mihailova, I.; Gerbreders, V.; Bulanovs, A.; Tamanis, E.; Sledevskis, E.; Ogurcovs, A.; Sarajevs, P.

    2014-10-01

    The application prospect of zinc oxide (ZnO) nanostructures largely relies on the ability to grow nanoobjects with necessary geometry. In this study well-aligned ZnO nanorod arrays with a high density and uniformity were successfully synthesized on the glass substrates by a hydrothermal method at low-temperature. The aqueous solutions of zinc nitrate hexahydrate and hexamethylenetetramine was used. The effect of seed layer (obtained by electrochemical method and by vacuum deposition method) on the alignment of ZnO nanorods has been investigated. The morphological properties of the ZnO nanorods were also examined in accordance with varying the magnetron sputtering angle for ZnO seeds deposition. It is also shown that the electric field can control the direction of the growth of ZnO nanorods. Morphological, structural and compositional characterizations of obtained films were carried out by scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction analysis methods.

  10. Control growth of single crystalline ZnO nanorod arrays and nanoflowers with enhanced photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Feng, Jiu-Ju; Wang, Zhen-Zhen; Li, Yong-Fang; Chen, Jian-Rong; Wang, Ai-Jun

    2013-04-01

    Single crystalline vertical nanorod arrays and nanoflowers of ZnO have been grown in situ on cheap zinc foils under hydrothermal conditions, by means of hexamethylenetetramine and ethanolamine, respectively. Their morphologies and crystal structures are characterized by X-ray diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy. The nanorods and flowers of ZnO grew along the { 10bar{1}1} and { 0001} planes, respectively. Both types of ZnO display high photocatalytic ability toward the degradation of methylene orange under UV irradiation. The ZnO nanorods show better performance than that of the ZnO nanoflowers, and the { 10bar{1}1} facets of the ZnO nanorods have higher photoactivity than that of the { 000bar{1}} or { 10bar{1}0} crystal planes. This is because the weaker coordinated O atoms on the surface are more likely to be saturated by H atoms in aqueous solution, thereby releasing more free OH radicals.

  11. Structural and morphology of ZnO nanorods synthesized using ZnO seeded growth hydrothermal method and its properties as UV sensing.

    PubMed

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

    2012-01-01

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

  12. Synthesis and Characterization of ZnO Nanorods and Nanodisks from Zinc Chloride Aqueous Solution.

    PubMed

    Long, Tengfa; Yin, Shu; Takabatake, Kouta; Zhnag, Peilin; Sato, Tsugio

    2008-12-16

    ZnO nanorods and nanodisks were synthesized by solution process using zinc chloride as starting material. The morphology of ZnO crystal changed greatly depending on the concentrations of Zn(2+) ion and ethylene glycohol (EG) additive in the solution. The effect of thermal treatment on the morphology was investigated. Photocatalytic activities of plate-like Zn(5)(OH)(8)Cl(2) . H(2)O and rod-like ZnO were characterized. About 18% of 1 ppm NO could be continuously removed by ZnO particles under UV light irradiation.

  13. Synthesis and Characterization of ZnO Nanorods and Nanodisks from Zinc Chloride Aqueous Solution

    PubMed Central

    2009-01-01

    ZnO nanorods and nanodisks were synthesized by solution process using zinc chloride as starting material. The morphology of ZnO crystal changed greatly depending on the concentrations of Zn2+ion and ethylene glycohol (EG) additive in the solution. The effect of thermal treatment on the morphology was investigated. Photocatalytic activities of plate-like Zn5(OH)8Cl2 · H2O and rod-like ZnO were characterized. About 18% of 1 ppm NO could be continuously removed by ZnO particles under UV light irradiation. PMID:20596478

  14. Raman silent modes in vertically aligned undoped ZnO nanorods

    NASA Astrophysics Data System (ADS)

    Sundara Venkatesh, P.; Ramakrishnan, V.; Jeganathan, K.

    2016-01-01

    We report the observation of Raman silent modes of B1low (276 cm-1) and B1high (582 cm-1) in vertically aligned ZnO nanorods due to the breakdown of translational symmetry. The structural studies reveal the high crystalline nature of the ZnO nanorods on the lattice mismatched silicon substrates. The dominant donor bound exciton emission and the phonon replicas signify the good quality of the nanorods which substantiate that the anomalous Raman modes could not be attributed to the intrinsic point defects. Further, our results show that the observed silent modes of wurtzite-ZnO become Raman active due to the breakdown of the wave-vector selection rule by loss of translational symmetry induced by nanorods geometry.

  15. Tuning of defects in ZnO nanorod arrays used in bulk heterojunction solar cells

    PubMed Central

    2012-01-01

    With particular focus on bulk heterojunction solar cells incorporating ZnO nanorods, we study how different annealing environments (air or Zn environment) and temperatures impact on the photoluminescence response. Our work gives new insight into the complex defect landscape in ZnO, and it also shows how the different defect types can be manipulated. We have determined the emission wavelengths for the two main defects which make up the visible band, the oxygen vacancy emission wavelength at approximately 530 nm and the zinc vacancy emission wavelength at approximately 630 nm. The precise nature of the defect landscape in the bulk of the nanorods is found to be unimportant to photovoltaic cell performance although the surface structure is more critical. Annealing of the nanorods is optimum at 300°C as this is a sufficiently high temperature to decompose Zn(OH)2 formed at the surface of the nanorods during electrodeposition and sufficiently low to prevent ITO degradation. PMID:23186280

  16. Ethanol-Sensing Characteristics of Nanostructured ZnO: Nanorods, Nanowires, and Porous Nanoparticles

    NASA Astrophysics Data System (ADS)

    Quy, Chu Thi; Hung, Chu Manh; Van Duy, Nguyen; Hoa, Nguyen Duc; Jiao, Mingzhi; Nguyen, Hugo

    2017-01-01

    The morphology and crystalline size of metal oxide-sensing materials are believed to have a strong influence on the performance of gas sensors. In this paper, we report a comparative study on the ethanol-sensing characteristics of ZnO nanorods, nanowires, and porous nanoparticles. The porous ZnO nanoparticles were prepared using a simple thermal decomposition of a sheet-like hydrozincite, whereas the nanorods and nanowires were grown by hydrothermal and chemical vapor deposition methods, respectively. The morphology and crystal structure of the synthesized materials were characterized by field-emission scanning electron microscopy and x-ray diffraction. Ethanol gas-sensing characteristics were systematically studied at different temperatures. Our findings show that for ethanol gas-sensing applications, ZnO porous nanoparticles exhibited the best sensitivity, followed by the nanowires and nanorods. Gas-sensing properties were also examined with respect to the role of crystal growth orientation, crystal size, and porosity.

  17. Photoactive area modification in bulk heterojunction organic solar cells using optimization of electrochemically synthesized ZnO nanorods

    NASA Astrophysics Data System (ADS)

    Mehdi, Ahmadi; Sajjad Rashidi, Dafeh

    2015-11-01

    In this work, ZnO nanorod arrays grown by an electrochemical deposition method are investigated. The crucial parameters of length, diameter, and density of the nanorods are optimized over the synthesize process and nanorods growth time. Crystalline structure, morphologies, and optical properties of ZnO nanorod arrays are studied by different techniques such as x-ray diffraction, scanning electron microscope, atomic force microscope, and UV-visible transmission spectra. The ZnO nanorod arrays are employed in an inverted bulk heterojunction organic solar cell of Poly (3-hexylthiophene):[6-6] Phenyl-(6) butyric acid methyl ester to introduce more surface contact between the electron transporter layer and the active layer. Our results show that the deposition time is a very important factor to achieve the aligned and uniform ZnO nanorods with suitable surface density which is required for effective infiltration of active area into the ZnO nanorod spacing and make a maximum interfacial surface contact for electron collection, as overgrowing causes nanorods to be too dense and thick and results in high resistance and lower visible light transmittance. By optimizing the thickness of the active layer on top of ZnO nanorods, an improved efficiency of 3.17% with a high FF beyond 60% was achieved.

  18. Visualization of localized photon modes of ZnO nanorods by scanning cathodoluminescence

    SciTech Connect

    Gruzintsev, A. N. Emelchenko, G. A.; Redkin, A. N.; Volkov, W. T.; Yakimov, E. E.; Visimberga, G.; Romanov, S. G.

    2009-04-15

    The scanning cathodoluminescence spectra and images of a ZnO nanorod with two mirrors at the end faces are studied at 10 K. Emission peaks of bound excitons and edge luminescence are observed in the ultraviolet spectral region. The spatial distribution pattern of emission intensity corresponding to localized photon modes of the nanorod is recorded at different wavelengths. A new method of visualization of localized optical modes in micro- and nano-sized laser cavities is suggested.

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

    SciTech Connect

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

    2014-04-24

    ZnO nanorods were grown by chemical bath deposition on sputtered, polycrystalline GaN buffer layers with and without ZnO seed layer. Scanning electron microscopy and X-ray diffraction show that the ZnO nanorods on GaN buffer layers are not vertically well aligned. Photoluminescence spectrum of ZnO nanorods grown on GaN buffer layer, however exhibits a much stronger near-band-edge emission and negligible defect emission, compared to the nanorods grown on ZnO buffer layer. These features are attributed to gallium incorporation at the ZnO-GaN interface. The introduction of a thin (25 nm) ZnO seed layer on GaN buffer layer significantly improves the morphology and vertical alignment of ZnO-NRs without sacrificing the high optical quality of ZnO nanorods on GaN buffer layer. The presence of a thick (200 nm) ZnO seed layer completely masks the effect of the underlying GaN buffer layer on the morphology and optical properties of nanorods.

  20. Low-temperature solution syntheses of hexagonal ZnO nanorods and morphology-controlled nanostructures

    NASA Astrophysics Data System (ADS)

    Son, Nguyen Thanh; Noh, Jin-Seo; Lee, In-Hwan

    2016-02-01

    Well-developed hexagonal ZnO nanorods and morphology-controlled nanostructures were synthesized at low temperatures using a simple solution method without the assistance of any templates or catalysts. Uniform conical nanorods with an average diameter of 35 nm and the aspect ratio of 14 could be obtained at a near-room temperature, while nanoplatelets with the planar aspect ratio of 2.4-4.8 were produced at higher temperatures. It was revealed that the morphology, dimensions, and the crystallinity of ZnO nanostructures could be controlled by elaborately adjusting experimental conditions such as the molar ratio of Zn2+ to OH-, EDA concentration, and temperature.

  1. ZnO nanorod/wire based gas sensors (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Liu, Jing; Duan, Xuexin; Zhang, Daihua; Zhang, Qing; Zhang, Qiankun; Chen, Yan

    2016-10-01

    ZnO nanorod/wire is a nanomaterial that possessing high surface area to volume ratio and excellent optical and electrical properties, indicating its promising sensing capabilities in various applications. Here, we present the research work of ZnO nanorod/wire based sensors carried out in our lab, which were used in the optical, electrical and mechanical sensing areas, respectively. In optical sensing, a ZnO nanorod array was fabricated at the endface of an optical fiber, forming a sensing probe, whose interference spectrum shifts upon the exposure to gas analyte. In electrical sensing, the ZnO nanowires decorated extended-gate field-effect transistor was used as a pH sensor, whose source-drain current changed dramatically under different pH values when applying the same gate voltage. Finally, regarding to the mechanical sensing, the ZnO nanorods were applied to the surface of the solidly mounted resonator for gas detecting, whose resonant frequency shifts due to the absorption of gas analytes.

  2. Crystallographic, luminescence and photoconductive characteristics of chemically tailored ZnO nanorods

    SciTech Connect

    Bayan, Sayan Chakraborty, Purushottam

    2014-04-24

    The optoelectronic properties of zinc oxide (ZnO) nanorods synthesized using two different chemical methods have been explored in the light of microstructural features. The presence/absence of band edge emission in the luminescence spectra of the nanorods is found to be governed by the crystallographic properties. Moreover, we observed a pronounced effect of variation in crystallite size on the UV photoconductivity of the nanorods. Understanding the influence of microstructural aspects on the optical and electronic properties of the nanostructures may help in the fabrication of prototype, miniaturized optoelectronic devices.

  3. Microwave assisted hydrothermal synthesize of ZnO nanorods and their characterization

    NASA Astrophysics Data System (ADS)

    Shojaee, Nadi; Ebadzadeh, Touradj; Aghaei, Alireza

    In present study ZnO nanorods were synthesized in an aqueous solution using a domestic microwave oven for irradiation. The nanorods have been grown on substrates immersed in an aqueous solution which contains zinc nitrate and hexamethylenetetramine as precursors. Eventually, effect of some parameters such as precursor's concentration and heating time on growth mechanism was characterized. The product phase was detected using X-ray diffraction (XRD). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) exhibited the resultant structure is uniform and single crystalline. Finally Uv-Vis spectroscopy was used to measure the nanorod's band gap.

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

    NASA Astrophysics Data System (ADS)

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

    2017-01-01

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

  5. The effect of modified layers on the performance of inverted ZnO nanorods/MEH-PPV solar cells

    NASA Astrophysics Data System (ADS)

    Yan, Yue; Zhao, SuLing; Xu, Zheng; Wei, Gong; Wang, LiHui

    2011-03-01

    We fabricate inverted organic/inorganic hybrid solar cells based on vertically oriented ZnO nanorods and polymer MEH-PPV. The morphology of ZnO nanorods and ZnO nanorods/MEH-PPV hybrid structure is depicted by using scanning electron microscopy (SEM), X-ray diffraction (XRD), and atomic force microscope (AFM), respectively. It is observed that ZnO nanorods array grows primarily aligned along the perpendicular direction of the ITO substrate. The MEH-PPV molecule does not enter the interspace between ZnO nanorods completely according to SEM picture. It results in the small and bad contact area between ZnO nanorods and MEH-PPV. To improve the photovoltaic performance, we also fabricate another kind of photovoltaic (PV) device modified by N719 dye, and exploit the effect of N719. After the modification of ZnO nanorods by N719, not only J sc increases from 0.257 mA/cm2 to 0.42 mA/cm2, but also V oc enhances from 0.37 V to 0.42 V. Insert LiF buffer layer between MEH-PPV and anode, J sc of 1.05 mA/cm2 is obtained, and it is 2.5 times that the device without LiF.

  6. Morphological and structural characterization of single-crystal ZnO nanorod arrays on flexible and non-flexible substrates.

    PubMed

    Farhat, Omar F; Halim, Mohd M; Abdullah, Mat J; Ali, Mohammed K M; Allam, Nageh K

    2015-01-01

    We report a facile synthesis of zinc oxide (ZnO) nanorod arrays using an optimized, chemical bath deposition method on glass, PET and Si substrates. The morphological and structural properties of the ZnO nanorod arrays were investigated using various techniques such as field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) measurements, which revealed the formation of dense ZnO nanorods with a single crystal, hexagonal wurtzite structure. The aspect ratio of the single-crystal ZnO nanorods and the growth rate along the (002) direction was found to be sensitive to the substrate type. The lattice constants and the crystallite size of the fabricated ZnO nanorods were calculated based on the XRD data. The obtained results revealed that the increase in the crystallite size is strongly associated with the growth conditions with a minor dependence on the type of substrate. The Raman spectroscopy measurements confirmed the existence of a compressive stress in the fabricated ZnO nanorods. The obtained results illustrated that the growth of high quality, single-crystal ZnO nanorods can be realized by adjusting the synthesis conditions.

  7. Growth of ZnO Nanorods on Stainless Steel Wire Using Chemical Vapour Deposition and Their Photocatalytic Activity

    PubMed Central

    Abd Aziz, Siti Nor Qurratu Aini; Pung, Swee-Yong; Ramli, Nurul Najiah; Lockman, Zainovia

    2014-01-01

    The photodegradation efficiency of ZnO nanoparticles in removal of organic pollutants deteriorates over time as a high percentage of the nanoparticles can be drained away by water during the wastewater treatment. This problem can be solved by growing the ZnO nanorods on stainless steel wire. In this work, ZnO nanorods were successfully grown on stainless steel wire by chemical vapour deposition. The SAED analysis indicates that ZnO nanorod is a single crystal and is preferentially grown in [0001] direction. The deconvoluted O 1s peak at 531.5 eV in XPS analysis is associated with oxygen deficient, revealing that the ZnO nanorods contain many oxygen vacancies. This observation is further supported by the finding of the small Iuv/Ivis ratio, that is, ~1 in the photoluminescence analysis. The growth of ZnO nanorods on stainless steel wire was governed by vapour-solid mechanism as there were no Fe particles observed at the tips of the nanorods. The photodegradation of Rhodamine B solution by ZnO nanorods followed the first-order kinetics. PMID:24587716

  8. Growth of isotopically enriched ZnO nanorods of excellent optical quality

    NASA Astrophysics Data System (ADS)

    Gray, Ciarán; Cullen, Joseph; Byrne, Conor; Hughes, Greg; Buyanova, Irina; Chen, Weimin; Henry, Martin O.; McGlynn, Enda

    2015-11-01

    We have produced isotopically enriched ZnO nanorods using Zn-enriched ZnO source powder by vapour phase transport on silicon substrates buffer-coated with unenriched ZnO seed layers. SEM and XRD data confirm successful growth of high quality, dense, c-axis aligned nanorods over a substantial surface area. Raman data show a shift of >1 cm-1 in the peak position of the Raman scattered peaks due to the E2low and E2high phonon modes when the Zn isotope is changed from 64Zn to 68Zn, consistent with previous work, thus confirming successful isotopic enrichment. SIMS data provides additional confirmation of enrichment. The optical quality (as determined by photoluminescence feature intensity and line width) is excellent. Samples with Zn isotopic enrichment ranging from 64ZnO to 68ZnO display a shift in recombination energy of the bound excitons at the band edge (3.34-3.37 eV) of ~0.6 meV. This blue-shift is also consistent with previously published data, further confirming both the excellent optical quality and successful isotopic substitution of ZnO nanorods using this relatively simple growth method.

  9. Position controlled and seed/catalyst free growth of ZnO nanorod arrays on reduced graphene oxide nanosheets

    NASA Astrophysics Data System (ADS)

    Yang, Hui; Li, Jinliang; Li, Lan; Mo, Zhaojun

    2016-09-01

    A new type of seed/catalyst-free and selective-growth process is developed for in situ grown vertically-aligned ZnO nanorods on the reduced graphene oxide (rGO) nanosheets. The dense and single-crystalline ZnO nanorods have been successfully grow on rGO nanosheets with the position- and size-controlled. The effect of rGO layer on the ZnO nanorods and the growth mechanism were investigated. The position of ZnO nanorod arrays correlates well with the size and position of rGO nanosheets, which is determined by dangling bonds such as oxygen-containing groups on rGO surface. Meanwhile, ZnO nanorods could grow laterally to form a continuous arrays with a large coverage on rGO substrates, which is mainly due to the step edges in rGO boundaries. The diameter and density of ZnO nanorods were readily determined by the growth temperature, and the length was easily controlled by the growth time. The absorption and PL spectrums suggest that ZnO nanorods/rGO have a strong UV absorption ranging from 330 to 375 nm and no obvious UV PL emission at room temperature, which indicates that the ZnO nanorods/rGO nanohybrids could be an excellent candidate for application in UV photodetectors. This work represents the success in seed/catalyst-free fabrication of aligned ZnO nanorod arrays directly on rGO nanosheets and the process can be readily scaled up for industrial applications of optoelectronic devices.

  10. Low-temperature hydrothermal synthesis of ZnO nanorods: Effects of zinc salt concentration, various solvents and alkaline mineralizers

    SciTech Connect

    Edalati, Khatereh; Shakiba, Atefeh; Vahdati-Khaki, Jalil; Zebarjad, Seyed Mojtaba

    2016-02-15

    Highlights: • We synthesized ZnO nanorods by a simple hydrothermal process at 60 °C. • Effects of zinc salt concentration, solvent and alkaline mineralizer was studied. • Increasing concentration of zinc salt changed ZnO nucleation system. • NaOH yielded better results in the production of nanorods in both solvents. • Methanol performed better in the formation of nanorods using the two mineralizers. - Abstract: ZnO has been produced using various methods in the solid, gaseous, and liquid states, and the hydrothermal synthesis at low temperatures has been shown to be an environmentally-friendly one. The current work utilizes a low reaction temperature (60 °C) for the simple hydrothermal synthesis of ZnO nanorod morphologies. Furthermore, the effects of zinc salt concentration, solvent type and alkaline mineralizer type on ZnO nanorods synthesis at a low reaction temperature by hydrothermal processing was studied. Obtained samples were analyzed using X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). Increasing the concentration of the starting zinc salt from 0.02 to 0.2 M changed ZnO nucleation system from the homogeneous to the heterogeneous state. The XRD results confirmed the production hexagonal ZnO nanostructures of with a crystallite size of 40.4 nm. Varying the experimental parameters (mineralizer and solvent) yielded ZnO nanorods with diameters ranging from 90–250 nm and lengths of 1–2 μm.

  11. Hydrothermal synthesis of highly crystalline ZnO nanorod arrays: Dependence of morphology and alignment on growth conditions

    NASA Astrophysics Data System (ADS)

    Azzez, Shrook A.; Hassan, Z.; Hassan, J. J.; Alimanesh, M.; Rasheed, Hiba S.; Sabah, Fayroz A.; Abdulateef, Sinan A.

    2016-07-01

    Highly oriented zinc oxide nanorod were successfully grown on seeded p-type silicone substrate by hydrothermal methode. The morphology and the crystallinty of ZnO c-axis (002) arrays were systematically studied using field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) methods. The effect of seed layer pre-annealing on nanorods properties was explained according to the nucleation site of ZnO nanoparticles on silicon substrate. In addition, the variation of the equal molarity of zinc nitrate hexahydrate and hexamine concentrations in the reaction vessel play a crucial role related to the ZnO nanorods.

  12. Ultrafast Formation of ZnO Nanorods via Seed-Mediated Microwave Assisted Hydrolysis Process

    NASA Astrophysics Data System (ADS)

    Tan, S. T.; Umar, A. A.; Yahaya, M.; Yap, C. C.; Salleh, M. M.

    2013-04-01

    One dimensional (1D) zinc oxide, ZnO nanostructures have shown promising results for usage in photodiode and optoelectronic device due to their high surface area. Faster and conventional method for synthesis ZnO nanorods has become an attention for researcher today. In this paper, ZnO nanorods have been successfully synthesized via two-step process, namely alcothermal seeding and seed-mediated microwave hydrolysis process. In typical process, the ZnO nanoseeds were grown in the growth solution that contained equimolar (0.04 M) of zinc nitrate hexahydrate, Zn (NO3).6H2O and hexamethylenetetramine, HMT. The growth process was carried inside the inverted microwave within 5- 20 s. The effect of growth parameters (i.e. concentration, microwave power, time reaction) upon the modification of ZnO morphology was studied. ZnO nanostructures were characterized by Field emission scanning electron microscope (FESEM) and X-ray diffraction (XRD). The densities of nanorods were evaluated by the Image J analysis. It was found that the morphology (e.g. shape and size) of nanostructures has changed drastically with the increment of growth solution concentration. The density of ZnO nanorods was proven to increase with the increasing of reaction time and microwave power. We hypothesize that the microwave power might enhance the rate of nucleation and promote the faster nanostructure growth as compared with the normal heating condition due to the superheating phenomenon. This method might promote a new and faster alternative way in nanostructure growth which can be applied in currently existing application.

  13. Hydrothermally Processed Photosensitive Field-Effect Transistor Based on ZnO Nanorod Networks

    NASA Astrophysics Data System (ADS)

    Kumar, Ashish; Bhargava, Kshitij; Dixit, Tejendra; Palani, I. A.; Singh, Vipul

    2016-11-01

    Formation of a stable, reproducible zinc oxide (ZnO) nanorod-network-based photosensitive field-effect transistor using a hydrothermal process at low temperature has been demonstrated. K2Cr2O7 additive was used to improve adhesion and facilitate growth of the ZnO nanorod network over the SiO2/Si substrate. Transistor characteristics obtained in the dark resemble those of the n-channel-mode field-effect transistor (FET). The devices showed I on/ I off ratio above 8 × 102 under dark condition, field-effect mobility of 4.49 cm2 V-1 s-1, and threshold voltage of -12 V. Further, under ultraviolet (UV) illumination, the FET exhibited sensitivity of 2.7 × 102 in off-state (-10 V) versus 1.4 in on-state (+9.7 V) of operation. FETs based on such nanorod networks showed good photoresponse, which is attributed to the large surface area of the nanorod network. The growth temperature for ZnO nanorod networks was kept at 110°C, enabling a low-temperature, cost-effective, simple approach for high-performance ZnO-based FETs for large-scale production. The role of network interfaces in the FET performance is also discussed.

  14. Time-dependent mechanical-electrical coupled behavior in single crystal ZnO nanorods

    PubMed Central

    Kim, Yong-Jae; Yun, Tae Gwang; Choi, In-Chul; Kim, Sungwoong; Park, Won Il; Han, Seung Min; Jang, Jae-il

    2015-01-01

    Nanoscale time-dependent mechanical-electrical coupled behavior of single crystal ZnO nanorods was systematically explored, which is essential for accessing the long-term reliability of the ZnO nanorod-based flexible devices. A series of compression creep tests combined with in-situ electrical measurement was performed on vertically-grown single crystal ZnO nanorods. Continuous measurement of the current (I)-voltage (V) curves before, during, after the creep tests revealed that I is non-negligibly increased as a result of the time-dependent deformation. Analysis of the I-V curves based on the thermionic emission-diffusion theory allowed extraction of nanorod resistance, which was shown to decrease as time-dependent deformation. Finally, based on the observations in this study, a simple analytical model for predicting the reduction in nanorod resistance as a function of creep strain that is induced from diffusional mechanisms is proposed, and this model was demonstrated to be in an excellent agreement with the experimental results. PMID:25982962

  15. ZnO Nanorod Array Grown on Ag Layer: A Highly Efficient Fluorescence Enhancement Platform

    PubMed Central

    Yin, Yongqi; Sun, Ye; Yu, Miao; Liu, Xiao; Jiang, Tingting; Yang, Bin; Liu, Danqing; Liu, Shaoqin; Cao, Wenwu

    2015-01-01

    ZnO nanorods (NRs) are known for ultra-sensitive biomolecule detection through fluorescence enhancement. In this work, we demonstrate that ZnO NR arrays grown on Ag layers can significantly improve the enhancement up to 86 times compared to that grown on bare Si, and the enhancement can be modified in a controlled manner by varying Ag thickness. The much improved waveguide properties are attributed to the high reflectance of the Ag layers and their tuning effect on the diameters of ZnO NRs. Our results provide a deep insight into the mechanism of NRs-based fluorescence enhancement platform. PMID:25633246

  16. Hydrogen peroxide generation and photocatalytic degradation of estrone by microstructural controlled ZnO nanorod arrays

    NASA Astrophysics Data System (ADS)

    Liu, Yangsi; Han, Jie; Qiu, Wei; Gao, Wei

    2012-12-01

    The strong oxidant, hydrogen peroxide (H2O2), generated by ZnO nanorod arrays under UV light irradiation was monitored by fluorescence analysis. The ZnO nanorod arrays were synthesized via a low temperature hydrothermal method and their dimensions, i.e., diameter and height, can be controlled by adjusting the concentration of zinc nitrate (Zn(NO3)2·6H2O) and hexamethylenetetramine (HMT). The morphology, nanostructure, surface roughness and optical property were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), atomic force microscopy (AFM) and transmittance spectra, respectively. The ZnO nanorod arrays were applied in the degradation of estrone, which is an emerging steroid estrogen contaminant. The results revealed that the ZnO nanorod array produced from 25 mM Zn2+ and HMT had the highest aspect ratio, the largest surface roughness and the lowest band gap energy, which was beneficial to the efficiency of UV light utilization, photocatalytic degradation of estrone and H2O2 generation.

  17. Non-enzymatic Fluorescent Biosensor for Glucose Sensing Based on ZnO Nanorods

    NASA Astrophysics Data System (ADS)

    Mai, Hong Hanh; Pham, Van Thanh; Nguyen, Viet Tuyen; Sai, Cong Doanh; Hoang, Chi Hieu; Nguyen, The Binh

    2017-02-01

    We have developed a non-enzymatic fluorescent biosensor for glucose sensing based on ZnO nanorods. ZnO nanorods of high density, high crystallinity, and good alignment were grown on low-cost industrial copper substrates at low temperature. To grow them directly on the substrates without using a seed layer, we utilized a simple one-step seedless hydrothermal method, which is based on galvanic cell structure. Herein, the glucose-treated ZnO nanorods together with the ultraviolet (UV) irradiation of the sample during the photoluminescent measurement played the role of a catalyst. They decomposed glucose into hydrogen peroxide (H2O2) and gluconic acid, which is similar to the glucose oxidase enzyme (GOx) used in enzymatic sensors. Due to the formation of H2O2, the photoluminescence intensity of the UV emission peak of ZnO nanorods decreased as the glucose concentration increased from 1 mM to 100 mM. In comparison with glucose concentration of a normal human serum, which is in the range of 4.4-6.6 mM, the obtained results show potential of non-enzymatic fluorescent biosensors in medical applications.

  18. Enhanced light extraction of GaN-based light-emitting diodes with periodic textured SiO2 on Al-doped ZnO transparent conductive layer

    NASA Astrophysics Data System (ADS)

    Yu, Zhao; Bingfeng, Fan; Yiting, Chen; Yi, Zhuo; Zhoujun, Pang; Zhen, Liu; Gang, Wang

    2016-07-01

    We report an effective enhancement in light extraction of GaN-based light-emitting diodes (LEDs) with an Al-doped ZnO (AZO) transparent conductive layer by incorporating a top regular textured SiO2 layer. The 2 inch transparent through-pore anodic aluminum oxide (AAO) membrane was fabricated and used as the etching mask. The periodic pore with a pitch of about 410 nm was successfully transferred to the surface of the SiO2 layer without any etching damages to the AZO layer and the electrodes. The light output power was enhanced by 19% at 20 mA and 56% at 100 mA compared to that of the planar LEDs without a patterned surface. This approach offers a technique to fabricate a low-cost and large-area regular pattern on the LED chip for achieving enhanced light extraction without an obvious increase of the forward voltage. ).

  19. CROSS-DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY: Effect of Annealing Conditions on Properties of Sol-Gel Derived Al-Doped ZnO Thin Films

    NASA Astrophysics Data System (ADS)

    Gao, Mei-Zhen; Zhang, Feng; Liu, Jing; Sun, Hui-Na

    2009-08-01

    Transparent conductive Al-doped ZnO (AZO) thin films are prepared on normal glass substrates by the sol-gel spin coating method. The effects of drying conditions, annealing temperature and cooling rate on the structural, electrical and optical properties of AZO films are investigated by x-ray diffraction, scanning electron microscopy, the four-point probe method and UV-VIS spectrophotometry, respectively. The deposited films show a hexagonal wurtzite structure and high preferential c-axis orientation. As the drying temperature increases from 100°C to 300°C the resistivity of AZO films decreases dramatically. In contrast to the annealed films cooled in a furnace and in air, the resistivity of the annealed film which is cooled at -15°C is greatly reduced. Increasing the cooling rate dramatically increases the electrical conductivity of AZO films.

  20. Enhanced photocatalytic activity of Co doped ZnO nanodisks and nanorods prepared by a facile wet chemical method.

    PubMed

    Kuriakose, Sini; Satpati, Biswarup; Mohapatra, Satyabrata

    2014-07-07

    Cobalt doped ZnO nanodisks and nanorods were synthesized by a facile wet chemical method and well characterized by X-ray diffraction, field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM) with energy dispersive X-ray spectroscopy, photoluminescence spectroscopy, Raman spectroscopy and UV-visible absorption spectroscopy. The photocatalytic activities were evaluated for sunlight driven degradation of an aqueous methylene blue (MB) solution. The results showed that Co doped ZnO nanodisks and nanorods exhibit highly enhanced photocatalytic activity, as compared to pure ZnO nanodisks and nanorods. The enhanced photocatalytic activities of Co doped ZnO nanostructures were attributed to the combined effects of enhanced surface area of ZnO nanodisks and improved charge separation efficiency due to optimal Co doping which inhibit recombination of photogenerated charge carriers. The possible mechanism for the enhanced photocatalytic activity of Co doped ZnO nanostructures is tentatively proposed.

  1. Effect of surface modifications on ZnO nanorod arrays electrode for dye-sensitized solar cells.

    PubMed

    Qin, Zi; Huang, Yunhua; Liao, Qingliang; Zhang, Zheng; Zhang, Yue

    2012-01-01

    High quality, large area and well-oriented ZnO nanorod arrays electrodes were successfully synthesized on conductive transparent oxide substrates by low-temperature hydrothermal methods for dye-sensitized solar cells. Aiming at getting further enhancement and study the effect of the surface modification on cell performance, ZnO thin film and ZnO nanoparticles are carried out to modify the as-grown ZnO nanorod arrays. The morphology, structure and photoluminescence property of the modified ZnO electrodes are characterized in detail. Furthermore, the I-V characterization result shows that these modification methods have distinct influences on the performance of the cell based on ZnO nanorod arrays electrode. The overall conversion efficiency can be optimized by choosing the suitable modification route.

  2. Fabrication of ZnO nanorod using spray-pyrolysis and chemical bath deposition method

    SciTech Connect

    Ramadhani, Muhammad F. Pasaribu, Maruli A. H. Yuliarto, Brian Nugraha

    2014-02-24

    ZnO thin films with nanorod structure were deposited using Ultrasonic Spray Pyrolysis method for seed growth, and Chemical Bath Deposition (CBD) for nanorod growth. High purity Zn-hydrate and Urea are used to control Ph were dissolved in ethanol and aqua bidest in Ultrasonic Spray Pyrolysis process. Glass substrate was placed above the heater plate of reaction chamber, and subsequently sprayed with the range duration of 5, 10 and 20 minutes at the temperatures of 3500 C. As for the Chemical Bath Deposition, the glass substrate with ZnO seed on the surface was immerse to Zn-hydrate, HMTA (Hexa Methylene Tetra Amine) and deionized water solution for duration of 3, 5 and 7 hour and temperatures of 600 C, washed in distilled water, dried, and annealed at 3500 C for an hour. The characterization of samples was carried out to reveal the surface morphology using Scanning Electron Microscopy (SEM). From the data, the combination of 5 minutes of Ultrasonic Spray Pyrolysis process and 3 hour of CBD has showed the best structure of nanorod. Meanwhile the longer Spraying process and CBD yield the bigger nanorod structure that have been made, and it makes the films more dense which make the nanorod collide each other and as a result produce unsymetric nanorod structure.

  3. ZnO nanorod growth by plasma-enhanced vapor phase transport with different growth durations

    SciTech Connect

    Kim, Chang-Yong; Oh, Hee-bong; Ryu, Hyukhyun; Yun, Jondo; Lee, Won-Jae

    2014-09-01

    In this study, the structural properties of ZnO nanostructures grown by plasma-enhanced vapor phase transport (PEVPT) were investigated. Plasma-treated oxygen gas was used as the oxygen source for the ZnO growth. The structural properties of ZnO nanostructures grown for different durations were measured by scanning electron microscopy, x-ray diffraction, and transmission electron microscopy. The authors comprehensively analyzed the growth of the ZnO nanostructures with different growth durations both with and without the use of plasma-treated oxygen gas. It was found that PEVPT has a significant influence on the growth of the ZnO nanorods. PEVPT with plasma-treated oxygen gas facilitated the generation of nucleation sites, and the resulting ZnO nanorod structures were more vertical than those prepared by conventional VPT without plasma-treated oxygen gas. As a result, the ZnO nanostructures grown using PEVPT showed improved structural properties compared to those prepared by the conventional VPT method.

  4. Fabrication of ZnO nanorods and assessment of changes in optical and gas sensing properties by increasing their lengths

    NASA Astrophysics Data System (ADS)

    Mehrabian, Masood; Mirabbaszadeh, Kavoos; Afarideh, Hossein

    2013-12-01

    We report a low-temperature process to synthesize highly oriented arrays of ZnO nanorods, based on the epitaxial growth of the ZnO seed layer at a low temperature of 70 °C. The ZnO seed layer was deposited by sol-gel process under mild conditions on the glass substrates. The morphologies and crystal structures of the film and nanorods were characterized by x-ray diffraction and scanning electron microscopy, respectively. ZnO nanorods were grown on ZnO seed layers by hydrothermal method. The effect of growth period on the morphology and optical characteristics (e.g. optical transmission and band-gap energy), hydrophilicity and gas sensing properties of the grown ZnO seed layer (film) and nanorods were investigated. The long nanorods on the seed layer were observed. The increase in the length of the nanorods resulted in a significant reduction in the optical band-gap energy of the nanorods, which was attributed to the formation of further defects in the nanorods during their fast growth. The surface of the ZnO nanorods grown for 6 h was relatively hydrophilic (with a water contact angle of 18°). The fabricated sensors were used to gauge different concentrations of ethanol vapor in the air at different temperatures and evaluated the surface resistance of the sensors as a function of operating temperature and ethanol concentrations. The results showed that the sensitivity of the nanorods changed from 1.3 to 6 (at 300 °C) by increasing the growth period.

  5. Eradication of Multi-drug Resistant Bacteria by Ni Doped ZnO Nanorods: Structural, Raman and optical characteristics

    NASA Astrophysics Data System (ADS)

    Jan, Tariq; Iqbal, Javed; Ismail, Muhammad; Mansoor, Qaisar; Mahmood, Arshad; Ahmad, Amaar

    2014-07-01

    In this paper, ZnO nanorods doped with varying amounts of Ni have been prepared by chemical co-precipitation technique. Structural investigations provide the evidence that Ni is successfully doped into ZnO host matrix without having any secondary phases. Scanning electron microscopy (SEM) images reveal the formation of rodlike structure of undoped ZnO with average length and diameter of 1 μm and 80 nm, respectively. Raman spectroscopy results show that the E1LO phonons mode band shifts to the higher values with Ni doping, which is attributed to large amount of crystal defects. Ni doping is also found to greatly influence the optical properties of ZnO nanorods. The influence of Ni doping on antibacterial characteristics of ZnO nanorods have been studied by measuring the growth curves of Escherichia coli (E. coli), Methicillin-resistant Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa) bacteria in the presence of prepared nanorods. ZnO nanorods antibacterial potency is found to increase remarkably with Ni doping against S. aureus and P. aeruginosa microbials, which might possibly be due to the increase in reactive oxygen species (ROS) generation. Interestingly, it is observed that Ni doped ZnO nanorods completely eradicates these multi-drug resistant bacteria.

  6. Ag nanoparticles-decorated ZnO nanorod array on a mechanical flexible substrate with enhanced optical and antimicrobial properties

    NASA Astrophysics Data System (ADS)

    Chen, Yi; Tse, Wai Hei; Chen, Longyan; Zhang, Jin

    2015-03-01

    Heteronanostructured zinc oxide nanorod (ZnO NR) array are vertically grown on polydimethylsiloxane (PDMS) through a hydrothermal method followed by an in situ deposition of silver nanoparticles (Ag NPs) through a photoreduction process. The Ag-ZnO heterostructured nanorods on PDMS are measured with an average diameter of 160 nm and an average length of 2 μm. ZnO NRs measured by high-resolution transmission electron microscope (HRTEM) shows highly crystalline with a lattice fringe of 0.255 nm, which corresponds to the (0002) planes in ZnO crystal lattice. The average diameter of the Ag NPs in situ deposited on the ZnO NRs is estimated at 22 ± 2 nm. As compared to the bare ZnO NRs, the heterostructured Ag-ZnO nanorod array shows enhanced ultraviolet (UV) absorption at 440 nm, and significant emission in the visible region (λem = 542 nm). In addition, the antimicrobial efficiency of Ag-ZnO heterostructured nanorod array shows obvious improvement as compared to bare ZnO nanorod array. The cytotoxicity of ZnO nanorod array with and without Ag NPs was studied by using 3 T3 mouse fibroblast cell line. No significant toxic effect is imposed on the cells.

  7. Electrical characteristics of ZnO nanorods reinforced polymer nanocomposite thin films

    SciTech Connect

    Bhattacharjee, Snigdha; Roy, Asim

    2015-05-15

    ZnO nanorods have been prepared by simple chemical method, which is used to fabricate organic bistable devices (OBDs). OBDs are fabricated by incorporating different weight percent (wt %) of chemically synthesized Zinc Oxide (ZnO) nanorods into polymethylmethacrylate (PMMA). Current-voltage (I-V) measurements of the spin coated ZnO+PMMA nanocomopsite thin film on indium tin oxide (ITO) coated glass substrate showed current hysteresis behaviour, which is an indication of memory effect. The samples exhibit two distinct resistance states, ON and OFF states, characterised by relatively low and high resistance of the OBDs, respectively. It is also observed that with change in ZnO dopant concentration the value of ON/OFF current changes. Higher ON/OFF current ratio is desired for practical applications. Current conduction mechanism of the devices has been explained invoking various existing models, and it has been found that the trapped-charge-limited conduction mechanism was dominant in our samples.

  8. Improved photovoltaic performance of inverted polymer solar cells through a sol-gel processed Al-doped ZnO electron extraction layer.

    PubMed

    Kim, Jun Young; Cho, Eunae; Kim, Jaehoon; Shin, Hyeonwoo; Roh, Jeongkyun; Thambidurai, Mariyappan; Kang, Chan-mo; Song, Hyung-Jun; Kim, SeongMin; Kim, Hyeok; Lee, Changhee

    2015-09-21

    We demonstrate that nanocrystalline Al-doped zinc oxide (n-AZO) thin film used as an electron-extraction layer can significantly enhance the performance of inverted polymer solar cells based on the bulk heterojunction of poly[[9-(1-octylnonyl)-9H-carbazole-2,7-diyl]-2,5-thiophenediyl-2,1,3-benzothiadiazole-4,7-diyl-2,5-thiophenediyl] (PCDTBT) and [6,6]-phenyl C(71)-butyric acid methyl ester (PC(70)BM). A synergistic study with both simulation and experiment on n-AZO was carried out to offer a rational guidance for the efficiency improvement. As a result, An n-AZO film with an average grain size of 13 to 22 nm was prepared by a sol-gel spin-coating method, and a minimum resistivity of 2.1 × 10(-3) Ω·cm was obtained for an Al-doping concentration of 5.83 at.%. When an n-AZO film with a 5.83 at.% Al concentration was inserted between the ITO electrode and the active layer (PCDTBT:PC(70)BM), the power conversion efficiency increased from 3.7 to 5.6%.

  9. Plasmonic enhancement of blue emission from ZnO nanorods grown on the anodic aluminum oxide (AAO) template

    NASA Astrophysics Data System (ADS)

    Norek, Małgorzata; Łuka, Grzegorz; Godlewski, Marek; Płociński, Tomasz; Michalska-Domańska, Marta; Stępniowski, Wojciech J.

    2013-04-01

    Luminescent properties of ZnO nanorods covered with Ag nanoparticles are examined. Nanorods were synthesized on AAO templates using Atomic Layer Deposition (ALD) technique. Two types of the samples were prepared with different arrangement of ZnO nanorods and doping conditions. Nanorods of the second type were codoped with Al, to stimulate defect-related emissions. The ZnO material fills heterogeneously the interior of the AAO nanopores and has hexagonal, wurtzite structure. Both types of structures exhibit a broad defect-related emission at about 440 nm, most probably related to recombination at zinc interstitial (Zni) defects. This emission in samples with a random distribution of ZnO:Al nanorods and finer Ag nanoparticles is enhanced by factor of ˜2.5 upon Ag deposition. The so-obtained material is interesting from the point of view of its application in blue range emitting diodes.

  10. Photorefractive Effect of a Liquid Crystal Cell with a ZnO Nanorod Doped in Only One PVA Layer

    NASA Astrophysics Data System (ADS)

    Guo, Yu-Bing; Chen, Yong-Hai; Xiang, Ying; Qu, Sheng-Chun; Wang, Zhan-Guo

    2011-09-01

    We observe obviously different diffraction efficiencies with forward and reverse dc voltages in a forced-light-scattering (FLS) experiment for a cell with ZnO nanorod doped in only one poly (vinyl alcohol) (PVA) layer. When a dc voltage with a positive pole on the ZnO nanorod doped side is applied, the excited charge carriers primarily move along the transverse direction, which results in a higher diffraction efficiency. Conversely, when the dc voltage with a negative pole on the ZnO nanorod doped side is applied, the excited charge carriers primarily move along the longitudinal direction, which leads to a lower diffraction efficiency. A largest diffraction efficiency of about 9% is achieved in the ZnO nanorod doped liquid crystal cell.

  11. Study on synthesis of ZnO nanorods and its UV-blocking properties on cotton fabrics coated with the ZnO quantum dot

    NASA Astrophysics Data System (ADS)

    Li, Rong; Che, Jiangning; Zhang, Heng; He, Jinsong; Bahi, Addie; Ko, Frank

    2014-09-01

    Crystalline ZnO quantum dots have been synthesized by hydrolysis of zinc acetate dihydrate with lithium hydroxide in ethanolic solution. The effects of different synthesis parameters on the structure and optical properties of ZnO QDs were investigated in detail. The UV-Vis optical spectra showed that the particle size is highly dependent on the precursor concentration and temperature, while the luminescence properties of as-prepared ZnO QDs depend on the both size and surface properties of particles. UV-blocking cotton fabrics were prepared by coated with ZnO nanorods. The preparation process was conducted in mild conditions, which involved the dip-coating ZnO QDs as crystal seeds, the dissolution-recrystallization of ZnO nanorods, and the hydrothermal growth of ZnO nanorods. The ZnO nanorods covered the cotton fibers uniformly and densely. The treated cotton textile exhibited an excellent UV-blocking property with an ultrahigh UPF value of 118.12.

  12. Performance of colloidal CdS sensitized solar cells with ZnO nanorods/nanoparticles

    PubMed Central

    Roy, Anurag; Das, Partha Pratim; Tathavadekar, Mukta; Das, Sumita

    2017-01-01

    As an alternative photosensitizer in dye-sensitized solar cells, bovine serum albumin (BSA) (a nonhazardous protein) was used in the synthesis of colloidal CdS nanoparticles (NPs). This system has been employed to replace the commonly used N719 dye molecule. Various nanostructured forms of ZnO, namely, nanorod and nanoparticle-based photoanodes, have been sensitized with colloidal CdS NPs to evaluate their effective performance towards quantum dot sensitized solar cells (QDSSCs). A polysulphide (Sx 2−)-based electrolyte and CuxS counter electrode were used for cell fabrication and testing. An interesting improvement in the performance of the device by imposing nanorods as a scattering layer on a particle layer has been observed. As a consequence, a maximum conversion efficiency of 1.06% with an open-circuit voltage (V OC) of 0.67 V was achieved for the ZnO nanorod/nanoparticle assembled structure. The introduction of ZnO nanorods over the nanoparticle led to a significant enhancement of the overall efficiency compared to the corresponding bare nanoparticles. PMID:28243559

  13. Investigation of the phototoxic effect of ZnO nanorods on fibroblasts and melanoma human cells

    NASA Astrophysics Data System (ADS)

    Kishwar, S.; Siddique, M.; Israr-Qadir, M.; Nur, O.; Willander, M.; Öllinger, K.

    2014-11-01

    Photocytotoxic effects of as-grown and zinc oxide (ZnO) nanorods coated with 5-aminolevulinic acid (ALA) have been studied on human cells, i.e. melanoma and foreskin fibroblast, under dark and ultraviolet light exposures. Zinc oxide nanorods have been grown on the very sharp tip (diameter = 700 nm) of borosilicate glass pipettes and then were coated by the photosensitizer for targeted investigations inside human cells. The coated glass pipette’s tip with photosensitizer has been inserted inside the cells with the help of a micro-manipulator and irradiated through ultraviolet light (UVA), which reduces the membrane potential of the mitochondria leading to cell death. Cell viability loss has been detected by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction assay when exposed to the dissolved ZnO nanorods and the production of the reactive oxygen species (ROS) has been detected along with the enhanced cytotoxic effect under UVA irradiation. Additionally, the influence of the lipid soluble antioxidant vitamin E and water-soluble N-acetyl-cysteine toward the enhancement or reduction of the toxicity has been investigated. A comparative analysis of the toxic nature of ZnO nanorods has been drawn between normal human fibroblast and melanoma cells, which can be favorable for understanding the clinical setting for killing tumor cells.

  14. Novel Gas Sensor Based on ZnO Nanorod Circular Arrays for C2H5OH Gas Detection.

    PubMed

    Jianjiao, Zhang; Hongyan, Yue; Erjun, Guo; Shaolin, Zhang; Liping, Wang; Chunyu, Zhang; Xin, Gao; Jing, Chang; Hong, Zhang

    2015-03-01

    Novel side-heating gas sensor based on ZnO nanorod circular arrays was firstly fabricated by hydrothermal treatment assisted with a kind of simple dip-coating technique. The structure and morphologies of ZnO nanorods were characterized by X-ray diffraction (XRD), Scanning Electron Microscope (SEM), respectively. XRD result indicates that the obtained ZnO nanorods have good crystalline with the hexagonal wurtzite structure. SEM result indicates that ZnO nanorod arrays are vertically growth on the surface of ceramic tube of side-heating sensor with controlled diameter and length, narrow size distribution and high orientation. The gas sensing properties of ZnO nanorod circular arrays are also evaluated. Comparative to the sensor based on scattered ZnO nanorods responding to 25 ppm H2, CO, C6H5CH3 and C2H5OH gas, respectively, the sensing values of high orientation gas sensor are generally increased by 5%. This novel sensor has good application promising for the fabrication of cost effective and high performance gas sensors.

  15. Ultraviolet band-pass Schottky barrier photodetectors formed by Al-doped ZnO contacts to n-GaN

    SciTech Connect

    Sheu, J.K.; Lee, M.L.; Tun, C.J.; Lin, S.W.

    2006-01-23

    This work prepared Al-doped ZnO(AZO) films using dc sputtering to form Schottky contacts onto GaN films with low-temperature-grown GaN cap layer. Application of ultraviolet photodetector showed that spectral responsivity exhibits a narrow bandpass characteristic ranging from 345 to 375 nm. Moreover, unbiased peak responsivity was estimated to be around 0.12 A/W at 365 nm, which corresponds to a quantum efficiency of around 40%. In our study, relatively low responsivity can be explained by the marked absorption of the AZO contact layer. When the reverse biases were below 5 V, the study revealed that dark currents were well below 5x10{sup -12} A even though the samples were annealed at increased temperatures.

  16. Fabrication of hexagonal ZnO nanorods on porous carbon matrix by microwave irradiation.

    PubMed

    Suresh, P; Vijaya, J Judith; Kennedy, L John

    2013-04-01

    The hexagonal ZnO nanorods supported activated carbon (ZSAC) was successfully prepared using zinc nitrate hexahydrate and urea through microwave irradiation. The method of preparation is simple and cost effective. The activated carbon (AC) with high surface area (446.44 m2/g), pore volume (00.21 cm3/g) and average pore diameter (01.89 nm) was employed as a matrix support for the growth of ZnO nanorods. The XRD results affirm the formation of wurtzite ZnO nanostructures. The FT-IR studies disclose the presence of varied functional groups present in ZSAC. The HR-SEM images reveal the pore morphology of AC and hexagonal shape of ZnO nanorods formed. The E(g) value obtained from Kubelka-Munk transformed reflectance spectra is about 3.43 eV. The photoluminescence emissions reveal the defects in the crystal lattice. The ZSAC thus prepared would perform substantial role in the area of catalysis.

  17. ZnO nanorods as catalyts for biodiesel production from olive oil

    NASA Astrophysics Data System (ADS)

    Molina, Carmen Maria Miralda

    The motivation to determine a viable alternative to petroleum based energy has risen in recent years due to increased greenhouse gas emissions, environmental pollution, and the fear of exhausting oil and natural gas reserves. Biodiesel derived from the transesterification of vegetable oils or animal fats has emerged as a viable alternative to petroleum diesel. However, for this to become an option available to the average consumer it is vital to find an effective catalyst. Metal oxides have emerged as potential heterogeneous catalysts. ZnO in particular is attractive because it is abundant. The use of nanostructures has been shown to improve the catalytic performance of ZnO. ZnO nanorods were synthesized using a solution approach. The crystalline structure, morphology, and surface area were confirmed using XRD, SEM, and BET surface area respectively. The characterized nanorods were used as catalysts for the production of biodiesel. The nanorods achieved conversions of 94.8% at 150°C for reaction times of eight hours. They also demonstrated better catalytic performance, attributed to their increased degree of crystallinity, than conventional ZnO. A kinetic study at 150°C to determine the reaction rate parameters was also conducted. Due to the presence of three distinct phases in the reaction, initially the reaction rate is dominated by mass transfer limitations. However, these are eventually overcome and the reaction proceeds with a pseudo-first order with respect to the oil and a reaction rate constant of 0.5136 h-1.

  18. Defects in ZnO nanorods prepared by a hydrothermal method.

    PubMed

    Tam, K H; Cheung, C K; Leung, Y H; Djurisić, A B; Ling, C C; Beling, C D; Fung, S; Kwok, W M; Chan, W K; Phillips, D L; Ding, L; Ge, W K

    2006-10-26

    ZnO nanorod arrays were fabricated using a hydrothermal method. The nanorods were studied by scanning electron microscopy, photoluminescence (PL), time-resolved PL, X-ray photoelectron spectroscopy, and positron annihilation spectroscopy before and after annealing in different environments and at different temperatures. Annealing atmosphere and temperature had significant effects on the PL spectrum, while in all cases the positron diffusion length and PL decay times were increased. We found that, while the defect emission can be significantly reduced by annealing at 200 degrees C, the rods still have large defect concentrations as confirmed by their low positron diffusion length and short PL decay time constants.

  19. Enhanced ethanol sensing properties of TiO2/ZnO core-shell nanorod sensors

    NASA Astrophysics Data System (ADS)

    Park, Sunghoon; An, Soyeon; Ko, Hyunsung; Lee, Sangmin; Kim, Hyoun Woo; Lee, Chongmu

    2014-06-01

    TiO2-core/ZnO-shell nanorods were synthesized using a two-step process: the synthesis of TiO2 nanorods using a hydrothermal method followed by atomic layer deposition of ZnO. The mean diameter and length of the nanorods were ˜300 nm and ˜2.3 μm, respectively. The cores and shells of the nanorods were monoclinic-structured single-crystal TiO2 and wurtzite-structured single-crystal ZnO, respectively. The multiple networked TiO2-core/ZnO-shell nanorod sensors showed responses of 132-1054 % at ethanol (C2H5OH) concentrations ranging from 5 to 25 ppm at 150 ∘C. These responses were 1-5 times higher than those of the pristine TiO2 nanorod sensors at the same C2H5OH concentration range. The substantial improvement in the response of the pristine TiO2 nanorods to C2H5OH gas by their encapsulation with ZnO may be attributed to the enhanced absorption and dehydrogenation of ethanol. In addition, the enhanced sensor response of the core-shell nanorods can be attributed partly to changes in resistance due to both the surface depletion layer of each core-shell nanorod and the potential barriers built in the junctions caused by a combination of homointerfaces and heterointerfaces.

  20. Defect-free ZnO nanorods for low temperature hydrogen sensor applications

    SciTech Connect

    Ranwa, Sapana; Kumar, Mahesh; Kulriya, Pawan K.; Sahu, Vikas Kumar; Kukreja, L. M.

    2014-11-24

    Uniformly distributed and defect-free vertically aligned ZnO nanorods (NRs) with high aspect ratio are deposited on Si by sputtering technique. X-ray diffraction along with transmission electron microscopy studies confirmed the single crystalline wurtzite structure of ZnO. Absence of wide band emission in photoluminescence spectra showed defect-free growth of ZnO NRs which was further conformed by diamagnetic behavior of the NRs. H{sub 2} sensing mechanism based on the change in physical dimension of channel is proposed to explain the fast response (∼21.6 s) and recovery times (∼27 s) of ZnO NRs/Si/ZnO NRs sensors. Proposed H{sub 2} sensor operates at low temperature (∼70 °C) unlike the existing high temperature (>150 °C) sensors.

  1. ZnO nanorod array random lasers fabricated by a laser-induced hydrothermal synthesis

    NASA Astrophysics Data System (ADS)

    Fujiwara, Hideki; Suzuki, Takemasa; Niyuki, Ryo; Sasaki, Keiji

    2016-10-01

    We demonstrate random lasing in ZnO nanorod array (NRA) structures fabricated by a laser-induced hydrothermal growth, which would make it possible to control structural parameters, such as diameter, length, density and so on, by adjusting the laser irradiation time and intensity. To realize low-threshold ZnO NRA random lasers, we attempt to optimize the structure by changing the laser irradiation time (growth time). From the results, we confirmed that the fabricated ZnO NRAs after CO2 laser annealing could induce UV random lasing and their thresholds strongly depend on the growth time. Thus, we succeed to realize ZnO NRA random lasers and suggest the possibility to control the random lasing properties by adjusting the irradiated laser conditions.

  2. Nanoscale elastic modulus of single horizontal ZnO nanorod using nanoindentation experiment.

    PubMed

    Soomro, Muhammad Yousuf; Hussain, Ijaz; Bano, Nargis; Broitman, Esteban; Nur, Omer; Willander, Magnus

    2012-02-21

    We measure the elastic modulus of a single horizontal ZnO nanorod [NR] grown by a low-temperature hydrothermal chemical process on silicon substrates by performing room-temperature, direct load-controlled nanoindentation measurements. The configuration of the experiment for the single ZnO NR was achieved using a focused ion beam/scanning electron microscope dual-beam instrument. The single ZnO NR was positioned horizontally over a hole on a silicon wafer using a nanomanipulator, and both ends were bonded with platinum, defining a three-point bending configuration. The elastic modulus of the ZnO NR, extracted from the unloading curve using the well-known Oliver-Pharr method, resulted in a value of approximately 800 GPa. Also, we discuss the NR creep mechanism observed under indentation. The mechanical behavior reported in this paper will be a useful reference for the design and applications of future nanodevices.

  3. Nanoscale elastic modulus of single horizontal ZnO nanorod using nanoindentation experiment

    PubMed Central

    2012-01-01

    We measure the elastic modulus of a single horizontal ZnO nanorod [NR] grown by a low-temperature hydrothermal chemical process on silicon substrates by performing room-temperature, direct load-controlled nanoindentation measurements. The configuration of the experiment for the single ZnO NR was achieved using a focused ion beam/scanning electron microscope dual-beam instrument. The single ZnO NR was positioned horizontally over a hole on a silicon wafer using a nanomanipulator, and both ends were bonded with platinum, defining a three-point bending configuration. The elastic modulus of the ZnO NR, extracted from the unloading curve using the well-known Oliver-Pharr method, resulted in a value of approximately 800 GPa. Also, we discuss the NR creep mechanism observed under indentation. The mechanical behavior reported in this paper will be a useful reference for the design and applications of future nanodevices. PMID:22353250

  4. Nanoscale elastic modulus of single horizontal ZnO nanorod using nanoindentation experiment

    NASA Astrophysics Data System (ADS)

    Soomro, Muhammad Yousuf; Hussain, Ijaz; Bano, Nargis; Broitman, Esteban; Nur, Omer; Willander, Magnus

    2012-02-01

    We measure the elastic modulus of a single horizontal ZnO nanorod [NR] grown by a low-temperature hydrothermal chemical process on silicon substrates by performing room-temperature, direct load-controlled nanoindentation measurements. The configuration of the experiment for the single ZnO NR was achieved using a focused ion beam/scanning electron microscope dual-beam instrument. The single ZnO NR was positioned horizontally over a hole on a silicon wafer using a nanomanipulator, and both ends were bonded with platinum, defining a three-point bending configuration. The elastic modulus of the ZnO NR, extracted from the unloading curve using the well-known Oliver-Pharr method, resulted in a value of approximately 800 GPa. Also, we discuss the NR creep mechanism observed under indentation. The mechanical behavior reported in this paper will be a useful reference for the design and applications of future nanodevices.

  5. Thiol dosing of ZnO single crystals and nanorods: Surface chemistry and photoluminescence

    NASA Astrophysics Data System (ADS)

    Singh, Jagdeep; Im, Jisun; Watters, Evan J.; Whitten, James E.; Soares, Jason W.; Steeves, Diane M.

    2013-03-01

    Adsorption of thiols on ZnO(0001) and ZnO nanorods has been investigated using X-ray and ultraviolet photoelectron spectroscopies (XPS and UPS). Ultrahigh vacuum (UHV) dosing of sputter-cleaned ZnO(0001) with methanethiol (MT), 1-dodecanethiol (DDT), and 3-mercaptopropyltrimethoxysilane (MPTMS) leads to S2p peaks with a binding energy of 163.3 eV. Similar results for MPTMS are obtained for sputter-cleaned ZnO(0001) that is pre-dosed with water to form hydroxyl groups. In all cases, the absence of a free thiol S2p peak at 164.2 eV indicates that bonding to the surface occurs via the thiol end of the molecule. A DDT-dosed ZnO(0001) sample stored for 10 days in UHV and heated to temperatures as high as 150 °C exhibits minimal changes in its S/Zn atomic ratio, confirming chemisorption and the presence of a strong bond to the surface. UPS shows that MT adsorption on sputtered ZnO(0001) leads to a 0.7 eV increase in work function and perturbation of the MT molecular orbitals, again consistent with chemisorption. Dry ZnO nanorods have been exposed to MT while monitoring their photoluminescence. XPS and Raman spectroscopy confirm thiol adsorption. Relative to dry ZnO, adsorption causes a decrease in intensity of the visible emission peak, but the UV peak remains unchanged. These results indicate that Znsbnd S bond formation quenches radiative decay to the valence band from defect states, possibly by methanethiolate adsorption filling oxygen vacancies.

  6. Chemical solution route to synthesize claw-like ZnO nanorod array and its optical properties

    NASA Astrophysics Data System (ADS)

    Hu, Ling-wei; Hu, Chun-hong; Tian, Hua; Zhang, Yu-xia; Jing, Ai-hua

    2014-03-01

    By using a low-cost and facile hydrothermal method, a peculiar claw-like ZnO nanorod array is successfully synthesized. The hydrothermal growth is done in an aqueous solution with equimolar zinc acetate (ZAc, Zn(CH3COO)2·2H2O) and hexamethylenetetramine (HMTA, C6H12N4). The obtained ZnO nanorod array is characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results indicate that the nanorods are high-quality monocrystals. The photoluminescence (PL) spectrum is performed to investigate the optical properties of this product.

  7. Engineering safer-by-design, transparent, silica-coated ZnO nanorods with reduced DNA damage potential

    PubMed Central

    Sotiriou, Georgios A.; Watson, Christa; Murdaugh, Kimberly M.; Darrah, Thomas H.; Pyrgiotakis, Georgios; Elder, Alison; Brain, Joseph D.; Demokritou, Philip

    2014-01-01

    Zinc oxide (ZnO) nanoparticles absorb UV light efficiently while remaining transparent in the visible light spectrum rendering them attractive in cosmetics and polymer films. Their broad use, however, raises concerns regarding potential environmental health risks and it has been shown that ZnO nanoparticles can induce significant DNA damage and cytotoxicity. Even though research on ZnO nanoparticle synthesis has made great progress, efforts on developing safer ZnO nanoparticles that maintain their inherent optoelectronic properties while exhibiting minimal toxicity are limited. Here, a safer-by-design concept was pursued by hermetically encapsulating ZnO nanorods in a biologically inert, nanothin amorphous SiO2 coating during their gas-phase synthesis. It is demonstrated that the SiO2 nanothin layer hermetically encapsulates the core ZnO nanorods without altering their optoelectronic properties. Furthermore, the effect of SiO2 on the toxicological profile of the core ZnO nanorods was assessed using the Nano-Cometchip assay by monitoring DNA damage at a cellular level using human lymphoblastoid cells (TK6). Results indicate significantly lower DNA damage (>3 times) for the SiO2-coated ZnO nanorods compared to uncoated ones. Such an industry-relevant, scalable, safer-by-design formulation of nanostructured materials can liberate their employment in nano-enabled products and minimize risks to the environment and human health. PMID:24955241

  8. ZnO Nanorods via Spray Deposition of Solutions Containing Zinc Chloride and Thiocarbamide.

    PubMed

    Dedova, Tatjana; Volobujeva, Olga; Klauson, Jelena; Mere, Arvo; Krunks, Malle

    2007-07-19

    In this work we present the results on formation of ZnO nanorods prepared by spray of aqueous solutions containing ZnCl2and thiocarbamide (tu) at different molar ratios. It has been observed that addition of thiocarbamide into the spray solution has great impact on the size, shape and phase composition of the ZnO crystals. Obtained layers were characterized by scanning electron microscopy (SEM) equipped with energy selected backscattered electron detection system (ESB), X-ray diffraction (XRD) and photoluminescence spectroscopy (PL). Small addition of thiocarbamide into ZnCl2solution (ZnCl2:tu = 1:0.25) supports development of significantly thinner ZnO nanorods with higher aspect ratio compared to those obtained from ZnCl2solution. Diameter of ZnO rods decreases from 270 to 100 nm and aspect ratio increases from ∼2.5 to 12 spraying ZnCl2and ZnCl2:tu solutions, respectively. According to XRD, well crystallized (002) orientated pure wurtzite ZnO crystals have been formed. However, tiny 'spot'-like formations of ZnS were detected on the side planes of hexagonal rods prepared from the thiocarbamide containing solutions. Being adsorbed on the side facets of the crystals ZnS inhibits width growth and promotes longitudinalc-axis growth.

  9. ZnO Nanorods via Spray Deposition of Solutions Containing Zinc Chloride and Thiocarbamide

    PubMed Central

    2007-01-01

    In this work we present the results on formation of ZnO nanorods prepared by spray of aqueous solutions containing ZnCl2and thiocarbamide (tu) at different molar ratios. It has been observed that addition of thiocarbamide into the spray solution has great impact on the size, shape and phase composition of the ZnO crystals. Obtained layers were characterized by scanning electron microscopy (SEM) equipped with energy selected backscattered electron detection system (ESB), X-ray diffraction (XRD) and photoluminescence spectroscopy (PL). Small addition of thiocarbamide into ZnCl2solution (ZnCl2:tu = 1:0.25) supports development of significantly thinner ZnO nanorods with higher aspect ratio compared to those obtained from ZnCl2solution. Diameter of ZnO rods decreases from 270 to 100 nm and aspect ratio increases from ∼2.5 to 12 spraying ZnCl2and ZnCl2:tu solutions, respectively. According to XRD, well crystallized (002) orientated pure wurtzite ZnO crystals have been formed. However, tiny ‘spot’—like formations of ZnS were detected on the side planes of hexagonal rods prepared from the thiocarbamide containing solutions. Being adsorbed on the side facets of the crystals ZnS inhibits width growth and promotes longitudinalc-axis growth. PMID:21794191

  10. Self-assembled, aligned ZnO nanorod buffer layers for high-current-density, inverted organic photovoltaics.

    PubMed

    Rao, Arun D; Karalatti, Suresh; Thomas, Tiju; Ramamurthy, Praveen C

    2014-10-08

    Two different soft-chemical, self-assembly-based solution approaches are employed to grow zinc oxide (ZnO) nanorods with controlled texture. The methods used involve seeding and growth on a substrate. Nanorods with various aspect ratios (1-5) and diameters (15-65 nm) are grown. Obtaining highly oriented rods is determined by the way the substrate is mounted within the chemical bath. Furthermore, a preheat and centrifugation step is essential for the optimization of the growth solution. In the best samples, we obtain ZnO nanorods that are almost entirely oriented in the (002) direction; this is desirable since electron mobility of ZnO is highest along this crystallographic axis. When used as the buffer layer of inverted organic photovoltaics (I-OPVs), these one-dimensional (1D) nanostructures offer: (a) direct paths for charge transport and (b) high interfacial area for electron collection. The morphological, structural, and optical properties of ZnO nanorods are studied using scanning electron microscopy, X-ray diffraction, and ultraviolet-visible light (UV-vis) absorption spectroscopy. Furthermore, the surface chemical features of ZnO films are studied using X-ray photoelectron spectroscopy and contact angle measurements. Using as-grown ZnO, inverted OPVs are fabricated and characterized. For improving device performance, the ZnO nanorods are subjected to UV-ozone irradiation. UV-ozone treated ZnO nanorods show: (i) improvement in optical transmission, (ii) increased wetting of active organic components, and (iii) increased concentration of Zn-O surface bonds. These observations correlate well with improved device performance. The devices fabricated using these optimized buffer layers have an efficiency of ∼3.2% and a fill factor of 0.50; this is comparable to the best I-OPVs reported that use a P3HT-PCBM active layer.

  11. Well-Aligned Arrays of Vertically Oriented ZnO Nanorod Films for Photocatalytic Degradation of Textile Dye

    NASA Astrophysics Data System (ADS)

    Nasr-Esfahani, Mojtaba; Nekoubin, Amin

    2011-05-01

    Well-aligned hexagonal ZnO nanorods arrays were synthesized via mild hydrothermal method under different conditions. A two-step approach was employed for the epitaxial growth of ZnO. First a ZnO seed layer was prepared by spin-coating process and then ZnO nanorods were deposited on it. The influences of growth time on the surface morphology, length, diameters and phase structure of ZnO rods films were investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The photocatalytic degradation of X6G an anionic monoazo dye, in aqueous solutions, was investigated and the effects of hydrothermal process time were examined. The results showed that the ZnO nonorods film hydrothermal treated for 4 h have a very high photocatalytic performance.

  12. Humidity sensor base on the ZnO nanorods and fiber modal interferometer

    NASA Astrophysics Data System (ADS)

    Wang, Jian; Zhang, Huan; Cao, Zhigang; Zhang, Xinyu; Yin, Chenchen; Li, Kang; Zhang, Guosheng; Yu, Benli

    2016-10-01

    A novel fiber relative humidity (RH) sensor is demonstrated in this paper. The sensor is composed of a fiber Michelson modal interferometer (MMI) and the ZnO nanorods which grown on the fiber to improve the sensitivity of the sensor. Two standard single mode fibers are spliced to form the MMI, misaligned splicing program is used at the spliced point. Relative humidity sensing experiment shows that the intensity of interference spectrum changes linearly with relative humidity. With the relative humidity increasing in the range from 30% to 85%, the intensity of the dip in the interference spectrum linearly increases higher than 50%. The relative humidity response of the sensor is induced by the interference between core mode and cladding mode. The ZnO nanorods with high surface to volume ratio grown outside of the fiber cladding enhance the sensitivity of the sensor.

  13. Impurity induced crystallinity and optical emissions in ZnO nanorod arrays

    NASA Astrophysics Data System (ADS)

    Panda, N. R.; Acharya, B. S.

    2015-01-01

    We report the growth of ZnO nanocrystallites doped with impurities such as B, N and S by green chemistry route using ultrasound. The effect of intrinsic defects and impurity doping on the structural and optical properties of ZnO nanostructures has been studied and discussed. Characterization studies carried out using x-ray diffraction (XRD) reveal the change in lattice parameters and crystallinity of ZnO in the presence of dopant. This has been explained on the basis of the dopant substitution at regular anion and interstitial sites. Study on surface morphology by field emission scanning electron microscopy (FESEM) shows a change from particle-like structure to aligned nanorods nucleated at definite sites. Elemental analysis such as x-ray photon electron spectroscopy (XPS) has been carried out to ascertain the dopant configuration in ZnO. This has been corroborated by the results obtained from FTIR and Raman studies. UV-vis light absorption and PL studies show an expansion of the band gap which has been explained on the basis of Moss-Burstein shift in the electronic band gap of ZnO by impurity incorporation. The optical emissions corresponding to excitonic transition and defect centres present in the band gap of ZnO is found to shift towards lower/higher wavelength sides. New PL bands observed have been assigned to the transitions related to the impurity states present in the band gap of ZnO along with intrinsic defects.

  14. Highly active lanthanum doped ZnO nanorods for photodegradation of metasystox.

    PubMed

    Korake, P V; Dhabbe, R S; Kadam, A N; Gaikwad, Y B; Garadkar, K M

    2014-01-05

    La-doped ZnO nanorods with different La contents were synthesized by microwave assisted method and characterized by various sophisticated techniques such as XRD, UV-Vis., EDS, XPS, SEM and TEM. The XRD patterns of the La-doped ZnO indicate hexagonal crystal structure with an average crystallite size of 30nm. It was found that the crystallite size of La-doped ZnO is much smaller as compared to pure ZnO and decreases with increasing La content. The photocatalytic activity of 0.5mol% La-doped ZnO in the degradation of metasystox was studied. It was observed that degradation efficiency of metasystox over La-doped ZnO increases up to 0.5mol% doping then decreases for higher doping levels. Among the catalyst studied, the 0.5mol% La-doped ZnO was the most active, showing high photocatalytic activity for the degradation of metasystox. The maximum reduction of concentration of metasystox was observed under static condition at pH 8. Reduction in the Chemical Oxygen Demand (COD) of metasystox was observed after 150min. The cytotoxicological studies of meristematic root tip cells of Allium cepa were studied. The results obtained indicate that photocatalytically degraded products of metasystox were less toxic as compared to metasystox.

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

    PubMed

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

    2017-01-01

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

  16. Selective photochemical synthesis of Ag nanoparticles on position-controlled ZnO nanorods for the enhancement of yellow-green light emission.

    PubMed

    Park, Hyeong-Ho; Zhang, Xin; Lee, Keun Woo; Sohn, Ahrum; Kim, Dong-Wook; Kim, Joondong; Song, Jin-Won; Choi, Young Su; Lee, Hee Kwan; Jung, Sang Hyun; Lee, In-Geun; Cho, Young-Dae; Shin, Hyun-Beom; Sung, Ho Kun; Park, Kyung Ho; Kang, Ho Kwan; Park, Won-Kyu; Park, Hyung-Ho

    2015-12-28

    A novel technique for the selective photochemical synthesis of silver (Ag) nanoparticles (NPs) on ZnO nanorod arrays is established by combining ultraviolet-assisted nanoimprint lithography (UV-NIL) for the definition of growth sites, hydrothermal reaction for the position-controlled growth of ZnO nanorods, and photochemical reduction for the decoration of Ag NPs on the ZnO nanorods. During photochemical reduction, the size distribution and loading of Ag NPs on ZnO nanorods can be tuned by varying the UV-irradiation time. The photochemical reduction is hypothesized to facilitate the adsorbed citrate ions on the surface of ZnO, allowing Ag ions to preferentially form Ag NPs on ZnO nanorods. The ratio of visible emission to ultraviolet (UV) emission for the Ag NP-decorated ZnO nanorod arrays, synthesized for 30 min, is 20.5 times that for the ZnO nanorod arrays without Ag NPs. The enhancement of the visible emission is believed to associate with the surface plasmon (SP) effect of Ag NPs. The Ag NP-decorated ZnO nanorod arrays show significant SP-induced enhancement of yellow-green light emission, which could be useful in optoelectronic applications. The technique developed here requires low processing temperatures (120 °C and lower) and no high-vacuum deposition tools, suitable for applications such as flexible electronics.

  17. Near-Ultraviolet Light-Emitting Devices Using Vertical ZnO Nanorod Arrays

    NASA Astrophysics Data System (ADS)

    Jha, S.; Wang, C. D.; Luan, C. Y.; Liu, C. P.; Bin, H.; Kutsay, O.; Bello, I.; Zapien, J. A.; Zhang, W. J.; Lee, S. T.

    2012-05-01

    Reports on electroluminescence (EL) in solid-state, nanomaterial-based devices emitting in the lower wavelength range of the visible spectrum are limited, and the emission stability of these devices is rarely reported. We have fabricated light-emitting devices (LEDs) based on integration of n-ZnO nanorods and p-GaN films, which emit in the violet to near-ultraviolet (NUV) region. We also present data on the stability of EL in fabricated devices. Vertical arrays on ZnO nanorods, with estimated ZnO nanorod density ~108 cm-2, were grown on p-GaN films with typical length of ~4 μm and width of ~120 nm. The NUV LEDs show low turn-on voltage (~3.0 V), small reverse saturation current (~10 μA), and more than two orders of magnitude rectification ratio, all of which indicates a good-quality p- n junction at the p-GaN/ n-ZnO nanorod interface. The EL spectra of LEDs present an emission band centered at ~403 nm. Gaussian fitting of the EL peak revealed three emission peaks at 378 nm, 405 nm, and 431 nm with dominant emission in the NUV region. Significantly, the fabricated NUV LEDs present stable and repeatable EL characteristics, as revealed by bias-stress stability tests. The good electrical properties and stable EL performance make these nanostructure-based NUV LEDs potential candidates for mass production of next-generation lighting devices.

  18. Preparation and photovoltaic properties of perovskite solar cell based on ZnO nanorod arrays

    NASA Astrophysics Data System (ADS)

    Xu, Yang; Liu, Tian; Li, Zhaosong; Feng, Bingjie; Li, Siqian; Duan, Jinxia; Ye, Cong; Zhang, Jun; Wang, Hao

    2016-12-01

    A careful control of ZnO nanorod arrays with various densities and thickness were achieved by hydrothermal method. An obvious increase in the ZnO nanorod density is observed as the concentrations of zinc acetate dropped as expected through the surface SEM images. On the other hand, samples with and without TiO2 compact layer were also studied and results had been analyzed to seek for an optimized substrate structure for light absorbing layer and increase the efficiency. What's more, a deep research for the drying temperature for perovskite layer was also conducted. As a result, SEM images discribe a promising surface appearance of perovskite layer which is finely attached onto the nanorod structure. Final power conversion efficiency (PCE) of FTO/ZnO seed layer/ZnO nanorods/perovskite/spiro-OMe-TAD/Au electrode photovoltaic device reached ∼9.15% together with open-circuit voltage of 957 mV, short-circuit current density of 17.8 mA/cm2 and fill factor of 0.537.

  19. Ligand capping effect for dye solar cells with a CdSe quantum dot sensitized ZnO nanorod photoanode.

    PubMed

    Sun, Xiao Wei; Chen, Jing; Song, Jun Ling; Zhao, De Wei; Deng, Wei Qiao; Lei, Wei

    2010-01-18

    We report a quantum dot sensitized solar cell (QDSSC) with a thioglycolic acid (TGA) capped CdSe quantum dot (QD) sensitized ZnO nanorod photoanode. As revealed by UV-Vis absorption spectrum and transmission electron microscopy, the quantum dots can be effectively adsorbed onto ZnO nanorods. By studying the emission decay, the quenching of the CdSe QDs by ZnO nanorod was verified, and an electron transfer (from QD to ZnO) rate constant of 1 x 10(8) s(-1) was obtained. The efficiency of the as-prepared QDSSC was 0.66% and an incident power conversion efficiency of 22% at 400 nm was achieved.

  20. Room Temperature Ferromagnetism of FeCo-Codoped ZnO Nanorods Prepared by Chemical Vapor Deposition

    SciTech Connect

    Chen, J.; Liu, J.; West, A.; Yan, Y.; Yu, M.; Zhou, W.

    2008-11-01

    FeCo-codoped ZnO nanorods with room temperature ferromagnetic ordering have been synthesized by chemical vapor deposition. Detailed nanostructures were investigated by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and nanoprobe X-ray energy dispersive spectroscopy (EDS). The ZnO nanorods were grown along c-axis of a single crystalline wurtzite structure and no second phase was observed by high resolution TEM. EDS analysis along the nanowires indicated that Co and Fe were successfully doped into the ZnO lattice with concentrations about 0.6-1.0 at.%. Magnetic measurement demonstrates a ferromagnetic ordering with Curie temperature higher than 300 K presents in the ZnO nanorods.

  1. Seedless Pattern Growth of Quasi-Aligned ZnO Nanorod Arrays on Cover Glass Substrates in Solution

    PubMed Central

    2010-01-01

    A hybrid technique for the selective growth of ZnO nanorod arrays on wanted areas of thin cover glass substrates was developed without the use of seed layer of ZnO. This method utilizes electron-beam lithography for pattern transfer on seedless substrate, followed by solution method for the bottom-up growth of ZnO nanorod arrays on the patterned substrates. The arrays of highly crystalline ZnO nanorods having diameter of 60 ± 10 nm and length of 750 ± 50 nm were selectively grown on different shape patterns and exhibited a remarkable uniformity in terms of diameter, length, and density. The room temperature cathodluminescence measurements showed a strong ultraviolet emission at 381 nm and broad visible emission at 585–610 nm were observed in the spectrum. PMID:20672029

  2. Electrochemical L-lactic acid sensor based on immobilized ZnO nanorods with lactate oxidase.

    PubMed

    Ibupoto, Zafar Hussain; Shah, Syed Muhammad Usman Ali; Khun, Kimleang; Willander, Magnus

    2012-01-01

    In this work, fabrication of gold coated glass substrate, growth of ZnO nanorods and potentiometric response of lactic acid are explained. The biosensor was developed by immobilizing the lactate oxidase on the ZnO nanorods in combination with glutaraldehyde as a cross linker for lactate oxidase enzyme. The potentiometric technique was applied for the measuring the output (EMF) response of l-lactic acid biosensor. We noticed that the present biosensor has wide linear detection range of concentration from 1 × 10(-4)-1 × 10(0) mM with acceptable sensitivity about 41.33 ± 1.58 mV/decade. In addition, the proposed biosensor showed fast response time less than 10 s, a good selectivity towards l-lactic acid in presence of common interfering substances such as ascorbic acid, urea, glucose, galactose, magnesium ions and calcium ions. The present biosensor based on immobilized ZnO nanorods with lactate oxidase sustained its stability for more than three weeks.

  3. Polyaniline hybridized surface defective ZnO nanorods with long-term stable photoelectrochemical activity

    NASA Astrophysics Data System (ADS)

    Bera, Susanta; Khan, Hasmat; Biswas, Indranil; Jana, Sunirmal

    2016-10-01

    We report surfactant/template free precursor solution based synthesis of polyaniline (PANI) hybridized surface defective ZnO nanorods by a two-step process. Initially, ZnO nanorods have been prepared at 95 °C, followed by hybridization (coating) of PANI onto the ZnO via in situ polymerization of aniline monomer, forming ZnO-PANI nanohybrid (ZP). The structural properties of ZP have been analyzed by X-ray diffraction (XRD) and transmission electron microscopic (TEM) studies. The presence of surface defects especially the oxygen vacancies in ZnO has been characterized by photoluminescence emission, high resolution TEM, X-ray photoelectron spectroscopy (XPS) and micro-Raman spectral measurements. The chemical interaction of PANI with ZnO has been examined by Fourier transform infrared (FTIR) and XPS analyses. A significant enhancement in visible absorption of ZP sample is found as evidenced from UV-vis diffused reflectance spectral study. BET nitrogen adsorption-desorption isotherm shows an improved textural property (pore size, pore volume) of ZP. Moreover, a long-term stable photoelectrochemical activity (PEC) of ZP is found compare to pristine ZnO. The synergic effect of PANI hybridization and the presence of surface defects in ZnO NRs can enhance the PEC by prolonging the recombination rate of photogenerated charge carriers. The effect can also provide large number of active sites to make electrolyte diffusion and mass transportation easier in the nanohybrid. This simple synthesis strategy can be adopted for PANI hybridization with different metal oxide semiconductors towards enhancing PEC activity of the hybrid materials.

  4. ZnO nanoplates surfaced-decorated by WO3 nanorods for NH3 gas sensing application

    NASA Astrophysics Data System (ADS)

    Dien Nguyen, Dac; Do, Duc Tho; Hien Vu, Xuan; Vuong Dang, Duc; Chien Nguyen, Duc

    2016-03-01

    Zinc oxide (ZnO) nanoplates and tungsten trioxide (WO3) nanorods were synthesized by hydrothermal treatment from zinc nitrate/potassium hydroxide and sodium tungstate/hydrochloric acid, respectively. The structure, morphology and compositions of the as-prepared WO3/ZnO nano-composites were characterized by x-ray diffraction, field emission scanning electron microscopy and energy dispersive spectroscopy. The obtained ZnO nanoplates have regular shape, single-crystal wurtzite structure with the thickness of 40 nm and 200 versus 400 nm in lateral dimensions. The WO3 nanorods possess the average diameter of 20 nm and the length of approximately 120 nm which were distributed on the surfaces of ZnO nanoplates. The WO3/ZnO nano-composites were prepared by grinding WO3 nanorods powder with ZnO nanoplates powder in various weight ratios (1:2, 1:1 and 2:1). The NH3 gas sensing properties of WO3/ZnO nano-composites were examined through the electrical resistance measurement. The gas sensing performance of the WO3/ZnO composite with weight ratio of 1:1 was better compared with that of other samples. For this sample, the maximum response to 300 ppm NH3 was 24 at the operating temperature of 250 °C. In addition, the gas sensing mechanism of the WO3/ZnO composites was discussed.

  5. Photoluminescence on cerium-doped ZnO nanorods produced under sequential atomic layer deposition-hydrothermal processes

    NASA Astrophysics Data System (ADS)

    Cervantes-López, J. L.; Rangel, R.; Espino, J.; Martínez, E.; García-Gutiérrez, R.; Bartolo-Pérez, P.; Alvarado-Gil, J. J.; Contreras, O. E.

    2017-01-01

    Doped and undoped ZnO nanorod arrays were produced combining atomic layer deposition and hydrothermal processes. First, a ZnO layer with preferential orientation normal to the c-axis was grown on the substrate by means of the decomposition of diethylzinc; subsequently, the nanorod arrays were produced through solvothermal process using a solution of Zn(NO3)2 as precursor. Doped ZnO nanorods were produced using Ce(C2H3O2)3·H2O as dopant agent precursor. Undoped and Ce-doped ZnO nanorod arrays showed high-intensity photoluminescence. The doping concentration of x = 0.04 (Zn1- x Ce x O) displayed the highest photoluminescence. Undoped ZnO showed an intense UV peak centered at 382 nm with a narrow full wide half maximum of 33 nm. Ce-doped ZnO PL spectra contain three bands, one signal in the UV region centered at 382 nm, other centered at 467 nm in the near-green region and other one emission centered at 560 nm. The results herein exposed demonstrate the capability to produce high-quality ZnO and Zn1- x Ce x O films.

  6. Enhancement in the structure quality of ZnO nanorods by diluted Co dopants: Analyses via optical second harmonic generation

    NASA Astrophysics Data System (ADS)

    Liu, Chung-Wei; Chang, Shoou-Jinn; Brahma, Sanjaya; Hsiao, Chih-Hung; Chang, Feng Ming; Wang, Peng Han; Lo, Kuang-Yao

    2015-02-01

    We report a systematic study about the effect of cobalt concentration in the growth solution over the crystallization, growth, and optical properties of hydrothermally synthesized Zn1-xCoxO [0 ≤ x ≤ 0.40, x is the weight (wt.) % of Co in the growth solution] nanorods. Dilute Co concentration of 1 wt. % in the growth solution enhances the bulk crystal quality of ZnO nanorods, and high wt. % leads to distortion in the ZnO lattice that depresses the crystallization, growth as well as the surface structure quality of ZnO. Although, Co concentration in the growth solution varies from 1 to 40 wt. %, the real doping concentration is limited to 0.28 at. % that is due to the low growth temperature of 80 °C. The enhancement in the crystal quality of ZnO nanorods at dilute Co concentration in the solution is due to the strain relaxation that is significantly higher for ZnO nanorods prepared without, and with high wt. % of Co in the growth solution. Second harmonic generation is used to investigate the net dipole distribution from these coatings, which provides detailed information about bulk and surface structure quality of ZnO nanorods at the same time. High quality ZnO nanorods are fabricated by a low-temperature (80 °C) hydrothermal synthesis method, and no post synthesis treatment is needed for further crystallization. Therefore, this method is advantageous for the growth of high quality ZnO coatings on plastic substrates that may lead toward its application in flexible electronics.

  7. Enhancement in the structure quality of ZnO nanorods by diluted Co dopants: Analyses via optical second harmonic generation

    SciTech Connect

    Liu, Chung-Wei; Hsiao, Chih-Hung; Brahma, Sanjaya; Chang, Feng Ming; Wang, Peng Han; Lo, Kuang-Yao

    2015-02-28

    We report a systematic study about the effect of cobalt concentration in the growth solution over the crystallization, growth, and optical properties of hydrothermally synthesized Zn{sub 1−x}Co{sub x}O [0 ≤ x ≤ 0.40, x is the weight (wt.) % of Co in the growth solution] nanorods. Dilute Co concentration of 1 wt. % in the growth solution enhances the bulk crystal quality of ZnO nanorods, and high wt. % leads to distortion in the ZnO lattice that depresses the crystallization, growth as well as the surface structure quality of ZnO. Although, Co concentration in the growth solution varies from 1 to 40 wt. %, the real doping concentration is limited to 0.28 at. % that is due to the low growth temperature of 80 °C. The enhancement in the crystal quality of ZnO nanorods at dilute Co concentration in the solution is due to the strain relaxation that is significantly higher for ZnO nanorods prepared without, and with high wt. % of Co in the growth solution. Second harmonic generation is used to investigate the net dipole distribution from these coatings, which provides detailed information about bulk and surface structure quality of ZnO nanorods at the same time. High quality ZnO nanorods are fabricated by a low-temperature (80 °C) hydrothermal synthesis method, and no post synthesis treatment is needed for further crystallization. Therefore, this method is advantageous for the growth of high quality ZnO coatings on plastic substrates that may lead toward its application in flexible electronics.

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

    PubMed Central

    2013-01-01

    We reported well-integrated zinc oxide (ZnO) nanorod arrays (NRAs) on conductive textiles (CTs) and their structural and optical properties. The integrated ZnO NRAs were synthesized by cathodic electrochemical deposition on the ZnO seed layer-coated CT substrate in ultrasonic bath. The ZnO NRAs were regularly and densely grown as well as vertically aligned on the overall surface of CT substrate, in comparison with the grown ZnO NRAs without ZnO seed layer or ultrasonication. Additionally, their morphologies and sizes can be efficiently controlled by changing the external cathodic voltage between the ZnO seed-coated CT substrate and the counter electrode. At an external cathodic voltage of −2 V, the photoluminescence property of ZnO NRAs was optimized with good crystallinity and high density. PMID:23316935

  9. Effect of internal stress on the electro-optical behaviour of Al-doped ZnO transparent conductive thin films

    NASA Astrophysics Data System (ADS)

    Proost, J.; Henry, F.; Tuyaerts, R.; Michotte, S.

    2016-08-01

    In this work, we will report on scientific efforts aimed at unraveling the quantitative effect of elastic strain on the electro-optical behaviour of Al-doped zinc oxide (AZO). AZO thin films have been deposited by reactive magnetron sputtering to thicknesses from 300 to 500 nm, both on extra-clear glass substrates as well as on oxidised Si wafers. This resulted in both cases in polycrystalline, strongly textured (002) films. During deposition, the internal stress evolution in the growing film was monitored in-situ using high resolution curvature measurements. The resulting growth-induced elastic strain, which was found to depend heavily on the oxygen partial pressure, could further be modulated by appropriately choosing the deposition temperature. The latter also induces an additional extrinsic thermal stress component, whose sign depends on the substrate used. As such, a wide range of biaxial internal stresses could be achieved, from -600 MPa in compression up to 800 MPa in tension. The resulting charge carrier mobilities, obtained independently from room temperature Hall measurements, were found to range between 5 and 25 cm2/V s. Interestingly, the maximum mobility occurred at the zero-stress condition, and together with a charge carrier concentration of about 8 × 1020 cm-3, this gave rise to a resistivity of only 300 μΩ cm. From the stress-dependent optical transmission spectra in the range of 200-1000 nm, the pressure coefficient of the optical bandgap was estimated from the corresponding Tauc plots to be 31 meV/GPa, indicating a very high strain-sensitivity as well.

  10. Evolution of the electrical and structural properties during the growth of Al doped ZnO films by remote plasma-enhanced metalorganic chemical vapor deposition

    SciTech Connect

    Volintiru, I.; Creatore, M.; Kniknie, B. J.; Spee, C. I. M. A.; Sanden, M. C. M. van de

    2007-08-15

    Al-doped zinc oxide (AZO) films were deposited by means of remote plasma-enhanced metalorganic chemical vapor deposition from oxygen/diethylzinc/trimethylaluminum mixtures. The electrical, structural (crystallinity and morphology), and chemical properties of the deposited films were investigated using Hall, four point probe, x-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), electron recoil detection (ERD), Rutherford backscattering (RBS), and time of flight secondary ion mass spectrometry (TOF-SIMS), respectively. We found that the working pressure plays an important role in controlling the sheet resistance R{sub s} and roughness development during film growth. At 1.5 mbar the AZO films are highly conductive (R{sub s}<6 {omega}/{open_square} for a film thickness above 1200 nm) and very rough (>4% of the film thickness), however, they are characterized by a large sheet resistance gradient with increasing film thickness. By decreasing the pressure from 1.5 to 0.38 mbar, the gradient is significantly reduced and the films become smoother, but the sheet resistance increases (R{sub s}{approx_equal}100 {omega}/{open_square} for a film thickness of 1000 nm). The sheet resistance gradient and the surface roughness development correlate with the grain size evolution, as determined from the AFM and SEM analyses, indicating the transition from pyramid-like at 1.5 mbar to pillar-like growth mode at 0.38 mbar. The change in plasma chemistry/growth precursors caused by the variation in pressure leads to different concentration and activation efficiency of Al dopant in the zinc oxide films. On the basis of the experimental evidence, a valid route for further improving the conductivity of the AZO film is found, i.e., increasing the grain size at the initial stage of film growth.

  11. Spatially resolved photoresponse on individual ZnO nanorods: correlating morphology, defects and conductivity

    PubMed Central

    Bandopadhyay, K.; Mitra, J.

    2016-01-01

    Electrically active native point defects have a significant impact on the optical and electrical properties of ZnO nanostructures. Control of defect distribution and a detailed understanding of their physical properties are central to designing ZnO in novel functional forms and architecture, which ultimately decides device performance. Defect control is primarily achieved by either engineering nanostructure morphology by tailoring growth techniques or doping. Here, we report conducting atomic force microscopy studies of spatially resolved photoresponse properties on ZnO nanorod surfaces. The photoresponse for super-band gap, ultraviolet excitations show a direct correlation between surface morphology and photoactivity localization. Additionally, the system exhibits significant photoresponse with sub-bandgap, green illumination; the signature energy associated with the deep level oxygen vacancy states. While the local current-voltage characteristics provide evidence of multiple transport processes and quantifies the photoresponse, the local time-resolved photoresponse data evidences large variations in response times (90 ms–50 s), across the surface of a nanorod. The spatially varied photoconductance and the range in temporal response display a complex interplay of morphology, defects and connectivity that brings about the true colour of these ZnO nanostructures. PMID:27334573

  12. Spatially resolved photoresponse on individual ZnO nanorods: correlating morphology, defects and conductivity

    NASA Astrophysics Data System (ADS)

    Bandopadhyay, K.; Mitra, J.

    2016-06-01

    Electrically active native point defects have a significant impact on the optical and electrical properties of ZnO nanostructures. Control of defect distribution and a detailed understanding of their physical properties are central to designing ZnO in novel functional forms and architecture, which ultimately decides device performance. Defect control is primarily achieved by either engineering nanostructure morphology by tailoring growth techniques or doping. Here, we report conducting atomic force microscopy studies of spatially resolved photoresponse properties on ZnO nanorod surfaces. The photoresponse for super-band gap, ultraviolet excitations show a direct correlation between surface morphology and photoactivity localization. Additionally, the system exhibits significant photoresponse with sub-bandgap, green illumination; the signature energy associated with the deep level oxygen vacancy states. While the local current-voltage characteristics provide evidence of multiple transport processes and quantifies the photoresponse, the local time-resolved photoresponse data evidences large variations in response times (90 ms–50 s), across the surface of a nanorod. The spatially varied photoconductance and the range in temporal response display a complex interplay of morphology, defects and connectivity that brings about the true colour of these ZnO nanostructures.

  13. ZnO nanorods array based field-effect transistor biosensor for phosphate detection.

    PubMed

    Ahmad, Rafiq; Ahn, Min-Sang; Hahn, Yoon-Bong

    2017-03-18

    A promising field-effect transistor (FET) biosensor has been fabricated based on pyruvate oxidase (PyO) functionalized ZnO nanorods (ZnO NRs) array grown on seeded SiO2/Si substrate. The direct and vertically grown ZnO NRs on the seeded SiO2/Si substrate offers high surface area for enhanced PyO immobilization, which further helps to detect phosphate with higher specificity. Under optimum conditions, the fabricated FET biosensor provided a convenient method for phosphate detection with high sensitivity (80.57μAmM(-1)cm(-2)) in a wide-linear range (0.1µM-7.0mM). Additionally, it also showed very low effect of electroactive species, stability and good reproducibility. Encouraging results suggest that this approach presents a promising method to be used for field measurements to detect phosphate.

  14. Controlling the conduction band offset for highly efficient ZnO nanorods based perovskite solar cell

    NASA Astrophysics Data System (ADS)

    Dong, Juan; Shi, Jiangjian; Li, Dongmei; Luo, Yanhong; Meng, Qingbo

    2015-08-01

    The mechanism of charge recombination at the interface of n-type electron transport layer (n-ETL) and perovskite absorber on the carrier properties in the perovskite solar cell is theoretically studied. By solving the one dimensional diffusion equation with different boundary conditions, it reveals that the interface charge recombination in the perovskite solar cell can be suppressed by adjusting the conduction band offset (ΔEC) at ZnO ETL/perovskite absorber interface, thus leading to improvements in cell performance. Furthermore, Mg doped ZnO nanorods ETL has been designed to control the energy band levels. By optimizing the doping amount of Mg, the conduction band minimum of the Mg doped ZnO ETL has been raised up by 0.29 eV and a positive ΔEC of about 0.1 eV is obtained. The photovoltage of the cell is thus significantly increased due to the relatively low charge recombination.

  15. Tailoring the surface of ZnO nanorods into corrugated nanorods via a selective chemical etch method

    NASA Astrophysics Data System (ADS)

    Duan, Xiangyang; Chen, Guangde; Li, Chu; Yin, Yuan; Jin, Wentao; Guo, Lu'an; Ye, Honggang; Zhu, Youzhang; Wu, Yelong

    2016-07-01

    Using the chemical vapour deposition method, we successfully converted smooth ZnO nanorods (NRs) into corrugated NRs by simply increasing the reaction time. The surface morphology and crystallographic structure of the corrugated NRs were investigated. The corrugated NRs were decorated by alternant (11\\bar{2}1) and (11\\bar{2}\\bar{1}) planes at the exposed side surfaces while the conventional \\{10\\bar{1}0\\} planes disappeared. No twinning boundaries were found in the periodically corrugated structures, indicating that they were type II corrugated NRs. Further investigation told us that they were selectively etched. We introduced a hydrothermal method to synthesize the smooth ZnO NRs and then etched them in a tube furnace at 950 °C with a flow of carbon monoxide. By separating the growth stage and the selective etching stage, we explicitly demonstrated a successfully selective etching effect on ZnO NRs with a carbon monoxide reducing atmosphere for the first time. An etching mechanism based on the selective reaction between carbon monoxide and the different exposed surfaces was proposed. Our results will improve the understanding of the growth mechanism on coarse or corrugated NRs and provide a new strategy for the application of surface controlled nanostructured materials.

  16. Investigations on the roles of position controlled Al layers incorporated into an Al-doped ZnO active channel during atomic layer deposition for thin film transistor applications

    NASA Astrophysics Data System (ADS)

    Kim, Eom-Ji; Lee, Won-Ho; Yoon, Sung-Min

    2016-03-01

    We investigated the effects of the distance between incorporated Al layers on the characteristics of thin-film transistors (TFTs) using Al-doped ZnO (AZO) as the active channels. The intervals between the Al layers were controlled by designing the sequences of Al cycles during the atomic-layer deposition. Two configurations were designed as “scatter” or “focus”, in which the incorporated Al layers were dispersed to bottom and top sides or concentrated on the center region. Electrical conductivities of “scatter” and “focus” films were observed to be different. While the dispersed Al layers could work as dopants, a too-close interval between the Al layers suppressed carrier transport, even with the same incorporated Al amounts. These differences were reflected on the device characteristics. The TFT performance of the “scatter” device was better than that of the “focus” device. Consequently, adequately dispersed Al layers in the AZO channel are very important for improving device performance.

  17. Influence of Y-doped induced defects on the optical and magnetic properties of ZnO nanorod arrays prepared by low-temperature hydrothermal process.

    PubMed

    Kung, Chung-Yuan; Young, San-Lin; Chen, Hone-Zern; Kao, Ming-Cheng; Horng, Lance; Shih, Yu-Tai; Lin, Chen-Cheng; Lin, Teng-Tsai; Ou, Chung-Jen

    2012-07-07

    One-dimensional pure zinc oxide (ZnO) and Y-doped ZnO nanorod arrays have been successfully fabricated on the silicon substrate for comparison by a simple hydrothermal process at the low temperature of 90°C. The Y-doped nanorods exhibit the same c-axis-oriented wurtzite hexagonal structure as pure ZnO nanorods. Based on the results of photoluminescence, an enhancement of defect-induced green-yellow visible emission is observed for the Y-doped ZnO nanorods. The decrease of E2(H) mode intensity and increase of E1(LO) mode intensity examined by the Raman spectrum also indicate the increase of defects for the Y-doped ZnO nanorods. As compared to pure ZnO nanorods, Y-doped ZnO nanorods show a remarked increase of saturation magnetization. The combination of visible photoluminescence and ferromagnetism measurement results indicates the increase of oxygen defects due to the Y doping which plays a crucial role in the optical and magnetic performances of the ZnO nanorods.

  18. Synthesis and enhanced NO2 gas sensing properties of ZnO nanorods/TiO2 nanoparticles heterojunction composites.

    PubMed

    Zou, C W; Wang, J; Xie, W

    2016-09-15

    ZnO nanorods/TiO2 nanoparticles composites were synthesized and the effects of TiO2 concentrations on the NO2 sensing properties were studied in detail. The as-prepared composites were characterized by XRD, SEM, TEM, PL, I-V and gas sensing measurements. The gas sensing results demonstrated that all the sensors based on ZnO/TiO2 nanocomposites exhibited much higher response than that of sensors based on pure ZnO nanorods. At the optimum operating temperature of 180°C, the response values of the sensors based on ZnO/TiO2 nanocomposites decorated with TiO2 concentrations of 0, 3, 5, 8 and 10wt% were 50, 140, 310, 350 and 258, respectively. The PL and I-V results indicated that the increased charge transfer between the ZnO nanorods mediated by TiO2 nanoparticles enhanced the conductivity of the ZnO/TiO2 nanocomposites. The gas sensing mechanism was also carefully analyzed. The attachment of TiO2 nanoparticles onto ZnO nanorods induced more active sites for the adsorption of oxygen molecules (O(2)) and O(2) which can be more easily adsorbed on the surface of ZnO nanorods. Furthermore, the conduction channel of ZnO/TiO2 was much narrower as a result of the formation of heterojunction which may further contribute to the enhanced NO2 sensing properties.

  19. Charge transfer in nanocrystalline-Au /ZnO nanorods investigated by x-ray spectroscopy and scanning photoelectron microscopy

    NASA Astrophysics Data System (ADS)

    Chiou, J. W.; Ray, S. C.; Tsai, H. M.; Pao, C. W.; Chien, F. Z.; Pong, W. F.; Tsai, M.-H.; Wu, J. J.; Tseng, C. H.; Chen, C.-H.; Lee, J. F.; Guo, J.-H.

    2007-05-01

    O K- and Zn and Au L3-edge x-ray absorption near-edge structure (XANES), x-ray emission spectroscopy (XES), and scanning photoelectron microscopy (SPEM) are performed to investigate the electronic structure of ZnO nanorods with nanocrystalline (nc)-Au particles grown on the surfaces. The XANES spectra of nc-Au /ZnO nanorods reveal the decrease of the number of both O 2p and Zn 4s/3d unoccupied states with the increase of the nc-Au particle size. The number of Au 6s /5d unoccupied states increases when the size of nc-Au particle decreases, indicating that the deposition of nc-Au particles on the surface of ZnO nanorods promotes charge transfer from the ZnO nanorods to nc-Au particles. Excitation energy dependent XES and SPEM spectra show that the number of electrons in the valence band of O 2p-Zn 4sp hybridized states decreases as the nc-Au particle size increases, revealing that more electrons are excited from the valence band to the conduction band of ZnO nanorods and the storage of electrons in nc-Au particles.

  20. Fabrication of well-aligned ZnO nanorods by hydrothermal process using GaN epitaxial layer

    NASA Astrophysics Data System (ADS)

    Jang, Jae-Min; Yi, Sung-Hak; Choi, Seung-Kyu; Kim, Jung-A.; Jung, Woo-Gwang

    2007-02-01

    One dimensional (1-D) ZnO nanorod structure of hexagonal shape was fabricated on epitaxial GaN layer by hydrothermal method. The growth of GaN epitaxial layer was carried out in a two-flow horizontal MOCVD reactor maintained at a pressure of 200 torr. Firstly, a 25 nm thick GaN buffer layer was grown at 520 °C. Then 2~3μm thick GaN epilayer was deposited at 1070 °C. Trimethylgallium (TMG) and NH 3 were used as Ga and N source, and H II gas was used as carrier gas. After the deposition of GaN epilayer thin-film, single crystalline ZnO nanorod was fabricated in aqueous solution. XRD and FE-SEM results showed ZnO nanorod arrays were oriented highly along the (002) plane. The ZnO nanorod was analyzed to have good quality crystallization by FE-TEM. The SAED pattern has shown that ZnO nanorod was grown in the direction along (002)-plane. Photoluminescence (PL) has shown that the GaN-ZnO hetero-structure has shown ultra-violet lasing action at room temperature. Narrow and strong ultra-violet peak was observed in comparison with PL result from epitaxial GaN layer. The analysis results have proved that aqueous solution growth method developed in the present work can be a good application for optical electronic device.

  1. Atomic layer deposition of Al-doped ZnO films using ozone as the oxygen source: A comparison of two methods to deliver aluminum

    SciTech Connect

    Yuan Hai; Luo Bing; Yu Dan; Cheng, An-jen; Campbell, Stephen A.; Gladfelter, Wayne L.

    2012-01-15

    Aluminum-doped ZnO films were prepared by atomic layer deposition at 250 deg. C using diethylzinc (DEZ), trimethylaluminum (TMA), and ozone as the precursors. Two deposition methods were compared to assess their impact on the composition, structural, electrical, and optical properties as a function of Al concentration. The first method controlled the Al concentration by changing the relative number of Al to Zn deposition cycles; a process reported in the literature where water was used as the oxygen source. The second method involved coinjection of the DEZ and TMA during each cycle where the partial pressures of the precursors control the aluminum concentration. Depth profiles of the film composition using Auger electron spectroscopy confirmed a layered microstructure for the films prepared by the first method, whereas the second method led to a homogeneous distribution of the aluminum throughout the ZnO film. Beneath the surface layer the carbon concentrations for all of the films were below the detection limit. Comparison of their electrical and optical properties established that films deposited by coinjection of the precursors were superior.

  2. Synthesis and photoluminescence properties of aligned Zn{sub 2}GeO{sub 4} coated ZnO nanorods and Ge doped ZnO nanocombs

    SciTech Connect

    Su Yong; Meng Xia Chen Yiqing; Li Sen; Zhou Qingtao; Liang Xuemei; Feng Yi

    2008-07-01

    Aligned Zn{sub 2}GeO{sub 4} coated ZnO nanorods and Ge doped ZnO nanocombs were synthesized on a silicon substrate by a simple thermal evaporation method. The structure and morphology of the as-synthesized nanostructure were characterized using scanning electron microscopy and transmission electron microscopy. The growth of aligned Zn{sub 2}GeO{sub 4} coated ZnO nanorods and Ge doped ZnO nanocombs follows a vapor-solid (VS) process. Photoluminescence properties were also investigated at room temperature. The photoluminescence spectrum reveals the nanostructures have a sharp ultraviolet luminescence peak centered at 382 nm and a broad green luminescence peak centered at about 494 nm.

  3. Dielectric properties of flower-type ZnO nanorods and ZnO-SnO2 nanocomposites

    NASA Astrophysics Data System (ADS)

    Stella, C.; Mariammal, R. N.; Ramachandran, K.

    2012-06-01

    ZnO and ZnO: SnO2 nanocomposites were synthesized by simple co-precipitation method and the structural characterization was done by XRD. The surface morphology was studied by SEM analysis which showed the formation of flower-type nanorods in ZnO and spherical particles in ZnO: SnO2. The variation of dielectric constant and ac conductivity has been studied at 90°C by varying signal frequency from 100 Hz-5 MHz. The dielectric constant decreases with increasing frequency whereas the electrical conductivity increases with increasing frequency.

  4. Growth mechanism of ZnO nanorod/Fe3O4 nanoparticle composites and their photocatalytic properties

    NASA Astrophysics Data System (ADS)

    Wang, Wenda; Yu, Leiming; Yang, Hanjia; Hong, Kunquan; Qiao, Zhenfang; Wang, Hai

    2015-11-01

    ZnO nanorods/Fe3O4 nanocomposites as the recyclable photocatalyst were synthesized by a co-precipitation method, with microwave assistant by dropping alkaline solution with Fe3O4 nanoparticles into the aqueous of zinc salt. These Fe3O4 nanoparticles were the nucleated centers for the ZnO nanorods growth so that these nanorods ended with aggregated Fe3O4 nanoparticles. The growth processes and mechanism are explained as those insoluble zinc hydroxides prefer to nucleate on the surface of Fe3O4 nanoparticles (heterogeneous nucleation) rather than nucleated as isolated ZnO nanostructures (homogeneous nucleation). These nanocomposites have strong photocatalytic ability to reduce RhB and moderate magnetization, which make them being good recyclable photocatalysts.

  5. Large-scale patterned ZnO nanorod arrays for efficient photoelectrochemical water splitting

    NASA Astrophysics Data System (ADS)

    Hu, Yaping; Yan, Xiaoqin; Gu, Yousong; Chen, Xiang; Bai, Zhiming; Kang, Zhuo; Long, Fei; Zhang, Yue

    2015-06-01

    Nowadays, the fabrication of photoanodes with high light-harvesting capability and charge transfer efficiency is a key challenge for photoelectrochemical (PEC) water splitting. In this paper, large-scale patterned ZnO nanorod arrays (NRAs) were designed and fabricated via two-beam laser interference lithography and hydrothermal synthesis, which were further applied as PEC photoanodes for the first time. By adopting the ZnO NRA photoanodes with square pattern, the PEC cells achieved a maximum efficiency of 0.18%, which was improved 135% compared to the control group with no patterned ZnO NRAs. The large-scale highly ordered ZnO NRAs have enhanced light-harvesting ability due to the light-scattering effect. In addition, the enlarged surface area of the patterned ZnO NRAs accelerated the charge transfer at the photoanode/electrolyte interface. This research demonstrates an effective mean to realize the efficient solar water splitting, and the results suggest that large-scale highly ordered nanostructures are promising candidates in the field of energy harvesting.

  6. Controllable synthesis of branched hierarchical ZnO nanorod arrays for highly sensitive hydrazine detection

    NASA Astrophysics Data System (ADS)

    Hu, Jie; Zhao, Zhenting; Sun, Yongjiao; Wang, Ying; Li, Pengwei; Zhang, Wendong; Lian, Kun

    2016-02-01

    In this paper, three different kinds of ZnO nanostructures were successfully synthesized on Au/Glass (Au/G) substrate by electrochemical deposition method. The morphology and crystalline structures of the obtained samples were characterized using SEM, XRD and HRTEM. Electrochemical responses of the as-prepared ZnO based sensors to hydrazine in 0.1 M phosphate buffer solution (PBS, pH 7.4) were analyzed by cyclic voltammetry and single-potential amperometry. The results confirmed that the electrochemical performances of ZnO sensors are strongly dependent on the specific surface area. Especially, the branched hierarchical ZnO nanorod arrays shows the highest sensitivity of 5.35 μA μM-1 cm-2, a short response time of 3 s, a low detection limit of 0.08 μM with a linear hydrazine concentration response range from 0.8 μM to 101 μM, and it also exhibits excellent anti-interference, stability and reproducibility abilities, which provide great potential method of ZnO branched hierarchical structures in the development of high-performance electrochemical sensor.

  7. Synthesis and Characterization of Mg-doped ZnO Nanorods for Biomedical Applications

    NASA Astrophysics Data System (ADS)

    Gemar, H.; Das, N. C.; Wanekaya, A.; Delong, R.; Ghosh, K.

    2013-03-01

    Nanomaterials research has become a major attraction in the field of advanced materials research in the area of Physics, Chemistry, and Materials Science. Bio-compatible and chemically stable metal nanoparticles have biomedical applications that includes drug delivery, cell and DNA separation, gene cloning, magnetic resonance imaging (MRI). This research is aimed at the fabrication and characterization of Mg-doped ZnO nanorods. Hydrothermal synthesis of undoped ZnO and Mg-doped ZnO nanorods is carried out using aqueous solutions of Zn(NO3)2 .6H2O, MgSO4, and using NH4OH as hydrolytic catalyst. Nanomaterials of different sizes and shapes were synthesized by varying the process parameters such as molarity (0.15M, 0.3M, 0.5M) and pH (8-11) of the precursors, growth temperature (130°C), and annealing time during the hydrothermal Process. Structural, morphological, and optical properties are studied using various techniques such as XRD, SEM, UV-vis and PL spectroscopy. Detailed structural, and optical properties will be discussed in this presentation. This work is partially supported by National Cancer Institute (1 R15 CA139390-01).

  8. ZnO nanorod arrays for various low-bandgap polymers in inverted organic solar cells.

    PubMed

    Ho, Ping-Yi; Thiyagu, Subramani; Kao, Shao-Hsuan; Kao, Chia-Yu; Lin, Ching-Fuh

    2014-01-07

    Due to the limited diffusion length of carriers in polymer solar cells (PSCs), the path of carriers is a crucial factor that determines the device performance. Zinc oxide nanorods (NRs) as the electron transport channel can reduce electron-hole recombination and transport the electron to the electrode efficiently for poly(3-hexylthiophene) (P3HT), but have been seldom demonstrated for low-bandgap polymers. Here we successfully applied ZnO NRs, which were grown via the hydrothermal method, as a platform to enhance PSC efficiency for various low-bandgap polymers. In order to assure that the nanorod morphology functioned properly for PSCs, the growth time, the concentration, and the resulting morphology were systematically investigated in depths. Such ZnO NRs were applied to different organic systems, resulting in the increase of the PCE for PBDTTT-C/PC71BM from 4.76% to 6.07% and PBDTTT-C-T/PC71BM from 5.40% to 7.34%. Through those experiments, we established a potentially universal and efficient ZnO NRs platform for various low-bandgap polymers to achieve high efficiency of inverted PSCs.

  9. Development of highly transparent seedless ZnO nanorods engineered for inverted polymer solar cells.

    PubMed

    Ambade, Swapnil B; Ambade, Rohan B; Lee, Wonjoo; Mane, Rajaram S; Yoon, Sung Cheol; Lee, Soo-Hyoung

    2014-10-21

    This work reports on inverted polymer solar cells (IPSCs) based on highly transparent (>95%), hydrophobic, seedless ZnO nanorods (NRs) as cathode buffers with extremely enhanced electrical characteristics. The transparent NR suspension with stability for more than a year is achieved by adding a small amount of 2-(2-methoxyethoxy) acetic acid (MEA). The ability of the stable nanorod suspension to easily spin-coat is certainly an advance to the fabrication of films over large areas and to replace the conventional seeding method to grow one-dimensional nanostructures for use in optoelectronic devices. We observe a strong correlation between the photovoltaic performance and the transparency of ZnO NRs. IPSCs using poly-3-hexylthiophene (P3HT) and [6,6]-phenyl C60 butyric acid methyl ester (PCBM) mixtures in the active layer and transparent (MEA-capped) ZnO NRs as cathode buffers exhibit a power conversion efficiency of 3.24% under simulated AM 1.5G, 100 mW cm(-2) illumination.

  10. Robust nonsticky superhydrophobicity by the tapering of aligned ZnO nanorods.

    PubMed

    Tian, Jian; Zhang, Yaping; Zhu, Jie; Yang, Zhongzhen; Gao, Xuefeng

    2014-04-04

    The robust nonsticky superhydrophobicity of aligned nanoneedle films is reported. A facile, efficient, cheap, and available method based on the diffusion-limited crystal growth principle is proposed for controlling the tapering of ZnO nanorods, the profiles of which can be tuned effectively by synergetic control over reaction time and temperature in an extremely strong alkaline reaction system. The synthesized nanoneedle, nanopencil, and nanorod arrays are chosen for studying the effects of nanoscale topography on anti-droplet-sticking ability. After silanization, all of them show excellent quasi-static anti-droplet-stickiness, and water adhesion along the normal and lateral directions can be greatly reduced by the tapering of nanorods and eliminated by sharp nanoneedles. However, their antisticking stability is distinct under the droplet impact: the nanoneedle sample is still nonsticky but the nanorod sample loses its antisticking ability. Only ensuring the liquid/air interface is in the suspended nonwetting state is insufficient to obtain robust nonsticky surfaces, which also require extremely low solid-liquid van der Waals attraction.

  11. Size effect of ZnO nanorods on physicochemical properties of plasticized starch composites.

    PubMed

    Guz, L; Famá, L; Candal, R; Goyanes, S

    2017-02-10

    This work demonstrates that the size of ZnO nanorods (ZnONR) with similar aspect ratio determines several physicochemical and microbiological properties of thermoplastic starch composites (TPS/ZnONR) at a given concentration of ZnONRs. A combination of sol-gel and hydrothermal methods was developed to synthesize ZnONR with different sizes but similar aspect ratios. Starch composites containing 1wt.% of ZnONR were prepared by casting. Composites with smaller size nanorods (ZnONR-S) showed more efficiency in shielding UVA radiation and had a higher solubility and water vapor permeability than those with larger nanorods (ZnONR-L). Mechanical properties, biodegradability and antibacterial activity were also influenced by the size of the ZnONR. X-ray diffraction analysis showed that composites with ZnONR-S maintained the typical B-V type starch structure, intensifying the V-type starch structure peaks, while composite with ZnONR-L induced the formation of an amorphous structure, preventing starch retrogradation during storage. Properties affected by nanorods size are fundamental in determining composite applications.

  12. Probing interaction of gram-positive and gram-negative bacterial cells with ZnO nanorods.

    PubMed

    Jain, Aanchal; Bhargava, Richa; Poddar, Pankaj

    2013-04-01

    In the present work, the physiological effects of the ZnO nanorods on the Gram positive (Staphylococcus aureus and Bacillus subtilis) and Gram-negative (Escherichia coli and Aerobacter aerogenes) bacterial cells have been studied. The analysis of bacterial growth curves for various concentrations of ZnO nanorods indicates that Gram positive and Gram negative bacterial cells show inhibition at concentrations of ~64 and ~256 μg/mL respectively. The marked difference in susceptibility towards nanorods was also validated by spread plate and disk diffusion methods. In addition, the scanning electron micrographs show a clear damage to the cells via changed morphology of the cells from rod to coccoid etc. The confocal optical microscopy images of these cells also demonstrate the reduction in live cell count in the presence of ZnO nanorods. These, results clearly indicate that the antibacterial activity of ZnO nanorods is higher towards Gram positive bacterium than Gram negative bacterium which indicates that the structure of the cell wall might play a major role in the interaction with nanostructured materials and shows high sensitivity to the particle concentration.

  13. Sensitized ZnO nanorod assemblies to detect heavy metal contaminated phytomedicines: spectroscopic and simulation studies.

    PubMed

    Bagchi, Damayanti; Maji, Tuhin Kumar; Sardar, Samim; Lemmens, Peter; Bhattacharya, Chinmoy; Karmakar, Debjani; Pal, Samir Kumar

    2017-01-18

    The immense pharmacological relevance of the herbal medicine curcumin including anti-cancer and anti-Alzheimer effects, suggests it to be a superior alternative to synthesised drugs. The diverse functionalities with minimal side effects intensify the use of curcumin not only as a dietary supplement but also as a therapeutic agent. Besides all this effectiveness, some recent literature reported the presence of deleterious heavy metal contaminants from various sources in curcumin leading to potential health hazards. In this regard, we attempt to fabricate ZnO based nanoprobes to detect metal conjugated curcumin. We have synthesized and structurally characterized the ZnO nanorods (NR). Three samples namely curcumin (pure), Zn-curcumin (non-toxic metal attached to curcumin) and Hg-curcumin (toxic heavy metal attached to curcumin) were prepared for consideration. The samples were electrochemically deposited onto ZnO surfaces and the attachment was confirmed by cyclic voltammetry experiments. Moreover, to confirm a molecular level interaction picosecond-resolved PL-quenching of ZnO NR due to Förster Resonance Energy Transfer (FRET) from donor ZnO NR to the acceptor curcumin moieties was employed. The attachment proximity of ZnO NR and curcumin moieties depends on the size of metals. First principles analysis suggests a variance of attachment sites and heavy metal Hg conjugated curcumin binds through a peripheral hydroxy group to NR. We fabricated a facile photovoltaic device consisting of ZnO NR as the working electrode with Pt counter electrode and iodide-triiodide as the electrolyte. The trend in photocurrent under visible light illumination suggests an enhancement in the case of heavy metal ions due to long range interaction and greater accumulation of charge at the active electrode. Our results provide a detailed physical insight into interfacial processes that are crucial for detecting heavy-metal attached phytomedicines and are thus expected to find vast

  14. Oxygen vacancies induced DX center and persistent photoconductivity properties of high quality ZnO nanorods

    NASA Astrophysics Data System (ADS)

    Xie, Yong; Madel, Manfred; Feneberg, Martin; Neuschl, Benjamin; Jie, Wanqi; Hao, Yue; Ma, Xiaohua; Thonke, Klaus

    2016-04-01

    Ultraviolet sensors based on homoepitaxially grown ZnO nanorods were fabricated using clean room technology. We study the spectral dependence and frequency dependence of the photoresponse of these rods at different temperatures and ambient conditions. Whereas the response for above-bandgap light is fast, we find a slow response to light below band gap and clear signatures of persistent photoconductivity. These findings are explained by switching oxygen vacancies by light from nonconductive to conductive state, whereas the oxygen vacancies undergo a large lattice relaxation. The threshold photon energy for this process is found to be 2.6 eV at room temperature.

  15. ZnO nanorod array-coated mesh film for the separation of water and oil.

    PubMed

    Li, Hong; Li, Yushan; Liu, Qinzhuang

    2013-04-20

    Dense and vertically aligned ZnO nanorod arrays with a large area have been fabricated successfully on the stainless steel mesh by a simple chemical vapor deposition method. The coated mesh exhibited both superoleophilic and superhydrophobic properties, even if it was not modified by low surface energy materials. The separation efficiencies were more than 97% in the filtration of water and oil. Besides, the wettability of the coated mesh was still stable after it was soaked in the corrosive solutions for 1 h. A detailed investigation showed that the coated mesh has the best superhydrophobic property when the stainless steel mesh pore size was about 75 μm.

  16. ZnO nanorod array-coated mesh film for the separation of water and oil

    NASA Astrophysics Data System (ADS)

    Li, Hong; Li, Yushan; Liu, Qinzhuang

    2013-04-01

    Dense and vertically aligned ZnO nanorod arrays with a large area have been fabricated successfully on the stainless steel mesh by a simple chemical vapor deposition method. The coated mesh exhibited both superoleophilic and superhydrophobic properties, even if it was not modified by low surface energy materials. The separation efficiencies were more than 97% in the filtration of water and oil. Besides, the wettability of the coated mesh was still stable after it was soaked in the corrosive solutions for 1 h. A detailed investigation showed that the coated mesh has the best superhydrophobic property when the stainless steel mesh pore size was about 75 μm.

  17. Comparative study of photocatalytic activities of hydrothermally grown ZnO nanorod on Si(001) wafer and FTO glass substrates

    NASA Astrophysics Data System (ADS)

    Jeon, Eun Hee; Yang, Sena; Kim, Yeonwoo; Kim, Namdong; Shin, Hyun-Joon; Baik, Jaeyoon; Kim, Hyun Sung; Lee, Hangil

    2015-09-01

    ZnO nanorods have been grown on Si(001) wafer and fluorine-doped tin oxide (FTO) glass substrates for 1 and 4 h with the hydrothermal methods. The morphologies and photocatalytic activities of the ZnO nanorods were found to depend on the substrates. We investigated their properties by using spectroscopic analysis and demonstrated that the shape of nanorod and the ratios of external defects can be controlled by varying the substrates. Our experiments revealed that the nanorods grown on Si(001) have a single-crystalline wurtzite structure with (002) facets and that the number of surface oxygen defects increases with their length as the growth time increases. The nanorods grown on Si(001) have different facets, in particular wider (002) facets, and a higher ratio of the oxygen defect than the nanorods on FTO glass substrate. Moreover, the photocatalytic activities with respect to 2-aminothiophenol (2-ATP) of these nanorods were investigated with high-resolution photoemission spectroscopy (HRPES). We demonstrated that their photocatalytic activity is influenced by the ratios of surface oxygen defects, which varies with the substrate surface.

  18. 40% Efficiency enhancement in solar cells using ZnO nanorods as shell prepared via novel hydrothermal synthesis

    NASA Astrophysics Data System (ADS)

    Ebadi, Mohammad; Zarghami, Zabihullah; Motevalli, Kourosh

    2017-03-01

    Herein, rod-like ZnO nanostructures were synthesized via a novel hydrothermal route using Zn(OAc)2, ethylenediamine and hydrazine as a new set of starting reagents. The as-synthesized products were characterized by techniques including XRD, EDS, SEM, XPS, Pl and FTIR. The prepared ZnO nanostructures were utilized as shell on TiO2 film in DSSCs. Effect of precursor type, morphology and thickness of ZnO shell (number of electrophoresis cycle) on solar cells efficiency were well studied. Our results showed that ethylenediamine has crucial effect on morphology of synthesized ZnO nanostructures and using ZnO nanostructures leads to an increase in DSSCs efficiency compared to bare TiO2 from 4.66 to 7.13% ( 40% improvement). Moreover, highest amount of solar cell efficiency (7.13%) was obtained by using ZnO nanorods with two cycle of electrophoresis for deposition.

  19. The effect of dopant concentration on properties of transparent conducting Al-doped ZnO thin films for efficient Cu2ZnSnS4 thin-film solar cells prepared by electrodeposition method

    NASA Astrophysics Data System (ADS)

    Mkawi, E. M.; Ibrahim, K.; Ali, M. K. M.; Farrukh, M. A.; Mohamed, A. S.

    2015-11-01

    Al-doped ZnO (AZO) thin films were potentiostatically deposited on indium tin oxide substrates. The influence of the doping level of the ZnO:Al films was investigated. The results of the X-ray diffraction and scanning electron microscopy analysis revealed that the structural properties of the AZO films were found polycrystalline with a hexagonal wurtzite-type structure along the (002) plane. The grain size of the AZO films was observed as approximately 3 μm in the film doping with 4 mol% ZnO:Al concentration. The thin films also exhibited an optical transmittance as high as 90 % in the wavelength range of 100-1,000 nm. The optical band gap increased from 3.33 to 3.45 eV. Based on the Hall studies, the lowest resistivity (4.78 × 10-3 Ω cm) was observed in the film doping with 3 mol% ZnO:Al concentration. The sheet resistant, carrier concentration and Hall mobility values were found as 10.78 Ω/ square, 9.03 × 1018 cm-3 and 22.01 cm2/v s, respectively, which showed improvements in the properties of AZO thin films. The ZnO:Al thin films were used as a buffer layer in thin-film solar cells with the structure of soda-lime glass/Mo/Cu2ZnSnS4/ZnS/ZnO/Al grid. The best solar cell efficiency was 2.3 % with V OC of 0.430 V, J SC of 8.24 mA cm-2 and FF of 68.1 %.

  20. High-performance InGaN/GaN MQW LEDs with Al-doped ZnO transparent conductive layers grown by MOCVD using H2O as an oxidizer

    NASA Astrophysics Data System (ADS)

    Lin, Jia-Yong; Pei, Yan-Li; Zhuo, Yi; Chen, Zi-Min; Hu, Rui-Qin; Cai, Guang-Shuo; Wang, Gang

    2016-11-01

    In this study, the high performance of InGaN/GaN multiple quantum well light-emitting diodes (LEDs) with Al-doped ZnO (AZO) transparent conductive layers (TCLs) has been demonstrated. The AZO-TCLs were fabricated on the n+-InGaN contact layer by metal organic chemical vapor deposition (MOCVD) using H2O as an oxidizer at temperatures as low as 400 °C without any post-deposition annealing. It shows a high transparency (98%), low resistivity (510-4 Ω·cm), and an epitaxial-like excellent interface on p-GaN with an n+-InGaN contact layer. A forward voltage of 2.82 V @ 20 mA was obtained. Most importantly, the power efficiencies can be markedly improved by 53.8%@20 mA current injection and 39.6%@350 mA current injection compared with conventional LEDs with indium tin oxide TCL (LED-III), and by 28.8%@20 mA current injection and 4.92%@350 mA current injection compared with LEDs with AZO-TCL prepared by MOCVD using O2 as an oxidizer (LED-II), respectively. The results indicate that the AZO-TCL grown by MOCVD using H2O as an oxidizer is a promising TCL for a low-cost and high-efficiency GaN-based LED application. Project supported by the National Natural Science Foundation of China (Grant Nos. 61204091, 61404177, 51402366, and U1201254) and the Science and Technology Planning Project of Guangdong Province, China (Grant No. 2015B010132006).

  1. Control of charge dynamics by blending ZnO nanoparticles with poly(3-hexylthiophene) for efficient hybrid ZnO nanorods/polymer solar cells

    NASA Astrophysics Data System (ADS)

    Ruankham, Pipat; Choopun, Supab; Sagawa, Takashi

    2015-10-01

    Photovoltaic performances of hybrid ZnO nanorods/polymer solar cells have been improved by controlling their charge dynamics through addition of ZnO nanoparticles into poly(3-hexylthiophene) (P3HT) photoactive layer. The inter-rod space of ZnO nanorod substrates is completely filled with the solution-processed ZnO nanoparticles/P3HT blends, forming homogeneous junction among the components. The optimum PCE of 1.020 % has been achieved from the device with 13 vol % ZnO nanoparticles loaded. The enhancement in external quantum efficiency has been also observed, indicating the improved excitons separation at the ZnO/P3HT interface. The information on charge dynamics in the system has been investigated by electrochemical impedance spectroscopy. It has been found that the additional space-charge layer formed at the ZnO nanoparticles-contact electrode interface is a reason behind the improvement of open-circuit voltage. Moreover, the formation of ZnO nanoparticles domain extending across the active layer and the percolation path for charge carriers promotes charge transport by reducing transit time of the carriers, extending charge carrier lifetime and enhancing the charge transfer at the ZnO/P3HT interface. Interestingly, it has been found that charge transport in the devices does not limit the device performances, even for the 400-nm-thick active layer.

  2. Growth behavior and electrical performance of Ga-doped ZnO nanorod/p-Si heterojunction diodes prepared using a hydrothermal method.

    PubMed

    Park, Geun Chul; Hwang, Soo Min; Lim, Jun Hyung; Joo, Jinho

    2014-01-01

    The incorporation of foreign elements into ZnO nanostructures is of significant interest for tuning the structure and optical and electrical properties in nanoscale optoelectronic devices. In this study, Ga-doped 1-D ZnO nanorods were synthesized using a hydrothermal route, in which the doping content of Ga was varied from 0% to 10%. The pn heterojunction diodes based on the n-type Ga-doped ZnO nanorod/p-type Si substrates were constructed, and the effect of the Ga doping on the morphology, chemical bonding structure, and optical properties of the ZnO nanorods was systematically investigated as well as the diode performance. With increasing Ga content, the average diameter of the ZnO nanorods was increased, whereas the amount of oxygen vacancies was reduced. In addition, the Ga-doped ZnO nanorod/p-Si diodes showed a well-defined rectifying behavior in the I-V characteristics and an improvement in the electrical conductivity (diode performance) by the Ga doping, which was attributed to the increased charge carrier (electron) concentration and the reduced defect states in the nanorods by incorporating Ga. The results suggest that Ga doping is an effective way to tailor the morphology, optical, electronic, and electrical properties of ZnO nanorods for various applications such as field-effect transistors (FETs), light-emitting diodes (LEDs), and laser diodes (LDs).

  3. Synthesis and characterization of Cr-doped ZnO nanorod-array photocatalysts with improved activity

    SciTech Connect

    Chang, Chi-Jung Yang, Tsung-Lin; Weng, Yu-Ching

    2014-06-01

    Immobilized photocatalysts with high catalytic activity under UV light were prepared by growing Cr-doped ZnO nanorods on glass substrates by a hydrothermal method. The effects of Cr dopant on the surface texture, crystallinity, surface chemistry, and photoinduced charge separation and their relation with the photocatalytic degradation of Cr-doped ZnO were investigated by scanning electron microscopy, diffuse reflectance spectra, photoelectrochemical scanning electrochemical microscopy, and X-ray photoemission spectroscopy. Adding the appropriate amount of Cr dopant is a powerful way to enhance the separation of charge carriers in ZnO photocatalyst. The photocatalytic activity was improved due to the increase in surface oxygen vacancies, the separation of charge carriers, modification of the band gap, and the large surface area of the doped ZnO nanorod photocatalyst. - Graphical abstract: Photoinduced charge separation and its relation with the photocatalytic degradation activity of Cr-doped ZnO were investigated by photoelectrochemical scanning electrochemical microscopy. - Highlights: • Cr dopant enhances separation of charge carries in ZnO nanorod photocatalyst. • Photoinduced charge carries separation monitored by PEC-SECM. • The higher the photocurrent is, the higher the photocatalytic activity is. • Degradation of DB86 dye solutions under visible light finished within 50 min. • Higher activity due to more oxygen vacancy, tuned band gap and more surface area.

  4. Selective photochemical synthesis of Ag nanoparticles on position-controlled ZnO nanorods for the enhancement of yellow-green light emission

    NASA Astrophysics Data System (ADS)

    Park, Hyeong-Ho; Zhang, Xin; Lee, Keun Woo; Sohn, Ahrum; Kim, Dong-Wook; Kim, Joondong; Song, Jin-Won; Choi, Young Su; Lee, Hee Kwan; Jung, Sang Hyun; Lee, In-Geun; Cho, Young-Dae; Shin, Hyun-Beom; Sung, Ho Kun; Park, Kyung Ho; Kang, Ho Kwan; Park, Won-Kyu; Park, Hyung-Ho

    2015-12-01

    A novel technique for the selective photochemical synthesis of silver (Ag) nanoparticles (NPs) on ZnO nanorod arrays is established by combining ultraviolet-assisted nanoimprint lithography (UV-NIL) for the definition of growth sites, hydrothermal reaction for the position-controlled growth of ZnO nanorods, and photochemical reduction for the decoration of Ag NPs on the ZnO nanorods. During photochemical reduction, the size distribution and loading of Ag NPs on ZnO nanorods can be tuned by varying the UV-irradiation time. The photochemical reduction is hypothesized to facilitate the adsorbed citrate ions on the surface of ZnO, allowing Ag ions to preferentially form Ag NPs on ZnO nanorods. The ratio of visible emission to ultraviolet (UV) emission for the Ag NP-decorated ZnO nanorod arrays, synthesized for 30 min, is 20.5 times that for the ZnO nanorod arrays without Ag NPs. The enhancement of the visible emission is believed to associate with the surface plasmon (SP) effect of Ag NPs. The Ag NP-decorated ZnO nanorod arrays show significant SP-induced enhancement of yellow-green light emission, which could be useful in optoelectronic applications. The technique developed here requires low processing temperatures (120 °C and lower) and no high-vacuum deposition tools, suitable for applications such as flexible electronics.A novel technique for the selective photochemical synthesis of silver (Ag) nanoparticles (NPs) on ZnO nanorod arrays is established by combining ultraviolet-assisted nanoimprint lithography (UV-NIL) for the definition of growth sites, hydrothermal reaction for the position-controlled growth of ZnO nanorods, and photochemical reduction for the decoration of Ag NPs on the ZnO nanorods. During photochemical reduction, the size distribution and loading of Ag NPs on ZnO nanorods can be tuned by varying the UV-irradiation time. The photochemical reduction is hypothesized to facilitate the adsorbed citrate ions on the surface of ZnO, allowing Ag ions to

  5. Core-shell TiO2@ZnO nanorods for efficient ultraviolet photodetection

    NASA Astrophysics Data System (ADS)

    Panigrahi, Shrabani; Basak, Durga

    2011-05-01

    Core-shell TiO2@ZnO nanorods (NRs) have been fabricated by a simple two step method: growth of ZnO NRs' array by an aqueous chemical technique and then coating of the NRs with a solution of titanium isopropoxide [Ti(OC3H7)4] followed by a heating step to form the shell. The core-shell nanocomposites are composed of single-crystalline ZnO NRs, coated with a thin TiO2 shell layer obtained by varying the number of coatings (one, three and five times). The ultraviolet (UV) emission intensity of the nanocomposite is largely quenched due to an efficient electron-hole separation reducing the band-to-band recombinations. The UV photoconductivity of the core-shell structure with three times TiO2 coating has been largely enhanced due to photoelectron transfer between the core and the shell. The UV photosensitivity of the nanocomposite becomes four times larger while the photocurrent decay during steady UV illumination has been decreased almost by 7 times compared to the as-grown ZnO NRs indicating high efficiency of these core-shell structures as UV sensors.

  6. Core-shell TiO2@ZnO nanorods for efficient ultraviolet photodetection.

    PubMed

    Panigrahi, Shrabani; Basak, Durga

    2011-05-01

    Core-shell TiO(2)@ZnO nanorods (NRs) have been fabricated by a simple two step method: growth of ZnO NRs' array by an aqueous chemical technique and then coating of the NRs with a solution of titanium isopropoxide [Ti(OC(3)H(7))(4)] followed by a heating step to form the shell. The core-shell nanocomposites are composed of single-crystalline ZnO NRs, coated with a thin TiO(2) shell layer obtained by varying the number of coatings (one, three and five times). The ultraviolet (UV) emission intensity of the nanocomposite is largely quenched due to an efficient electron-hole separation reducing the band-to-band recombinations. The UV photoconductivity of the core-shell structure with three times TiO(2) coating has been largely enhanced due to photoelectron transfer between the core and the shell. The UV photosensitivity of the nanocomposite becomes four times larger while the photocurrent decay during steady UV illumination has been decreased almost by 7 times compared to the as-grown ZnO NRs indicating high efficiency of these core-shell structures as UV sensors.

  7. Hierarchically structured ZnO nanorods-nanosheets for improved quantum-dot-sensitized solar cells.

    PubMed

    Tian, Jianjun; Uchaker, Evan; Zhang, Qifeng; Cao, Guozhong

    2014-03-26

    ZnO nanorods (NRs) and nanosheets (NSs) were fabricated by adjusting the growth orientation of ZnO crystals in the reaction solution, respectively. The thin ZnO NSs were slowly assembled on the surface of NRs to form a hierarchically structured NR-NS photoelectrode for constructing CdS/CdSe quantum-dot-sensitized solar cells (QDSCs). This hierarchical structure had two advantages in improving the power conversion efficiency (PCE) of the solar cells: (a) it increased the surface area and modified the surface profile of the ZnO NRs to aid in harvesting more quantum dots, which leads to a high short-current density (Jsc); (b) it facilitated transportation of the electrons in this compact structure to reduce the charge recombination, which led to enhancement of the open-circuit voltage (Voc) and fill factor (FF). As a result, the QDSC assembled with the hierarchical NR-NS photoelectrode exhibited a high PCE of 3.28%, which is twice as much as that of the NR photoelectrode (1.37%).

  8. Schottky-contacted vertically self-aligned ZnO nanorods for hydrogen gas nanosensor applications

    SciTech Connect

    Ranwa, Sapana; Kumar, Mohit; Kumar, Mahesh; Singh, Jitendra; Fanetti, Mattia

    2015-07-21

    Vertically well aligned ZnO nanorods (NRs) were grown on Si(100) substrate using RF magnetron sputtering technique. Scanning electron microscopy images confirms uniform distribution of NRs on 2 in. wafer with average diameter, height and density being ∼75 nm, ∼850 nm, and ∼1.5 × 10{sup 10} cm{sup −2}, respectively. X-ray diffraction reveals that the ZnO NRs are grown along c-axis direction with wurtzite crystal structure. Cathodoluminescence spectroscopy, which shows a single strong peak around 3.24 eV with full width half maxima 130 meV, indicates the high crystalline and optical quality of ZnO and very low defect density. Vertically aligned nanosensors were fabricated by depositing gold circular Schottky contacts on ZnO NRs. Resistance responses of nanosensors were observed in the range from 50 to 150 °C in 1% and 5% hydrogen in argon environment, which is below and above the explosive limit (4%) of hydrogen in air. The nanosensor's sensitivity increases from 11% to 67% with temperature from 50 to 150 °C and also shows fast response time (9–16 s) and moderate recovery time (100–200 s). A sensing mechanism is proposed based on Schottky barrier changes at heterojunctions and change in depletion region of NRs.

  9. Gold nanoparticles modified ZnO nanorods with improved photocatalytic activity.

    PubMed

    Sun, Lanlan; Zhao, Dongxu; Song, Zhiming; Shan, Chongxin; Zhang, Zhenzhong; Li, Binghui; Shen, Dezhen

    2011-11-01

    Well-aligned ZnO nanorods (NRs) were grown on indium-tin-oxide (ITO) slide by the hydrothermal method and used as templates for preparing ZnO/Au composite nanoarrays. The optical and morphological properties of ZnO/Au composites under various HAuCl(4) concentrations were explored via UV-vis absorption spectroscopy, photoluminescence (PL) and scanning electron microscopy (SEM). The density and size of gold nanoparticles (Au NPs) on ZnO NRs can be controlled by adjusting the concentration of HAuCl(4). The optimal ZnO/Au composites display complete photocatalytic degradation of methyl blue (MB) within 60 min, which is superior to that with pure ZnO NRs prepared by the same method. The reason of better photocatalytic performance is that Au NPs act as electron traps and it prevents the rapid recombination of electrons and holes, resulting in the improvement of photocatalytic efficiency. The photocatalytic performance of ZnO/Au composites is mainly controlled by the density of Au NPs formed on ZnO NRs. The application in rapid photodegradation of MB shows the potential of ZnO/Au composite as a convenient catalyst for the environmental purification of organic pollutants.

  10. Electrochemically-deposited ZnO nanorods arrays on ITO seeding layers

    NASA Astrophysics Data System (ADS)

    Petrov, M.; Lovchinov, K.; Nichev, H.; Dimova-Malinovska, D.

    2016-03-01

    In this paper, results are reported from the study of the structural and optical properties of ZnO nanostructured arrays with nanorods (NRs) grown electrochemically on ITO seeding layers with two different thicknesses deposited on a glass substrate. The properties are compared of the ZnO NRs grown on ITO seeding layers with resistivity 6.4 × 10-4 Ω cm, sheet resistance 80 Ω/□ and 8 Ω/□ and different ITO thicknesses - 80 and 800 nm, respectively. The optical spectra of reflectance, transmittance, diffused reflection and diffused transmission and the haze ratio in transmission and reflection of the samples carried out before and after ZnO NRs deposition are compared and discussed. The structures' properties are studied by scanning electron microscopy (SEM). The ZnO NRs arrays with increased values of diffused transmission and reflection compared to the seeding layer substrates can be used in thin-film solar cells for increasing the light trapping.

  11. Highly photoresponsive, ZnO nanorod-based photodetector for operation in the visible spectral range

    NASA Astrophysics Data System (ADS)

    Choi, Daniel S.; Hansen, Matthew; Van Keuren, Edward; Hahm, Jong-in

    2017-04-01

    While significant advances have been made for gold nanoparticle (AuNP)-coupled zinc oxide (ZnO) as visibly blind, ultraviolet photodetection devices, very few ZnO nanomaterial systems have been developed specifically for use in the visible wavelength regime. Further efforts to develop ZnO-based visible photodetectors (PDs) are still highly warranted in order to better understand the precise effect of AuNP load, operation wavelength, and beam position on the device output. In this study, we demonstrate significantly enhanced, photoresponse behaviors of AuNP-coupled ZnO nanorod (NR) network devices in the visible wavelength range with their photoresponse capacity comparable to, if not far exceeding, most commercial PDs as well as recently reported, visible, AuNP-coupled ZnO detectors. In addition, the nature and degree of the photoresponsivity enhancement are systematically elucidated by investigating their light-triggered electrical signals under varying incident wavelengths, AuNP amounts, and illumination positions. We discuss a possible photoconduction mechanism of our AuNP-coupled ZnO NR PDs and the origins of the high photoresponsivity. Specifically related to the AuNP amount-dependent photoresponse behaviors, the nanoparticle density yielding photoresponse maxima is explained as the interplay between localized surface plasmon resonance, plasmonic heating, and scattering in our photothermoelectric effect-driven device. We show that the AuNP-coupled ZnO NR PDs can be constructed via a straightforward method without the need for ultrahigh vacuum, sputtering procedures, or photo/electron-beam lithographic tools. Hence, the approach demonstrated in this study may serve as a convenient and viable means to advance the current state of ZnO-based PDs for operation in the visible spectral range with greatly increased photoresponsivity.

  12. Highly photoresponsive, ZnO nanorod-based photodetector for operation in the visible spectral range.

    PubMed

    Choi, Daniel S; Hansen, Matthew; Van Keuren, Edward; Hahm, Jong-In

    2017-04-07

    While significant advances have been made for gold nanoparticle (AuNP)-coupled zinc oxide (ZnO) as visibly blind, ultraviolet photodetection devices, very few ZnO nanomaterial systems have been developed specifically for use in the visible wavelength regime. Further efforts to develop ZnO-based visible photodetectors (PDs) are still highly warranted in order to better understand the precise effect of AuNP load, operation wavelength, and beam position on the device output. In this study, we demonstrate significantly enhanced, photoresponse behaviors of AuNP-coupled ZnO nanorod (NR) network devices in the visible wavelength range with their photoresponse capacity comparable to, if not far exceeding, most commercial PDs as well as recently reported, visible, AuNP-coupled ZnO detectors. In addition, the nature and degree of the photoresponsivity enhancement are systematically elucidated by investigating their light-triggered electrical signals under varying incident wavelengths, AuNP amounts, and illumination positions. We discuss a possible photoconduction mechanism of our AuNP-coupled ZnO NR PDs and the origins of the high photoresponsivity. Specifically related to the AuNP amount-dependent photoresponse behaviors, the nanoparticle density yielding photoresponse maxima is explained as the interplay between localized surface plasmon resonance, plasmonic heating, and scattering in our photothermoelectric effect-driven device. We show that the AuNP-coupled ZnO NR PDs can be constructed via a straightforward method without the need for ultrahigh vacuum, sputtering procedures, or photo/electron-beam lithographic tools. Hence, the approach demonstrated in this study may serve as a convenient and viable means to advance the current state of ZnO-based PDs for operation in the visible spectral range with greatly increased photoresponsivity.

  13. Low-temperature growth of aligned ZnO nanorods: effect of annealing gases on the structural and optical properties.

    PubMed

    Umar, Ahmad; Hahn, Yoon-Bong; Al-Hajry, A; Abaker, M

    2014-06-01

    Aligned ZnO nanorods were grown on ZnO/Si substrate via simple aqueous solution process at low-temperature of - 65 degrees C by using zinc nitrate and hexamethylenetetramine (HMTA). The detailed morphological and structural properties measured by FESEM, XRD, EDS and TEM confirmed that the as-grown nanorods are vertically aligned, well-crystalline possessing wurtzite hexagonal phase and grown along the [0001] direction. The room-temperature photoluminescence spectrum of the grown nanorods exhibited a strong and broad green emission and small ultraviolet emission. The as-prepared ZnO nanorods were post-annealed in nitrogen (N2) and oxygen (O2) environments and further characterized in terms of their morphological, structural and optical properties. After annealing the nanorods exhibit well-crystallinity and wurtzite hexagonal phase. Moreover, by annealing the PL spectra show the enhancement in the UV emission and suppression in the green emission. The presented results demonstrate that simply by post-annealing process, the optical properties of ZnO nanostructures can be controlled.

  14. Impact of hydrogen concentrations on the impedance spectroscopic behavior of Pd-sensitized ZnO nanorods

    PubMed Central

    2013-01-01

    ZnO nanorods were synthesized using a low-cost sol-gel spin coating technique. The synthesized nanorods were consisted of hexagonal phase having c-axis orientation. SEM images reflected perpendicular ZnO nanorods forming bridging network in some areas. The impact of different hydrogen concentrations on the Pd-sensitized ZnO nanorods was investigated using an impedance spectroscopy (IS). The grain boundary resistance (Rgb) significantly contributed to the sensing properties of hydrogen gas. The boundary resistance was decreased from 11.95 to 3.765 kΩ when the hydrogen concentration was increased from 40 to 360 ppm. IS gain curve showed a gain of 6.5 for 360 ppm of hydrogen at room temperature. Nyquist plot showed reduction in real part of impedance at low frequencies on exposure to different concentrations of hydrogen. Circuit equivalency was investigated by placing capacitors and resistors to identify the conduction mechanism according to complex impedance Nyquist plot. Variations in nanorod resistance and capacitance in response to the introduction of various concentrations of hydrogen gas were obtained from the alternating current impedance spectra. PMID:23399029

  15. Enhanced performance with bismuth ferrite perovskite in ZnO nanorod solid state solar cells

    NASA Astrophysics Data System (ADS)

    Loh, Leonard; Briscoe, Joe; Dunn, Steve

    2014-05-01

    This paper reports for the first time the use of perovskite bismuth ferrite (BiFeO3 or BFO) on ZnO-based solid state solar cells using only chemical solution methods for materials synthesis. As ZnO has poor chemical stability in acidic and corrosive environments, a buffer method using aminosilane ((3-aminopropyltriethoxysilane or H2N(CH2)3Si(OC2H5)3)) coating was used to provide a protective coating on the ZnO nanorods. The aminosilane layer was removed after BFO coating. The solid state solar cells, sensitized by N719, used CuSCN as the hole conductor and were tested under 100 mW cm-2, AM 1.5G simulated sunlight. The photovoltaic performance showed current density improvement from 0.64 mA cm-2 to 1.4 mA cm-2 and efficiencies from 0.1% to 0.38% when comparing between ZnO and ZnO/BFO solar cells. The observed ca. 400% improved performance is shown to result from BFO's role as an electron blocking layer.This paper reports for the first time the use of perovskite bismuth ferrite (BiFeO3 or BFO) on ZnO-based solid state solar cells using only chemical solution methods for materials synthesis. As ZnO has poor chemical stability in acidic and corrosive environments, a buffer method using aminosilane ((3-aminopropyltriethoxysilane or H2N(CH2)3Si(OC2H5)3)) coating was used to provide a protective coating on the ZnO nanorods. The aminosilane layer was removed after BFO coating. The solid state solar cells, sensitized by N719, used CuSCN as the hole conductor and were tested under 100 mW cm-2, AM 1.5G simulated sunlight. The photovoltaic performance showed current density improvement from 0.64 mA cm-2 to 1.4 mA cm-2 and efficiencies from 0.1% to 0.38% when comparing between ZnO and ZnO/BFO solar cells. The observed ca. 400% improved performance is shown to result from BFO's role as an electron blocking layer. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr00911h

  16. Effect of growth time on Ti-doped ZnO nanorods prepared by low-temperature chemical bath deposition

    NASA Astrophysics Data System (ADS)

    Bidier, Shaker A.; Hashim, M. R.; Al-Diabat, Ahmad M.; Bououdina, M.

    2017-04-01

    Ti-doped ZnO nanorod arrays were grown onto Si substrate using chemical bath deposition (CBD) method at 93 °C. To investigate the effect of time deposition on the morphological, and structural properties, four Ti-doped ZnO samples were prepared at various deposition periods of time (2, 3.5, 5, and 6.5 h). FESEM images displayed high-quality and uniform nanorods with a mean length strongly dependent upon deposition time; i.e. it increases for prolonged growth time. Additionally, EFTEM images reveal a strong erosion on the lateral side for the sample prepared for 6.5 h as compared to 5 h. This might be attributed to the dissolution reaction of ZnO with for prolonged growth time. XRD analysis confirms the formation of a hexagonal wurtzite-type structure for all samples with a preferred growth orientation along the c-axis direction. The (100) peak intensity was enhanced and then quenched, which might be the result of an erosion on the lateral side of nanorods as seen in EFTEM. This study confirms the important role of growth time on the morphological features of Ti-doped ZnO nanorods prepared using CBD.

  17. Effect of growth time on Ti-doped ZnO nanorods prepared by low-temperature chemical bath deposition.

    PubMed

    Bidier, Shaker A; Hashim, M R; Al-Diabat, Ahmad M; Bououdina, M

    2017-04-01

    Ti-doped ZnO nanorod arrays were grown onto Si substrate using chemical bath deposition (CBD) method at 93 °C. To investigate the effect of time deposition on the morphological, and structural properties, four Ti-doped ZnO samples were prepared at various deposition periods of time (2, 3.5, 5, and 6.5 h). FESEM images displayed high-quality and uniform nanorods with a mean length strongly dependent upon deposition time; i.e. it increases for prolonged growth time. Additionally, EFTEM images reveal a strong erosion on the lateral side for the sample prepared for 6.5 h as compared to 5 h. This might be attributed to the dissolution reaction of ZnO with for prolonged growth time. XRD analysis confirms the formation of a hexagonal wurtzite-type structure for all samples with a preferred growth orientation along the c-axis direction. The (100) peak intensity was enhanced and then quenched, which might be the result of an erosion on the lateral side of nanorods as seen in EFTEM. This study confirms the important role of growth time on the morphological features of Ti-doped ZnO nanorods prepared using CBD.

  18. Biopolymer-assisted self-assembly of ZnO nanoarchitectures from nanorods

    NASA Astrophysics Data System (ADS)

    Lupan, O.; Chow, L.; Chai, G.; Schulte, A.; Park, S.; Lopatiuk-Tirpak, O.; Chernyak, L.; Heinrich, H.

    2008-04-01

    We have investigated three-dimensional (3-D) architectures-microspheres and radial structures-based on biopolymer-assisted self-assembly from one-dimensional ZnO nanorods. The developed method is simple, rapid and cost-effective and can be used for self-assembly of different complex superstructures. A possible model of 3-D architectures self-assembled with biopolymer assistance is presented using minimum energy considerations. Scanning electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, transmission electron microscopy, micro-Raman spectroscopy and cathode luminescence investigations show that the novel 3-D architectures are built from high-purity ZnO nanorods with a wurtzite structure. The resulting radial structures show an intense ultraviolet (UV) cathode luminescence emission suggesting applications as UV light emitting diodes or lasers. Their structural characteristics endow them with a broad area of applications and offer a possibility to be used as fundamental low-dimensional building units. These building units open opportunities for the self-assembly of multifunctional nanostructured systems with applications in bioscience and nanomedicine, electronics and photonics.

  19. Preparation of ZnO nanorods on conductive PET-ITO-Ag fibers

    NASA Astrophysics Data System (ADS)

    Li, Yiwen; Ji, Shuai; Chen, Yuanyu; Zhang, Hong; Gong, Yumei; Guo, Jing

    2016-12-01

    We studied the vertical ZnO nanorods grown on conductive conventional polyethylene terephthalate (PET) fibers which are prepared by electroless silver depositing on tin-doped indium oxide (ITO) coated PET fibers through an efficient and low-cost green approach. The PET fibers were firstly functionalized with a layer of ITO gel synthesized through a sol-gel process at rather low temperature, simply by immersing the fibers into ITO sol for several minutes followed by gelation at 120 °C. Once the ITO gel layer surface was activated by SnCl2, a continuous, uniform, and compact layer of silver was carried out on the surface of the PET-ITO fibers through electroless plating operation at room temperature. The as-prepared PET-ITO-Ag fibers had good electrical conductivity, with surface resistivity as low as 0.23 mΩ cm. The overall procedure is simple, efficient, nontoxic, and controllable. The conductive PET-ITO-Ag fiber was used successfully as a flexible basal material to plant vertical ZnO nanorods through controlling the seeding and growth processes. The morphology of the PET-ITO, PET-ITO-Ag, and PET-ITO-Ag-ZnO fibers were observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Undergone the whole process, although the tensile strength of the fiber decreased slightly, they may still exert their applications in flexible electronic such as photovoltaic and piezoelectric devices.

  20. Confined Formation of Ultrathin ZnO Nanorods/Reduced Graphene Oxide Mesoporous Nanocomposites for High-Performance Room-Temperature NO2 Sensors.

    PubMed

    Xia, Yi; Wang, Jing; Xu, Jian-Long; Li, Xian; Xie, Dan; Xiang, Lan; Komarneni, Sridhar

    2016-12-28

    Here we demonstrate high-performance room-temperature NO2 sensors based on ultrathin ZnO nanorods/reduced graphene oxide (rGO) mesoporous nanocomposites. Ultrathin ZnO nanorods were loaded on rGO nanosheets by a facile two-step additive-free solution synthesis involving anchored seeding followed by oriented growth. The ZnO nanorod diameters were simply controlled by the seed diameters associated with the spatial confinement effects of graphene oxide (GO) nanosheets. Compared to the solely ZnO nanorods and rGO-based sensors, the optimal sensor based on ultrathin ZnO nanorods/rGO nanocomposites exhibited higher sensitivity and quicker p-type response to parts per million level of NO2 at room temperature, and the sensitivity to 1 ppm of NO2 was 119% with the response and recovery time being 75 and 132 s. Moreover, the sensor exhibited full reversibility, excellent selectivity, and a low detection limit (50 ppb) to NO2 at room temperature. In addition to the high transport capability of rGO as well as excellent NO2 adsorption ability derived from ultrathin ZnO nanorods and mesoporous structures, the superior sensing performance of the nanocomposites was attributed to the synergetic effect of ZnO and rGO, which was realized by the electron transfer across the ZnO-rGO interfaces through band energy alignment.

  1. Effect of Postannealing Treatment on Structural and Optical Properties of ZnO Nanorods Prepared Using Chemical Bath Deposition

    NASA Astrophysics Data System (ADS)

    Bidier, Shaker A.; Hashim, M. R.; Aldiabat, Ahmad M.

    2017-03-01

    ZnO nanorods have been synthesized on glass substrate by the chemical bath deposition technique. To investigate the effect of postannealing treatment on their crystalline and optical quality, the films were annealed at various temperatures of 300°C, 400°C, and 500°C in air ambient for 1 h. The morphological and chemical composition of the ZnO films were investigated using field-emission scanning electron microscopy (FESEM) with energy-dispersive spectroscopy (EDS). The structural properties were characterized by employing x-ray diffraction analysis and Raman spectroscopy. Finally, the optical properties were investigated by photoluminescence measurements. FESEM images revealed high-quality ZnO nanorods grown on the substrate surface. EDS results demonstrated a slight reduction in the quantity of oxygen after annealing. XRD and Raman results showed noticeable improvement in the crystalline quality of the ZnO films after annealing. The crystallite size increased significantly after annealing, from 40.5 nm for the nonannealed film to a maximum for 46.2 nm for the annealed samples. The photoluminescence results exhibited an increment in the optical quality [ultraviolet (UV) versus visible emission] after postannealing treatment. The enhancement in the crystalline and optical quality of the annealed films compared with the nonannealed sample is due to recrystallization of ZnO particles into a ZnO wurtzite lattice structure as well as relaxation of oxygen molecules adsorbed on the surface of the ZnO nanorods. This enhancement is conducive to improved efficiency for potential applications of ZnO.

  2. Plasmon-enhanced Electrically Light-emitting from ZnO Nanorod Arrays/p-GaN Heterostructure Devices

    PubMed Central

    Lu, Junfeng; Shi, Zengliang; Wang, Yueyue; Lin, Yi; Zhu, Qiuxiang; Tian, Zhengshan; Dai, Jun; Wang, Shufeng; Xu, Chunxiang

    2016-01-01

    Effective and bright light-emitting-diodes (LEDs) have attracted broad interests in fundamental research and industrial application, especially on short wavelength LEDs. In this paper, a well aligned ZnO nanorod arrays grown on the p-GaN substrate to form a heterostructured light-emitting diode and Al nanoparticles (NPs) were decorated to improve the electroluminescence performance. More than 30-folds enhancement of the electroluminescence intensity was obtained compared with the device without Al NPs decoration. The investigation on the stable and transient photoluminescence spectraof the ZnO nanorod arrays before and after Al NPs decoration demonstrated that the metal surface plasmon resonance coupling with excitons of ZnO leads to the enhancement of the internal quantum efficiency (IQE). Our results provide aneffective approach to design novel optoelectronic devices such as light-emitting diodes and plasmonic nanolasers. PMID:27181337

  3. Electrosynthesis of ZnO nanorods and nanotowers: Morphology and X-ray Absorption Near Edge Spectroscopy studies

    NASA Astrophysics Data System (ADS)

    Sigircik, Gokmen; Erken, Ozge; Tuken, Tunc; Gumus, Cebrail; Ozkendir, Osman M.; Ufuktepe, Yuksel

    2015-06-01

    Deposition mechanism of nano-structured ZnO films has been investigated in the absence and presence of chloride ions from aqueous solution. The resulting opto-electronic properties were interpreted extensively, using X-ray diffraction (XRD), X-ray Absorption Near Edge Spectroscopy (XANES), field emission scanning electron microscopy (FE-SEM), UV-Visible spectroscopy and four probe techniques. The ZnO deposition is mass transport controlled process and the interaction of chloride ions with the surface has great influence on diffusion kinetics, considering the substantial species (Zn2+ and OH-) involved in the construction of ZnO film. This effect does not change major lattice parameters, as shown with detailed analysis of XRD data. However, the texture coefficient (Tc) (0 0 2) value is higher in presence of chloride ions containing synthesis solution which gave vertically aligned, well defined and uniformly dispersed nanorods structure. The calculated Eg values are in the range 3.28-3.41 eV and 3.22-3.31 eV for ZnO nanorods and nanotowers synthesized at different deposition periods, respectively. Furthermore, the charge mobility values regarding the deposition periods were measured to be in the ranges from 130.4 to 449.2 cm2 V-1 s-1 and 126.2 to 204.7 cm2 V-1 s-1 for nanorods and nanotowers, respectively. From XANES results, it was shown that the Zn K-edge spectrum is dominated by the transition of Zn 1s core electrons into the unoccupied Zn 4p states of the conduction band. Comparing the rod and tower nano-structured ZnO thin films, the excitation behavior of valence band electrons is different. Moreover, the density states of Zn 4p are higher for ZnO nanorods.

  4. High performance Ce-doped ZnO nanorods for sunlight-driven photocatalysis

    PubMed Central

    Chouchene, Bilel; Ben Chaabane, Tahar; Balan, Lavinia; Girot, Emilien; Mozet, Kevin; Medjahdi, Ghouti

    2016-01-01

    Summary Ce-doped ZnO (ZnO:Ce) nanorods have been prepared through a solvothermal method and the effects of Ce-doping on the structural, optical and electronic properties of ZnO rods were studied. ZnO:Ce rods were characterized by XRD, SEM, TEM, XPS, BET, DRS and Raman spectroscopy. 5% Ce-doped ZnO rods with an average length of 130 nm and a diameter of 23 nm exhibit the highest photocatalytic activity for the degradation of the Orange II dye under solar light irradiation. The high photocatalytic activity is ascribed to the substantially enhanced light absorption in the visible region, to the high surface area of ZnO:Ce rods and to the effective electron–hole pair separation originating from Ce doping. The influence of various experimental parameters like the pH, the presence of salts and of organic compounds was investigated and no marked detrimental effect on the photocatalytic activity was observed. Finally, recyclability experiments demonstrate that ZnO:Ce rods are a stable solar-light photocatalyst. PMID:27826508

  5. Controlled Defects of Fluorine-incorporated ZnO Nanorods for Photovoltaic Enhancement

    PubMed Central

    Lee, Hock Beng; Ginting, Riski Titian; Tan, Sin Tee; Tan, Chun Hui; Alshanableh, Abdelelah; Oleiwi, Hind Fadhil; Yap, Chi Chin; Jumali, Mohd Hafizuddin Hj.; Yahaya, Muhammad

    2016-01-01

    Anion passivation effect on metal-oxide nano-architecture offers a highly controllable platform for improving charge selectivity and extraction, with direct relevance to their implementation in hybrid solar cells. In current work, we demonstrated the incorporation of fluorine (F) as an anion dopant to address the defect-rich nature of ZnO nanorods (ZNR) and improve the feasibility of its role as electron acceptor. The detailed morphology evolution and defect engineering on ZNR were studied as a function of F-doping concentration (x). Specifically, the rod-shaped arrays of ZnO were transformed into taper-shaped arrays at high x. A hypsochromic shift was observed in optical energy band gap due to the Burstein-Moss effect. A substantial suppression on intrinsic defects in ZnO lattice directly epitomized the novel role of fluorine as an oxygen defect quencher. The results show that 10-FZNR/P3HT device exhibited two-fold higher power conversion efficiency than the pristine ZNR/P3HT device, primarily due to the reduced Schottky defects and charge transfer barrier. Essentially, the reported findings yielded insights on the functions of fluorine on (i) surface –OH passivation, (ii) oxygen vacancies (Vo) occupation and (iii) lattice oxygen substitution, thereby enhancing the photo-physical processes, carrier mobility and concentration of FZNR based device. PMID:27587295

  6. PDMS-based triboelectric and transparent nanogenerators with ZnO nanorod arrays.

    PubMed

    Ko, Yeong Hwan; Nagaraju, Goli; Lee, Soo Hyun; Yu, Jae Su

    2014-05-14

    Vertically-grown ZnO nanorod arrays (NRAs) on indium tin oxide (ITO)-coated polyethylene terephthalate (PET), as a top electrode of nanogenerators, were investigated for the antireflective property as well as an efficient contact surface in bare polydimethysiloxane (PDMS)-based triboelectric nanogenerators. Compared to conventional ITO-coated PET (i.e., ITO/PET), the ZnO NRAs considerably suppressed the reflectance from 20 to 9.7% at wavelengths of 300-1100 nm, creating a highly transparent top electrode, as demonstrated by theoretical analysis. Also, the interval time between the peaks of generated output voltage under external pushing forces was significantly decreased from 1.84 to 0.19 s because the reduced contact area of the PDMS by discrete surfaces of the ZnO NRAs on ITO/PET causes a rapid sequence for triboelectric charge generation process including rubbing and separating. Therefore, the use of this top electrode enabled to operate the transparent PDMS-based triboelectric nanogenerator at high frequency of external pushing force. Under different external forces of 0.3-10 kgf, the output voltage and current were also characterized.

  7. High performance Ce-doped ZnO nanorods for sunlight-driven photocatalysis.

    PubMed

    Chouchene, Bilel; Ben Chaabane, Tahar; Balan, Lavinia; Girot, Emilien; Mozet, Kevin; Medjahdi, Ghouti; Schneider, Raphaël

    2016-01-01

    Ce-doped ZnO (ZnO:Ce) nanorods have been prepared through a solvothermal method and the effects of Ce-doping on the structural, optical and electronic properties of ZnO rods were studied. ZnO:Ce rods were characterized by XRD, SEM, TEM, XPS, BET, DRS and Raman spectroscopy. 5% Ce-doped ZnO rods with an average length of 130 nm and a diameter of 23 nm exhibit the highest photocatalytic activity for the degradation of the Orange II dye under solar light irradiation. The high photocatalytic activity is ascribed to the substantially enhanced light absorption in the visible region, to the high surface area of ZnO:Ce rods and to the effective electron-hole pair separation originating from Ce doping. The influence of various experimental parameters like the pH, the presence of salts and of organic compounds was investigated and no marked detrimental effect on the photocatalytic activity was observed. Finally, recyclability experiments demonstrate that ZnO:Ce rods are a stable solar-light photocatalyst.

  8. Controlled Defects of Fluorine-incorporated ZnO Nanorods for Photovoltaic Enhancement

    NASA Astrophysics Data System (ADS)

    Lee, Hock Beng; Ginting, Riski Titian; Tan, Sin Tee; Tan, Chun Hui; Alshanableh, Abdelelah; Oleiwi, Hind Fadhil; Yap, Chi Chin; Jumali, Mohd Hafizuddin Hj.; Yahaya, Muhammad

    2016-09-01

    Anion passivation effect on metal-oxide nano-architecture offers a highly controllable platform for improving charge selectivity and extraction, with direct relevance to their implementation in hybrid solar cells. In current work, we demonstrated the incorporation of fluorine (F) as an anion dopant to address the defect-rich nature of ZnO nanorods (ZNR) and improve the feasibility of its role as electron acceptor. The detailed morphology evolution and defect engineering on ZNR were studied as a function of F-doping concentration (x). Specifically, the rod-shaped arrays of ZnO were transformed into taper-shaped arrays at high x. A hypsochromic shift was observed in optical energy band gap due to the Burstein-Moss effect. A substantial suppression on intrinsic defects in ZnO lattice directly epitomized the novel role of fluorine as an oxygen defect quencher. The results show that 10-FZNR/P3HT device exhibited two-fold higher power conversion efficiency than the pristine ZNR/P3HT device, primarily due to the reduced Schottky defects and charge transfer barrier. Essentially, the reported findings yielded insights on the functions of fluorine on (i) surface –OH passivation, (ii) oxygen vacancies (Vo) occupation and (iii) lattice oxygen substitution, thereby enhancing the photo-physical processes, carrier mobility and concentration of FZNR based device.

  9. Controlling the conduction band offset for highly efficient ZnO nanorods based perovskite solar cell

    SciTech Connect

    Dong, Juan; Shi, Jiangjian; Li, Dongmei; Luo, Yanhong; Meng, Qingbo

    2015-08-17

    The mechanism of charge recombination at the interface of n-type electron transport layer (n-ETL) and perovskite absorber on the carrier properties in the perovskite solar cell is theoretically studied. By solving the one dimensional diffusion equation with different boundary conditions, it reveals that the interface charge recombination in the perovskite solar cell can be suppressed by adjusting the conduction band offset (ΔE{sub C}) at ZnO ETL/perovskite absorber interface, thus leading to improvements in cell performance. Furthermore, Mg doped ZnO nanorods ETL has been designed to control the energy band levels. By optimizing the doping amount of Mg, the conduction band minimum of the Mg doped ZnO ETL has been raised up by 0.29 eV and a positive ΔE{sub C} of about 0.1 eV is obtained. The photovoltage of the cell is thus significantly increased due to the relatively low charge recombination.

  10. Enhanced performance with bismuth ferrite perovskite in ZnO nanorod solid state solar cells.

    PubMed

    Loh, Leonard; Briscoe, Joe; Dunn, Steve

    2014-06-21

    This paper reports for the first time the use of perovskite bismuth ferrite (BiFeO3 or BFO) on ZnO-based solid state solar cells using only chemical solution methods for materials synthesis. As ZnO has poor chemical stability in acidic and corrosive environments, a buffer method using aminosilane ((3-aminopropyltriethoxysilane or H2N(CH2)3Si(OC2H5)3)) coating was used to provide a protective coating on the ZnO nanorods. The aminosilane layer was removed after BFO coating. The solid state solar cells, sensitized by N719, used CuSCN as the hole conductor and were tested under 100 mW cm(-2), AM 1.5G simulated sunlight. The photovoltaic performance showed current density improvement from 0.64 mA cm(-2) to 1.4 mA cm(-2) and efficiencies from 0.1% to 0.38% when comparing between ZnO and ZnO/BFO solar cells. The observed ca. 400% improved performance is shown to result from BFO's role as an electron blocking layer.

  11. The role of Zn vacancies in UV sensing with ZnO nanorods

    NASA Astrophysics Data System (ADS)

    Barbagiovanni, E. G.; Strano, V.; Franzò, G.; Mirabella, S.

    2016-10-01

    The UV sensing properties of ZnO nanorods (NRs) fabricated by a chemical bath deposition using two different hexamethylenetetramine (HMTA) concentrations, 25 mM and 50 mM, are studied in this work. The NRs are investigated by scanning electron microscopy (SEM), photoluminescence (PL) spectroscopy, and photoconductivity measurements. The SEM images indicate that 25 mM HMTA NRs exhibit merging that increases the growth induced defects in this sample with respect to the 50 mM sample. PL measurements demonstrate a higher optical transition from the doubly ionized Zn vacancy ( VZ n 2 - ) at 2.52 eV in the 50 mM ZnO NRs due to the reduced growth defect density. The photoconductivity measurements indicate better sensitivity and spectral selectivity in the 50 mM NRs, which we present as a result of the VZ n 2 - state. These results are summarised with a UV sensing model based on the optical properties of ZnO NRs, which provides a route for the development of improved sensors.

  12. Growing vertical ZnO nanorod arrays within graphite: efficient isolation of large size and high quality single-layer graphene.

    PubMed

    Ding, Ling; E, Yifeng; Fan, Louzhen; Yang, Shihe

    2013-07-18

    We report a unique strategy for efficiently exfoliating large size and high quality single-layer graphene directly from graphite into DMF dispersions by growing ZnO nanorod arrays between the graphene layers in graphite.

  13. Rapid fabrication of ZnO nanorod arrays with controlled spacing by micelle-templated solvothermal growth.

    PubMed

    Pelligra, Candice I; Toth, Kristof; Hu, Hanqiong; Osuji, Chinedum O

    2016-01-07

    We present a facile method for the synthesis of nanorod arrays over large areas with fine control over the average rod-rod spacing. Block copolymer micelles are used to template solvothermal synthesis of ZnO nanorods by preferentially enabling reactant diffusion through the micelle cores to an underlying seed layer. The distance between nanorod centers is defined by the micelle number density which is in turn controlled by the molecular weight of the block copolymer, and the block copolymer concentration in a templating film. We demonstrate the ability to control the resulting nanorod number density from ∼100 μm(-2) down to ∼10 μm(-2) with high fidelity. Correspondingly, the distance between nanorod surfaces was varied from ∼60 nm to 230 nm. The method developed here provides a viable approach for rapidly fabricating large-area nanostructured electrodes comprised of nanorod arrays with controlled geometries. The ability to tailor nanorod spacing over a broad range suggests applications in photovoltaics and sensors based on optical resonances can be readily addressed.

  14. In situ generated AgBr-enhanced ZnO nanorod-based photoelectrochemical aptasensing via layer-by-layer assembly.

    PubMed

    Li, Jing; Tu, Wenwen; Li, Hongbo; Bao, Jianchun; Dai, Zhihui

    2014-02-28

    A robust aptasensor for Ag(+) was proposed for the first time using an enhanced ZnO nanorod-based photoelectrochemistry by in situ generated AgBr via layer-by-layer assembly. This work opens up new avenues for application of one-dimensional ZnO nanorod arrays in photoelectrochemical sensing. Additionally, the strategy of employing in situ generated narrow-bandgap semiconductors paves a new way for photoelectrochemical sensing.

  15. Synthesis of amorphous TiO2 modified ZnO nanorod film with enhanced photocatalytic properties

    NASA Astrophysics Data System (ADS)

    Xiao, Shanshan; Zhao, Lei; Leng, Xuning; Lang, Xingyou; Lian, Jianshe

    2014-04-01

    Amorphous TiO2 modified ZnO nanorod films were synthesized via multi-step processes: ZnO nanorod films were prepared by a wet chemical method. Amorphous TiO2 was then anchored on the tops and sides of the nanorods through immersion in tetrabutyltitanate solution for hydrolysis. The as-prepared samples were characterized for the phase structure, chemical state and surface morphology as well as optical absorption using X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and ultraviolet-visible (UV-vis) spectrophotometer. The results showed that the nanorod films were covered by amorphous TiO2 layers, and their visible light absorption ability was strengthened. The photocatalytic studies revealed that TiO2 modified films exhibited enhanced photocatalytic efficiency for decomposition of methyl orange under ultraviolet-visible excitation, which might be attributed to the increased UV-vis light absorption and the separation of the charge carrier and prolonged electron lifetime due to the interface between TiO2 and ZnO.

  16. Structural and optical investigations on seed layer assisted hydrothermally grown ZnO nanorods on flat and textured substrates

    NASA Astrophysics Data System (ADS)

    Rayerfrancis, Arokiyadoss; Balaji Bhargav, P.; Ahmed, Nafis; Balaji, C.; Dhara, Sandip

    2016-12-01

    In this article we report the synthesis of vertically aligned ZnO nanorods on plain as well as textured fluorine doped tin oxide (FTO) coated glass substrate using hydrothermal method. Prior to hydrothermal method, AZO seed layer of thickness 5, 10 and 15 nm were deposited on the chosen substrates by DC magnetron sputtering. The as-grown nanorods were annealed at 450 °C for 3 h to improve the crystallinity. Morphology and structure of the nanorods was observed by field emission scanning electron microscopy. The formation of wurtzite structure was confirmed through x-ray diffraction studies. The optical mode of ZnO, E2 (high) at 434 cm-1 present in the samples was confirmed by Raman spectroscopy. The seed layer assisted growth of ZnO nanorods were defect free, which is confirmed from the photoluminescence spectra, and the intensity of band to band emission is much greater than the emission from the defects at the deep level.

  17. Facile synthesis and enhanced ultraviolet emission of ZnO nanorods prepared by vapor-confined face-to-face annealing.

    PubMed

    Nam, Giwoong; Park, Youngbin; Ji, Iksoo; Kim, Byunggu; Lee, Sang-Heon; Kim, Do Yeob; Kim, Soaram; Kim, Sung-O; Leem, Jae-Young

    2015-01-14

    In this study, we report a novel regrowth method of sol-gel-prepared ZnO films using a vapor-confined face-to-face annealing (VC-FTFA) technique in which mica was inserted between two films, followed by annealing with the FTFA method. The ZnO nanorods are regrown when zinc acetate dihydrate and zinc chloride (ZnCl2) are used as the solvent, because these generate ZnCl2 vapor. The near-band-edge emission intensity of the ZnO nanorods was enhanced through the VC-FTFA method, increasing significantly by a factor of 56 compared to that of ZnO films annealed in open air at 700 °C. Our method may provide a route toward the facile fabrication of ZnO nanorods.

  18. Numerical calculation of plasmonic field absorption enhancement in CdSe-quantum dot sensitized ZnO nanorods by Ag nanoparticle periodic arrays

    NASA Astrophysics Data System (ADS)

    Kohnehpoushi, Saman; Eskandari, Mehdi; Nejand, Bahram Abdollahi; Ahmadi, Vahid

    2016-12-01

    Plasmonic field absorption enhancement (PFAE) of Ag nanoparticles (Ag NPs) periodic arrays in CdSe-quantum dot (QD) sensitized ZnO nanorods was numerically investigated by the three-dimensional finite difference time domain (FDTD). The Ag NPs with spherical morphology were found to have an optimum PFAE compared to other Ag NP morphologies such as cubic and pyramidal. The results also showed that PFAE intensity in CdSe-QD-sensitized ZnO nanorods is increased with the reduction of Ag NP diameter until 10 nm and decreases thereafter. Moreover, the optimum density of spherical Ag NPs for optimum PFAE was observed as 20%. PFAE in CdSe-QD-sensitized ZnO nanorods is improved with increasing space between ZnO nanorods until 180 nm and reduces thereafter. Finally, the results showed that PFAE of Ag NPs for the high distance between ZnO nanorods is dependent on radiation angle; while for the low distance between ZnO nanorods it is free of radiation angle.

  19. The effect of oxygen-plasma treatment on the mechanical and piezoelectrical properties of ZnO nanorods

    NASA Astrophysics Data System (ADS)

    Hussain, Mushtaque; Khan, Azam; Nur, Omer; Willander, Magnus; Broitman, Esteban

    2014-07-01

    We have studied the effect of oxygen plasma treatment on piezoelectric response and on the mechanical stability of ZnO nanorods synthesized on FTO by using ACG method. XRD and SEM techniques have shown highly dense and uniformly distributed nanorods. The piezoelectric properties and mechanical stability of as-grown and oxygen plasma treated samples were investigated by using nanoindentation technique. The comparison of load-displacement curves showed that the oxygen plasma treated samples are much stiffer and show higher generated piezo-voltage. This study demonstrates that the oxygen-plasma treatment is a good option to fabricate reliable and efficient nanodevices for enhanced generation of piezoelectricity.

  20. Enhancement of photocatalytic activity of Cu-doped ZnO nanorods for the degradation of an insecticide: Kinetics and reaction pathways.

    PubMed

    Shirzad-Siboni, Mehdi; Jonidi-Jafari, Ahmad; Farzadkia, Mahdi; Esrafili, Ali; Gholami, Mitra

    2017-01-15

    The photocatalytic degradation of organophosphorus pesticide such as diazinon was investigated by Cu-doped ZnO nanorods. Cu-doped ZnO nanorods were synthesized via a facile co-precipitation method. The catalyst was characterized by XRD, FESEM, EDX, VSM, XPS, and pHzpc techniques. The effects of some operational parameters such as solution pH, Cu-doped ZnO nanorods dosage, initial diazinon concentration, oxygen and nitrogen gases, H2O2 concentration, and type of organic compounds on the degradation efficiency were discussed through the photocatalytic experiments using the Cu-doped ZnO nanorods. Neutral pH was selected as an optimal pH condition due to a photo-corrosion of ZnO in acidic and basic conditions. As the Cu-doped ZnO nanorods dosage increased up to 0.2 g/L, degradation efficiency of diazinon was continuously enhanced. Pseudo-first-order rate constant (kobs) was decreased from 0.051 to 0.0052 min(-1) and electrical energy per order (EEo) was increased from 94.12 to 923.08 (kWh/m(3)) by increasing diazinon concentration from 10 to 50 mg/L, respectively. The efficiency of the UV/Cu-doped ZnO for diazinon removal was approximately 96.97%, which was more effective than the UV/ZnO process (58.52%). Photocatalytic activity was maintained even after five successive cycles.

  1. Effect of TiO2 thickness on nanocomposited aligned ZnO nanorod/TiO2 for dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Saurdi, I.; Shafura, A. K.; Azhar, N. E. A.; Ishak, A.; Malek, M. F.; Alrokayan, A. H. Salman; Khan, Haseeb A.; Mamat, M. H.; Rusop, M.

    2016-07-01

    The TiO2 films were deposited on glass substrate at different thicknesses with different deposition frequencies (1, 2, 3 and 4 times) using spin coating technique and their structural properties were investigated. Subsequently, the nanocomposited aligned ZnO nanorods and TiO2 were formed by deposited the TiO2 on top of aligned ZnO Nanorod on ITO-coated glass at different thicknesses using the same method of TiO2 deposited on glass substrate. The nanocomposited aligned ZnO nanorod/TiO2 were coated with different thicknesses of 900µm, 1815µm, 2710µm, 3620µm and ZnO without TiO2. The dye-sensitized solar cells were fabricated from the nanocomposited aligned ZnO nanorod/TiO2 with thickness of 900µm, 1815µm, 2710µm and 3620µm and ZnO without TiO2 and their photovoltaic properties of the DSSCs were investigated. From the solar simulator measurement the solar energy conversion efficiency (η) of 2.543% under AM 1.5 was obtained for the ZnO nanorod/TiO2 photoanode-2710µm Dye-Sensitized solar cell.

  2. Micro-twins TiO2 nanorods grown on seeded ZnO film

    NASA Astrophysics Data System (ADS)

    Zhao, Lei; Xia, Maosheng; Liu, Yuhua; Zheng, Biju; Jiang, Qing; Lian, Jianshe

    2012-04-01

    TiO2 anatase nanorods (NRs) epitaxially grew along the [001] direction at 600 °C on seeded c-axis oriented ZnO films which were deposited on a quartz glass substrate. The length of TiO2 NRs was about 450 nm. Micro-twins (MTs) were found in the TiO2 NRs with the (103) plane as the twin planes. The possible growth mechanisms of these TiO2 MTs have been studied using X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). The photo-degradation experiment showed that the TiO2 NRs have a high degradation efficiency of 32.9%. The effects of structural defects and MTs on the photocatalytic activity have been discussed.

  3. Surface characterization of ZnO nanorods grown by chemical bath deposition

    NASA Astrophysics Data System (ADS)

    Mbulanga, C. M.; Urgessa, Z. N.; Tankio Djiokap, S. R.; Botha, J. R.; Duvenhage, M. M.; Swart, H. C.

    2016-01-01

    The surface composition of as-grown and annealed ZnO nanorods (ZNs) grown by a two-step chemical bath deposition method is investigated by the following surface-sensitive techniques: Time-of-Flight Secondary Ion Mass Spectroscopy (TOF-SIMS), X-ray Photoelectron Spectroscopy (XPS) and Auger Electron Spectroscopy (AES). The presence of H on the surface and throughout the entire thickness of ZNs is confirmed by TOF-SIMS. Based on TOF-SIMS results, the O2 XPS peak mostly observable at 531.5 is assigned to O bound to H. Furthermore, it is found that the near surface region of as-grown ZNs is Zn-rich, and annealing at high temperature ( 850 °C) removes H-related defects from the surface of ZNs and affect the balance of zinc and oxygen concentrations.

  4. Synthesis, structural and optical properties of ZnO and Ni-doped ZnO hexagonal nanorods by Co-precipitation method.

    PubMed

    Raja, K; Ramesh, P S; Geetha, D

    2014-01-01

    Ni doped ZnO (Zn1-xNixO, x=0.0, 0.03, 0.06 and 0.09) nanorods have been synthesized by Co-precipitation method. Zinc acetate dehydrate [Zn(CH3COO)2⋅2H2O], nickel nitrate [Ni(NO3)3⋅6H2O], sodium hydroxide and poly (vinyl pyrrolidone) (PVP) were mixed together. The morphology, optical and microstructure were determined by X-ray diffraction (XRD), scanning electron microscopy (SEM), Energy dispersive spectrum (EDS), atomic force microscopy (AFM), UV-DRS spectrum, photoluminescence spectra (PL) and Fourier transformer infrared spectroscopy (FT-IR). The presence of functional groups and chemical bonding is confirmed by FTIR. PL spectra of the Zn1-xNixO systems shows that the shift in near band edge (NBE) UV emission from 321 to 322 nm and a shift in red band (RB) emission from 620 to 631 nm which conforms the substitution of Ni into the ZnO lattice. The investigation conformed that the products were of the wurtzite structure of ZnO. The hexagonal nanorods have edge length 31 nm and thickness of 39 nm. EDS result showed that the amount of Ni in the product is about 9%, these Ni doped hexagonal nanorods exhibits a blue shifts and weak (UV) emission peak, compared with pure ZnO, which may be induced by the Ni-doping different concentrations 0.0, 0.3, 0.6 and 0.9 M. The growth mechanism of the doped hexagonal nanorods was also discussed.

  5. Physical properties of fish gelatin-based bio-nanocomposite films incorporated with ZnO nanorods.

    PubMed

    Rouhi, Jalal; Mahmud, Shahrom; Naderi, Nima; Ooi, Ch Raymond; Mahmood, Mohamad Rusop

    2013-08-27

    Well-dispersed fish gelatin-based nanocomposites were prepared by adding ZnO nanorods (NRs) as fillers to aqueous gelatin. The effects of ZnO NR fillers on the mechanical, optical, and electrical properties of fish gelatin bio-nanocomposite films were investigated. Results showed an increase in Young's modulus and tensile strength of 42% and 25% for nanocomposites incorporated with 5% ZnO NRs, respectively, compared with unfilled gelatin-based films. UV transmission decreased to zero with the addition of a small amount of ZnO NRs in the biopolymer matrix. X-ray diffraction showed an increase in the intensity of the crystal facets of (10ī1) and (0002) with the addition of ZnO NRs in the biocomposite matrix. The surface topography of the fish gelatin films indicated an increase in surface roughness with increasing ZnO NR concentrations. The conductivity of the films also significantly increased with the addition of ZnO NRs. These results indicated that bio-nanocomposites based on ZnO NRs had great potentials for applications in packaging technology, food preservation, and UV-shielding systems.

  6. Physical properties of fish gelatin-based bio-nanocomposite films incorporated with ZnO nanorods

    PubMed Central

    2013-01-01

    Well-dispersed fish gelatin-based nanocomposites were prepared by adding ZnO nanorods (NRs) as fillers to aqueous gelatin. The effects of ZnO NR fillers on the mechanical, optical, and electrical properties of fish gelatin bio-nanocomposite films were investigated. Results showed an increase in Young's modulus and tensile strength of 42% and 25% for nanocomposites incorporated with 5% ZnO NRs, respectively, compared with unfilled gelatin-based films. UV transmission decreased to zero with the addition of a small amount of ZnO NRs in the biopolymer matrix. X-ray diffraction showed an increase in the intensity of the crystal facets of (10ī1) and (0002) with the addition of ZnO NRs in the biocomposite matrix. The surface topography of the fish gelatin films indicated an increase in surface roughness with increasing ZnO NR concentrations. The conductivity of the films also significantly increased with the addition of ZnO NRs. These results indicated that bio-nanocomposites based on ZnO NRs had great potentials for applications in packaging technology, food preservation, and UV-shielding systems. PMID:23981366

  7. Organic solvent wetting properties of UV and plasma treated ZnO nanorods: printed electronics approach

    NASA Astrophysics Data System (ADS)

    Sliz, Rafal; Suzuki, Yuji; Nathan, Arokia; Myllyla, Risto; Jabbour, Ghassan

    2012-09-01

    Due to low manufacturing costs, printed organic solar cells are on the short-list of renewable and environmentally- friendly energy production technologies of the future. However, electrode materials and each photoactive layer require different techniques and approaches. Printing technologies have attracted considerable attention for organic electronics due to their potentially high volume and low cost processing. A case in point is the interface between the substrate and solution (ink) drop, which is a particularly critical issue for printing quality. In addition, methods such as UV, oxygen and argon plasma treatments have proven suitable to increasing the hydrophilicity of treated surfaces. Among several methods of measuring the ink-substrate interface, the simplest and most reliable is the contact angle method. In terms of nanoscale device applications, zinc oxide (ZnO) has gained popularity, owing to its physical and chemical properties. In particular, there is a growing interest in exploiting the unique properties that the so-called nanorod structure exhibits for future 1-dimensional opto-electronic devices. Applications, such as photodiodes, thin-film transistors, sensors and photo anodes in photovoltaic cells have already been demonstrated. This paper presents the wettability properties of ZnO nanorods treated with UV illumination, oxygen and argon plasma for various periods of time. Since this work concentrates on solar cell applications, four of the most common solutions used in organic solar cell manufacture were tested: P3HT:PCBM DCB, P3HT:PCBM CHB, PEDOT:PSS and water. The achieved results prove that different treatments change the contact angle differently. Moreover, solvent behaviour varied uniquely with the applied treatment.

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

    NASA Astrophysics Data System (ADS)

    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.

  9. On the Synthesis and characterization of Rhodamine 6G doped ZnO Nanorod Arrays for Solar cell

    NASA Astrophysics Data System (ADS)

    Haque, Fozia Z.; Shastri, Lokesh; Pandey, Krishna S.; Husain, Mushahid

    2010-03-01

    Dye sensitized solar cell (DSSC) using ZnO nanoparticles provides a technically and economically credible alternative concept to present day p-n junction photovoltic device. The conventional systems where the semiconductors assume both the task of light absorption and charge carrier transport the two junctions are seprated here. In DSSC the light is absorbed by a sensitizer. In our investigation the DSSC consist of Zno nanoparticles that have a large surface area are used to harvest sunlight. Firstly the ZnO nanoparticals were grown on FTO substrate and then this nanoparticals were used as seed layers to grow aligned nanorods and used them as the wide band gap semiconductor electrod for solar cell. ZnO electrodes were sensitized by Rhodamine 6G dye. ZnO nanoparticles and nanorods were observed through SEM and their crystallinity were investigated using XRD. The higher efficiency in DSSC is possible due to the increased surface area from the nanoparticles facilitating the fast electron transport through the nanowires.

  10. Facile boosting light-scattering of ZnO nanorods in broadband spectrum region

    NASA Astrophysics Data System (ADS)

    Yu, Xuan; Yu, Xiaoming; Zhang, Jianjun; Zhang, Dekun; Chen, Liqiao; Long, Yunqian

    2017-04-01

    We first report that the light-scattering characteristic of ZnO nanorods (NRs) can be controlled by a ramping annealing rate of the seed layer. The NRs were characterized by atomic force microscope (AFM), scanning electron microscopy (SEM), X-ray diffraction and UV-Vis spectrophotometry. The results indicate that based on the seed layer with ramping rate, the average diameter and length of the NRs increased, which leads to about 1.74% mismatches and 7.57 GPa tensile stress between the NRs and substrate. The resulting NRs show a boosting light-scattering with an average Haze of 54.73% throughout 300-850 nm, obtaining an improvement of 43.93% than the NRs based on the regular heating seed layer throughout broadband spectrum region from 300 to 1000 nm. The work presents a facile solution way for strengthening the light-trapping of ZnO NRs and most importantly, it is especially suitable for the commercialized production of the thin films solar cells because the NRs can be fabricated using an inexpensive and scalable processes.

  11. Study of growth time and post annealing effect on the performance of ZnO nanorods ultraviolet photodetector

    NASA Astrophysics Data System (ADS)

    Shasti, M.; Dariani, R. S.

    2017-02-01

    In this paper, Zinc Oxide nanorods with different thicknesses are grown on a glass substrate by a hydrothermal method to fabricate an ultraviolet photodetector. The sample is post annealed in an argon environment as an annealing process can have a positive effect on the photodetector performance. The morphology, crystalline structure, and optical properties of ZnO nanorods (NRs) are investigated by SEM, XRD, UV-Visible spectrometer, and PL spectra. The goal of this study is to investigate the effect of both growth time and post annealing on enhancement of photoresponse of the ZnO NR photodetector. Measurements indicate that the sample with higher thickness exhibits a higher photocurrent and photoresponsivity. Also, with post annealing, an increase in photocurrent and photoresponsivity is observed due to decreasing defect levels.

  12. ZnO nanorod array polydimethylsiloxane composite solid phase micro-extraction fiber coating: fabrication and extraction capability.

    PubMed

    Wang, Dan; Wang, Qingtang; Zhang, Zhuomin; Chen, Guonan

    2012-01-21

    ZnO nanorod array coating is a novel kind of solid-phase microextraction (SPME) fiber coating which shows good extraction capability due to the nanostructure. To prepare the composite coating is a good way to improve the extraction capability. In this paper, the ZnO nanorod array polydimethylsiloxane (PDMS) composite SPME fiber coating has been prepared and its extraction capability for volatile organic compounds (VOCs) has been studied by headspace sampling the typical volatile mixed standard solution of benzene, toluene, ethylbenzene and xylene (BTEX). Improved detection limit and good linear ranges have been achieved for this composite SPME fiber coating. Also, it is found that the composite SPME fiber coating shows good extraction selectivity to the VOCs with alkane radicals.

  13. The effect of annealing temperatures to prepare ZnO seeds layer on ZnO nanorods array/TiO2 nanoparticles photoanode

    NASA Astrophysics Data System (ADS)

    Chou, Hsueh-Tao; Hsu, Ho-Chun

    2016-02-01

    In this study, we have fabricated a ZnO nanorods array/TiO2 nanoparticles thin-film as a photoanode, and also investigated the annealing effect at various temperatures (as grown, 250 °C, 350 °C, 450 °C and 550 °C) on ZnO seeds layer. The material properties of ZnO nanorods array were investigated by field emission scanning electron microscopy (FE-SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD) and ultraviolet visible spectroscopy. Besides, the performances of solar cells were evaluated using a source meter (Keithley 2400), which included open-circuit voltage (VOC), short-circuit current density (JSC), fill factor (F.F.) and power conversion efficiency (η%) at one sun (A.M. 1.5G, 100 mW/cm2). The electrochemical properties of the cells were analyzed by electrochemical impedance spectroscopy (EIS). From the EIS results, the cell performances were affected by annealing temperature, especially the fill-factor, at an annealing temperature of 550 °C due to the annealing treatment can enhance the connection between the interfaces of ZnO seeds/TCO, improving the electron lifetime, reducing the electron recombination loss. Finally, the sample annealing at 550 °C has the highest fill-factor of 44, power conversion efficiency of 0.19%, the highest Rct2 of 162.8 Ω and long electron lifetime of 7.25 ms.

  14. The role of seeding in the morphology and wettability of ZnO nanorods films on different substrates

    NASA Astrophysics Data System (ADS)

    Rodríguez, Juan; Onna, Diego; Sánchez, Luis; Marchi, M. Claudia; Candal, Roberto; Ponce, Silvia; Bilmes, Sara A.

    2013-08-01

    Spray pyrolysis (SP) and spray-gel (SG) techniques were used to deposit ZnO seeds on Fluor doped tin oxide glasses (FTO), heated at 350 °C or 130 °C, and PET heated at 90 °C. The effect of seeding on the morphology and wettability of ZnO nanorods (NRs) films grown by wet chemical methods was analyzed. The morphology and wettability of ZnO NRs films depend on the seeding process. SP seeds formed from zinc acetate dissolved in water ethanol mixtures yield vertically aligned ZnO NRs, whose diameters and dispersion size are determined by the ethanol/water ratio in the precursor solution. SG seeds formed from a methanol ZnO sol produce a ring patterned distribution on the FTO substrate. The drying of ZnO sol drops impinging on the substrate produces high density of seeds along a ring yielding textured films with NRs vertically oriented on the rings and multi-oriented outside them. This effect was not observed when ZnO NRs grown onto the ZnO/PET substrate, however rod diameter is related with the density of seeds. This way to control the density and diameter of NRs deposited onto a substrate modify the wettability and opens new possibilities for the design of tailored nanomaterials for photochemical applications. Both type of NRs films showed a strong luminescence emission in the UV and in the blue, associated with surface and intrinsic defects.

  15. Vertically aligned ZnO nanorod core-polypyrrole conducting polymer sheath and nanotube arrays for electrochemical supercapacitor energy storage

    PubMed Central

    2014-01-01

    Nanocomposite electrodes having three-dimensional (3-D) nanoscale architecture comprising of vertically aligned ZnO nanorod array core-polypyrrole (PPy) conducting polymer sheath and the vertical PPy nanotube arrays have been investigated for supercapacitor energy storage. The electrodes in the ZnO nanorod core-PPy sheath structure are formed by preferential nucleation and deposition of PPy layer over hydrothermally synthesized vertical ZnO nanorod array by controlled pulsed current electropolymerization of pyrrole monomer under surfactant action. The vertical PPy nanotube arrays of different tube diameter are created by selective etching of the ZnO nanorod core in ammonia solution for different periods. Cyclic voltammetry studies show high areal-specific capacitance approximately 240 mF.cm-2 for open pore and approximately 180 mF.cm-2 for narrow 30-to-36-nm diameter PPy nanotube arrays attributed to intensive faradic processes arising from enhanced access of electrolyte ions through nanotube interior and exterior. Impedance spectroscopy studies show that capacitive response extends over larger frequency domain in electrodes with PPy nanotube structure. Simulation of Nyquist plots by electrical equivalent circuit modeling establishes that 3-D nanostructure is better represented by constant phase element which accounts for the inhomogeneous electrochemical redox processes. Charge-discharge studies at different current densities establish that kinetics of the redox process in PPy nanotube electrode is due to the limitation on electron transport rather than the diffusive process of electrolyte ions. The PPy nanotube electrodes show deep discharge capability with high coulomb efficiency and long-term charge-discharge cyclic studies show nondegrading performance of the specific areal capacitance tested for 5,000 cycles. PMID:25246867

  16. Tuning of deep level emission in highly oriented electrodeposited ZnO nanorods by post growth annealing treatments

    SciTech Connect

    Simimol, A.; Manikandanath, N. T.; Chowdhury, Prasanta; Barshilia, Harish C.; Anappara, Aji A.

    2014-08-21

    Highly dense and c-axis oriented zinc oxide (ZnO) nanorods with hexagonal wurtzite facets were deposited on fluorine doped tin oxide coated glass substrates by a simple and cost-effective electrodeposition method at low bath temperature (80 °C). The as-grown samples were then annealed at various temperatures (T{sub A} = 100–500 °C) in different environments (e.g., zinc, oxygen, air, and vacuum) to understand their photoluminescence (PL) behavior in the ultra-violet (UV) and the visible regions. The PL results revealed that the as-deposited ZnO nanorods consisted of oxygen vacancy (V{sub O}), zinc interstitial (Zn{sub i}), and oxygen interstitial (O{sub i}) defects and these can be reduced significantly by annealing in different environments at optimal annealing temperatures. However, the intensity of deep level emission increased for T{sub A} greater than the optimized values for the respective environments due to the introduction of various defect centers. For example, for T{sub A} ≥ 450 °C in the oxygen and air environments, the density of O{sub i} defects increased, whereas, the green emission associated with V{sub O} is dominant in the vacuum annealed (T{sub A} = 500 °C) ZnO nanorods. The UV peak red shifted after the post-growth annealing treatments in all the environments and the vacuum annealed sample exhibited highest UV peak intensity. The observations from the PL data are supported by the micro-Raman spectroscopy. The present study gives new insight into the origin of different defects that exist in the electrodeposited ZnO nanorods and how these defects can be precisely controlled in order to get the desired emissions for the opto-electronic applications.

  17. Studies on ZnO nanorods/CuInS2 coaxial n-p heterojunction arrays

    NASA Astrophysics Data System (ADS)

    Panigrahi, Shrabani; Basak, Durga

    2013-02-01

    We have fabricated an n-p nanorods (NRs) heterojunction consisting of n-type ZnO NR and p-type CuInS2 by a simple, low cost solution method through an ion-exchange route. The heterojunction shows a rectifying behavior with an ideality factor of 1.66. Furthermore, the heterojunction is promising candidates for applications in electro-optic devices.

  18. Preparation and Photovoltaic Properties of Dye Sensitized Solar Cells Using ZnO Nanorods Stacking Films on AZO Substrate as Photoanode.

    PubMed

    Xu, Yang; Wang, Xina; Liu, Rong; Wang, Hao

    2016-04-01

    Three-dimensional stacking of ZnO nanorods on conducting aluminum-doped ZnO (AZO) glass were studied as efficient photoanodes of dye sensitized solar cells (DSSCs). By changing hydrothermal growth time and cycle times, the thickness of ZnO nanorods stacking films varied from 30 µm to 64 µm, and its influence on the energetic conversion efficiency of the DSSCs based on the stacking films photoanodes was investigated. The loading density of N719 on the surface of ZnO nanorods was studied to increase the efficiency of the cells. Annealing experiments showed that the AZO substrates remained good conductors until heated above 350 °C. A photoelectric conversion efficiency as high as ~2.0% together with ISC of ~9.5 mA/cm2, VOC of ~0.5 V and FF of ~41.4% was achieved for the DSSC using 50 µm-thick film stacking by ZnO nanorods as photoanode and N719 as sensitizer under illumination of AM1.5G solar light (power density of 100 mW/cm2). A charge separation and transfer mechanism was proposed for the ZnO nanorods stacking electrode-based DSSCs.

  19. Efficiency enhancement of silicon solar cells with vertically aligned ZnO nanorod arrays as an antireflective layer

    NASA Astrophysics Data System (ADS)

    Sardana, Sanjay K.; Chandrasekhar, P. S.; Kumar, Rupesh; Komarala, Vamsi K.

    2017-04-01

    Vertically aligned ZnO nanorods grown by the hydrothermal method have been explored as an antireflection layer on polished, textured, and antireflection coating (ARC) coated textured silicon (Si) wafers. Average reflectance (from 380 to 1100 nm) of polished and textured Si wafers reduced from 32 to 9% and 14 to 2%, respectively. With nanorods, multiple light interactions and good optical impedance matching with graded refractive index (effective medium) from air to Si favored for light confinement in Si. Optimized nanorods on ARC coated textured Si cell led to an enhancement of photocurrent from 34.30 to 36.38 mA/cm2 and efficiency from 15.11 to 16.43%.

  20. Novel ZnO microflowers on nanorod arrays: local dissolution-driven growth and enhanced light harvesting in dye-sensitized solar cells

    PubMed Central

    2014-01-01

    ZnO nanostructures were manipulated, via a low-temperature solution process, from pure nanorod arrays to complex nanostructures of microflowers on nanorod arrays with adjusted quantities of flowers. We proposed the mechanism of local dissolution-driven growth to rationally discuss the novel growth process. These nanostructures were used as photoanodes in dye-sensitized solar cells. Compared to pure nanorod arrays, the nanorod array-microflower hierarchical structures improved the power conversion efficiency from 0.41% to 0.92%, corresponding to a 124% efficiency increase. The enhancement of the efficiency was mainly ascribed to the synergistic effect of the enhanced surface area for higher dye loading and the improved light harvesting from efficient light scattering. Present results provide a promising route to improve the capability of light-harvesting for ZnO nanorod array-based DSSCs. PMID:24731603

  1. Type-II ZnO nanorod-SnO2 nanoparticle heterostructures: characterization of structural, optical and photocatalytic properties.

    PubMed

    Huang, Xing; Shang, Lu; Chen, Shu; Xia, Jing; Qi, Xiaopeng; Wang, Xuecong; Zhang, Tierui; Meng, Xiang-Min

    2013-05-07

    In this work we report, for the first time, on the preparation of ZnO nanorod-SnO2 nanoparticle (ZnO NR-SnO2 NP) heterostructures by a simple two-step thermal evaporation approach. Systematical characterization of the product reveals that the rutile SnO2 NPs, with a diameter of about 20 nm, are uniformly and tightly decorated on the entire ZnO NRs. Photoluminescence (PL) investigation on the ZnO NR-SnO2 NP heterostructures shows that they exhibit a significantly decreased UV emission compared with the bare ZnO NRs, revealing an efficient charge separation arising from the type-II band alignment. Enlightened by this merit, photocatalytic behavior of the synthesized heterostructures is studied, which shows a remarkably enhanced photodegradation performance of rhodamine B (RhB) in contrast to the pure ZnO NRs. We also carry out the stability test of the ZnO NR-SnO2 NP heterostructures and the result indicates an extremely high adhesion nature between the ZnO NR and the coated SnO2 NPs. This advantage endowed with the thermal evaporation approach can lead to an efficient spatial charge separation between the ZnO NR and the SnO2 NPs and thus effectively minimize the charge recombination along three-dimensional heterointerfaces, which makes such ZnO NR-SnO2 NP architectures highly promising for a wide range of photovoltaic and photocatalytic applications.

  2. H2- and NH3-treated ZnO nanorods sensitized with CdS for photoanode enhanced in photoelectrochemical performance

    NASA Astrophysics Data System (ADS)

    Vuong, Nguyen Minh; Hien, Truong Thi; Quang, Nguyen Duc; Chinh, Nguyen Duc; Lee, Dong Suk; Kim, Dahye; Kim, Dojin

    2016-06-01

    A ZnO/CdS core-shell nanorod structure is studied for use as photoanode in photoelectrochemical cell for water splitting. The focus is to examine the effect of hydrogen and/or nitrogen doping of ZnO nanorods on its performance as photoanode. ZnO nanorods hydrothermally synthesized on ITO glass substrate are heat-treated in pure hydrogen ambient and then in atmospheric pressure of ammonia for H- and N-doping of ZnO. The H- and/or N-doped ZnO nanorod structure (N/H:ZnO) reveal an enhanced photocurrent and photo-to-current conversion efficiency in comparison to untreated ZnO nanorods by shifting the absorption edge towards visible region and increasing absorption of infrared region wavelengths. CdS sensitization of the nanorods is also studied. The morphology and properties of the samples are examined by SEM, XRD, UV-vis absorption and photoluminescence. Optimization of the ZnO nanorod growth and CdS coating processes are also undertaken. An optimized N/H:ZnO nanorods sensitized by CdS layer yields a photocurrent density of ∼12.61 mA cm-2 at 0 V (vs. SCE) and photon-to-current conversion efficiency of ∼4.5% (at -0.73 V vs. SCE) in 0.5 M Na2S solution under a simulated solar light. The H2 gas generation with the optimal structure is about 6 mL h-1 cm-2.

  3. Sub-coherent growth of ZnO nanorod arrays on three-dimensional graphene framework as one-bulk high-performance photocatalyst

    NASA Astrophysics Data System (ADS)

    Yu, Mei; Ma, Yuxiao; Liu, Jianhua; Li, Xinjie; Li, Songmei; Liu, Shenyao

    2016-12-01

    Highly ordered ZnO nanorod arrays were grown vertically on the surface of three-dimensional graphene (3DG) framework bulk to prepare a one-bulk structure. In such structure, ZnO exhibits outstanding photocatalyst performance due to its hybridization with 3DG. The sub-coherency between ZnO and 3DG ensures the template-free growth of ZnO nanorod arrays and the exposing of its most active crystal surfaces {0001}. The hybridization prevents the agglomeration of ZnO nanoparticles, helping the formation of nanorod array morphology, enhancing the mass transfer of reactants and the separation of photogenerated holes. In the efficiency test, with tiny amount of ZnO catalyst (∼5.03 × 10-3 g), the concentration of methyl orange decreased to ∼11% of the initial value within four hours. The structure possesses high average photocatalytic efficiency of 6.56 × 10-3 h-1, much higher than that of bare ZnO nanorods.

  4. Hydrothermal growth and conductivity enhancement of (Al, Cu) co-doped ZnO nanorods thin films

    NASA Astrophysics Data System (ADS)

    Chakraborty, Mohua; Mahapatra, Preetilata; Thangavel, R.

    2016-05-01

    The incorporation of Al, Cu co-doping in ZnO host lattice plays an important role in modification of structural, optical and electrical properties in optoelectronic devices. In the present work, we were grown one dimensional ZnO nanorods (NRs) doped with different concentration of Al (0%~5%) and Cu was kept 20 M% on ITO glass substrates using a facile hydrothermal method, and investigated the effect of the codoping on the surface morphology and the electrical and optical performances of the doped ZnO NRs as photo anodes for solar water splitting applications. The crystallite size of NRs shows tuning in the band gap between 3.194 (Zn0.79Al0.01Cu0.2O) to 3.212 eV (Zn0.75Al0.05Cu0.2O) with Aluminium doping concentration and a remarkable improvement in current density (J) from 0.05 mA/cm2 to 4.98 mA/cm2 was achieved by incorporating Al and Cu has a critical effect of ZnO nanorods.

  5. Enhanced photoelectrochemical property of ZnO nanorods array synthesized on reduced graphene oxide for self-powered biosensing application.

    PubMed

    Kang, Zhuo; Gu, Yousong; Yan, Xiaoqin; Bai, Zhiming; Liu, Yichong; Liu, Shuo; Zhang, Xiaohui; Zhang, Zheng; Zhang, Xueji; Zhang, Yue

    2015-02-15

    We have realized the direct synthesis of ZnO nanorods (ZnO NRs) array on reduced graphene layer (rGO), and demonstrated the enhanced photoelectrochemical (PEC) property of the rGO/ZnO based photoanode under UV irradiation compared with the pristine ZnO NRs array. The introduction of the rGO layer resulted in a favorable energy band structure for electron migration, which finally led to the efficient photoinduced charge separation. Such nanostructure was subsequently employed for self-powered PEC biosensing of glutathione in the condition of 0 V bias, with a linear range from 10 to 200 µM, a detection limit of 2.17 µM, as well as excellent selectivity, reproducibility and stability. The results indicated the rGO/ZnO nanostructure is a competitive candidate in the PEC biosensing field.

  6. Effect of gamma irradiation on Schottky-contacted vertically aligned ZnO nanorod-based hydrogen sensor

    NASA Astrophysics Data System (ADS)

    Ranwa, Sapana; Singh Barala, Surendra; Fanetti, Mattia; Kumar, Mahesh

    2016-08-01

    We report the impact of gamma irradiation on the performance of a gold Schottky-contacted ZnO nanorod-based hydrogen sensor. RF-sputtered vertically aligned highly c-axis-oriented ZnO NRs were grown on Si(100) substrate. X-ray diffraction shows no significant change in crystal structure at low gamma doses from 1 to 5 kGy. As gamma irradiation doses increase to 10 kGy, the single crystalline ZnO structure converts to polycrystalline. The photoluminescence spectra also shows suppression of the near-band emission peak and the huge wide-band spectrum indicates the generation of structural defects at high gamma doses. At 1 kGy, the hydrogen sensor response was enhanced from 67% to 77% for 1% hydrogen in pure argon at a 150 °C operating temperature. However, at 10 kGy, the relative response decreases to 33.5%. High gamma irradiation causes displacement damage and defects in ZnO NRs, and as a result, degrades the sensor’s performance as a result. Low gamma irradiation doses activate the ZnO NR surface through ionization, which enhances the sensor performance. The relative response of the hydrogen sensor was enhanced by ∼14.9% with respect to pristine ZnO using 1 kGy gamma ray treatment.

  7. Flexible piezoelectric nanogenerators based on a transferred ZnO nanorod/Si micro-pillar array.

    PubMed

    Baek, Seong-Ho; Park, Il-Kyu

    2017-03-03

    Flexible piezoelectric nanogenerators (PNGs) based on a composite of ZnO nanorods (NRs) and an array of Si micro-pillars (MPs) are demonstrated by a transfer process. The flexible composite structure was fabricated by hydrothermal growth of ZnO NRs on an electrochemically etched Si MP array with various lengths followed by mechanically delaminating the Si MP arrays from the Si substrate after embedding them in a polydimethylsiloxane matrix. Because the Si MP arrays act as a supporter to connect the ZnO NRs electrically and mechanically, verified by capacitance measurement, the output voltage from the flexible PNGs increased systematically with the increased density ZnO NRs depending on the length of the Si MPs. The flexible PNGs showed 3.2 times higher output voltage with a small change in current with increasing Si MP length from 5 to 20 μm. The enhancement of the output voltage is due to the increased number of series-connected ZnO NRs and the beneficial effect of a ZnO NR/Si MP heterojunction on reducing free charge screening effects. The flexible PNGs can be attached on fingers as a wearable electrical power source or motion sensor.

  8. Flexible piezoelectric nanogenerators based on a transferred ZnO nanorod/Si micro-pillar array

    NASA Astrophysics Data System (ADS)

    Baek, Seong-Ho; Park, Il-Kyu

    2017-03-01

    Flexible piezoelectric nanogenerators (PNGs) based on a composite of ZnO nanorods (NRs) and an array of Si micro-pillars (MPs) are demonstrated by a transfer process. The flexible composite structure was fabricated by hydrothermal growth of ZnO NRs on an electrochemically etched Si MP array with various lengths followed by mechanically delaminating the Si MP arrays from the Si substrate after embedding them in a polydimethylsiloxane matrix. Because the Si MP arrays act as a supporter to connect the ZnO NRs electrically and mechanically, verified by capacitance measurement, the output voltage from the flexible PNGs increased systematically with the increased density ZnO NRs depending on the length of the Si MPs. The flexible PNGs showed 3.2 times higher output voltage with a small change in current with increasing Si MP length from 5 to 20 μm. The enhancement of the output voltage is due to the increased number of series-connected ZnO NRs and the beneficial effect of a ZnO NR/Si MP heterojunction on reducing free charge screening effects. The flexible PNGs can be attached on fingers as a wearable electrical power source or motion sensor.

  9. Performance of inverted polymer solar cells with randomly oriented ZnO nanorods coupled with atomic layer deposited ZnO

    NASA Astrophysics Data System (ADS)

    Zafar, Muhammad; Yun, Ju-Young; Kim, Do-Heyoung

    2017-03-01

    Nanostructuring of the electron transport layer (ETL) in organic photovoltaic cells (OPV) is of great interest because it increases the surface area of the cell and electron transport. In this work, hydrothermally grown, randomly oriented, and low areal density ZnO nanorods (NRs) have been adopted as the ETL, and the effect of adding atomic layer deposited (ALD) ZnO on the ZnO NRs on the inverted organic solar cell performance has been investigated. The fabricated inverted organic solar cell with 5-nm-thick ALD-ZnO grown on the ZnO NRs showed the highest power conversion efficiency (PCE) of 3.08%, which is an enhancement of 85% from that of the cell without ALD-ZnO (PCE = 1.67%). The ultrathin ALD-ZnO was found to act as a curing layer of the surface defects on the hydrothermally grown ZnO NRs, resulting in an improvement in photovoltaic performance.

  10. ZnO nanorod arrays prepared by chemical bath deposition combined with rapid thermal annealing: structural, photoluminescence and field emission characteristics

    NASA Astrophysics Data System (ADS)

    Chen, Hung-Wei; Yang, Hsi-Wen; He, Hsin-Min; Lee, Yi-Mu

    2016-01-01

    ZnO nanorod arrays were prepared by low temperature chemical bath deposition (CBD) combined with rapid thermal annealing (RTA) under different ambient conditions. The structure and morphology of the synthesized ZnO have been characterized by field-emission scanning electron microscopy (FESEM) and x-ray diffraction (XRD). The obtained ZnO samples are highly crystalline with a hexagonal wurtzite phase and also display well-aligned array structure. A pronounced effect on increased nanorod length was found for the RTA-treated ZnO as compared to the as-grown ZnO. Analysis of XRD indicates that the (0 0 2) feature peak of the as-grown ZnO was shifted towards a lower angle as compared to the peaks of RTA-treated ZnO samples due to the reduction of tensile strain along the c-axis by RTA. Photoluminescence (PL) studies reveal that the ZnO nanorod arrays receiving RTA in an O2 environment have the sharpest UV emission band and greatest intensity ratio of near band-edge emission (NBE) to deep level emission (DLE). Additionally, the effects of RTA on the field emission properties were evaluated. The results demonstrate that RTA an O2 environment can lower the turn-on field and improve the field enhancement factor. The stability of the field emission current was also tested for 4 h.

  11. Hierarchical ZnO Nanosheet-Nanorod Architectures for Fabrication of Poly(3-hexylthiophene)/ZnO Hybrid NO2 Sensor.

    PubMed

    Wang, Jing; Li, Xian; Xia, Yi; Komarneni, Sridhar; Chen, Haoyuan; Xu, Jianlong; Xiang, Lan; Xie, Dan

    2016-04-06

    A facile one-step solution method has been developed here to fabricate hierarchical ZnO nanosheet-nanorod architectures for compositing with poly(3-hexylthiophene) (P3HT) for fabricating a hybrid NO2 sensor. The hierarchical ZnO nanosheet-nanorod architectures were controllably synthesized by aging the solutions containing 0.05 mol·L(-1) Zn(2+) and 0.33 mol·L(-1) OH(-) at 60 °C through a metastable phase-directed mechanism. The concentration of OH(-) played a huge role on the morphology evolution. When the [OH(-)] concentration was decreased from 0.5 to 0.3 mol·L(-1), the morphology of the ZnO nanostructures changed gradually from monodispersed nanorods (NR) to nanorod assemblies (NRA), and then to nanosheet-nanorod architectures (NS-NR) and nanosheet assemblies (NSA), depending on the formation of various metastable, intermediate phases. The formation of NS-NR included the initial formation of ZnO nanosheets/γ-Zn(OH)2 mixed intermediates, followed by the dissolution of Zn(OH)2, which served as soluble zinc source. Soluble Zn(OH)2 facilitated the dislocation-driven secondary growth of ZnO nanorod arrays on the primary defect-rich nanosheet substrates. Hybrid sensors based on composite films composed of P3HT and the as-prepared ZnO nanostructures were fabricated for the detection of NO2 at room temperature. The P3HT/ZnO NS-NR bilayer film exhibited not only the highest sensitivity but also good reproducibility and selectivity to NO2 at room temperature. The enhanced sensing performance was attributed to the formation of the P3HT/ZnO heterojunction in addition to the enhanced adsorption of NO2 by NS-NR ZnO rich in oxygen-vacancy defects.

  12. Al-doping effects on the photovoltaic performance of inverted polymer solar cells

    NASA Astrophysics Data System (ADS)

    Yu, Xuan; Shi, Ya-feng; Yu, Xiao-ming; Zhang, Jian-jun; Ge, Ya-ming; Chen, Li-qiao; Pan, Hong-jun

    2016-03-01

    The properties of Al-doped ZnO (AZO) play an important role in the photovoltaic performance of inverted polymer solar cells (PSCs), which is used as electron transport and hole blocking buffer layers. In this work, we study the effects of Al-doping level in AZO on device performance in detail. Results indicate that the device performance intensely depends on the Al-doping level. The AZO thin films with Al-doping atomic percentage of 1.0% possess the best conductivity. The resulting solar cells show the enhanced short current density and the fill factor ( FF) simultaneously, and the power conversion efficiency ( PCE) is improved by 74%, which are attributed to the reduced carrier recombination and the optimized charge transport and extraction between AZO and the active layer.

  13. A novel fabrication methodology for sulfur-doped ZnO nanorods as an active photoanode for improved water oxidation in visible-light regime.

    PubMed

    Khan, A; Ahmed, M I; Adam, A; Azad, A-M; Qamar, M

    2017-02-03

    Incorporation of foreign moiety in the lattice of semiconductors significantly alters their optoelectronic behavior and opens a plethora of new applications. In this paper, we report the synthesis of sulfur-doped zinc oxide (S-doped ZnO) nanorods by reacting ZnO nanorods with diammonium sulfide in vapor phase. Microscopic investigation revealed that the morphological features, such as, the length (2-4 μm) and width (100-250 nm) of the original hexagonal ZnO nanorods remained intact post-sulfidation. X-ray photoelectron spectroscopy analysis of the sulfide sample confirmed the incorporation of sulfur into ZnO lattice. The optical measurements suggested the extension of absorption threshold into visible region upon sulfidation. Photoelectrochemical (PEC) activities of pure and S-doped ZnO nanorods were compared for water oxidation in visible light (λ > 420 nm), which showed several-fold increment in the performance of S-doped ZnO sample; the observed amelioration in the PEC activity was rationalized in terms of preferred visible light absorption and low resistance of sulfide sample, as evidenced by optical and electrochemical impedance spectroscopy.

  14. A novel fabrication methodology for sulfur-doped ZnO nanorods as an active photoanode for improved water oxidation in visible-light regime

    NASA Astrophysics Data System (ADS)

    Khan, A.; Ahmed, M. I.; Adam, A.; Azad, A.-M.; Qamar, M.

    2017-02-01

    Incorporation of foreign moiety in the lattice of semiconductors significantly alters their optoelectronic behavior and opens a plethora of new applications. In this paper, we report the synthesis of sulfur-doped zinc oxide (S-doped ZnO) nanorods by reacting ZnO nanorods with diammonium sulfide in vapor phase. Microscopic investigation revealed that the morphological features, such as, the length (2-4 μm) and width (100-250 nm) of the original hexagonal ZnO nanorods remained intact post-sulfidation. X-ray photoelectron spectroscopy analysis of the sulfide sample confirmed the incorporation of sulfur into ZnO lattice. The optical measurements suggested the extension of absorption threshold into visible region upon sulfidation. Photoelectrochemical (PEC) activities of pure and S-doped ZnO nanorods were compared for water oxidation in visible light (λ > 420 nm), which showed several-fold increment in the performance of S-doped ZnO sample; the observed amelioration in the PEC activity was rationalized in terms of preferred visible light absorption and low resistance of sulfide sample, as evidenced by optical and electrochemical impedance spectroscopy.

  15. Structure of ZnO Nanorods using X-ray Diffraction

    SciTech Connect

    Howdyshell, Marci; /Albion Coll. /SLAC

    2007-11-07

    Many properties of zinc oxide, including wide bandgap semiconductivity, photoconductivity, and chemical sensing, make it a very promising material for areas such as optoelectronics and sensors. This research involves analysis of the formation, or nucleation, of zinc oxide by electrochemical deposition in order to gain a better understanding of the effect of different controlled parameters on the subsequently formed nanostructures. Electrochemical deposition involves the application of a potential to an electrolytic solution containing the species of interest, which causes the ions within to precipitate on one of the electrodes. While there are other ways of forming zinc oxide, this particular process is done at relatively low temperatures, and with the high amount of x-ray flux available at SSRL it is possible to observe such nucleation in situ. Additionally, several parameters can be controlled using the x-ray synchrotron; the concentration of Zn{sup 2+} and the potential applied were controlled during this project. The research involved both gathering the X-ray diffraction data on SSRL beamline 11-3, and analyzing it using fit2d, Origin 6.0 and Microsoft Excel. A time series showed that both the in-plane and out-of-plane components of the ZnO nanorods grew steadily at approximately the same rate throughout deposition. Additionally, analysis of post-scans showed that as potential goes from less negative to more negative, the resulting nanostructures become more oriented.

  16. Chemically grown vertically aligned 1D ZnO nanorods with CdS coating for efficient quantum dot sensitized solar cells (QDSSC): a controlled synthesis route.

    PubMed

    Mali, Sawanta S; Kim, Hyungjin; Patil, Pramod S; Hong, Chang Kook

    2013-12-28

    In the present article, vertically aligned ZnO nanorod arrays were synthesized by an aqueous chemical growth (ACG) route on a fluoride doped tin oxide (FTO) coated glass substrate. These nanorods were further sensitized with cadmium sulfide (CdS) quantum dots (QDs) by a successive ionic layer adsorption and reaction (SILAR) technique. The synthesized CdS coated ZnO nanorods were characterized for their structural and morphological properties with X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and field emission scanning electron microscopy (FESEM). Finally, prepared CdS coated 1D ZnO photoelectrodes were tested for their photoelectrochemical performance. Our results show that the sample deposited after 40 SILAR cycles shows 5.61 mA cm(-2) short current density (JSC) with η = 1.61% power conversion efficiency.

  17. A comparative study of pure and copper (Cu)-doped ZnO nanorods for antibacterial and photocatalytic applications with their mechanism of action

    NASA Astrophysics Data System (ADS)

    Bhuyan, Tamanna; Khanuja, Manika; Sharma, R.; Patel, S.; Reddy, M. R.; Anand, S.; Varma, A.

    2015-07-01

    The present study reports the synthesis of pure and Cu-doped ZnO nanorods for antibacterial and photocatalytic applications. The samples were synthesized by simple, low cost mechanical-assisted thermal decomposition process. The synthesized materials were characterized by scanning electron microscopy, UV-Visible spectroscopy, and photoluminescence studies. The antibacterial activity of characterized samples was determined against Gram-positive bacteria such as Staphylococcus aureus and Streptococcus pyogenes and Gram-negative bacteria such as Escherichia coli using shake flask method with respect to time. The significant antibacterial activity was perceived from scanning electron micrographs that clearly revealed bacterial cell lysis resulting in the release of cytoplasmic content followed by cell death. The degradation of methylene blue was used as a model organic dye for photocatalytic activity. The present study demonstrates the superior photocatalytic and antibacterial activity of Cu-doped ZnO nanorods with respect to pure ZnO nanorods.

  18. Sequential microwave-assisted ultra-fast ZnO nanorod growth on optimized sol-gel seedlayers

    NASA Astrophysics Data System (ADS)

    Soleimanzadeh, Reza; Mousavi, Matin Sadat Saneei; Mehrfar, Amin; Esfahani, Zahra Kolahdouz; Kolahdouz, Mohammadreza; Zhang, Kouchi

    2015-09-01

    Recently, the studies on ZnO nanostructure characteristics and their fabrication methods have been increased significantly in order to be able to use its magnificent properties by reaching the desired optimum features. Very high growth rate and high quality growth have always been the center of attention. In this study, a sequential microwave-assisted ZnO nanorod (NR) growth as an ultra-fast, highly efficient method for vertical growth of high quality ZnO NRs on different substrates is proposed. A NRs' growth rate of 4.2 μm/h was obtained which led to uniformly distributed, high aspect ratio and vertically-aligned NRs. Furthermore, the influences of spinner's speed as an important parameter on the quality of ZnO seed and annealing treatment have been studied. The sol-gel casting approach is optimized for the layer. Different seed layers were used to grow the nanostructures and the optimum spinner speed is found to be 2000 rpm. In order to diminish the dependency of the uniformity of ZnO NRs on the quality of seed layers, a remedy is suggested.

  19. Effect of self-organization, defects, impurities, and autocatalytic processes on the parameters of ZnO films and nanorods

    SciTech Connect

    Mezdrogina, M. M. Eremenko, M. V.; Levitskii, V. S.; Petrov, V. N.; Terukov, E. I.; Kaidashev, E. M.; Langusov, N. V.

    2015-11-15

    The effects of the parameters of ZnO-film deposition onto different substrates using the method of ac magnetron sputtering in a gas mixture of argon and oxygen hare studied. The phenomenon of self-organization is observed, which leads to invariability of the surface morphology of the ZnO films upon a variation in the substrate materials and deposition parameters. The parameters of the macro- and micro-photoluminescence spectra of the films differ insignificantly from the parameters of the photoluminescence spectra of bulk ZnO crystals obtained by the method of hydrothermal growth. The presence of intense emission with a narrow full-width at half-maximum (FWHM) in different regions of the spectrum allows ZnO films obtained by magnetron sputtering doped with rare-earth metal impurities (REIs) to be considered as a promising material for the creation of optoelectronic devices working in a broad spectral range. The possibility of the implementation of magnetic ordering upon legierung with REIs significantly broadens the functional possibilities of ZnO films. The parameters of the photoluminescence spectra of ZnO nanorods are determined by their geometrical parameters and by the concentration and type of the impurities introduced.

  20. Evolution of CuO poly-crystalline layers to coherent single-crystalline dots on ZnO nanorods upon annealing

    NASA Astrophysics Data System (ADS)

    Wang, Ruey-Chi; Hou, Yuan-Ru; Chen, Yi-Wen

    2017-02-01

    ZnO/CuO p-n heterojunctions have attracted much attention for device applications, but coherent junctions, which are crucial for controlling electrical properties, still remain a challenge due to different crystal structure. In this work, CuO single-crystalline dots are coherently synthesized on ZnO nanorods by using a proposed two-step process. Transmission electron microscopy images confirm the formation of CuO coherent dots on single-crystalline ZnO nanorods upon annealing the nanorods covered with a poly-crystalline CuxO layer. The coherent dots exhibit two types of epitaxial orientations: CuO [002] ǀǀ ZnO [ 10 1 bar 1 ], CuO [111] ǀǀ ZnO [0002], and CuO [002] ǀǀ ZnO [ 10 1 bar 1 bar ], CuO [111] ǀǀ ZnO [ 000 2 bar ]. As the thickness of the as-deposited CuxO layer increases from 10 to 30 nm, the aspect ratio of the resulting CuO dots decreases from 0.43 to 0.21, approaching a film-like morphology. This work provides a route to prepare CuO coherent single-crystalline structures on ZnO, which is one step further toward fabricating excellent CuO/ZnO nanodevices.

  1. Electrical and optical study of ultrasonic-assisted hydrothermal synthesized Ga doped ZnO nanorods for polymer solar cell application

    NASA Astrophysics Data System (ADS)

    Ahmadi, M.; Rashidi Dafeh, S.

    2016-08-01

    Ga doped ZnO nanorods with homogeneous morphology grown by ultrasonic-assisted hydrothermal method on ITO substrate. The effect of hydrothermal growth times 30, 60, 90 and 120 min on the characteristics of ZnO nanorods was examined. The samples were analyzed by X-ray diffraction, scanning electron microscopy, UV-Vis spectrometer and conductivity measurement. With the optimization of the growth times (60 min), we employed Ga doped ZnO nanorods with diverse dopant concentration in fabrication of polymer solar cell. By comparing the effect of Ga doped ZnO thin films with various dopant ratio (0, 0.5, 1.0 and 2 %) on the performance of Ga doped ZnO thin films, 0.5 % Ga doped ZnO was found as the most effective doping level among the selected doping concentrations. Also using 0.5 % Ga doped ZnO thin film, Jsc of 7.54 mA/cm2, Voc of 0.541 V, and fill factor of 64.81 % were achieved, which led to power conversion efficiency of 2.64 %.

  2. Ultra-Low Level Detection of L-Histidine Using Solution-Processed ZnO Nanorod on Flexible Substrate.

    PubMed

    Sasmal, Milan; Maiti, Tapas Kumar; Bhattacharyya, Tarun Kanti

    2015-09-01

    This work demonstrates a novel label free and sensitive approach for the detection of L-histidine. This is a simple and reliable method for ultra-low level detection of L-histidine. All solution processed synthesizing technique was utilized to develop such type of detection scheme. Silicon substrate was replaced by normal transparent sheet to make it more facile and cost-effective detection technique. Fabricated device for L-histidine detection works upon the variation of current through the ZnO nanorod with L-histidine concentration. Operation principle strongly depends upon the electron charge transfer between metal cation and L-histidine inside the chelating complex. Morphological, structural and optical characterization of solution processed synthesized ZnO nanorod (ZnO NR) was carried out prior to sensor device fabrication. Our sensor device exhibits the sensitivity around 0.86 nA/fM and lower limit of detection (LOD) ∼ 0.1 fM(S/N=3).

  3. Enhanced photoelectrochemical water-splitting effect with a bent ZnO nanorod photoanode decorated with Ag nanoparticles

    NASA Astrophysics Data System (ADS)

    Wei, Yuefan; Ke, Lin; Kong, Junhua; Liu, Hong; Jiao, Zhihui; Lu, Xuehong; Du, Hejun; Sun, Xiao Wei

    2012-06-01

    Zinc oxide (ZnO) nanorods coated with silver (Ag) film on a polyethylene terephthalate (PET) flexible substrate were used as the photoanode for water splitting. The hybrid nanostructures were prepared via low-temperature hydrothermal growth and electron beam evaporation. The effects of plasmonic enhanced absorption, surface recombination inhibition and improved charge transport are investigated by varying the Ag thickness. Light trapping and absorption enhancement are further studied by optimizing the curvature of the PET substrates. The maximum short circuit current density (JSC, 0.616 mA cm-2) and the photoelectron conversion efficiency (PCE, 0.81%) are achieved with an optimized Ag film thickness of 10 nm and substrate bending radius of 6.0 mm. The maximum JSC and PCE are seven times and ten times, respectively, higher than those of the bare ZnO nanorods on flexible substrates without bending. The overall PEC performance improvement is attributed to the plasmonic effects induced by Ag film and improved charge transport due to inhibition of ZnO surface charge recombination. Enhanced light trapping (harvesting) induced by bending the PET substrates further improved the overall efficiency.

  4. Optimization of processing parameters on the controlled growth of ZnO nanorod arrays for the performance improvement of solid-state dye-sensitized solar cells

    SciTech Connect

    Lee, Yi-Mu; Yang, Hsi-Wen

    2011-03-15

    High-transparency and high quality ZnO nanorod arrays were grown on the ITO substrates by a two-step chemical bath deposition (CBD) method. The effects of processing parameters including reaction temperature (25-95 {sup o}C) and solution concentration (0.01-0.1 M) on the crystal growth, alignment, optical and electrical properties were systematically investigated. It has been found that these process parameters are critical for the growth, orientation and aspect ratio of the nanorod arrays, showing different structural and optical properties. Experimental results reveal that the hexagonal ZnO nanorod arrays prepared under reaction temperature of 95 {sup o}C and solution concentration of 0.03 M possess highest aspect ratio of {approx}21, and show the well-aligned orientation and optimum optical properties. Moreover the ZnO nanorod arrays based heterojunction electrodes and the solid-state dye-sensitized solar cells (SS-DSSCs) were fabricated with an improved optoelectrical performance. -- Graphical abstract: The ZnO nanorod arrays demonstrate well-alignment, high aspect ratio (L/D{approx}21) and excellent optical transmittance by low-temperature chemical bath deposition (CBD). Display Omitted Research highlights: > Investigate the processing parameters of CBD on the growth of ZnO nanorod arrays. > Optimization of CBD process parameters: 0.03 M solution concentration and reaction temperature of 95 {sup o}C. > The prepared ZnO samples possess well-alignment and high aspect ratio (L/D{approx}21). > An n-ZnO/p-NiO heterojunction: great rectifying behavior and low leakage current. > SS-DSSC has J{sub SC} of 0.31 mA/cm{sup 2} and V{sub OC} of 590 mV, and an improved {eta} of 0.059%.

  5. Single and multi-layered core-shell structures based on ZnO nanorods obtained by aerosol assisted chemical vapor deposition

    SciTech Connect

    Sáenz-Trevizo, A.; Amézaga-Madrid, P.; Pizá-Ruiz, P.; Antúnez-Flores, W.; Ornelas-Gutiérrez, C.; Miki-Yoshida, M.

    2015-07-15

    Core–shell nanorod structures were prepared by a sequential synthesis using an aerosol assisted chemical vapor deposition technique. Several samples consisting of ZnO nanorods were initially grown over TiO{sub 2} film-coated borosilicate glass substrates, following the synthesis conditions reported elsewhere. Later on, a uniform layer consisting of individual Al, Ni, Ti or Fe oxides was grown onto ZnO nanorod samples forming the so-called single MO{sub x}/ZnO nanorod core–shell structures, where MO{sub x} was the metal oxide shell. Additionally, a three-layer core–shell sample was developed by growing Fe, Ti and Fe oxides alternately, onto the ZnO nanorods. The microstructure of the core–shell materials was characterized by grazing incidence X-ray diffraction, scanning and transmission electron microscopy. Energy dispersive X-ray spectroscopy was employed to corroborate the formation of different metal oxides. X-ray diffraction outcomes for single core–shell structures showed solely the presence of ZnO as wurtzite and TiO{sub 2} as anatase. For the multi-layered shell sample, the existence of Fe{sub 2}O{sub 3} as hematite was also detected. Morphological observations suggested the existence of an outer material grown onto the nanorods and further microstructural analysis by HR-STEM confirmed the development of core–shell structures in all cases. These studies also showed that the individual Al, Fe, Ni and Ti oxide layers are amorphous; an observation that matched with X-ray diffraction analysis where no apparent extra oxides were detected. For the multi-layered sample, the development of a shell consisting of three different oxide layers onto the nanorods was found. Overall results showed that no alteration in the primary ZnO core was produced during the growth of the shells, indicating that the deposition technique used herein was and it is suitable for the synthesis of homogeneous and complex nanomaterials high in quality and purity. In addition

  6. Experimental and theoretical investigation of silver-coated ZnO nanorod arrays as antennas for the visible and near-IR spectral range

    NASA Astrophysics Data System (ADS)

    Kaidashev, E. M.; Lyanguzov, N. V.; Lerer, A. M.; Raspopova, E. A.

    2014-04-01

    A new design of optical antennas consisting of zinc oxide (ZnO) nanorods covered by a thin metal film is proposed. Arrays of highly oriented ZnO nanorods perpendicular to a substrate and covered by a thin silver film have been obtained using methods of carbothermal synthesis and magnetron sputtering. The problems of electromagnetic wave diffraction on a single metal/dielectric nanovibrator (situated at the interface of dielectrics) and on a two-dimensional periodic array of these nanovibrators have been solved. The results of calculations of the electrodynamic characteristics of optical antennas with various lengths have been compared to experimental data.

  7. Co-functionalized organic/inorganic hybrid ZnO nanorods as electron transporting layers for inverted organic solar cells.

    PubMed

    Ambade, Swapnil B; Ambade, Rohan B; Eom, Seung Hun; Baek, Myung-Jin; Bagde, Sushil S; Mane, Rajaram S; Lee, Soo-Hyoung

    2016-03-07

    In an unprecedented attempt, we present an interesting approach of coupling solution processed ZnO planar nanorods (NRs) by an organic small molecule (SM) with a strong electron withdrawing cyano moiety and the carboxylic group as binding sites by a facile co-functionalization approach. Direct functionalization by SMs (SM-ZnO NRs) leads to higher aggregation owing to the weaker solubility of SMs in solutions of ZnO NRs dispersed in chlorobenzene (CB). A prior addition of organic 2-(2-methoxyethoxy)acetic acid (MEA) over ZnO NRs not only inhibits aggregation of SMs over ZnO NRs, but also provides enough sites for the SM to strongly couple with the ZnO NRs to yield transparent SM-MEA-ZnO NRs hybrids that exhibited excellent capability as electron transporting layers (ETLs) in inverted organic solar cells (iOSCs) of P3HT:PC60BM bulk-heterojunction (BHJ) photoactive layers. A strongly coupled SM-MEA-ZnO NR hybrid reduces the series resistance by enhancing the interfacial area and tunes the energy level alignment at the interface between the (indium-doped tin oxide, ITO) cathode and BHJ photoactive layers. A significant enhancement in power conversion efficiency (PCE) was achieved for iOSCs comprising ETLs of SM-MEA-ZnO NRs (3.64%) advancing from 0.9% for pristine ZnO NRs, while the iOSCs of aggregated SM-ZnO NRs ETL exhibited a much lower PCE of 2.6%, thus demonstrating the potential of the co-functionalization approach. The superiority of the co-functionalized SM-MEA-ZnO NRs ETL is also evident from the highest PCE of 7.38% obtained for the iOSCs comprising BHJ of PTB7-Th:PC60BM compared with extremely poor 0.05% for non-functionalized ZnO NRs.

  8. Fe solubility, growth mechanism, and luminescence of Fe doped ZnO nanowires and nanorods grown by evaporation-deposition

    NASA Astrophysics Data System (ADS)

    Alemán, Belén; Ortega, Yanicet; García, José Ángel; Fernández, Paloma; Piqueras, Javier

    2011-07-01

    Fe doped ZnO nanowires, nanorods, and urchin-like nanostructures have been grown using an evaporation-deposition method with compacted mixtures of ZnS and Fe2O3 powders, with different Fe contents as precursors. Treatments at 950 °C under argon flow lead to the growth of iron doped nanowires, nanorods, and other nanostructures on the surface of the compacted sample. The incorporation of iron into the nanostructures has been investigated via energy dispersive spectroscopy as well as by cathodoluminescence in a scanning electron microscope and photoluminescence in an optical microscope. The iron content in the structures is limited to the range of 0.5-0.7 at.% and does not depend on the content in the precursor. Bright and dark field imaging and twist contour analysis via transmission electron microscopy support the possibility of a dislocation driven growth of the nanowires.

  9. Highly Transparent and UV-Resistant Superhydrophobic SiO2-Coated ZnO Nanorod Arrays

    PubMed Central

    2015-01-01

    Highly transparent and UV-resistant superhydrophobic arrays of SiO2-coated ZnO nanorods are prepared in a sequence of low-temperature (<150 °C) steps on both glass and thin sheets of PET (2 × 2 in.2), and the superhydrophobic nanocomposite is shown to have minimal impact on solar cell device performance under AM1.5G illumination. Flexible plastics can serve as front cell and backing materials in the manufacture of flexible displays and solar cells. PMID:24495100

  10. Down-conversion photoluminescence sensitizing plasmonic silver nanoparticles on ZnO nanorods to generate hydrogen by water splitting photochemistry

    SciTech Connect

    Kung, Po-Yen; Huang, Li-Wen; Shen, Tin-Wei; Wang, Wen-Lin; Su, Yen-Hsun; Lin, Melody I.

    2015-01-12

    Silver nanoparticles fabricated onto the surface of the ZnO nanorods form the photoanode and generate photoelectric current due to surface plasmon resonance, which serves as anode electrodes in photoelectrochemical hydrogen production. In order to increase the absorption spectrum of photoanode, organic pigments were utilized as photo-sensitizers to generate down-conversion photoluminescence to excite surface plasmon resonances of silver nanoparticles. The way of using light to carry the energy in electronic scattering regime runs the system for the enhancement of solar water splitting efficiency. It was significantly tuned in environmentally sustainable applications for power generation and development of alternative energy.

  11. Down-conversion photoluminescence sensitizing plasmonic silver nanoparticles on ZnO nanorods to generate hydrogen by water splitting photochemistry

    NASA Astrophysics Data System (ADS)

    Kung, Po-Yen; Huang, Li-Wen; Shen, Tin-Wei; Wang, Wen-Lin; Su, Yen-Hsun; Lin, Melody I.

    2015-01-01

    Silver nanoparticles fabricated onto the surface of the ZnO nanorods form the photoanode and generate photoelectric current due to surface plasmon resonance, which serves as anode electrodes in photoelectrochemical hydrogen production. In order to increase the absorption spectrum of photoanode, organic pigments were utilized as photo-sensitizers to generate down-conversion photoluminescence to excite surface plasmon resonances of silver nanoparticles. The way of using light to carry the energy in electronic scattering regime runs the system for the enhancement of solar water splitting efficiency. It was significantly tuned in environmentally sustainable applications for power generation and development of alternative energy.

  12. Ultraviolet photodetectors based on ZnO nanorods-seed layer effect and metal oxide modifying layer effect.

    PubMed

    Zhou, Hai; Fang, Guojia; Liu, Nishuang; Zhao, Xingzhong

    2011-02-15

    Pt/ZnO nanorod (NR) and Pt/modified ZnO NR Schottky barrier ultraviolet (UV) photodetectors (PDs) were prepared with different seed layers and metal oxide modifying layer materials. In this paper, we discussed the effect of metal oxide modifying layer on the performance of UV PDs pre- and post-deposition annealing at 300°C, respectively. For Schottky barrier UV PDs with different seed layers, the MgZnO seed layer-PDs without metal oxide coating showed bigger responsivity and larger detectivity (Dλ*) than those of PDs with ZnO seed layer, and the reason was illustrated through energy band theory and the electron transport mechanism. Also the ratio of D254* to D546* was calculated above 8 × 102 for all PDs, which demonstrated that our PDs showed high selectivity for detecting UV light with less influence of light with long wavelength.

  13. Hexagonal core-shell and alloy Au/Ag nanodisks on ZnO nanorods and their optical enhancement effect

    NASA Astrophysics Data System (ADS)

    Zhang, Junming; Lai, Boya; Chen, Zuxin; Chu, Sheng; Chu, Guang; Peng, Rufang

    2014-05-01

    Au and Ag hybrid hexagonal nanodisks were synthesized on ZnO nanorods' (0002) surface via a new two-step deposition-annealing method. The structural, compositional, as well as optical investigations were carried out systematically to find out the nanodisks' formation mechanism and optical enhancement effect. It was shown that the core-shell Au/Ag nanodisk can be formed under rapid annealing temperature of 500°C, while Au/Ag alloy nanodisks are formed if higher temperatures (>550°C) are applied. The optical effect from these nanodisks was studied through photoluminescence and absorption spectroscopy. It was found that the carrier-plasmon coupling together and carrier transfer between metal and ZnO contribute to the emission enhancement. Furthermore, the results suggest that the composition of nanodisk on the vicinity of metal/ZnO interface plays an important role in terms of the enhancement factors.

  14. Structural and optical properties of dense vertically aligned ZnO nanorods grown onto silver and gold thin films by galvanic effect with iron contamination

    SciTech Connect

    Scarpellini, D.; Paoloni, S.; Medaglia, P.G.; Pizzoferrato, R.; Orsini, A.; Falconi, C.

    2015-05-15

    Highlights: • ZnO nanorods were grown on Au and Ag films in aqueous solution by galvanic effect. • The method is prone to metal contamination which can influence the ZnO properties. • Iron doping improves the lattice matching between ZnO and the substrate. • Energy levels of point defects are lowered and the light emission is red-shifted. • Galvanic-induced nucleation starts and proceeds continuously during the growth. - Abstract: Dense arrays of vertically aligned ZnO nanorods have been grown onto either silver or gold seedless substrates trough a simple hydrothermal method by exploiting the galvanic effect between the substrate and metallic parts. The nanorods exhibit larger bases and more defined hexagonal shapes, in comparison with standard non-galvanic wet-chemistry synthesis. X-ray diffraction (XRD) shows that the iron contamination, associated with the galvanic contact, significantly improves the in-plane compatibility of ZnO with the Au and Ag cubic lattice. Photoluminescence (PL) measurements indicate that the contamination does not affect the number density of localized defects, but lowers their energy levels uniformly; differently, the band-edge emission is not altered appreciably. Finally, we have found that the ZnO hetero-nucleation by galvanic effect initiates at different times in different sites of the substrate area. Our results can be useful for the fabrication of high performance piezonanodevices comprising high-density metal-to-ZnO nanoscaled junctions without intermediate polycrystalline layers.

  15. Solution-processed Cu2ZnSnS4 superstrate solar cell using vertically aligned ZnO nanorods.

    PubMed

    Lee, Dongwook; Yong, Kijung

    2014-02-14

    One-dimensional (1D) zinc oxide (ZnO) nanostructures are considered to be promising materials for use in thin film solar cells because of their high light harvesting and charge collection efficiencies. We firstly report enhanced photovoltaic performances in Cu2ZnSnS4 (CZTS) thin film solar cells prepared using ZnO nanostructures. A CdS-coated, vertically well-aligned ZnO nanorod (NR) array was prepared via a hydrothermal reaction and nanocrystal layer deposition (NCLD) and was used as a transparent window/buffer layer in a CZTS thin film photovoltaic. A light absorber CZTS thin film was prepared on the CdS/ZnO NRs in air by depositing a non-toxic precursor solution that was annealed in two steps at temperatures up to 250 °C. The crystallized CZTS phase completely infiltrated the CdS/ZnO NR array. The nanostructured ZnO array provided improved light harvesting behavior compared to a thin film configuration by measuring UV-vis transmittance spectroscopy. The prepared CZTS/CdS/ZnO NR device exhibited a solar energy conversion efficiency of 1.2%, which is the highest efficiency yet reported for nanostructured superstrate CZTS solar cells.

  16. Synergistic effect of dual interfacial modifications with room-temperature-grown epitaxial ZnO and adsorbed indoline dye for ZnO nanorod array/P3HT hybrid solar cell.

    PubMed

    Chen, Dian-Wei; Wang, Ting-Chung; Liao, Wen-Pin; Wu, Jih-Jen

    2013-09-11

    ZnO nanorod (NR)/poly(3-hexylthiophene) (P3HT) hybrid solar cells with interfacial modifications are investigated in this work. The ZnO NR arrays are modified with room-temperature (RT)-grown epitaxial ZnO shells or/and D149 dye molecules prior to the P3HT infiltration. A synergistic effect of the dual modifications on the efficiency of the ZnO NR/P3HT solar cell is observed. The open-circuit voltage and fill factor are considerable improved through the RT-grown ZnO and D149 modifications in sequence on the ZnO NR array, which brings about a 2-fold enhancement of the efficiency of the ZnO NR/P3HT solar cell. We suggested that the more suitable surface of RT-grown ZnO for D149 adsorption, the chemical compatibility of D149 and P3HT, and the elevated conduction band edge of the RT-grown ZnO/D149-modified ZnO NR array construct the superior interfacial morphology and energetics in the RT-grown ZnO/D149-modified ZnO NR/P3HT hybrid solar cell, resulting in the synergistic effect on the cell efficiency. An efficiency of 1.16% is obtained in the RT-grown ZnO/D149-modified ZnO NR/P3HT solar cell.

  17. Synthesis of novel AuPd nanoparticles decorated one-dimensional ZnO nanorod arrays with enhanced photoelectrochemical water splitting activity.

    PubMed

    Lu, Yan; Zhang, Junlong; Ge, Lei; Han, Changcun; Qiu, Ping; Fang, Siman

    2016-12-01

    The vertically aligned one-dimensional (1D) ZnO nanorod arrays decorated with AuPd alloy nanoparticles have been synthesized with ZnO nanorod arrays as template via a mild hydrothermal method. In this work, the as-prepared AuPd/ZnO nanorod arrays demonstrated high light-harvesting efficiency. The microstructures, morphologies and chemical properties of the obtained AuPd/ZnO composite photocatalyst were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-vis diffuse reflectance spectra (DRS) and X-ray photoelectron spectroscopy (XPS). The photoelectrochemical (PEC) performances of as-obtained AuPd/ZnO nanorod arrays were examined, and the photocurrent density was up to 0.98mAcm(-2) at 0.787V versus Ag/AgCl, which was about 2.4 times higher than the pure ZnO sample. A possible photocatalytic mechanism of the AuPd/ZnO hybrid nanostructures under the simulated sunlight irradiation was proposed to guide further improvement of other desirable materials. According to the above experiment results, it can be clearly found that AuPd/ZnO composite nanorod arrays showed excellent PEC performance and had promising applications in the utilization of solar energy.

  18. Controlling the orientation of ZnO nanorod arrays using TiO2 thin film templates dip-coated by sol-gel

    NASA Astrophysics Data System (ADS)

    Yang, Anli; Cui, Zuolin

    2007-04-01

    The oriented ZnO nanorod arrays have been synthesized on a silicon wafer that coated with TiO2 films by aqueous chemical method. The morphologies, phase structure and the photoluminescence (PL) properties of the as-obtained product were investigated by field-emission scanning electron microscopy (FE-SEM), X-ray diffractometer (XRD), transmission electron microscope (TEM) and PL spectrum. The nanorods were about 100 nm in diameter and more than 1 µm in length, which possessed wurtzite structure with a c axis growth direction. The room-temperature PL measurement of the nanorod arrays showed strong ultraviolet emission. The effect of the crystal structure and the thickness of TiO2 films on the morphologies of ZnO nanostructures were investigated. It was found that the rutile TiO2 films were appropriate to the oriented growth of ZnO nanorod arrays in comparison with anatase TiO2 films. Moreover, flakelike ZnO nanostructures were obtained with increasing the thickness of anatase TiO2 films.

  19. ZnO nanorods/graphene/Ni/Au hybrid structures as transparent conductive layer in GaN LED for low work voltage and high light extraction

    NASA Astrophysics Data System (ADS)

    Xu, Kun; Xie, Yiyang; Ma, Huali; Du, Yinxiao; Zeng, Fanguang; Ding, Pei; Gao, Zhiyuan; Xu, Chen; Sun, Jie

    2016-12-01

    In this paper, by virtue of one-dimensional ZnO nanorods and two-dimensional graphene film hybrid structures, both the enhanced current spreading and enhanced light extraction were realized at the same time. A 1 nm/1 nm Ni/Au layer was used as an interlayer between graphene and pGaN to form ohmic contact, which makes the device have a good forward conduction properties. Through the comparison of the two groups of making ZnO nanorods or not, it was found that the 30% light extraction efficiency of the device was improved by using the ZnO nanorods. By analysis key parameters of two groups such as the turn-on voltage, work voltage and reverse leakage current, it was proved that the method for preparing surface nano structure by hydrothermal method self-organization growth ZnO nanorods applied in GaN LEDs has no influence to device's electrical properties. The hybrid structure application in GaN LED, make an achievement of a good ohmic contact, no use of ITO and enhancement of light extraction at the same time, meanwhile it does not change the device structure, introduce additional process, worsen the electrical properties.

  20. Effect of Nb-doped TiO2 on nanocomposited aligned ZnO nanorod/TiO2:Nb for dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Saurdi, I.; Shafura, A. K.; Azhar, N. E. A.; Ishak, A.; Malek, M. F.; Alrokayan, A. H. Salman; Khan, Haseeb A.; Mamat, M. H.; Rusop, M.

    2016-07-01

    The Nb-doped TiO2 films were deposited on glass substrate at different Nb concentrations of 0 at.%, 1 at.%, 3 at.%, 5 at.% and 7 at.%, respectively and their electrical and structural properties were investigated. Subsequently, the Nb-doped TiO2 films were deposited on top of aligned ZnO Nanorod on ITO glass substrates using spin coating technique. The nanocomposited aligned ZnO nanorod/Nb-doped TiO2 (TiO2:Nb) were coated with different Nb concentrations of 0 at.%, 1 at.%, 3 at.%, 5 at.% and 7 at.%, respectively. The Dye-sensitized solar cells were fabricated from the nanocomposited aligned ZnO nanorod/TiO2:Nb photoanodes and their effects on the performance of the DSSCs were investigated. From the solar simulator measurement of DSSC the solar energy conversion efficiency (η) of 5.376% under AM 1.5 was obtained for the ZnO nanorod/TiO2:Nb-5at.%.

  1. Low-temperature growth and characterization of single crystalline ZnO nanorod arrays using a catalyst-free inductively coupled plasma-metal organic chemical vapor deposition.

    PubMed

    Jeong, Sang-Hun; Lee, Chang-Bae; Moon, Won-Jin; Song, Ho-Jun

    2008-10-01

    Vertically aligned ZnO nanorod arrays have been synthesized on c-plane sapphires at a low temperature of 400 degrees C using catalyst-free inductively coupled plasma (ICP) metal organic chemical vapor deposition (MOCVD) technique by varying the ICP powers. Diameters of the ZnO nanorods changed from 200 nm to 400 nm as the ICP power increased from 200 to 400 Watt. TEM and XRD investigations indicated that the ZnO nanorod arrays grown at ICP powers above 200 Watt had a homogeneous in-plane alignment and single crystalline nature. PL study at room temperature (RT) and 6 K confirmed that the ZnO nanorod arrays in the present study are of high optical quality as well as good crystalline quality, showing only exciton-related emission peaks without any trace of defect-related deep level emissions in visible range. The blueshift of exciton emission peak in RTPL spectra was also found as rod diameter decreased and it is deduced that this shift in emission energy may be due to the surface resonance effect resulted from the increased surface-to-volume ratio, based on the observation and behavior of the surface exciton (SX) emission in the high-resolution 6 K PL spectra.

  2. Light trapping considerations in self-assembled ZnO nanorod arrays for quantum dot sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Luan, ChunYan; Cheung, King Tai; Foo, Yishu; Yu, Li Yu; Shen, Qing; Zapien, Juan Antonio

    2014-03-01

    We study light absorption in ZnO nanorod arrays sensitized with CdSe quantum dots as one of the factors affecting solar cell performance in need of improvement given their current performance well below expectations. Light trapping in nanorod arrays (NRAs) as it relates to array density and length as well as quantum dot (QD) loading is studied using the Finite Difference Time Domain model. It is shown that light absorption in such solar cell architecture is a sensitive function of the morphological dimensions and that a higher NRA density does not necessarily correspond to large absorption in the solar cell. Instead, light trapping efficiency depends significantly on the array density, QD axial distribution and refractive index contrast between NR and QDs thus suggesting strategies for improved quantum dot solar cell (QDSC) fabrication. In addition, we present experimental data showing dramatic improvement in photo conversion efficiency performance for relatively short ZnO NRAs (~1 μm) of low NRA density, but whose efficiency improvement can not be solely explained based on our current light trapping estimates from the numerical simulations.

  3. Modeling and experiment of dye-sensitized solar cell with vertically aligned ZnO nanorods through chemical bath deposition

    NASA Astrophysics Data System (ADS)

    Wahyuono, Ruri Agung; Risanti, Doty D.

    2015-01-01

    A theoretical model based on electron diffusion differential equation and Schottky barrier model was developed to determine the current-voltage characteristics of DSSC. To verify the model DSSC with ZnO nanorods photoelectrode which was chemically bath deposited onto the TCO was fabricated. According to modeling results, increasing of recombination current density J at these interfaces results in a decrease in Schottky barrier height φb and therefore improves the photovoltage under the open-circuit condition. It is found that the open-circuit voltage remains constant when the TCO/ZnO Schottky barrier height was varied in the range of 0.45 - 0.6 eV. This theoretical model consistents with the experimental result in which the fabricated DSSCs can produce conversion efficiency in the range of 0.98 - 1.16%. The trend in photovoltage calculated in the theoretical model basically agrees with the experimental result, although the calculated photocurrent is somewhat over estimated compared to the experimental results. The model presents that the ideality factor for ZnO nanorods, which also contributes to the enhancement of photovoltage, increases in the range of 2.75 - 3.0 as the annealing temperature is increased in the experiment.

  4. Significant Enhancement in the Conductivity of Al-Doped Zinc Oxide thin Films for TCO Application

    NASA Astrophysics Data System (ADS)

    Mohite, R. M.; Ansari, J. N.; Roy, A. S.; Kothawale, R. R.

    2016-03-01

    Nanostructured Al-doped Zinc oxide (ZnO) thin films were deposited on glass substrate by chemical bath deposition (CBD) using aqueous zinc nitrate solution and subjected for different characterizations. Effect of Al3+ substitution on the properties of ZnO annealed at 400∘C was studied by XRD and UV-Vis for structural studies, SEM and TEM for surface morphology and DC four probe resistivity measurements for electrical properties. Al3+ substitution does not influence the morphology and well-known peaks related to wurtzite structure of ZnO. Electron microscopy (SEM and TEM) confirms rod shaped Al-doped ZnO nanocrystals with average width of 50nm. The optical band gap determined by UV-Visible spectroscopy was found to be in the range 3.37eV to 3.44eV. An EPR spectrum of AZO reveals peak at g=1.96 is due to shallow donors Zn interstitial. The DC electrical resistivity measurements of Al-doped ZnO show a minimum resistivity of 3.77×10-2Ω-cm. Therefore, these samples have potential use in n-type window layer in optoelectronic devices, organic solar cells, photonic crystals, photo-detectors, light emitting diodes (LEDs), gas sensors and chemical sensors.

  5. CdS and CdS/CdSe sensitized ZnO nanorod array solar cells prepared by a solution ions exchange process

    SciTech Connect

    Chen, Ling; Gong, Haibo; Zheng, Xiaopeng; Zhu, Min; Zhang, Jun; Yang, Shikuan; Cao, Bingqiang

    2013-10-15

    Graphical abstract: - Highlights: • CdS and CdS/CdSe quantum dots are assembled on ZnO nanorods by ion exchange process. • The CdS/CdSe sensitization of ZnO effectively extends the absorption spectrum. • The performance of ZnO/CdS/CdSe cell is improved by extending absorption spectrum. - Abstract: In this paper, cadmium sulfide (CdS) and cadmium sulfide/cadmium selenide (CdS/CdSe) quantum dots (QDs) are assembled onto ZnO nanorod arrays by a solution ion exchange process for QD-sensitized solar cell application. The morphology, composition and absorption properties of different photoanodes were characterized with scanning electron microscope, transmission electron microscope, energy-dispersive X-ray spectrum and Raman spectrum in detail. It is shown that conformal and uniform CdS and CdS/CdSe shells can grow on ZnO nanorod cores. Quantum dot sensitized solar cells based on ZnO/CdS and ZnO/CdS/CdSe nanocable arrays were assembled with gold counter electrode and polysulfide electrolyte solution. The CdS/CdSe sensitization of ZnO can effectively extend the absorption spectrum up to 650 nm, which has a remarkable impact on the performance of a photovoltaic device by extending the absorption spectrum. Preliminary results show one fourth improvement in solar cell efficiency.

  6. Performance of natural-dye-sensitized solar cells by ZnO nanorod and nanowall enhanced photoelectrodes.

    PubMed

    Saadaoui, Saif; Ben Youssef, Mohamed Aziz; Ben Karoui, Moufida; Gharbi, Rached; Smecca, Emanuele; Strano, Vincenzina; Mirabella, Salvo; Alberti, Alessandra; Puglisi, Rosaria A

    2017-01-01

    In this work, two natural dyes extracted from henna and mallow plants with a maximum absorbance at 665 nm were studied and used as sensitizers in the fabrication of dye-sensitized solar cells (DSSCs). Fourier transform infrared (FTIR) spectra of the extract revealed the presence of anchoring groups and coloring constituents. Two different structures were prepared by chemical bath deposition (CBD) using zinc oxide (ZnO) layers to obtain ZnO nanowall (NW) or nanorod (NR) layers employed as a thin film at the photoanode side of the DSSC. The ZnO layers were annealed at different temperatures under various gas sources. Indeed, the forming gas (FG) (N2/H2 95:5) was found to enhance the conductivity by a factor of 10(3) compared to nitrogen (N2) or oxygen (O2) annealing gas. The NR width varied between 40 and 100 nm and the length from 500 to 1000 nm, depending on the growth time. The obtained NWs had a length of 850 nm. The properties of the developed ZnO NW and NR layers with different thicknesses and their effect on the photovoltaic parameters were studied. An internal coverage of the ZnO NWs was also applied by the deposition of a thin TiO2 layer by reactive sputtering to improve the cell performance. The application of this layer increased the overall short circuit current Jsc by seven times from 2.45 × 10(-3) mA/cm(2) to 1.70 × 10(-2) mA /cm(2).

  7. Performance of natural-dye-sensitized solar cells by ZnO nanorod and nanowall enhanced photoelectrodes

    PubMed Central

    Saadaoui, Saif; Ben Youssef, Mohamed Aziz; Ben Karoui, Moufida; Smecca, Emanuele; Strano, Vincenzina; Mirabella, Salvo; Alberti, Alessandra; Puglisi, Rosaria A

    2017-01-01

    In this work, two natural dyes extracted from henna and mallow plants with a maximum absorbance at 665 nm were studied and used as sensitizers in the fabrication of dye-sensitized solar cells (DSSCs). Fourier transform infrared (FTIR) spectra of the extract revealed the presence of anchoring groups and coloring constituents. Two different structures were prepared by chemical bath deposition (CBD) using zinc oxide (ZnO) layers to obtain ZnO nanowall (NW) or nanorod (NR) layers employed as a thin film at the photoanode side of the DSSC. The ZnO layers were annealed at different temperatures under various gas sources. Indeed, the forming gas (FG) (N2/H2 95:5) was found to enhance the conductivity by a factor of 103 compared to nitrogen (N2) or oxygen (O2) annealing gas. The NR width varied between 40 and 100 nm and the length from 500 to 1000 nm, depending on the growth time. The obtained NWs had a length of 850 nm. The properties of the developed ZnO NW and NR layers with different thicknesses and their effect on the photovoltaic parameters were studied. An internal coverage of the ZnO NWs was also applied by the deposition of a thin TiO2 layer by reactive sputtering to improve the cell performance. The application of this layer increased the overall short circuit current J sc by seven times from 2.45 × 10−3 mA/cm2 to 1.70 × 10−2 mA /cm2. PMID:28243567

  8. Strong Red Luminescent Twin ZnO Nanorods for Nano-thermometry and Phonon Tunnel Device Application

    NASA Astrophysics Data System (ADS)

    Singh, Avanendra; Senapati, Kartik; Nanda, Karunakar; Satpati, Biswarup; Sahoo, Pratap

    Two segments of horizontally grown crystalline ZnO nanorods (NRs) connected with an amorphous layer have been successfully synthesized using aqueous growth technique. The amorphous layer between the crystalline ZnO sections is tunable with growth parameters and confirmed by transmission electron microscopy. The confocal photoluminescence (PL) imaging and spectroscopy of twin ZnO NRs at different temperature shows stable and intense red emission with comparably weak UV emission. Red emission from the twin NRs are the consequence of surface defect and structural imperfections of lattice disorder. The disappearance of asymmetry in UV emission after 293K indicates the weak exciton-phonon coupling at higher temperature while the coupling is stronger at lower temperatures. An indirect analysis from phonon bands of PL shows that the amorphous layer acts as a phonon barrier beyond certain thickness. Such crystalline-amorphous-crystalline architecture may be suitable for fundamental studies of the phonon tunneling in nanostructure. We also show that the individual NRs can be used for sensing and mapping of temperature in a wide range of 80-373 K with an accuracy of 0.1K with good sensitivity. These NRs may have suitable application for non-contact nano-thermometry.

  9. Selective growth of ZnO nanorods by the hydrothermal technique

    NASA Astrophysics Data System (ADS)

    Nozaki, Shinji; Sarangi, Sachin N.; Sahu, Surendra N.; Uchida, Kazuo

    2013-03-01

    Zinc oxide nanorods were selectively grown on engineered substrates, Ag-patterned and photoresist-patterned substrates, by the hydrothermal technique using zinc nitrate (Zn(NO3)2) and hexamethylenetetramine ((CH2)6N4). The nanorod growth was affected by the substrate to be used. The nanorods were vertically grown on a GaN substrate but not on a Si substrate because of lattice mismatch. However, since the nanorods were grown on a thick Ag film no matter what substrate was used, a thick Ag film was deposited on a Si substrate to prepare the Ag-patterned substrate. Accordingly, the nanorods were grown only on the Ag pads. When the sizes of Ag pads were small such as 100 nm × 100 nm, one single nanorod was grown on an Ag pad. As another engineered substrate, the photoresist was patterned to prepare an array of holes on a GaN-on-sapphire substrate by e-beam lithography. When the hole size was 10 nm × 10 nm and higher, concentrations of Zn(NO3)2 and ((CH2)6N4) were employed, all holes were successfully filled with a single nanorod. Invited talk at the 6th International Workshop on Advanced Materials Science and Nanotechnology IWAMSN2012, 30 October 2 November 2012, Ha Long, Vietnam.

  10. Studies on the structural and optical properties of zinc oxide nanobushes and Co-doped ZnO self-aggregated nanorods synthesized by simple thermal decomposition route

    SciTech Connect

    Freedsman, Joseph J.; Kennedy, L. John; Kumar, R. Thinesh; Sekaran, G.; Vijaya, J. Judith

    2010-10-15

    Pure and Co-doped zinc oxide nanomaterials were prepared by a simple low temperature synthesis and were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution-transmission electron microscopy (HR-TEM), diffused reflectance spectroscopy (DRS) and electron paramagnetic resonance (EPR) techniques. The results showed the formation of nanobushes that consists of several nanowires for pure ZnO and the nanorods formed by self-aggregation for Co-doped ZnO. The presence of Co{sup 2+} ions replacing some of the Zn{sup 2+} in the ZnO lattice was confirmed by EPR and DRS studies. The mechanism for the formation of self-aggregated and self-aligned ZnO rods after the incorporation of cobalt in the lattice by the building block units is discussed in this study. Morphological studies were carried out using SEM and HR-TEM, which supports the validity of the proposed mechanism for the formation of ZnO nanobushes and Co-doped ZnO nanorods. The synthesized nanomaterials were found to have good optoelectronic properties.

  11. Green material: ecological importance of imperative and sensitive chemi-sensor based on Ag/Ag2O3/ZnO composite nanorods

    PubMed Central

    2013-01-01

    In this report, we illustrate a simple, easy, and low-temperature growth of Ag/Ag2O3/ZnO composite nanorods with high purity and crystallinity. The composite nanorods were structurally characterized by field emission scanning electron microscopy, X-ray powder diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy which confirmed that synthesized product have rod-like morphology having an average cross section of approximately 300 nm. Nanorods are made of silver, silver oxide, and zinc oxide and are optically active having absorption band at 375 nm. The composite nanorods exhibited high sensitivity (1.5823 μA.cm−2.mM−1) and lower limit of detection (0.5 μM) when applied for the recognition of phenyl hydrazine utilizing I-V technique. Thus, Ag/Ag2O3/ZnO composite nanorods can be utilized as a redox mediator for the development of highly proficient phenyl hydrazine sensor. PMID:24011288

  12. Green material: ecological importance of imperative and sensitive chemi-sensor based on Ag/Ag2O3/ZnO composite nanorods

    NASA Astrophysics Data System (ADS)

    Asiri, Abdullah M.; Khan, Sher Bahadar; Rahman, Mohammed M.; Al-Sehemi, Abdullah G.; Al-Sayari, Saleh A.; Al-Assiri, Mohammad Sultan

    2013-09-01

    In this report, we illustrate a simple, easy, and low-temperature growth of Ag/Ag2O3/ZnO composite nanorods with high purity and crystallinity. The composite nanorods were structurally characterized by field emission scanning electron microscopy, X-ray powder diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy which confirmed that synthesized product have rod-like morphology having an average cross section of approximately 300 nm. Nanorods are made of silver, silver oxide, and zinc oxide and are optically active having absorption band at 375 nm. The composite nanorods exhibited high sensitivity (1.5823 μA.cm-2.mM-1) and lower limit of detection (0.5 μM) when applied for the recognition of phenyl hydrazine utilizing I-V technique. Thus, Ag/Ag2O3/ZnO composite nanorods can be utilized as a redox mediator for the development of highly proficient phenyl hydrazine sensor.

  13. Evaluation of kinetics parameters in the X-irradiated TSL studies of RE3+-doped (RE=Eu, Tb) ZnO nanorods for dosimetric applications

    NASA Astrophysics Data System (ADS)

    Pal, Partha P.; Manam, J.

    2013-07-01

    This paper reports the detail description of the structural and thermoluminescence of the RE3+-doped (RE=Eu, Tb) ZnO nanorods prepared by adopting co-precipitation method. Formation of as synthesized ZnO nanorods were confirmed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD pattern showed monophasic nature of the as prepared ZnO doped with Eu3+ and Tb3+ ions. The SEM image elaborates the nanorod morphology of RE3+ doped ZnO with diameter ranging between 60-90 nm and length between 600-900 nm. The thermoluminescence spectra of the X-ray irradiated ZnO:Eu3+ and ZnO:Tb3+ show the prominent peak for the broad glow curve peaked at 365 °C and 350 °C, respectively, which have been generated via the recombination of the released electrons from the traps upon thermal stimulation. The peaks are found to obey first order kinetics and the activation energy for the ZnO:Eu3+ and ZnO:Tb3+ samples, estimated via isothermal luminescence glow peak decay method, are found to be 0.8 eV and 0.9 eV respectively. Furthermore, the TL dose response and reproducibility were also studied in details, which could be very useful to establish the potentiality of the present phosphors in the field of radiation dosimetry.

  14. Highly efficient hybrid solar cell using ZnO nanorods and assessment of changes in cell performance by varying the growth period

    NASA Astrophysics Data System (ADS)

    Mehrabian, Masood; Aslyousefzadeh, Sonya; Maleki, M. Hadi

    2015-05-01

    Zinc oxide nanorod arrays (ZnO NRs) were grown from ZnO seed-coated substrates in an aqueous solution by using the hydrothermal method for different growth periods varying from 5 min to 1 hour. The influence of the growth period of the ZnO nanorods on photovoltaic applications was studied in detail. Experimental results showed that utilization of the nanorod arrays lead to an enhanced the cell performance by increasing of light absorption and creation of a vertical direction for electron transport in the solar cells. A power conversion efficiency of 3.33% with an opencircuit voltage of V OC = 0.58 V, a short-circuit current of J SC = 10.05 mA/cm2 and a fill factor of FF = 54.35% was achieved for solar cells based on ZnO NRs with growth period of 20 min. Such solar cells with an optimal growth period are effective in light trapping, which leads to a significant enhancement in the absorption of light, and thereby, show an obvious increase in the power conversion efficiency.

  15. Microstructural Analysis and the Multicolor UV/Violet/Blue/Green/Yellow PL Observed from the Synthesized ZnO Nano-leaves and Nano-rods

    NASA Astrophysics Data System (ADS)

    Validžić, Ivana Lj.; Mitrić, Miodrag; Ahrenkiel, S. Phillip; Čomor, Mirjana I.

    2015-08-01

    We report the synthesis of zinc oxide (ZnO) nano-leaves and nano-rods under high and extremely high alkaline experimental conditions, via a simple and low-temperature method. By performing transmission electron microscopy it is found that the nano-leaves and nano-rods grow along the (001) direction. Anisotropic, i.e., hkl-dependent line-shape broadening is observed in ZnO powder diffraction patterns. Rietveld analysis using Fullprof with model for handling the anisotropic size-like broadening is performed on these diffraction patterns. The refinement showed that ZnO powders belong to the hexagonal ZnS structure type with space group P63mc, and confirmed that the nano-leaves and nano-rods are oriented along the (001) direction. Results of visualization in 3D of the average crystallite shape obtained from refinement of spherical harmonics coefficients showed elongated shapes in the both samples, exhibiting a slight twisting for nano-leaves. Diffuse reflectance measurements reveal that the optical band-gap energies found for the ZnO nano-leaves and nano-rods is somewhat smaller than a wide-direct band gap of 3.37 eV. We argued that well defined and strong photoluminescence (PL) bands in the visible part that belong to the defects may influence the observed displacement of a ultraviolet (UV) near-band-edge emission, and which is related with obtained slightly lower band-gap energies than the established band gap of bulk ZnO. We discuss processes behind the multicolor UV/violet/blue/green/yellow emission band in PL spectra.

  16. Enhancement of two photon absorption with Ni doping in the dilute magnetic semiconductor ZnO crystalline nanorods

    NASA Astrophysics Data System (ADS)

    Rana, Amit Kumar; J, Aneesh; Kumar, Yogendra; M. S, Arjunan; Adarsh, K. V.; Sen, Somaditya; Shirage, Parasharam M.

    2015-12-01

    In this letter, we have investigated the third-order optical nonlinearities of high-quality Ni doped ZnO nanorods crystallized in wurtzite lattice, prepared by the wet chemical method. In our experiments, we found that the two photon absorption coefficient (β) increases by as much as 14 times, i.e., 7.6 ± 0.4 to 112 ± 6 cm/GW, when the Ni doping is increased from 0% to 10%. The substantial enhancement in β is discussed in terms of the bandgap scaling and Ni doping. Furthermore, we also show that the optical bandgap measured by UV-Vis and photoluminescence spectroscopies, continuously redshift with increasing Ni doping concentration. We envision that the strong nonlinear optical properties together with their dilute magnetic effects, they form an important class of materials for potential applications in magneto-optical and integrated optical chips.

  17. Enhancement of two photon absorption with Ni doping in the dilute magnetic semiconductor ZnO crystalline nanorods

    SciTech Connect

    Rana, Amit Kumar; Kumar, Yogendra; Arjunan, M.S.; Sen, Somaditya; Shirage, Parasharam M. E-mail: paras.shirage@gmail.com; J, Aneesh; Adarsh, K. V.

    2015-12-07

    In this letter, we have investigated the third-order optical nonlinearities of high-quality Ni doped ZnO nanorods crystallized in wurtzite lattice, prepared by the wet chemical method. In our experiments, we found that the two photon absorption coefficient (β) increases by as much as 14 times, i.e., 7.6 ± 0.4 to 112 ± 6 cm/GW, when the Ni doping is increased from 0% to 10%. The substantial enhancement in β is discussed in terms of the bandgap scaling and Ni doping. Furthermore, we also show that the optical bandgap measured by UV-Vis and photoluminescence spectroscopies, continuously redshift with increasing Ni doping concentration. We envision that the strong nonlinear optical properties together with their dilute magnetic effects, they form an important class of materials for potential applications in magneto-optical and integrated optical chips.

  18. Low-temperature growth of well-aligned ZnO nanorods/nanowires on flexible graphite sheet and their photoluminescence properties

    SciTech Connect

    Zhong, Guo; Kalam, Abul; Al-Shihri, Ayed Sad; Su, Qingmei; Li, Jie; Du, Gaohui

    2012-06-15

    Highlights: ► Well-aligned ZnO nanostructures were grown on flexible graphite sheets at 500–650 °C. ► ZnO nanostructures are formed via self-catalytic vapor–solid process assisted by immiscibility of ZnO with graphite. ► The ZnO nanostructures show intensive green emission. ► The photoluminescence property can be easily tuned by changing growth condition or annealing treatment. -- Abstract: We have grown large-scale well-aligned ZnO nanorods/nanowires on commercial flexible graphite sheet (FGS) at low temperature via chemical vapor deposition method. The products were characterized by X-ray diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy. The effects of the growth temperature and oxygen flow rate on the morphology of ZnO nanostructures have been investigated. The growth mechanism of ZnO is found to be a self-catalytic vapor–solid process assisted by the immiscibility of ZnO with graphite. The as-grown ZnO/FGS products show strong green emission and their photoluminescence properties can be tuned by changing growth condition or annealing treatment.

  19. Co-functionalized organic/inorganic hybrid ZnO nanorods as electron transporting layers for inverted organic solar cells

    NASA Astrophysics Data System (ADS)

    Ambade, Swapnil B.; Ambade, Rohan B.; Eom, Seung Hun; Baek, Myung-Jin; Bagde, Sushil S.; Mane, Rajaram S.; Lee, Soo-Hyoung

    2016-02-01

    In an unprecedented attempt, we present an interesting approach of coupling solution processed ZnO planar nanorods (NRs) by an organic small molecule (SM) with a strong electron withdrawing cyano moiety and the carboxylic group as binding sites by a facile co-functionalization approach. Direct functionalization by SMs (SM-ZnO NRs) leads to higher aggregation owing to the weaker solubility of SMs in solutions of ZnO NRs dispersed in chlorobenzene (CB). A prior addition of organic 2-(2-methoxyethoxy)acetic acid (MEA) over ZnO NRs not only inhibits aggregation of SMs over ZnO NRs, but also provides enough sites for the SM to strongly couple with the ZnO NRs to yield transparent SM-MEA-ZnO NRs hybrids that exhibited excellent capability as electron transporting layers (ETLs) in inverted organic solar cells (iOSCs) of P3HT:PC60BM bulk-heterojunction (BHJ) photoactive layers. A strongly coupled SM-MEA-ZnO NR hybrid reduces the series resistance by enhancing the interfacial area and tunes the energy level alignment at the interface between the (indium-doped tin oxide, ITO) cathode and BHJ photoactive layers. A significant enhancement in power conversion efficiency (PCE) was achieved for iOSCs comprising ETLs of SM-MEA-ZnO NRs (3.64%) advancing from 0.9% for pristine ZnO NRs, while the iOSCs of aggregated SM-ZnO NRs ETL exhibited a much lower PCE of 2.6%, thus demonstrating the potential of the co-functionalization approach. The superiority of the co-functionalized SM-MEA-ZnO NRs ETL is also evident from the highest PCE of 7.38% obtained for the iOSCs comprising BHJ of PTB7-Th:PC60BM compared with extremely poor 0.05% for non-functionalized ZnO NRs.In an unprecedented attempt, we present an interesting approach of coupling solution processed ZnO planar nanorods (NRs) by an organic small molecule (SM) with a strong electron withdrawing cyano moiety and the carboxylic group as binding sites by a facile co-functionalization approach. Direct functionalization by SMs (SM

  20. Origin of p-type conductivity of Sb-doped ZnO nanorods and the local structure around Sb ions

    SciTech Connect

    Liang, J. K.; Su, H. L. E-mail: ycwu@hfut.edu.cn Wu, Y. C. E-mail: ycwu@hfut.edu.cn; Chuang, P. Y.; Kuo, C. L.; Huang, S. Y.; Chan, T. S.; Huang, J. C. A. E-mail: ycwu@hfut.edu.cn

    2015-05-25

    To probe the origin of p-type conductivity in Sb-doped ZnO, a careful and detailed synchrotron radiation study was performed. The extended X-ray absorption fine structure and X-ray photoelectron spectroscopy investigations provided the evidence for the formation of the complex defects comprising substitution Sb ions at Zn sites (Sb{sub Zn}) and Zn vacancies within the Sb-doped ZnO lattice. Such complex defects result in the increases of Sb-O coordination number and the Sb valence and thereby lead to the p-type conductivity of Sb-doped ZnO. The back-gate field-effect-transistors based on single nanorod of Sb-doped ZnO were constructed, and the stable p-type conduction behavior was confirmed.

  1. Enhancement of light extraction efficiency of GaN-based light-emitting diodes by ZnO nanorods with different sizes.

    PubMed

    Oh, Semi; Shin, Kyung-Sik; Kim, Sang-Woo; Lee, Sangbin; Yu, Hyeongwoo; Cho, Soohaeng; Kim, Kyoung-Kook

    2013-05-01

    The improvement of the optical output power of GaN-based light emitting diodes (LEDs) was achieved by employing nano-sized flat-top hexagonal ZnO rods. ZnO nanorods (NRs) with the average diameters of 250, 350, and 580 nm were grown on p-GaN top surfaces by a simple wet-chemical method at relatively low temperature (90 degrees C) to investigate the effect of the diameter of ZnO NRs on the light extraction efficiency. Consequently, the enhancement by the factor of as high as 2.63 in the light output intensity at 20 mA for the LED with 350 nm ZnO NRs was demonstrated without the increase in the operation voltage compared to the reference LED.

  2. Sensitivity gains in chemosensing by optical and structural modulation of ordered assembly arrays of ZnO nanorods.

    PubMed

    Zhu, Defeng; He, Qingguo; Chen, Qing; Fu, Yanyan; He, Chao; Shi, Liqi; Meng, Xin; Deng, Changmin; Cao, Huimin; Cheng, Jiangong

    2011-06-28

    Nanomaterials and -structures have attracted much attention owing to their applications to ultrasensitive nanodevices. In this work, ordered assembly arrays of ZnO nanorods have been hydrothermally fabricated and used as optical substrates of fluorescence sensors for toxic vapors. The unique fastigiate nanorod assembly combines merits of single fibers and clusters, possessing identical orientation, large surface-to-volume ratio, evanescent transmission, and evanescent coupling. As coated on the assembly arrays, different sensing materials all generated amplified spontaneous emission (ASE) action such that the fluorescence intensity of the narrowed spectrum was 52.4-fold enhanced. Results of sensing experiments indicate that sensors based on the assembly arrays displayed 100% elevated normalized quenching rate and several times longer full-load time compared with reference sensors. This work provides a facile method to fabricate secondary structures of 1D rigid material and presents a new way to design highly sensitive optic sensors. Furthermore, evanescent excitation caused ASE action of fluorescent organics, and the correlative sensitivity gain is of interest in both theoretical research and the applications field.

  3. N Doping to ZnO Nanorods for Photoelectrochemical Water Splitting under Visible Light: Engineered Impurity Distribution and Terraced Band Structure

    NASA Astrophysics Data System (ADS)

    Wang, Meng; Ren, Feng; Zhou, Jigang; Cai, Guangxu; Cai, Li; Hu, Yongfeng; Wang, Dongniu; Liu, Yichao; Guo, Liejin; Shen, Shaohua

    2015-08-01

    Solution-based ZnO nanorod arrays (NRAs) were modified with controlled N doping by an advanced ion implantation method, and were subsequently utilized as photoanodes for photoelectrochemical (PEC) water splitting under visible light irradiation. A gradient distribution of N dopants along the vertical direction of ZnO nanorods was realized. N doped ZnO NRAs displayed a markedly enhanced visible-light-driven PEC photocurrent density of ~160 μA/cm2 at 1.1 V vs. saturated calomel electrode (SCE), which was about 2 orders of magnitude higher than pristine ZnO NRAs. The gradiently distributed N dopants not only extended the optical absorption edges to visible light region, but also introduced terraced band structure. As a consequence, N gradient-doped ZnO NRAs can not only utilize the visible light irradiation but also efficiently drive photo-induced electron and hole transfer via the terraced band structure. The superior potential of ion implantation technique for creating gradient dopants distribution in host semiconductors will provide novel insights into doped photoelectrode materials for solar water splitting.

  4. N Doping to ZnO Nanorods for Photoelectrochemical Water Splitting under Visible Light: Engineered Impurity Distribution and Terraced Band Structure

    PubMed Central

    Wang, Meng; Ren, Feng; Zhou, Jigang; Cai, Guangxu; Cai, Li; Hu, Yongfeng; Wang, Dongniu; Liu, Yichao; Guo, Liejin; Shen, Shaohua

    2015-01-01

    Solution-based ZnO nanorod arrays (NRAs) were modified with controlled N doping by an advanced ion implantation method, and were subsequently utilized as photoanodes for photoelectrochemical (PEC) water splitting under visible light irradiation. A gradient distribution of N dopants along the vertical direction of ZnO nanorods was realized. N doped ZnO NRAs displayed a markedly enhanced visible-light-driven PEC photocurrent density of ~160 μA/cm2 at 1.1 V vs. saturated calomel electrode (SCE), which was about 2 orders of magnitude higher than pristine ZnO NRAs. The gradiently distributed N dopants not only extended the optical absorption edges to visible light region, but also introduced terraced band structure. As a consequence, N gradient-doped ZnO NRAs can not only utilize the visible light irradiation but also efficiently drive photo-induced electron and hole transfer via the terraced band structure. The superior potential of ion implantation technique for creating gradient dopants distribution in host semiconductors will provide novel insights into doped photoelectrode materials for solar water splitting. PMID:26262752

  5. Structural and optical properties of ZnO nanorods by electrochemical growth using multi-walled carbon nanotube-composed seed layers.

    PubMed

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

    2012-01-05

    We reported the enhancement of the structural and optical properties of electrochemically synthesized zinc oxide [ZnO] nanorod arrays [NRAs] using the multi-walled carbon nanotube [MWCNT]-composed seed layers, which were formed by spin-coating the aqueous seed solution containing MWCNTs on the indium tin oxide-coated glass substrate. The MWCNT-composed seed layer served as the efficient nucleation surface as well as the film with better electrical conductivity, thus leading to a more uniform high-density ZnO NRAs with an improved crystal quality during the electrochemical deposition process. For ZnO NRAs grown on the seed layer containing MWCNTs (2 wt.%), the photoluminescence peak intensity of the near-band-edge emission at a wavelength of approximately 375 nm was enhanced by 2.8 times compared with that of the ZnO nanorods grown without the seed layer due to the high crystallinity of ZnO NRAs and the surface plasmon-meditated emission enhancement by MWCNTs. The effect of the MWCNT-composed seed layer on the surface wettability was also investigated.PACS: 81.07.-b; 81.16.-c; 81.07.Pr; 61.48.De.

  6. Hydrothermal fabrication of ZnO nanorod-based grating patterns with arrays of optical fiber cores as templates

    NASA Astrophysics Data System (ADS)

    Jing, Wei-Xuan; Cheng, Yan-Yan; Qi, Han; Jiang, Zhuang-De; Zhou, Fan; Shi, Jia-Fan; Gao, Kun

    2015-06-01

    A hydrothermal fabrication of ZnO nanorod-based grating patterns on Si substrates is reported. The arrays of optical fiber cores were manually assembled as templates with nominal pitches of 250 μm and 375 μm. The profiles of the templates and the grating patterns were extracted and quantitatively characterized based on micrographs of scanning electron microscopy (SEM) and Image Processing Toolbox of MATLAB. The errors of the actual pitches and the parallelism demonstrate that the process capability of manually assembling the optical fiber cores can meet the quality requirement of the templates. The critical dimensions (CDs) show that the size of the trough formed by the template and the Si substrate determines the location of the grating pattern. The characteristic parameters, including line edge roughness (LER), line width roughness (LWR), skewness (Sk), kurtosis (Ku), and correlation length (ζ), exhibit that the three-phase contact lines among the trapped air bubble, ZnO seed solution, and Si substrate (or the optical fiber core) decide the form of the grating pattern. The research found that larger nominal pitch of the template resulted in larger size of the trough which further led to less CD, and higher hydrophilicity of the Si surfaces resulted in smoother profiles whilst lower hydrophilicity of the optical fiber core surfaces led to rougher ones.

  7. Efficient Donor Impurities in ZnO Nanorods by Polyethylene Glycol for Enhanced Optical and Glutamate Sensing Properties

    PubMed Central

    Elhag, Sami; Khun, Kimleang; Khranovskyy, Volodymyr; Liu, Xianjie; Willander, Magnus; Nur, Omer

    2016-01-01

    In this paper, we show that the possibility of using polyethylene glycol (EG) as a hydrogen source and it is used to assist the hydrothermal synthesis of ZnO nanorods (ZNRs). EG doping in ZNRs has been found to significantly improve their optical and chemical sensing characteristics toward glutamate. The EG was found to have no role on the structural properties of the ZNRs. However, the x-ray photoelectron spectroscopy (XPS) suggests that the EG could induce donor impurities effect in ZnO. Photoluminescence (PL) and UV-Vis. spectra demonstrated this doping effect. Mott-Schottky analysis at the ZNRs/electrolyte interface was used to investigate the charge density for the doped ZNRs and showed comparable dependence on the used amount of EG. Moreover, the doped ZNRs were used in potentiometric measurements for glutamate for a range from 10−6 M to 10−3 M and the potential response of the sensor electrode was linear with a slope of 91.15 mV/decade. The wide range and high sensitivity of the modified ZNRs based glutamate biosensor is attributed to the doping effect on the ZNRs that is dictated by the EG along with the high surface area-to-volume ratio. The findings in the present study suggest new avenues to control the growth of n-ZnO nanostructures and enhance the performance of their sensing devices. PMID:26861342

  8. Synergistic Effect of Surface Plasmonic particles and Surface Passivation layer on ZnO Nanorods Array for Improved Photoelectrochemical Water Splitting

    NASA Astrophysics Data System (ADS)

    Liu, Yichong; Yan, Xiaoqin; Kang, Zhuo; Li, Yong; Shen, Yanwei; Sun, Yihui; Wang, Li; Zhang, Yue

    2016-07-01

    One-dimensional zinc oxide nanorods array exhibit excellent electron mobility and thus hold great potential as photoanode for photoelelctrochemical water splitting. However, the poor absorption of visible light and the prominent surface recombination hider the performance improvement. In this work, Au nanoparticles and aluminium oxide were deposited onto the surface of ZnO nanorods to improve the PEC performance. The localized surface plasmon resonance of Au NPs could expand the absorption spectrum to visible region. Simultaneously, the surface of passivation with Au NPs and Al2O3 largely suppressed the photogenerated electron-hole recombination. As a result, the optimal solar-to-hydrogen efficiency of ZnO/Au/Al2O3 with 5 cycles was 6.7 times that of pristine ZnO, ascribed to the synergistic effect of SPR and surface passivation. This research reveals that the synergistic effect could be used as an important method to design efficient photoanodes for photoelectrochemical devices.

  9. Arginine-assisted immobilization of silver nanoparticles on ZnO nanorods: an enhanced and reusable antibacterial substrate without human cell cytotoxicity

    NASA Astrophysics Data System (ADS)

    Agnihotri, Shekhar; Bajaj, Geetika; Mukherji, Suparna; Mukherji, Soumyo

    2015-04-01

    Silver-based hybrid nanomaterials are gaining interest as potential alternatives for conventional antimicrobial agents. Herein, we present a simple, facile and eco-friendly approach for the deposition of silver nanoparticles (AgNPs) on ZnO nanorods, which act as a nanoreactor for in situ synthesis and as an immobilizing template in the presence of arginine. The presence of arginine enhanced the stability of ZnO deposition on the glass substrate by hindering the dissolution of zinc under alkaline conditions. Various Ag/ZnO hybrid nanorod (HNR) samples were screened to obtain a high amount of silver immobilization on the ZnO substrate. Ag/ZnO HNRs displayed potent antibacterial ability and could achieve 100% kill for both Escherichia coli and Bacillus subtilis strains under various test conditions. The hybrid material mediated its dual mode of antibacterial action through direct contact-killing and release of silver ions/nanoparticles and showed superior bactericidal performance compared to pure ZnO nanorods and colloidal AgNPs. No significant decline in antibacterial efficacy was observed even after the same substrate was repeatedly reused multiple times. Interestingly, the amount of Ag and Zn release was much below their maximal limit in drinking water, thus preventing potential health hazards. Immobilized AgNPs showed no cytotoxic effects on the human hepatocarcinoma cell line (HepG2). Moreover, treating cells with the antibacterial substrate for 24 hours did not lead to significant generation of reactive oxygen species (ROS). The good biocompatibility and bactericidal efficacy would thus make it feasible to utilize this immobilization strategy for preparing new-generation antibacterial coatings.Silver-based hybrid nanomaterials are gaining interest as potential alternatives for conventional antimicrobial agents. Herein, we present a simple, facile and eco-friendly approach for the deposition of silver nanoparticles (AgNPs) on ZnO nanorods, which act as a

  10. Influence of Growth Time and Temperature on the Morphology of ZnO Nanorods via Hydrothermal

    NASA Astrophysics Data System (ADS)

    Shaziman, Syahirah; Syakirin Ismail@rosdi, Ahmad; Hafiz Mamat, Mohamad; Sabirin Zoolfakar, Ahmad

    2015-11-01

    This research investigates the effect of temperature and growth duration on the morphology of ZnO. ZnO nanostructure can be synthesized via hydrothermal method using Zinc Acetate and hexamethylenetetramine (HMT) as precursor and glass slide as a substrate. The temperature and growth time vary from 50-95 °C and 50-100 minutes, respectively. The substrates with ZnO nanostructures are annealed at different temperatures which are 200°C and 500°C. The result indicates that different temperature and growth time produces different morphologies in size. Thus, the morphology of ZnO nanostructure affects by the parameters such as temperature and growth time via hydrothermal grown.

  11. Enhanced Photocatalytic Performance of ZnO Nanorods Coupled by Two-Dimensional α-MoO3 Nanoflakes under UV and Visible Light Irradiation.

    PubMed

    Hang, Da-Ren; Sharma, Krishna Hari; Chen, Chun-Hu; Islam, Sk Emdadul

    2016-08-26

    We exploit the utilization of two-dimensional (2D) molybdenum oxide nanoflakes as a co-catalyst for ZnO nanorods (NRs) to enhance their photocatalytic performance. The 2D nanoflakes of orthorhombic α-MoO3 were synthesized through a sonication-aided exfoliation technique. The 2D MoO3 nanoflakes can be further converted to substoichiometric quasi-metallic MoO3-x by using UV irradiation. Subsequently, 1D-2D MoO3 /ZnO NR and MoO3-x /ZnO NR composite photocatalysts have been successfully synthesized. The photocatalytic performances of the novel nanosystems in the decomposition of methylene blue are studied by using UV- and visible-illumination setup. The incorporated 2D nanoflakes show a positive influence on the photocatalytic activity of the ZnO. The obtained rate constant values follow the order of pristine ZnO NRZnO NRZnO NR composites. The enhancement of the photocatalytic efficiency can be ascribed to a fast charge carrier separation and transport within the heterojunctions of the MoO3 /ZnO NRs. In particular, the best photocatalytic performance of the MoO3-x /ZnO NR composite can be additionally attributed to a quasi-metallic conductivity and substoichiometry-induced mid-gap states, which extend the light absorption range. A tentative photocatalytic degradation mechanism was proposed. The strategy presented in this work not only demonstrates that coupling with nanoscale molybdenum oxide nanoflakes is a promising approach to significantly enhance the photocatalytic activity of ZnO but also hints at new type of composite catalyst with extended applications in energy conversion and environmental purification.

  12. Anisotropic growth and formation mechanism investigation of 1D ZnO nanorods in spin-coating sol-gel process.

    PubMed

    Song, Yijian; Zheng, Maojun; Ma, Li; Shen, Wenzhong

    2010-01-01

    ZnO nanorods are fabricated on glass substrate by spin-coating sol-gel process using non-basic aged solution and annealing. Sample solutions reserved in room temperature for different time (one day, one month, two months and four months) are prepared for the experiment. The morphology study indicates that the aging time has direct influence on the final products. This is verified by the Transmission Electron Microscopy and Photon Correlation Spectroscopy study. Small crystalline nanoparticles would gradually nucleate and aggregate in the sol during the aging process. They act as nucleation site for the secondary crystal growth into nanorods during anneal. Both the size of crystalline particles in the sol and the size of nanorods will grow bigger as the aging time increases. The products' structure and optical property are further studied by X-ray diffraction spectroscopy, Photoluminescence and Raman spectroscopy. This work also helps to further clarify the formation mechanism of ZnO nanorods by solution-based method.

  13. High quality interconnected core/shell ZnO nanorod architectures grown by pulsed laser deposition on ZnO-seeded Si substrates

    NASA Astrophysics Data System (ADS)

    Inguva, Saikumar; Vijayaraghavan, Rajani K.; McGlynn, Enda; Mosnier, Jean-Paul

    2017-01-01

    We report the production of vertically aligned and interconnected ZnO core/shell nanorods using pulsed laser deposition (PLD) in a continuous two-step growth process. X-ray diffraction studies showed wurtzite structure and c-axis orientation with a high degree of verticality. Scanning electron microscopy showed a characteristic interconnection morphology between the nanorod tips uniformly present over the entire sample surface area, while transmission electron microscopy revealed crystalline core/amorphous shell architecture. Strong bands at 98.7 cm-1 and 437.2 cm-1 (wurtzite ZnO low and high non-polar E2 modes) were the main features of the nanorod Raman spectra, again showing the high sample quality. Low-temperature PL data exhibited strong I6 emission and structured green band showing high optical quality. Electrical studies indicated n-type material with ohmic behaviour. The results are discussed in the context of the advantages offered by interconnected architectures of core/shell ZnO nanostructures for various applications.

  14. Enhancement of the Luminescence of ZnO Nanorod Arrays by SILAR Coating with a CdS Nanocrystalline Shell Layer

    NASA Astrophysics Data System (ADS)

    Krishnaveni, M.; Devadason, Suganthi

    2015-02-01

    ZnO/CdS core/shell-type nanorod arrays (NRAs) have been synthesized by a simple chemical method. The thickness of the CdS shell layers was controlled by varying the number of successive ionic layer adsorption and reaction cycles. X-ray diffraction analysis revealed the ZnO had a hexagonal crystal structure and the CdS had a cubic crystal structure. High-resolution transmission electron microscopy revealed that a highly conforming CdS shell layer ˜5 nm thick had been deposited on the ZnO nanorods. High-resolution scanning electron microscopy revealed the presence of hexagonal ZnO nanorods entirely coated with a nanocrystalline CdS shell. The ultraviolet-visible-near infrared absorption spectra of the films were red shifted and the calculated optical energy band gap decreased from 3.25 to 2.46 eV with progressive increase of CdS shell layer thickness. Photoluminescence spectra revealed enhancement of the near-band-edge emission centered at 380 nm of the ZnO NRAs after coating with the CdS shell layer. The observed shift in deep level emissions from yellow to green in the ZnO/CdS core/shell heterostructures has been explained. The measured electrical resistivity of bare ZnO and ZnO/CdS core/shell NRAs was 5.43 × 10-3 Ω cm and 1.25 × 10-3 Ω cm, respectively, when the films were illuminated with visible light.

  15. Effect of Cobalt Concentration and Oxygen Vacancy on Magnetism of Co Doped ZnO Nanorods.

    PubMed

    Li, Congli; Che, Ping; Sun, Changyan; Li, Wenjun

    2016-03-01

    Zn(1-x)Co(x)O (x = 0-0.07) single-crystalline nanorods were prepared by a modified microemulsion route. The crystalline structure, morphology, optical, and hysteresis loop at low and room temperature of as-prepared materials were characterized by XRD, TEM, PL spectra, and magnetic measurement respectively. The nanorods are 80-250 nm in diameter and about 3 μm in length. X-ray diffraction data, TEM images confirm that the materials synthesized in optimal conditions are ZnO:Co single crystalline solid solution without any impurities related to Co. The PL spectra show that the ferromagnetic samples exhibit strong Zn interstitials and oxygen vacancy emission indicating defects may stabilize ferromagnetic order in the obtained diluted magnetic semiconductors. Magnetic measurements show that the Zn(1-x)Co(x)O nanorods exist obvious ferromagnetic characteristics with T(c) above 300 K. M(s) and coercivities first increase and then decrease with dopant concentration increasing, reaching the highest for 3% doping level. The structural and magnetic properties of these samples support the hypothesis that the FM of DMS nanorods is due to a defect mediated mechanism instead of cobalt nanoclusters and carrier mediated.

  16. Vertically aligned ZnO nanorod grown by hydrothermal based chemical method on glass substrate

    NASA Astrophysics Data System (ADS)

    Srivastava, R.; Majumdar, S.; Bhunia, S.

    2012-06-01

    A low-temperature and effective precursor-based method has been demonstrated to synthesize nanostructured ZnO. It is found that the morphology of ZnO precursors has a strong dependence on the reaction conditions that include the molar ratio of reagents, solvent, and reaction temperature. In this work, ZnO nanostructures were synthesized via hydrothermal based chemical method. Zinc acetate dehydrate [Zn(Ac)2 2H2O] and 1-propanol(C3H8O) were adopted for a seed layer growth on glass substrate via spin coating technique. Zinc nitrate hexahydrate [Zn(NO3)2 6H2O], hexamethylenetetramine(C6H12N4) and diethylamine(C4H11N) were adopted as synthesis precursors. The ZnO nanostructures obtained were characterized by scanning electronic microscopy (SEM) and the PL method. The SEM image of the sample showed that the thin film of ZnO on glass substrate has, predominantly, a nanometric rod-like morphology with hexagonal wurtzite structure.

  17. Electrochemical Synthesis of ZnO Nanorods/Nanotubes/Nanopencils on Transparent Aluminium-Doped Zinc Oxide Thin Films for Photocatalytic Applications.

    PubMed

    Le, Thi Ngoc Tu; Pham, Tan Thi; Ngo, Quang Minh; Vu, Thi Hanh Thu

    2015-09-01

    We report an electrochemical synthesis of homogeneous and well-aligned ZnO nanorods (NRs) on transparent conducting aluminium-doped zinc oxide (AZO) thin films as electrodes. The selected ZnO NRs was then chemically corroded in HCl and KCl aqueous solutions to form nanopencils (NPs), and nanotubes (NTs), respectively. A DC magnetron sputtering was employed to fabricate AZO thin films at various thicknesses. The obtained AZO thin films have a c-direction orientation, transmittance above 80% in visible region, and sheet resistance approximately 40 Ω/sq. They are considered to be relevant as electrodes and seeding layers for electrochemical. The ZnO NRs are directly grown on the AZOs without a need of catalysts or additional seeding layers at temperature as low as 85 degrees C. Their shapes are strongly associated with the AZO thickness that provides a valuable way to control the diameter of ZnO NRs grown atop. With the addition of HCI and KCl aqueous solutions, ZnO NRs were modified their shape to NPs and NTs with the reaction time, respectively. All the ZnO NRs, NPs, and NTs are preferred to grow along c-direction that indicates a lattice matching between AZO thin films and ZnO nanostructrures. Photoluminescence spectra and XRD patterns show that they have good crystallinities. A great photocatalytic activity of ZnO nanostructures promises potential application in environmental treatment and protection. The ZnO NTs exhibits a higher photocatalysis than others possibly due to the oxygen vacancies on the surface and the polarizability of Zn2+ and O2-.

  18. Room temperature synthesis of needle-shaped ZnO nanorods via sonochemical method

    NASA Astrophysics Data System (ADS)

    Wahab, Rizwan; Ansari, S. G.; Kim, Young-Soon; Seo, Hyung-Kee; Shin, Hyung-Shik

    2007-07-01

    Single crystalline needle-shaped zinc oxide nanorods were synthesized via sonochemical methods using zinc acetate dihydrate and sodium hydroxide at room temperature. Morphological investigation revealed that the nanoneedles are of hexagonal surfaces along the length. The typical diameter and length vary from 120 to 160 nm and 3 to 5 μm, respectively. Sonication time appears to be a critical parameter for the shape determination. Detailed structural characterization confirmed that the nanorods are single crystalline with wurtzite hexagonal phase. A standard peak of zinc oxide was observed at 520 cm -1 from the Fourier transform infrared spectroscopy. The ultra-violet visible and room temperature photoluminescence (PL) spectroscopic results demonstrate that the synthesized material has good optical properties.

  19. Fabrication of fluoroalkylsilane modified ZnO nanorod films for electrode protection of electrophoretic displays.

    PubMed

    Li, Zhengyuan; Meng, Xianwei; Tang, Fangqiong

    2011-11-01

    The electrode protection has gained importance because of its positive robust role for the long term display quality of electrophoretic displays. A simple method of zinc oxide nanorod films prepared by electrochemical deposition and coupling with fluoroalkylsilane (FAS) is introduced to fabricate electrode protection films for Indium Tin Oxide (ITO) electrodes. The surface microstructures of zinc oxide films were characterized by scanning electron microscopy, showing a regular nanorods array. After treated by FAS the surface showed extremely low surface free energy with a water contact angle of 148.0 +/- 2.0 degrees. The settlement of pigments was considerably reduced according to the reflectance measurement by ultraviolet spectrophotometer. A weight experiment further confirmed that 90% of the pigment conglutination was prevented by the surface modification. This research can provide an economical approach to improve reliability and long-term image quality of the electrophoretic displays.

  20. Nanoscale interface engineering in ZnO twin nanorods for proposed phonon tunnel devices.

    PubMed

    Singh, Avanendra; Senapati, Kartik; Satpati, Biswarup; Kumar, Mohit; Sahoo, Pratap K

    2015-02-14

    Zinc oxide twin nanorods, with two identical crystalline sections connected by an amorphous layer, were reproducibly grown using a simple one-step hydrothermal technique. The thickness of the amorphous layer between the crystalline segments was tunable with growth parameters, as confirmed by high resolution transmission electron microscopy. The photoluminescence spectra of these twin nanorods exhibit strong near band edge emission in the UV range, with convoluted phonon sidebands. De-convolution analyses of these spectra showed that the amorphous interlayers act as effective phonon barriers beyond a certain thickness. Such oriented grown individual crystalline-amorphous-crystalline structures may be a suitable test system for fundamental studies of phonon tunneling in the nanostructure. While physical vapor deposition techniques are seriously constrained in realizing crystalline-amorphous-crystalline structures, our results show the viability of engineering embedded interfaces via chemical routes.

  1. Strong adsorption of Al-doped carbon nanotubes toward cisplatin

    NASA Astrophysics Data System (ADS)

    Li, Wei; Li, Guo-Qing; Lu, Xiao-Min; Ma, Juan-Juan; Zeng, Peng-Yu; He, Qin-Yu; Wang, Yin-Zhen

    2016-08-01

    The adsorption of cisplatin molecule on Al-doped CNTs is investigated using density functional theory. The obtained results indicate that Al-doped carbon nanotubes can strongly absorb cisplatin. After absorbing cisplatin, the symmetry of CNTs has some changes. We innovatively defined a parameter of symmetry variation which relates to the adsorption. By analyzing the electronic structure, it can be concluded that under the circumstance that cisplatin was absorbed by Al-doped CNTs through aluminum atom of Al-doped CNTs. In conclusion, Al-doped CNTs is a kind of potential delivery carrier with high quality for anticancer drug cisplatin.

  2. Arginine-assisted immobilization of silver nanoparticles on ZnO nanorods: an enhanced and reusable antibacterial substrate without human cell cytotoxicity.

    PubMed

    Agnihotri, Shekhar; Bajaj, Geetika; Mukherji, Suparna; Mukherji, Soumyo

    2015-04-28

    Silver-based hybrid nanomaterials are gaining interest as potential alternatives for conventional antimicrobial agents. Herein, we present a simple, facile and eco-friendly approach for the deposition of silver nanoparticles (AgNPs) on ZnO nanorods, which act as a nanoreactor for in situ synthesis and as an immobilizing template in the presence of arginine. The presence of arginine enhanced the stability of ZnO deposition on the glass substrate by hindering the dissolution of zinc under alkaline conditions. Various Ag/ZnO hybrid nanorod (HNR) samples were screened to obtain a high amount of silver immobilization on the ZnO substrate. Ag/ZnO HNRs displayed potent antibacterial ability and could achieve 100% kill for both Escherichia coli and Bacillus subtilis strains under various test conditions. The hybrid material mediated its dual mode of antibacterial action through direct contact-killing and release of silver ions/nanoparticles and showed superior bactericidal performance compared to pure ZnO nanorods and colloidal AgNPs. No significant decline in antibacterial efficacy was observed even after the same substrate was repeatedly reused multiple times. Interestingly, the amount of Ag and Zn release was much below their maximal limit in drinking water, thus preventing potential health hazards. Immobilized AgNPs showed no cytotoxic effects on the human hepatocarcinoma cell line (HepG2). Moreover, treating cells with the antibacterial substrate for 24 hours did not lead to significant generation of reactive oxygen species (ROS). The good biocompatibility and bactericidal efficacy would thus make it feasible to utilize this immobilization strategy for preparing new-generation antibacterial coatings.

  3. Texture vs morphology in ZnO nano-rods: On the x-ray diffraction characterization of electrochemically grown samples

    NASA Astrophysics Data System (ADS)

    Ariosa, D.; Elhordoy, F.; Dalchiele, E. A.; Marotti, R. E.; Stari, C.

    2011-12-01

    Texture characterization in thin films from standard powder x-ray diffraction (XRD) rely on the comparison between observed peak relative intensities with those of powder diffraction standards of the same compound, trough the so-called texture coefficient (TC). While these methods apply for polycrystalline materials with isotropic grains, they are less accurate—and even wrong—for anisotropic materials like ZnO oriented single-crystal nano-rods, which would require the use of dedicated XRD texture setups. By using simple geometrical considerations, we succeed in discriminating between texture and morphology contributions to the observed intensity ratios in powder diffraction patterns. On this basis, we developed a method that provides a quantitative determination of both texture (polar distribution) and morphology (aspect ratio of nano-rods), using simple x-ray powder diffraction. The method is illustrated on a typical sample from a series of Zinc oxide (ZnO) nano-rod arrays grown onto a gold thin film sputtered onto a F:SnO2-coated glass substrate (FTO) by using cathodic electro-deposition. In order to check the consistency of our method, we confronted our findings with scanning electron microscope (SEM) images, grazing incidence diffraction (GID), and XRD pole-figures of the same sample. Nevertheless, the proposed method is self-consistent and only requires the use of a standard powder diffractometer, nowadays available in most solid-state laboratories.

  4. Sensitive electrochemiluminescence detection for CA15-3 based on immobilizing luminol on dendrimer functionalized ZnO nanorods.

    PubMed

    Jiang, Xinya; Wang, Haijun; Yuan, Ruo; Chai, Yaqin

    2015-01-15

    In this study, we constructed a novel electrochemiluminescence (ECL) immunosensor for sensitive and selective detection of carbohydrate antigen 15-3 (CA15-3) by using polyamidoamine (PAMAM)-functionalized ZnO nanorods (ZNs-PAMAM) as carriers. PAMAM dendrimers with hyper-branched and three-dimensional structure were used as linked reagents for co-immobilization of luminol and CA15-3 detection antibody on the ZNs to prepare the signal probe. In addition, ZNs could hasten the decomposition of H2O2 to generate various reactive oxygen species (ROSs) which accelerated the ECL reaction of luminol with amplified ECL intensity. Compared with luminol in the detection solution, the ECL efficiencies of luminol could be improved by immobilizing luminol on the electrode due to the smaller distance between luminescence reagent and the electrode surface. Moreover, the electrodepositing gold nanoparticles (AuNPs) on the bare glass carbon electrode (GCE) with enhanced surface area could capture a large amount of primary anti-CA15-3 to improve the sensitivity of the immunosensor. Under the optimized experimental conditions, a wide linear range of 0.1-120 U mL(-1) was acquired with a relatively low detection limit of 0.033 U mL(-1) (S/N=3) for CA15-3.

  5. Monolayer graphene film on ZnO nanorod array for high-performance Schottky junction ultraviolet photodetectors.

    PubMed

    Nie, Biao; Hu, Ji-Gang; Luo, Lin-Bao; Xie, Chao; Zeng, Long-Hui; Lv, Peng; Li, Fang-Ze; Jie, Jian-Sheng; Feng, Mei; Wu, Chun-Yan; Yu, Yong-Qiang; Yu, Shu-Hong

    2013-09-09

    A new Schottky junction ultraviolet photodetector (UVPD) is fabricated by coating a free-standing ZnO nanorod (ZnONR) array with a layer of transparent monolayer graphene (MLG) film. The single-crystalline [0001]-oriented ZnONR array has a length of about 8-11 μm, and a diameter of 100∼600 nm. Finite element method (FEM) simulation results show that this novel nanostructure array/MLG heterojunction can trap UV photons effectively within the ZnONRs. By studying the I-V characteristics in the temperature range of 80-300 K, the barrier heights of the MLG film/ZnONR array Schottky barrier are estimated at different temperatures. Interestingly, the heterojunction diode with typical rectifying characteristics exhibits a high sensitivity to UV light illumination and a quick response of millisecond rise time/fall times with excellent reproducibility, whereas it is weakly sensitive to visible light irradiation. It is also observed that this UV photodetector (PD) is capable of monitoring a fast switching light with a frequency as high as 2250 Hz. The generality of the above results suggest that this MLG film/ZnONR array Schottky junction UVPD will have potential application in future optoelectronic devices.

  6. Electrocatalytic Behavior of Hemoglobin Oxidation of Hydrazine Based on ZnO Nano-rods with Carbon Nanofiber Modified Electrode.

    PubMed

    Wu, Min; Ding, Wen; Meng, Junli; Ni, Henmei; Li, Ying; Ma, Quanhong

    2015-01-01

    A novel biosensor was developed by immobilizing hemoglobin (Hb) on a glassy carbon electrode (GCE) modified with a composite of ZnO nano-rods and carbon nanofiber (CNF), a strong reducer, hydrazine, was firstly used to evaluate the electrochemical behavior of Hb on Hb/ZnO/CNF/GCE. UV-vis and circular dichroism (CD) spectra indicated the conformational structure of Hb interaction with ZnO/CNF was predominantly an α-helical structure. The modified electrodes were characterized by scanning electron microscopy (SEM), electron impedance spectroscopy (EIS), and cyclic voltammetry. Electrocatalytic mechanism of Hb to oxidation reaction of hydrazine was suggested. The bioelectrocatalytic activity, kinetic parameters of Michaelis-Menten constant (Km), stability and reproducibility were also investigated. A linear dependence of peak currents to the concentrations of hydrazine was observed in the range from 1.98 × 10(-5) to 1.71 × 10(-3) mol L(-1) with a correlation coefficient of 0.998, and a detection limit (S/N = 3) of 6.60 μmol L(-1) was estimated.

  7. ZnO nanorods prepared via ablation of Zn with millisecond laser in liquid media.

    PubMed

    Honda, Mitsuhiro; Goto, Taku; Owashi, Tatsuki; Rozhin, Alex G; Yamaguchi, Shigeru; Ito, Tsuyohito; Kulinich, Sergei A

    2016-09-14

    ZnO nanomaterials with controlled size, shape and surface chemistry are required for applications in diverse areas, such as optoelectronics, photocatalysis, biomedicine and so on. Here, we report on ZnO nanostructures with rod-like and spherical shapes prepared via laser ablation in liquid using a laser with millisecond-long pulses. By changing laser parameters (such as pulse width and peak power), the size or aspect ratio of such nanostructures could be tuned. The surface chemistry and defects of the products were also strongly affected by applied laser conditions. The preparation of different structures is explained by the intense heating of liquid media caused by millisecond-long pulses and secondary irradiation of already-formed nanostructures.

  8. Optical and structural properties of electrochemically deposited ZnO nanorod arrays suitable for improvement of the light harvesting in thin film solar cells

    NASA Astrophysics Data System (ADS)

    Petrov, M.; Lovchinov, K.; Mews, M.; Leendertz, C.; Dimova-Malinovska, D.

    2014-11-01

    The results of study of the optical and structural properties of ZnO nanorods (NR) arrays electrochemically deposited on two type substrates - the ITO surface on the front side of Si heterojunction (SHJ) solar cells and on stainless steel plate used for formation of a-Si:H thin film solar cells, are reported. The surface morphology of the NS arrays is examined by Scanning Electron Microscopy and AFM. The spectra of specular diffused and total reflection, and haze ratio in reflectance are compared before and after deposition of the ZnO NR arrays. In the case of deposition on ITO surface of SHJ solar cells the values of the direct and diffused reflection of the ZnO NR array decrease demonstrating good antireflection properties. Deposition of ZnO NS arrays on stainless steel plates leads to increasing the values of the diffused reflection and the total reflectance. Possible application of ZnO NS structures for the processing of advanced Si based solar cells for increasing light harvesting is discussed.

  9. Development and characterization of a novel ZnO nanorods-SnO2:F nanoflakes thin film for room-temperature ammonia and humidity sensing

    NASA Astrophysics Data System (ADS)

    Calaque, Precy Mae; Vergara, Christopher Jude; Ballesteros, Laureen Ida; Somintac, Armando

    2017-03-01

    A unique and novel thin film of fluorine-doped tin oxide (SnO2:F) nanoflakes on ZnO nanorods were fabricated using nebulized spray pyrolysis technique (NSPT) and hydrothermal growth method, respectively, for ammonia and humidity sensing applications. XRD studies confirm the growth of a hexagonal wurtzite ZnO and a tetragonal SnO2:F. SEM images of the film fabricated for preliminary studies evidently revealed ZnO nanorods and SnO2:F nanoflakes. The response of the fabricated ZnO-SnO2:F nanostructure thin film sensor on varying concentrations of water vapor and ammonia at room temperature were investigated. Results have shown that it had higher sensor response to ammonia than to water vapor. Moreover, it was observed to have a higher sensor response on ammonia and humidity compared to the fabricated sensor of SnO2:F thin film alone. The films could detect humidity and ammonia even at a low level of 9 ppm and 5 ppm, respectively, showing its potential use for various fields such as environmental monitoring and chemical industries.

  10. Ag-doped ZnO nanorods coated metal wire meshes as hierarchical photocatalysts with high visible-light driven photoactivity and photostability.

    PubMed

    Hsu, Mu-Hsiang; Chang, Chi-Jung

    2014-08-15

    Ag-doped ZnO nanorods were grown on stainless-steel wire meshes to fabricate the hierarchical photocatalysts with excellent visible light driven activity and anti-photocorrosion property. Effects of Ag doping and the surface structure on the surface chemistry, surface wetting properties, absorption band shift, photoelectrochemical response, and photocatalytic decolorization properties of the hierarchical photocatalysts, together with the stability of photocatalytic activity for recycled photocatalysts were investigated. Ag doping leads to red-shift in the absorption band and increased visible light absorption. Nanorods coated wire meshes hierarchical structure not only increases the surface area of photocatalysts but also makes the surface hydrophilic. The photocatalytic activity enhancement and reduced photocorrosion can be achieved because of increased surface area, enhanced hydrophilicity, and the interaction between the metal wire/ZnO and Ag/ZnO heterostructure interface which can improve the charge separation of photogenerated charge carriers.

  11. Radiative mechanism and surface modification of four visible deep level defect states in ZnO nanorods

    NASA Astrophysics Data System (ADS)

    Barbagiovanni, E. G.; Reitano, R.; Franzò, G.; Strano, V.; Terrasi, A.; Mirabella, S.

    2015-12-01

    Visible luminescence from ZnO nanorods (NRs) is attracting large scientific interest for light emission and sensing applications. We study visible luminescent defects in ZnO NRs as a function of post growth thermal treatments, and find four distinct visible deep level defect states (VDLSs): blue (2.52 eV), green (2.23 eV), orange (2.03 eV), and red (1.92 eV). Photoluminescence (PL) studies reveal a distinct modification in the UV (3.25 eV) emission intensity and a shift in the visible spectra after annealing. Annealing at 600 °C in Ar (Ar600) and O2 (O600) causes a blue and red-shift in the visible emission band, respectively. All samples demonstrate orange emission from the core of the NR, with an additional surface related green, blue, and red emission in the As-Prep, Ar600, and O600 samples, respectively. From PL excitation (PLE) measurements we determine the onset energy for population of the various VDLSs, and relate it to the presence of an Urbach tail below the conduction band due to a presence of ionized Zni or Zni complexes. We measured an onset energy of 3.25 eV for the as prepared sample. The onset energy red-shifts in the annealed samples by about 0.05 to 0.1 eV indicating a change in the defect structure, which we relate to the shift in the visible emission. We then used X-ray photoemission spectroscopy (XPS), and elastic recoil detection analysis (ERDA) to understand changes in the surface structure, and H content, respectively. The results of the XPS and ERDA analysis explain how the chemical states are modified due to annealing. We summarize our results by correlating our VDLSs with specific intrinsic defect states to build a model for PL emission in ZnO NRs. These results are important for understanding how to control defect related visible emission for sensing and electroluminescence applications.Visible luminescence from ZnO nanorods (NRs) is attracting large scientific interest for light emission and sensing applications. We study visible

  12. Three-dimensional carbon cloth-supported ZnO nanorod arrays as a binder-free anode for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Huang, Lanyan; Wang, Xin; Yin, Fuxing; Zhang, Chengwei; Gao, Jinwei; Liu, Junming; Zhou, Guofu; Zhang, Yongguang; Bakenov, Zhumabay

    2017-02-01

    Three-dimensional ZnO nanorod arrays on flexible high surface area carbon cloth were successfully synthesized and directly used as negative electrodes for lithium-ion batteries without using any binder additive. The structure and morphology of the as-prepared hybrid ZnO electrode were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM). When tested as anodes in a lithium cell, the hybrid electrode demonstrated a high discharge capacity along with excellent rate capability and good cycling stability, delivering a reversible capacity of 891 mAh g-1 at the second cycle and retaining a capacity of 469 mAh g-1 after 100 cycles.

  13. Controllable electrodeposition of ZnO nanorod arrays on flexible stainless steel mesh substrate for photocatalytic degradation of Rhodamine B

    NASA Astrophysics Data System (ADS)

    Lu, Hui; Zhang, Mei; Guo, Min

    2014-10-01

    Well-aligned single-crystalline ZnO nanorod arrays (ZNRAs) were prepared on flexible stainless steel mesh (SSM) substrate in large-scale by using a direct electrodeposition method. The effects of electrochemical parameters, such as applied potential, applied nucleation potential time, substrate pretreatment, electrodeposition duration and times, on the orientation, morphology and density of ZNRAs were systematically studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM) and the selected area electron diffraction (SAED). The results showed that ZNRAs on SSM substrate with [0 0 1] preferred orientation and well crystallization were obtained by controlling the applied potential in the range of -0.9 to -1.1 V. The density of ZNRAs could be increased obviously by applying a nucleation potential (-1.3 V for more than 10 s before deposition) or by means of substrate pretreatment (the SSM immersed in zinc acetate colloid for more than 10 min before deposition), meanwhile, the deposited ZNRAs also had small average diameter (<46 ± 4 nm), narrow size distribution and good orientation. In addition, it was also found that the average diameter of ZNRAs could be increased from 89 to 201 ± 5 nm by extending the electrodeposition duration from 1800 to 7200 s, and the length of rods was from 0.8 to 2.2 ± 0.1 μm when the times of the electrodeposition from one to six times. Furthermore, the band gap energy (Eg) of as-prepared ZNTAs was not closely related to the electrodeposition times (only changed from 3.30 to 3.32 eV). The ZNRAs prepared with more electrodeposition times showed enhanced photocatalytic performance under the UV-lamp for degradation of Rhodamine B. The degradation efficiency of ZNRAs improved from 89.4% to 98.3% with the deposition times from one to six times.

  14. Indirect Determination of Mercury Ion by Inhibition of a Glucose Biosensor Based on ZnO Nanorods

    PubMed Central

    Chey, Chan Oeurn; Ibupoto, Zafar Hussain; Khun, Kimleang; Nur, Omer; Willander, Magnus

    2012-01-01

    A potentiometric glucose biosensor based on immobilization of glucose oxidase (GOD) on ZnO nanorods (ZnO-NRs) has been developed for the indirect determination of environmental mercury ions. The ZnO-NRs were grown on a gold coated glass substrate by using the low temperature aqueous chemical growth (ACG) approach. Glucose oxidase in conjunction with a chitosan membrane and a glutaraldehyde (GA) were immobilized on the surface of the ZnO-NRs using a simple physical adsorption method and then used as a potentiometric working electrode. The potential response of the biosensor between the working electrode and an Ag/AgCl reference electrode was measured in a 1mM phosphate buffer solution (PBS). The detection limit of the mercury ion sensor was found to be 0.5 nM. The experimental results provide two linear ranges of the inhibition from 0.5 × 10−6 mM to 0.5 × 10−4 mM, and from 0.5 × 10−4 mM to 20 mM of mercury ion for fixed 1 mM of glucose concentration in the solution. The linear range of the inhibition from 10−3 mM to 6 mM of mercury ion was also acquired for a fixed 10 mM of glucose concentration. The working electrode can be reactivated by more than 70% after inhibition by simply dipping the used electrode in a 10 mM PBS solution for 7 min. The electrodes retained their original enzyme activity by about 90% for more than three weeks. The response to mercury ions was highly sensitive, selective, stable, reproducible, and interference resistant, and exhibits a fast response time. The developed glucose biosensor has a great potential for detection of mercury with several advantages such as being inexpensive, requiring minimum hardware and being suitable for unskilled users. PMID:23202200

  15. Oriented ZnO nanorods grown on a porous polyaniline film as a novel coating for solid-phase microextraction.

    PubMed

    Zeng, Jingbin; Zhao, Cuiying; Chong, Fayun; Cao, Yingying; Subhan, Fazle; Wang, Qianru; Yu, Jianfeng; Zhang, Maosheng; Luo, Liwen; Ren, Wei; Chen, Xi; Yan, Zifeng

    2013-12-06

    In this work, oriented ZnO nanorods (ZNRs) were in situ hydrothermally grown on a porous polyaniline (PANI) film to function as a solid-phase microextraction (SPME) coating. Scanning electron microscopy (SEM) study revealed that the majority of oriented ZNRs grew from pores of PANI matrix, which protected the ZNRs from easily peeling off during operation. Furthermore, in this process, a thin layer of PANI was found to cover the ZNRs, which can enlarge the effective surface area of the composite coating. This ZNRs/PANI composite coating combined the merits of both ZNRs and PANI and, thus, has several advantages over that of sole PANI film and ZNRs coating such as improved extraction efficiency for benzene homologues, enhanced mechanical stability and longer service life (over 150 cycles of SPME-GC operation). Coupled with gas chromatography-flame ionization detector (GC-FID), the optimized SPME-GC-FID method was used for the analysis of six benzene homologues in water samples. The calibration curves were linear from 1 to 1000μgL(-1) for each analyte, and the limits of detection were between 0.001 and 0.024μgL(-1). Single fiber repeatability and fiber-to-fiber reproducibility were in the range of 1.3-6.8% and 5.3-11.2%, respectively. The spiked recoveries at 100 and 5μgL(-1) for three environmental water samples were in the range of 79.8-115.4% and 73.7-117.4%, respectively.

  16. Octadecyltrimethoxysilane functionalized ZnO nanorods as a novel coating for solid-phase microextraction with strong hydrophobic surface.

    PubMed

    Zeng, Jingbin; Liu, Haihong; Chen, Jinmei; Huang, Jianli; Yu, Jianfeng; Wang, Yiru; Chen, Xi

    2012-09-21

    In this paper, we have, for the first time, proposed an approach by combining self-assembled monolayers (SAMs) and nanomaterials (NMs) for the preparation of novel solid-phase microextraction (SPME) coatings. The self-assembly of octadecyltrimethoxysilane (OTMS) on the surface of ZnO nanorods (ZNRs) was selected as a model system to demonstrate the feasibility of this approach. The functionalization of OTMS on the surface of ZNRs was characterized and confirmed using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The OTMS-ZNRs coated fiber exhibited stronger hydrophobicity after functionalization, and its extraction efficiency for non-polar benzene homologues was increased by a factor of 1.5-3.6 when compared to a ZNRs fiber with almost identical thickness and façade. In contrast, the extraction efficiency of the OTMS-ZNRs coated fiber for polar aldehydes was 1.6-4.0-fold lower than that of the ZNRs coated fiber, further indicating its enhanced surface hydrophobicity. The OTMS-ZNRs coated fiber revealed a much higher capacity upon increasing the OTMS layer thickness to 5 μm, leading to a factor of 12.0-13.4 and 1.8-2.5 increase in extraction efficiency for the benzene homologues relative to a ZNRs coated fiber and a commercial PDMS fiber, respectively. The developed HS-SPME-GC method using the OTMS-ZNRs coated fiber was successfully applied to the determination of the benzene homologues in limnetic water samples with recovery ranging from 83 to 113% and relative standard deviations (RSDs) of less than 8%.

  17. Hydrothermally Grown In-doped ZnO Nanorods on p-GaN Films for Color-tunable Heterojunction Light-emitting-diodes

    PubMed Central

    Park, Geun Chul; Hwang, Soo Min; Lee, Seung Muk; Choi, Jun Hyuk; Song, Keun Man; Kim, Hyun You; Kim, Hyun-Suk; Eum, Sung-Jin; Jung, Seung-Boo; Lim, Jun Hyung; Joo, Jinho

    2015-01-01

    The incorporation of doping elements in ZnO nanostructures plays an important role in adjusting the optical and electrical properties in optoelectronic devices. In the present study, we fabricated 1-D ZnO nanorods (NRs) doped with different In contents (0% ~ 5%) on p-GaN films using a facile hydrothermal method, and investigated the effect of the In doping on the morphology and electronic structure of the NRs and the electrical and optical performances of the n-ZnO NRs/p-GaN heterojunction light emitting diodes (LEDs). As the In content increased, the size (diameter and length) of the NRs increased, and the electrical performance of the LEDs improved. From the electroluminescence (EL) spectra, it was found that the broad green-yellow-orange emission band significantly increased with increasing In content due to the increased defect states (oxygen vacancies) in the ZnO NRs, and consequently, the superposition of the emission bands centered at 415 nm and 570 nm led to the generation of white-light. These results suggest that In doping is an effective way to tailor the morphology and the optical, electronic, and electrical properties of ZnO NRs, as well as the EL emission property of heterojunction LEDs. PMID:25988846

  18. Enhanced photoelectrochemical performance of ZnO nanorod arrays decorated with CdS shell and Ag2S quantum dots

    NASA Astrophysics Data System (ADS)

    Holi, Araa Mebdir; Zainal, Zulkarnain; Talib, Zainal Abidin; Lim, Hong-Ngee; Yap, Chi-Chin; Chang, Sook-Keng; Ayal, Asmaa Kadim

    2017-03-01

    Ternary nanostructured Ag2S/CdS/ZnO thin film was prepared by using a simple low-cost hydrothermal method. The hexagonal phase of ZnO nanorods and CdS shells combined with monoclinic Ag2S quantum dots resulted in improved optical and photoelectrochemical properties. CdS shell with high absorption property efficiently compliment the energy levels of ZnO and improved the ability of light absorption. Furthermore, narrow band gap Ag2S also played a vital part in the light harvesting. The photoelectrochemical performance of the ternary nanostructured Ag2S/CdS/ZnO NRs was investigated in a mixture of Na2S and Na2SO3 aqueous solutions under visible light illumination. The Ag2S/CdS/ZnO NRs were found to be more efficient than ZnO NRs, CdS/ZnO NRs, and Ag2S/ZnO NRs as this particular sample gave a maximum photocurrent of 5.69 mA cm-2, which is around 2 and 1.5 times greater than CdS/ZnO NRs and Ag2S/ZnO NRs, respectively. Besides that, it was found that this ternary film possessed 15 times higher photocurrent density than plain ZnO NRs. This is attributed to the larger amount of visible light absorbed by the ternary nanostructured composite.

  19. Stabilization of organometal halide perovskite films by SnO2 coating with inactive surface hydroxyl groups on ZnO nanorods

    NASA Astrophysics Data System (ADS)

    Wang, Peng; Zhao, Jinjin; Liu, Jinxi; Wei, Liyu; Liu, Zhenghao; Guan, Lihao; Cao, Guozhong

    2017-01-01

    Perovskite solar cells have advanced rapid in the last few years, however the thermal instability of perovskite film on ZnO nanorods (NRs) remains a big challenge limiting its commercialization. The present work demonstrated effective suppression of the decomposition of CH3NH3PbI3 perovskite through inserting a thin tin oxide (SnO2) passivation layer between ZnO NRs and perovskite films. Although X-ray photoelectron spectroscopy (XPS) results showed no distinct difference in the amount of hydroxyl groups and oxygen vacancies on the surface of ZnO NRs and ZnO@SnO2 NRs, Raman spectra suggested the hydroxyl groups might be trapped in oxygen vacancies on SnO2 surface, preventing the decomposition of CH3NH3PbI3 perovskite through reacting with the hydroxyl groups. The power conversion efficiency of perovskite solar cells was significantly increased from 6.92% to 12.17% and became hysteresis-free by applying SnO2 passivating layer between perovskite and ZnO layers.

  20. Contact light-emitting diodes based on vertical ZnO nanorods

    NASA Astrophysics Data System (ADS)

    Panin, G. N.; Cho, Hak Dong; Lee, Sang Wuk; Kang, Tae Won

    2014-05-01

    We report vertical contact light-emitting diodes (VCLEDs), that are based on heterojunctions formed by using the point contacts of n-ZnO nanorods (NRs) to the p-type semiconductor substrate and that are fabricated using a new approach to the formation of LEDs (Appl. Phys. Lett. 98, 093110 (2011)). A p-type GaN film grown on a sapphire substrate was used to form n-ZnO NRs/p-GaN VCLEDs on a large area of about 4 cm2. The VCLEDs emitted a pure blue electroluminescence with high efficiency. Electroluminescence at 470 nm, which is visible to the naked eye, started at small current of about 50 μA and is attributed to the good optical properties of the structurallyperfect heterojunctions in the point contacts. The VCLED configuration allows the creation of ZnO/p-GaN nano-LEDs of high density and high-quality with a greatly reduced concentration of nonradiative defects in the active regions. The VCLEDs showed the high brightness of light required for active matrix displays and general solid-state lighting.

  1. The effect of deposition power on the electrical properties of Al-doped zinc oxide thin films

    SciTech Connect

    Chun, B. S.; Choi, Daniel S.; Wu, H. C.; Shvets, I. V.; Abid, M.; Chu, I. C.; Serrano-Guisan, S.

    2010-08-23

    We investigated the effect on the electronic properties of aluminum (Al)-zinc oxide (ZnO) films by modulating the radio frequency sputtering power. Our experimental results show that increasing the sputtering power increases the Al doping concentration, decreases the resistivity, and also shifts the Zn 2p and O 1s to higher binding energy states. Our local-density approximation (LDA) and LDA+U calculations show that the shift in higher binding energy and resistivity decrease are due to an enhancement of the O 2p-Zn 3d coupling and the modification of the Zn 4s-O 2p interaction in ZnO induced by Al doping.

  2. Synergistic Effect of Surface Plasmonic particles and Surface Passivation layer on ZnO Nanorods Array for Improved Photoelectrochemical Water Splitting

    PubMed Central

    Liu, Yichong; Yan, Xiaoqin; Kang, Zhuo; Li, Yong; Shen, Yanwei; Sun, Yihui; Wang, Li; Zhang, Yue

    2016-01-01

    One-dimensional zinc oxide nanorods array exhibit excellent electron mobility and thus hold great potential as photoanode for photoelelctrochemical water splitting. However, the poor absorption of visible light and the prominent surface recombination hider the performance improvement. In this work, Au nanoparticles and aluminium oxide were deposited onto the surface of ZnO nanorods to improve the PEC performance. The localized surface plasmon resonance of Au NPs could expand the absorption spectrum to visible region. Simultaneously, the surface of passivation with Au NPs and Al2O3 largely suppressed the photogenerated electron-hole recombination. As a result, the optimal solar-to-hydrogen efficiency of ZnO/Au/Al2O3 with 5 cycles was 6.7 times that of pristine ZnO, ascribed to the synergistic effect of SPR and surface passivation. This research reveals that the synergistic effect could be used as an important method to design efficient photoanodes for photoelectrochemical devices. PMID:27443692

  3. In situ plasma sputtering synthesis of ZnO nanorods-Ag nanoparticles hybrids and their application in non-enzymatic hydrogen peroxide sensing

    NASA Astrophysics Data System (ADS)

    Zhang, Dan; Zhang, Yuxia; Yang, Chi; Ge, Cunwang; Wang, Yuanhong; Wang, Hao; Liu, Hongying

    2015-08-01

    In this paper, ZnO nanorods-Ag nanoparticles hybrids were first synthesized via a facile, rapid, and in situ plasma sputtering method without using any silver precursor. The obtained materials were then characterized by scanning electron microscopy, high-resolution transmission electron microscopy, energy-dispersive x-ray spectroscopy, and cyclic voltammetry. Based on the electrochemical catalytic properties of the obtained nanohybrids, a non-enzymatic hydrogen peroxide biosensor was constructed by immobilizing the obtained ZnO nanorods-Ag nanoparticles hybrids on the surface of a glassy carbon electrode. Under optimal conditions, the resulting biosensor displayed a good response for H2O2 with a linear range of 0.2 to 12.8 mM, and a detection limit of 7.8 μM at a signal-to-noise ratio of 3. In addition, it exhibited excellent anti-interference ability and fast response. The current work provides a feasible platform to fabricate a variety of non-enzymatic biosensors.

  4. Facile synthesis and photocatalytic properties of ZnO core/ZnS-CdS solid solution shell nanorods grown vertically on reductive graphene oxide.

    PubMed

    Xu, Jimeng; Sang, Huanxin; Wang, Xitao; Wang, Kang

    2015-05-28

    In the present study, ZnS-CdS solid solution sensitized ZnO nanorods were anchored on graphene sheets by combining a hydrothermal process and ion exchange technique, and the significant influence of CdS content in the shell on photo absorption and photocatalytic performance were investigated. Electron microscopic images reveal that the as-prepared nanocomposites display a sandwich-like 3D structure, consisting of ZnO nanorods with a ZnxCd1-xS or CdS shell grown vertically on both sides of the graphene sheets. UV/Vis DRS shows that the solid solution sensitized nanocomposites have enhanced visible light absorption and also exhibited a red-shift of the band-edge as compared to RGO/ZnO and RGO/ZnO@ZnS. Fluorescence emission spectra indicate that the deposition of CdS on the shell with an appropriate CdS/ZnS ratio and the incorporation of graphene causes improved charge separation. The photocatalytic experiments demonstrate that the RGO/ZnO@ZnxCd1-xS nanocomposites possess much higher photocatalytic activity for H2 evolution than the RGO/ZnO nanorods and RGO/ZnO@ZnS core/shell nanorods. Under the irradiation of a 300 W Xe lamp, the highest photocatalytic hydrogen production rate of 1865 μmol h(-1) g(-1) is observed over the RGO/ZnO@Zn0.6Zn0.4S sample, which is about 2.1 and 1.4 times more active than RGO/ZnO and RGO/ZnO@ZnS, respectively. Under the irradiation of visible light (>420 nm), the RGO/ZnO and RGO/ZnO@ZnS nanorods are barely active, whereas RGO/ZnO@Zn0.6Zn0.4S displays a hydrogen production rate of 160 μmol h(-1) g(-1). The highly improved performance of the composites can be ascribed to the increased light absorption and efficient charge separation.

  5. Zn K edge and O K edge x-ray absorption spectra of ZnO surfaces: implications for nanorods.

    PubMed

    Šipr, O; Rocca, F

    2011-08-10

    Zn K edge and O K edge x-ray absorption near-edge structure (XANES) spectra of ZnO surfaces are calculated. The difference between theoretical XANES for ZnO surfaces and ZnO bulk is then compared to the earlier observed differences between experimental XANES for ZnO nanostructures and ZnO bulk as taken from the literature. It follows from our calculations that the differences between the experimental XANES of bulk ZnO and nanocrystalline ZnO is not due to the enhanced role of the surfaces in nanostructures. Rather, the difference in XANES has to reflect differences in the local geometry around the photoabsorbing sites. The dependence of XANES of ZnO surfaces on the polarization of the incoming radiation is also investigated theoretically and found to be similar as in the bulk.

  6. Piezoelectric and opto-electrical properties of silver-doped ZnO nanorods synthesized by low temperature aqueous chemical method

    SciTech Connect

    Nour, E. S. Echresh, A.; Willander, M.; Nur, O.; Liu, Xianjie; Broitman, E.

    2015-07-15

    In this paper, we have synthesized Zn{sub 1−x}Ag{sub x}O (x = 0, 0.03, 0.06, and 0.09) nanorods (NRs) via the hydrothermal method at low temperature on silicon substrate. The characterization and comparison between the different Zn{sub 1−x}Ag{sub x}O samples, indicated that an increasing Ag concentration from x = 0 to a maximum of x = 0.09; All samples show a preferred orientation of (002) direction with no observable change of morphology. As the quantity of the Ag dopant was changed, the transmittances, as well as the optical band gap were decreased. X-ray photoelectron spectroscopy data clearly indicate the presence of Ag in ZnO crystal lattice. A nanoindentation-based technique was used to measure the effective piezo-response of different concentrations of Ag for both direct and converse effects. The value of the piezoelectric coefficient (d{sub 33}) as well as the piezo potential generated from the ZnO NRs and Zn{sub 1−x}Ag{sub x}O NRs was found to decrease with the increase of Ag fraction. The finding in this investigation reveals that Ag doped ZnO is not suitable for piezoelectric energy harvesting devices.

  7. Piezoelectric and opto-electrical properties of silver-doped ZnO nanorods synthesized by low temperature aqueous chemical method

    NASA Astrophysics Data System (ADS)

    Nour, E. S.; Echresh, A.; Liu, Xianjie; Broitman, E.; Willander, M.; Nur, O.

    2015-07-01

    In this paper, we have synthesized Zn1-xAgxO (x = 0, 0.03, 0.06, and 0.09) nanorods (NRs) via the hydrothermal method at low temperature on silicon substrate. The characterization and comparison between the different Zn1-xAgxO samples, indicated that an increasing Ag concentration from x = 0 to a maximum of x = 0.09; All samples show a preferred orientation of (002) direction with no observable change of morphology. As the quantity of the Ag dopant was changed, the transmittances, as well as the optical band gap were decreased. X-ray photoelectron spectroscopy data clearly indicate the presence of Ag in ZnO crystal lattice. A nanoindentation-based technique was used to measure the effective piezo-response of different concentrations of Ag for both direct and converse effects. The value of the piezoelectric coefficient (d33) as well as the piezo potential generated from the ZnO NRs and Zn1-xAgxO NRs was found to decrease with the increase of Ag fraction. The finding in this investigation reveals that Ag doped ZnO is not suitable for piezoelectric energy harvesting devices.

  8. Efficiency Enhancement of Quantum Dot Sensitized TiO2/ZnO Nanorod Arrays Solar Cells by Plasmonic Ag Nanoparticles.

    PubMed

    Zhao, Haifeng; Huang, Fei; Hou, Juan; Liu, Zhiyong; Wu, Qiang; Cao, Haibin; Jing, Qun; Peng, Shanglong; Cao, Guozhong

    2016-10-12

    A high efficiency quantum dot sensitized solar cell (QDSC) based on Ag nanoparticles (NPs) decorated TiO2/ZnO nanorod arrays (NAs) photoelectrode has been constructed. The incorporation of Ag NPs to TiO2/ZnO NAs photoelectrode not only increases light harvesting efficiency and facilitates exciton dissociation but also decreases surface charge recombination and prolongs electron lifetime, which collectively contribute to improving the Jsc of the CdS/CdSe QDs cosensitized solar cells. The direct contact of Ag NPs with TiO2 NPs is undergoing Fermi level alignment; thus, the apparent Fermi level is supposed to trigger an upward shift of more negative potential, which results in an increase the Voc of the QDSCs. As a result, the power conversion efficiency of the QDSCs with Ag NPs decorated TiO2/ZnO NAs photoelectrode reached 5.92%, which is about 22% enhancement of the efficiency for the solar cells without Ag NPs (4.80%).

  9. ZnO nanorod arrays and direct wire bonding on GaN surfaces for rapid fabrication of antireflective, high-temperature ultraviolet sensors

    NASA Astrophysics Data System (ADS)

    So, Hongyun; Senesky, Debbie G.

    2016-11-01

    Rapid, cost-effective, and simple fabrication/packaging of microscale gallium nitride (GaN) ultraviolet (UV) sensors are demonstrated using zinc oxide nanorod arrays (ZnO NRAs) as an antireflective layer and direct bonding of aluminum wires to the GaN surface. The presence of the ZnO NRAs on the GaN surface significantly reduced the reflectance to less than 1% in the UV and 4% in the visible light region. As a result, the devices fabricated with ZnO NRAs and mechanically stable aluminum bonding wires (pull strength of 3-5 gf) showed higher sensitivity (136.3% at room temperature and 148.2% increase at 250 °C) when compared with devices with bare (uncoated) GaN surfaces. In addition, the devices demonstrated reliable operation at high temperatures up to 300 °C, supporting the feasibility of simple and cost-effective UV sensors operating with higher sensitivity in high-temperature conditions, such as in combustion, downhole, and space exploration applications.

  10. Sputtering deposition of Al-doped zinc oxide thin films using mixed powder targets

    NASA Astrophysics Data System (ADS)

    Ohshima, Tamiko; Maeda, Takashi; Tanaka, Yuki; Kawasaki, Hiroharu; Yagyu, Yoshihito; Ihara, Takeshi; Suda, Yoshiaki

    2016-01-01

    Sputtering deposition generally uses high-density bulk targets. Such a fabrication process has various problems including deterioration of the material during heating and difficulty in mixing a large number of materials in precise proportions. However, these problems can be solved by using a powder target. In this study, we prepared Al-doped ZnO (AZO) as transparent conductive thin films by radio-frequency magnetron sputtering with powder and bulk targets. Both the powder and bulk targets formed crystalline structures. The ZnO (002) peak was observed in the X-ray diffraction measurements. The mean transparency and resistivity of the films prepared with the powder target were 82% and 0.548 Ω · cm, respectively. The deposition rate with the powder target was lower than that with the bulk target.

  11. Study of NBE emission enhancement with an absence of DL emission from ZnO nanorods through controlled growth on ultra-thin Ag films

    NASA Astrophysics Data System (ADS)

    Pal, Anil Kumar; Bharathi Mohan, D.

    2015-04-01

    ZnO nanorods (NRs) exhibiting enhanced ultra-violet near band edge (UV-NBE) emission without a broad visible deep level (DL) emission has been investigated on catalytically grown ZnO/Ag hybrid nanostructure. The hybrid structure is fabricated in two steps, (1) Thermal evaporation of ultra-thin catalytic layer of Ag with mass thickness ∼1 nm on glass substrate followed by annealing process from 50 to 250 °C and (2) vertical growth of ZnO NRs by hydrothermal reaction process on all Ag films. The surface properties of Ag layer such as particle size, inter-particle distance, particles number density, surface roughness and surface coverage area were altered through annealing process. Annealing at 100 °C modifies Ag from quasi-amorphous to nanocrystalline leading to high density growth and high aspect ratio of ZnO NRs where as a random and less density growth was realized at 250 °C due to increase of both particle size and inter-particles distance in Ag layer. X-ray diffraction reveals a predominant growth of (0 0 2) plane at 100 °C confirming the formation of wurtzite phase of ZnO NRs with highest texture coefficient of 2.35. Raman spectra verify the chemical structure of ZnO with very good crystallinity. Absorption spectra demonstrates the overlapping of surface plasmon resonance (SPR) and exciton bands up to 200 °C while the excitonic absorption band is resolved at above 200 °C because of the red shift in SPR due to change in surface properties of Ag layer. At 250 °C, a broad optical absorption spectra from 300 to 800 nm attributed to the dominant properties of SPR and exciton. Besides acting as a catalyst, Ag interlayer enhances the NBE emission at above 200 °C through electrons transfer from Ag to ZnO which is quite possible because of the direct contact between them, explained by giving energy band diagram. The morphology is such that there is an increase in passage for light interaction due to less density and random growth of ZnO NRs leading to increase

  12. Solvothermal Preparation of ZnO Nanorods as Anode Material for Improved Cycle Life Zn/AgO Batteries

    PubMed Central

    Ullah, Shafiq; Ahmed, Fiaz; Badshah, Amin; Ali Altaf, Ataf; Raza, Ramsha; Lal, Bhajan; Hussain, Rizwan

    2013-01-01

    Nano materials with high surface area increase the kinetics and extent of the redox reactions, thus resulting in high power and energy densities. In this study high surface area zinc oxide nanorods have been synthesized by surfactant free ethylene glycol assisted solvothermal method. The nanorods thus prepared have diameters in the submicron range (300∼500 nm) with high aspect ratio. They have uniform geometry and well aligned direction. These nanorods are characterized by XRD, SEM, Specific Surface Area Analysis, solubility in alkaline medium, EDX analysis and galvanostatic charge/discharge studies in Zn/AgO batteries. The prepared zinc oxide nanorods have low solubility in alkaline medium with higher structural stability, which imparts the improved cycle life stability to Zn/AgO cells. PMID:24146807

  13. Solvothermal preparation of ZnO nanorods as anode material for improved cycle life Zn/AgO batteries.

    PubMed

    Ullah, Shafiq; Ahmed, Fiaz; Badshah, Amin; Ali Altaf, Ataf; Raza, Ramsha; Lal, Bhajan; Hussain, Rizwan

    2013-01-01

    Nano materials with high surface area increase the kinetics and extent of the redox reactions, thus resulting in high power and energy densities. In this study high surface area zinc oxide nanorods have been synthesized by surfactant free ethylene glycol assisted solvothermal method. The nanorods thus prepared have diameters in the submicron range (300 ~ 500 nm) with high aspect ratio. They have uniform geometry and well aligned direction. These nanorods are characterized by XRD, SEM, Specific Surface Area Analysis, solubility in alkaline medium, EDX analysis and galvanostatic charge/discharge studies in Zn/AgO batteries. The prepared zinc oxide nanorods have low solubility in alkaline medium with higher structural stability, which imparts the improved cycle life stability to Zn/AgO cells.

  14. The influence of annealing temperature on the interface and photovoltaic properties of CdS/CdSe quantum dots sensitized ZnO nanorods solar cells.

    PubMed

    Qiu, Xiaofeng; Chen, Ling; Gong, Haibo; Zhu, Min; Han, Jun; Zi, Min; Yang, Xiaopeng; Ji, Changjian; Cao, Bingqiang

    2014-09-15

    Arrays of ZnO/CdS/CdSe core/shell nanocables with different annealing temperatures have been investigated for CdS/CdSe quantum dots sensitized solar cells (QDSSCs). CdS/CdSe quantum dots were synthesized on the surface of ZnO nanorods that serve as the scaffold via a simple ion-exchange approach. The uniform microstructure was verified by scanning electron microscope and transmission electron microscope. UV-Visible absorption spectrum and Raman spectroscopy analysis indicated noticeable influence of annealing temperature on the interface structural and optical properties of the CdS/CdSe layers. Particularly, the relationship between annealing temperatures and photovoltaic performance of the corresponding QDSSCs was investigated employing photovoltaic conversion, quantum efficiency and electrochemical impedance spectra. It is demonstrated that higher cell efficiency can be obtained by optimizing the annealing temperature through extending the photoresponse range and improving QD layer crystal quality.

  15. Central composite design and genetic algorithm applied for the optimization of ultrasonic-assisted removal of malachite green by ZnO Nanorod-loaded activated carbon.

    PubMed

    Ghaedi, M; Azad, F Nasiri; Dashtian, K; Hajati, S; Goudarzi, A; Soylak, M

    2016-10-05

    Maximum malachite green (MG) adsorption onto ZnO Nanorod-loaded activated carbon (ZnO-NR-AC) was achieved following the optimization of conditions, while the mass transfer was accelerated by ultrasonic. The central composite design (CCD) and genetic algorithm (GA) were used to estimate the effect of individual variables and their mutual interactions on the MG adsorption as response and to optimize the adsorption process. The ZnO-NR-AC surface morphology and its properties were identified via FESEM, XRD and FTIR. The adsorption equilibrium isotherm and kinetic models investigation revealed the well fit of the experimental data to Langmuir isotherm and pseudo-second-order kinetic model, respectively. It was shown that a small amount of ZnO-NR-AC (with adsorption capacity of 20mgg(-1)) is sufficient for the rapid removal of high amount of MG dye in short time (3.99min).

  16. Central composite design and genetic algorithm applied for the optimization of ultrasonic-assisted removal of malachite green by ZnO Nanorod-loaded activated carbon

    NASA Astrophysics Data System (ADS)

    Ghaedi, M.; Azad, F. Nasiri; Dashtian, K.; Hajati, S.; Goudarzi, A.; Soylak, M.

    2016-10-01

    Maximum malachite green (MG) adsorption onto ZnO Nanorod-loaded activated carbon (ZnO-NR-AC) was achieved following the optimization of conditions, while the mass transfer was accelerated by ultrasonic. The central composite design (CCD) and genetic algorithm (GA) were used to estimate the effect of individual variables and their mutual interactions on the MG adsorption as response and to optimize the adsorption process. The ZnO-NR-AC surface morphology and its properties were identified via FESEM, XRD and FTIR. The adsorption equilibrium isotherm and kinetic models investigation revealed the well fit of the experimental data to Langmuir isotherm and pseudo-second-order kinetic model, respectively. It was shown that a small amount of ZnO-NR-AC (with adsorption capacity of 20 mg g- 1) is sufficient for the rapid removal of high amount of MG dye in short time (3.99 min).

  17. Unusual Rectifying Response of Nanojunctions Using Randomly Oriented Nanorods (RON) of ZnO Irradiated with 80-MeV Oxygen Ions

    NASA Astrophysics Data System (ADS)

    Bayan, Sayan; Mohanta, Dambarudhar

    2012-07-01

    The present work highlights the improved Schottky behavior of Ag/ZnO nanojunctions which make use of unirradiated and 80-MeV oxygen ion (O6+) irradiated randomly oriented ZnO nanorods. While leakage current is apparently low, the rectifying nature of the nanojunctions was clearly evident from room-temperature current-voltage ( I- V) measurements. In case of use of irradiated nanorods, the Schottky barrier height ( ϕ B) of the Ag/ZnO nanojunctions was found to be enhanced from 0.78 eV to 0.95 eV along with decrease of the ideality factor ( η) from 17.7 to 6.9. This is ascribed to reorganization and modification of the native defect states via creation and annihilation events as revealed by photoluminescence spectroscopy. The fluence-dependent variation of ϕ B and η was assigned to competition among donor and acceptor types of defects. The current transport mechanism of the Schottky contacts was found to be dominated by trap-assisted recombination tunneling and space charge-limited conduction in the mobility and ballistic regime.

  18. Preparation and photoelectrocatalytic activity of ZnO nanorods embedded in highly ordered TiO(2) nanotube arrays electrode for azo dye degradation.

    PubMed

    Zhang, Zhonghai; Yuan, Yuan; Liang, Linhong; Cheng, Yuxiao; Shi, Guoyue; Jin, Litong

    2008-10-30

    In this article, the ZnO nanorods embedded in highly ordered TiO(2) nanotube arrays (ZnO/TiO(2) NR/Ts) electrodes were fabricated through two steps: (1) electrosynthesis of TiO(2) nanotube arrays (TiO(2) NTs) in HF solution by anodization method; (2) followed by cathodic electrodeposition of ZnO embedded in the TiO(2) nanotube arrays. The morphological characteristics and structures of ZnO/TiO(2) NR/Ts electrodes were examined by field-emission scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDX) spectroscopy, X-ray diffraction (XRD) analysis, and UV-vis spectra. The linear-sweep photovoltammetry response on the ZnO/TiO(2) NR/Ts electrode was presented and the photocurrent was dramatically enhanced on the ZnO/TiO(2) NR/Ts electrode, comparing with that on bare TiO(2) NTs electrode. The photocatalytic and photoelectrocatalytic activity of ZnO/TiO(2) NR/Ts electrode was evaluated in degradation of methyl orange (MO) in aqueous solution.

  19. A flexible field-limited ordered ZnO nanorod-based self-powered tactile sensor array for electronic skin.

    PubMed

    Deng, W; Jin, L; Zhang, B; Chen, Y; Mao, L; Zhang, H; Yang, W

    2016-09-15

    A tactile sensor is an essential component for realizing biomimetic robots, while the flexibility of the tactile sensor is a pivotal feature for its application, especially for electronic skin. In this work, a flexible self-powered tactile sensor array was designed based on the piezoelectricity of ZnO nanorods (NRs). The field-limited ordered ZnO NRs were synthesized on a flexible Kapton substrate to serve as the functional layer of the tactile sensor. The electrical output performances of the as-fabricated tactile sensor were measured under pressing and bending forces. Moreover, we measured the human-finger pressure detection performance of the tactile sensor array, suggesting that the corresponding mapping figure of finger pressure could be displayed on the monitor of a personal computer (PC) in the form of lighted LED and color density through a LabVIEW system. This as-grown sensory feedback system should be of potential valuable assistance for the users of hand prostheses to reduce the risk and obtain a greater feeling of using the prostheses.

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

    NASA Astrophysics Data System (ADS)

    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.

  1. Arrays of ZnO nanorods decorated with Au nanoparticles as surface-enhanced Raman scattering substrates for rapid detection of trace melamine

    NASA Astrophysics Data System (ADS)

    Yi, Zao; Yi, Yong; Luo, Jiangshan; Li, Xibo; Xu, Xibin; Jiang, Xiaodong; Yi, Yougen; Tang, Yongjian

    2014-10-01

    In this paper, as a new, highly sensitive and uniform hybrid surface-enhanced Raman scattering (SERS) substrate, arrays of ZnO nanorods (ZnO-NRs) decorated with Au nanoparticles (Au-NPs) have been prepared. This hybrid substrate manifests high SERS sensitivity to melamine and a detection limit as low as 1.0×10-10 M (1.26 μg L-1). A maximum enhancement factor of 1.0×109 can be obtained with the ZnO NF-Au (sample 2) film. Au-NPs gaps in the array can create lots of SERS “hot spots” that mainly contribute to the high SERS sensitivity. Moreover, the supporting chemical enhancement effect of ZnO-NRs and the better enrichment effect ascribed to the large surface area of the substrate also help to achieve a lower detection limit. The promising advantages of easy sample pretreatment, short detection time and low cost makes the arrays of ZnO-NRs decorated with Au-NPs substrate a potential detection tool in the field of food safety.

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

    PubMed Central

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

    2017-01-01

    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 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. PMID:28155879

  3. Annealing effects on the optical and morphological properties of ZnO nanorods on AZO substrate by using aqueous solution method at low temperature.

    PubMed

    Hang, Da-Ren; Islam, Sk Emdadul; Sharma, Krishna Hari; Kuo, Shiao-Wei; Zhang, Cheng-Zu; Wang, Jun-Jie

    2014-01-01

    Vertically aligned ZnO nanorods (NRs) on aluminum-doped zinc oxide (AZO) substrates were fabricated by a single-step aqueous solution method at low temperature. In order to optimize optical quality, the effects of annealing on optical and structural properties were investigated by scanning electron microscopy, X-ray diffraction, photoluminescence (PL), and Raman spectroscopy. We found that the annealing temperature strongly affects both the near-band-edge (NBE) and visible (defect-related) emissions. The best characteristics have been obtained by employing annealing at 400°C in air for 2 h, bringing about a sharp and intense NBE emission. The defect-related recombinations were also suppressed effectively. However, the enhancement decreases with higher annealing temperature and prolonged annealing. PL study indicates that the NBE emission is dominated by radiative recombination associated with hydrogen donors. Thus, the enhancement of NBE is due to the activation of radiative recombinations associated with hydrogen donors. On the other hand, the reduction of visible emission is mainly attributed to the annihilation of OH groups. Our results provide insight to comprehend annealing effects and an effective way to improve optical properties of low-temperature-grown ZnO NRs for future facile device applications.

  4. Outstanding H2 sensing performance of Pd nanoparticle-decorated ZnO nanorod arrays and the temperature-dependent sensing mechanisms.

    PubMed

    Chang, Chia-Ming; Hon, Min-Hsiung; Leu, Ing-Chi

    2013-01-01

    The nearly monodispersed Pd nanoparticles with controllable density on ZnO nanorod arrays were prepared by the unique PVP-mediated photochemical deposition (PCD). The changes in morphology and dispersion of Pd on ZnO surface are ascribed to the stabilizing property and self-assembly characteristic of PVP being exploited during PCD. There are three temperature-dependent H(2) sensing mechanisms in those Pd/ZnO NRs, including general oxygen adsorption/desorption mode within 200-300 °C, surface conductivity mode at 60-120 °C and palladium hydride (PdH(x)) formation at room temperature, which causes a significant discrepancy in sensitivity variations as a function of Pd density. It is also verified that the electronic sensitization related to the transition of Pd(2+)/Pd(0) redox couple predominates the promoting mechanism in Pd/ZnO NRs used for sensing H(2) at 200-300 °C. Therefore, the gas sensitivity to 500 ppm H(2) of Pd/ZnO NRs can be significantly improved by around 553-fold (S, R(a)/R(g) = 1106) at 260 °C through decorating an adequate amount of discrete Pd nanoparticles instead of the Pd clusters, moreover, the corresponding sensitivity at room temperature is 16.9 that is superior to some promising devices reported in the literatures.

  5. Plasmon enhanced CdS-quantum dot sensitized solar cell using ZnO nanorods array deposited with Ag nanoparticles as photoanode

    NASA Astrophysics Data System (ADS)

    Eskandari, M.; Ahmadi, V.; Yousefi rad, M.; Kohnehpoushi, S.

    2015-04-01

    CdS-quantum dot sensitized solar cell using ZnO nanorods (ZnO NRs) array deposited with Ag nanoparticles (Ag NPs) as photoanode was fabricated. Light absorption effect of Ag NPs on improvement of the cell performance was investigated. Performance improvement of metal nanoparticles (MNPs) was controlled by the structure design and architecture. Different decorations and densities of Ag NPs were utilized on the photoanode. Results showed that using 5% Ag NPs in the photoanode results in the increased efficiency, fill factor, and circuit current density from 0.28% to 0.60%, 0.22 to 0.29, and 2.18 mA/cm2 to 3.25 mA/cm2, respectively. Also, incident photon-to-current efficiencies (IPCE) results showed that cell performance improvement is related to enhanced absorption in the photoanode, which is because of the surface plasmonic resonance and light scattering of Ag NPs in the photoanode. Measurements of electrochemical impedance spectroscopy revealed that hole transfer kinetics increases with introduction of Ag NPs into photoanode. Also, it is shown that chemical capacitance increases with introduction of Ag NPs. Such increase can be attributed to the surface palsmonic resonance of Ag NPs which leads to absorption of more light in the photoanode and generation of more photoelectron in the photoanode.

  6. Local photoelectric conversion properties of titanyl-phthalocyanine (TiOPc) coated aligned ZnO nanorods.

    PubMed

    Heng, Liping; Tian, Dongliang; Chen, Long; Su, Junxin; Zhai, Jin; Han, Dong; Jiang, Lei

    2010-02-21

    The direct electrical pathway for rapid collection of charge carriers generated in aligned TiOPc/ZnO nanorod is visualized by using photoconductive atomic force microscopy (pc-AFM), which can provide theoretical guidance for preparing high efficiency solar cells.

  7. Seesawed fluorescence nano-aptasensor based on highly vertical ZnO nanorods and three-dimensional quantitative fluorescence imaging for enhanced detection accuracy of ATP.

    PubMed

    Shrivastava, Sajal; Triet, Nguyen Minh; Son, Young-Min; Lee, Won-Il; Lee, Nae-Eung

    2017-04-15

    Probe-mediated fluorescence biosensing methods based on spectrophotometry still have limitations such as detection inaccuracy caused by the occurrence of false signals and lack of simultaneous qualitative and quantitative read-outs with an ultra-low detection limit. Herein, we describe a novel seesawed fluorescence detection strategy based on dual-colour imaging-based quantitation in which the green fluorescence of the capture aptamer decreases and the red fluorescence of the detection aptamer increases simultaneously upon their respective interactions with the target biomolecule. This approach enhances detection accuracy through facilitating identification of probable false-positives in biological samples. Furthermore, combining the seesawed detection scheme with three-dimensional imaging of fluorescence signal enhanced by highly vertical ZnO nanorods increases signal-to-noise ratio, which addresses the limited performance of digital cameras and, in turn, enhances sensitivity and dynamic range. This simple, robust, scalable, imaging-based and label-free fluorescence method allows highly specific and sensitive quantification of biomolecules with excellent reliability.

  8. One-step solvothermal deposition of ZnO nanorod arrays on a wood surface for robust superamphiphobic performance and superior ultraviolet resistance.

    PubMed

    Yao, Qiufang; Wang, Chao; Fan, Bitao; Wang, Hanwei; Sun, Qingfeng; Jin, Chunde; Zhang, Hong

    2016-10-24

    In the present paper, uniformly large-scale wurtzite-structured ZnO nanorod arrays (ZNAs) were deposited onto a wood surface through a one-step solvothermal method. The as-prepared samples were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetry (TG), and differential thermal analysis (DTA). ZNAs with a diameter of approximately 85 nm and a length of approximately 1.5 μm were chemically bonded onto the wood surface through hydrogen bonds. The superamphiphobic performance and ultraviolet resistance were measured and evaluated by water or oil contact angles (WCA or OCA) and roll-off angles, sand abrasion tests and an artificially accelerated ageing test. The results show that the ZNA-treated wood demonstrates a robust superamphiphobic performance under mechanical impact, corrosive liquids, intermittent and transpositional temperatures, and water spray. Additionally, the as-prepared wood sample shows superior ultraviolet resistance.

  9. Synthesis of ZnO nanorods and their application in the construction of a nanostructure-based electrochemical sensor for determination of levodopa in the presence of carbidopa.

    PubMed

    Molaakbari, Elahe; Mostafavi, Ali; Beitollahi, Hadi; Alizadeh, Reza

    2014-09-07

    A novel carbon paste electrode modified with ZnO nanorods and 5-(4'-amino-3'-hydroxy-biphenyl-4-yl)-acrylic acid (3,4'-AAZCPE) was fabricated. The electrochemical study of the modified electrode, as well as its efficiency for the electrocatalytic oxidation of levodopa, is described. The electrode was employed to study the electrocatalytic oxidation of levodopa, using cyclic voltammetry (CV), chronoamperometry (CHA), and square-wave voltammetry (SWV) as diagnostic techniques. It has been found that the oxidation of levodopa at the surface of the modified electrode occurs at a potential of about 370 mV less positive than that of an unmodified carbon paste electrode. The SWV results exhibit a linear dynamic range from 1.0 × 10(-7) M to 7.0 × 10(-5) M and a detection limit of 3.5 × 10(-8) M for levodopa. In addition, this modified electrode was used for the simultaneous determination of levodopa and carbidopa. Finally, the modified electrode was used for the determination of levodopa and carbidopa in some real samples.

  10. High performance of Mn-doped CdSe quantum dot sensitized solar cells based on the vertical ZnO nanorod arrays

    NASA Astrophysics Data System (ADS)

    Hou, Juan; Zhao, Haifeng; Huang, Fei; Jing, Qun; Cao, Haibin; Wu, Qiang; Peng, Shanglong; Cao, Guozhong

    2016-09-01

    Doping transition metal ions Mn2+ to semiconductor quantum dots (QDs) are extremely interesting for the development of photovoltaic devices. Quantum dot sensitized solar cells (QDSCs) are able to show promising power conversion efficiencies (PCE) by employing Mn2+ doped QDs. Herein we achieve effective CdS/Mnsbnd CdSe/ZnS QDs co-sensitized vertical ZnO nanorod arrays film that provides an appreciable enhancement in photovoltaic performance. The measured PCE of the solar cells with Mn2+ doped CdSe QDs is 4.14%, which is higher than the efficiency of 2.91% for the solar cells without Mn2+ or a ∼42% increase. The improvement in PCE is ascribed to a higher open-circuit voltage (Voc = 0.74 V) and a superior short-circuit current density (Jsc = 12.6 mA cm-2) with the introduction of Mn2+ into CdSe QDs. The enhancement seen with Mn2+ doped CdSe QDs are investigated and explained by the fact that the enhanced light absorption and reduced charge recombination by the formation of Mnsbnd CdSe passivation layer covering the QDs.

  11. One-step solvothermal deposition of ZnO nanorod arrays on a wood surface for robust superamphiphobic performance and superior ultraviolet resistance

    PubMed Central

    Yao, Qiufang; Wang, Chao; Fan, Bitao; Wang, Hanwei; Sun, Qingfeng; Jin, Chunde; Zhang, Hong

    2016-01-01

    In the present paper, uniformly large-scale wurtzite-structured ZnO nanorod arrays (ZNAs) were deposited onto a wood surface through a one-step solvothermal method. The as-prepared samples were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetry (TG), and differential thermal analysis (DTA). ZNAs with a diameter of approximately 85 nm and a length of approximately 1.5 μm were chemically bonded onto the wood surface through hydrogen bonds. The superamphiphobic performance and ultraviolet resistance were measured and evaluated by water or oil contact angles (WCA or OCA) and roll-off angles, sand abrasion tests and an artificially accelerated ageing test. The results show that the ZNA-treated wood demonstrates a robust superamphiphobic performance under mechanical impact, corrosive liquids, intermittent and transpositional temperatures, and water spray. Additionally, the as-prepared wood sample shows superior ultraviolet resistance. PMID:27775091

  12. Simple chemical aqueous synthesis of dahlia nanoflower consisting of finger-like ZnO nanorods and observation of stable ultraviolet photoluminescence emission

    NASA Astrophysics Data System (ADS)

    Chakraborty, S.; Tiwary, C. S.; Kumbhakar, P.

    2015-03-01

    In this work, we have reported the synthesis of dahlia flower-like ZnO nanostructures consisting of human finger-like nanorods by the hydrothermal method at 120 °C and without using any capping agent. Optical properties of the samples, including UV-vis absorption and photoluminescence (PL) emission characteristics are determined by dispersing the samples in water as well as in ethanol media. The quenching of PL emission intensity along-with the red shifting of the PL emission peak are observed when the samples are dispersed in water in comparison to those obtained after dispersing the samples in ethanol. It has been found that PL emission characteristic, particularly the spectral nature of PL emission, of the samples remains almost unaltered (except some improvement in UV PL emission) even after thermally annealing it for 2 h at the temperature of 300 °C. Also the synthesized powder samples, kept in a plastic container, showed a very stable PL emission even after 15 months of synthesis. Therefore, the synthesized samples might be useful for their applications in future optoelectronics devices.

  13. Fabrication and characterization of novel semolina-based antimicrobial films derived from the combination of ZnO nanorods and nanokaolin.

    PubMed

    Jafarzadeh, Shima; Alias, Abd Karim; Ariffin, Fazilah; Mahmud, Shahrom; Najafi, Ali; Ahmad, Mehraj

    2017-01-01

    This study aimed to provide novel biopolymer-based antimicrobial films as food packaging that may assist in reducing environmental pollution caused by the accumulation of synthetic food packaging. The blend of ZnO nanorods (ZnO-nr) and nanokaolin in different ratios (1:4, 2:3, 3:2 and 4:1) was incorporated into semolina, and nanocomposite films were prepared using solvent casting. The resulting films were characterized through field-emission scanning electron microscopy and X-ray diffraction. The mechanical, optical, physical, and antimicrobial properties of the films were also analyzed. The water vapor permeability of the films decreased with increasing ZnO-nr percentage, but their tensile strength and modulus of elasticity increased with increasing nanokaolin percentage. The UV transmittance of the semolina films were greatly influenced by an increase in the amount of ZnO-nr. The addition of ZnO-nr: nanokaolin at all ratios (except 1:4) into semolina reduced UV transmission to almost 0%. Furthermore, the ZnO-nr/nanokaolin/semolina films exhibited a strong antimicrobial activity against Staphylococcus aureus. These properties suggest that the combination of ZnO-nr and nanokaolin are potential fillers in semolina-based films to be used as active packaging for food and pharmaceuticals.

  14. Multiplexed enzyme-free electrochemical immunosensor based on ZnO nanorods modified reduced graphene oxide-paper electrode and silver deposition-induced signal amplification strategy.

    PubMed

    Sun, Guoqiang; Zhang, Lina; Zhang, Yan; Yang, Hongmei; Ma, Chao; Ge, Shenguang; Yan, Mei; Yu, Jinghua; Song, Xianrang

    2015-09-15

    Herein, an origami multiplexed enzyme-free electrochemical (EC) immunodevice is developed for the first time. Typically, ZnO nanorods (ZNRs) modified reduced graphene oxide (rGO)-paper electrode is used as a sensor platform, in which rGO improves the electronic transmission rate and ZNRs provide abundant sites for capture probes binding. Furthermore, by combining the large surface area of rGO and high catalytic activity of bovine serum protein (BSA)-stabilized silver nanoparticles (Ag@BSA) toward H2O2 reduction, rGO/Ag@BSA composites can be used as an excellent signal labels. The current signal is generated from the reduction of H2O2 and further amplified by a subsequent signal labels-promoted deposition of silver. Under optimal conditions, the proposed immunoassays exhibit excellent precision, high sensitivity and a wide linear range of 0.002-120 mIU mL(-1) for human chorionic gonadotropin, 0.001-110 ng mL(-1) for prostate-specific antigen, and 0.001-100 ng mL(-1) for carcinoembryonic antigen. The results for real sample analysis demonstrate that the newly constructed immunosensor arrays provide a simple and cost-effective method for clinical applications.

  15. One-step solvothermal deposition of ZnO nanorod arrays on a wood surface for robust superamphiphobic performance and superior ultraviolet resistance

    NASA Astrophysics Data System (ADS)

    Yao, Qiufang; Wang, Chao; Fan, Bitao; Wang, Hanwei; Sun, Qingfeng; Jin, Chunde; Zhang, Hong

    2016-10-01

    In the present paper, uniformly large-scale wurtzite-structured ZnO nanorod arrays (ZNAs) were deposited onto a wood surface through a one-step solvothermal method. The as-prepared samples were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetry (TG), and differential thermal analysis (DTA). ZNAs with a diameter of approximately 85 nm and a length of approximately 1.5 μm were chemically bonded onto the wood surface through hydrogen bonds. The superamphiphobic performance and ultraviolet resistance were measured and evaluated by water or oil contact angles (WCA or OCA) and roll-off angles, sand abrasion tests and an artificially accelerated ageing test. The results show that the ZNA-treated wood demonstrates a robust superamphiphobic performance under mechanical impact, corrosive liquids, intermittent and transpositional temperatures, and water spray. Additionally, the as-prepared wood sample shows superior ultraviolet resistance.

  16. Aluminum doping tunes band gap energy level as well as oxidative stress-mediated cytotoxicity of ZnO nanoparticles in MCF-7 cells

    PubMed Central

    Akhtar, Mohd Javed; Alhadlaq, Hisham A.; Alshamsan, Aws; Majeed Khan, M.A.; Ahamed, Maqusood

    2015-01-01

    We investigated whether Aluminum (Al) doping tunes band gap energy level as well as selective cytotoxicity of ZnO nanoparticles in human breast cancer cells (MCF-7). Pure and Al-doped ZnO nanoparticles were prepared by a simple sol-gel method. Characterization study confirmed the formation of single phase of AlxZn1-xO nanocrystals with the size range of 33–55 nm. Al-doping increased the band gap energy of ZnO nanoparticles (from 3.51 eV for pure to 3.87 eV for Al-doped ZnO). Al-doping also enhanced the cytotoxicity and oxidative stress response of ZnO nanoparticles in MCF-7 cells. The IC50 for undoped ZnO nanoparticles was 44 μg/ml while for the Al-doped ZnO counterparts was 31 μg/ml. Up-regulation of apoptotic genes (e.g. p53, bax/bcl2 ratio, caspase-3 & caspase-9) along with loss of mitochondrial membrane potential suggested that Al-doped ZnO nanoparticles induced apoptosis in MCF-7 cells through mitochondrial pathway. Importantly, Al-doping did not change the benign nature of ZnO nanoparticles towards normal cells suggesting that Al-doping improves the selective cytotoxicity of ZnO nanoparticles toward MCF-7 cells without affecting the normal cells. Our results indicated a novel approach through which the inherent selective cytotoxicity of ZnO nanoparticles against cancer cells can be further improved. PMID:26347142

  17. Aluminum doping tunes band gap energy level as well as oxidative stress-mediated cytotoxicity of ZnO nanoparticles in MCF-7 cells.

    PubMed

    Akhtar, Mohd Javed; Alhadlaq, Hisham A; Alshamsan, Aws; Majeed Khan, M A; Ahamed, Maqusood

    2015-09-08

    We investigated whether Aluminum (Al) doping tunes band gap energy level as well as selective cytotoxicity of ZnO nanoparticles in human breast cancer cells (MCF-7). Pure and Al-doped ZnO nanoparticles were prepared by a simple sol-gel method. Characterization study confirmed the formation of single phase of Al(x)Zn(1-x)O nanocrystals with the size range of 33-55 nm. Al-doping increased the band gap energy of ZnO nanoparticles (from 3.51 eV for pure to 3.87 eV for Al-doped ZnO). Al-doping also enhanced the cytotoxicity and oxidative stress response of ZnO nanoparticles in MCF-7 cells. The IC50 for undoped ZnO nanoparticles was 44 μg/ml while for the Al-doped ZnO counterparts was 31 μg/ml. Up-regulation of apoptotic genes (e.g. p53, bax/bcl2 ratio, caspase-3 &caspase-9) along with loss of mitochondrial membrane potential suggested that Al-doped ZnO nanoparticles induced apoptosis in MCF-7 cells through mitochondrial pathway. Importantly, Al-doping did not change the benign nature of ZnO nanoparticles towards normal cells suggesting that Al-doping improves the selective cytotoxicity of ZnO nanoparticles toward MCF-7 cells without affecting the normal cells. Our results indicated a novel approach through which the inherent selective cytotoxicity of ZnO nanoparticles against cancer cells can be further improved.

  18. Aluminum doping tunes band gap energy level as well as oxidative stress-mediated cytotoxicity of ZnO nanoparticles in MCF-7 cells

    NASA Astrophysics Data System (ADS)

    Akhtar, Mohd Javed; Alhadlaq, Hisham A.; Alshamsan, Aws; Majeed Khan, M. A.; Ahamed, Maqusood

    2015-09-01

    We investigated whether Aluminum (Al) doping tunes band gap energy level as well as selective cytotoxicity of ZnO nanoparticles in human breast cancer cells (MCF-7). Pure and Al-doped ZnO nanoparticles were prepared by a simple sol-gel method. Characterization study confirmed the formation of single phase of AlxZn1-xO nanocrystals with the size range of 33-55 nm. Al-doping increased the band gap energy of ZnO nanoparticles (from 3.51 eV for pure to 3.87 eV for Al-doped ZnO). Al-doping also enhanced the cytotoxicity and oxidative stress response of ZnO nanoparticles in MCF-7 cells. The IC50 for undoped ZnO nanoparticles was 44 μg/ml while for the Al-doped ZnO counterparts was 31 μg/ml. Up-regulation of apoptotic genes (e.g. p53, bax/bcl2 ratio, caspase-3 & caspase-9) along with loss of mitochondrial membrane potential suggested that Al-doped ZnO nanoparticles induced apoptosis in MCF-7 cells through mitochondrial pathway. Importantly, Al-doping did not change the benign nature of ZnO nanoparticles towards normal cells suggesting that Al-doping improves the selective cytotoxicity of ZnO nanoparticles toward MCF-7 cells without affecting the normal cells. Our results indicated a novel approach through which the inherent selective cytotoxicity of ZnO nanoparticles against cancer cells can be further improved.

  19. Spatially branched hierarchical ZnO nanorod-TiO2 nanotube array heterostructures for versatile photocatalytic and photoelectrocatalytic applications: towards intimate integration of 1D-1D hybrid nanostructures

    NASA Astrophysics Data System (ADS)

    Xiao, Fang-Xing; Hung, Sung-Fu; Tao, Hua Bing; Miao, Jianwei; Yang, Hong Bin; Liu, Bin

    2014-11-01

    Hierarchically ordered ZnO nanorods (NRs) decorated nanoporous-layer-covered TiO2 nanotube array (ZnO NRs/NP-TNTAs) nanocomposites have been prepared by an efficient, two-step anodization route combined with an electrochemical deposition strategy, by which monodispersed one-dimensional (1D) ZnO NRs were uniformly grown on the framework of NP-TNTAs. The crystal phases, morphologies, optical properties, photocatalytic as well as photoelectrocatalytic performances of the well-defined ZnO NRs/NP-TNTAs heterostructures were systematically explored to clarify the structure-property correlation. It was found that the ZnO NRs/NP-TNTAs heterostructure exhibits significantly enhanced photocatalytic and photoelectrocatalytic performances, along with favorable photostability toward degradation of organic pollutants under UV light irradiation, as compared to the single component counterparts. The remarkably enhanced photoactivity of ZnO NRs/NP-TNTAs heterostructure is ascribed to the intimate interfacial integration between ZnO NRs and NP-TNTAs substrate imparted by the unique spatially branched hierarchical structure, thereby contributing to the efficient transfer and separation of photogenerated electron-hole charge carriers. Moreover, the specific active species during the photocatalytic process was unambiguously determined and photocatalytic mechanism was tentatively presented. It is anticipated that our work could provide new insights for the construction of various hierarchical 1D-1D hybrid nanocomposites for extensive photocatalytic applications.Hierarchically ordered ZnO nanorods (NRs) decorated nanoporous-layer-covered TiO2 nanotube array (ZnO NRs/NP-TNTAs) nanocomposites have been prepared by an efficient, two-step anodization route combined with an electrochemical deposition strategy, by which monodispersed one-dimensional (1D) ZnO NRs were uniformly grown on the framework of NP-TNTAs. The crystal phases, morphologies, optical properties, photocatalytic as well as

  20. Antifouling properties of zinc oxide nanorod coatings.

    PubMed

    Al-Fori, Marwan; Dobretsov, Sergey; Myint, Myo Tay Zar; Dutta, Joydeep

    2014-01-01

    In laboratory experiments, the antifouling (AF) properties of zinc oxide (ZnO) nanorod coatings were investigated using the marine bacterium Acinetobacter sp. AZ4C, larvae of the bryozoan Bugula neritina and the microalga Tetraselmis sp. ZnO nanorod coatings were fabricated on microscope glass substrata by a simple hydrothermal technique using two different molar concentrations (5 and 10 mM) of zinc precursors. These coatings were tested for 5 h under artificial sunlight (1060 W m(-2) or 530 W m(-2)) and in the dark (no irradiation). In the presence of light, both the ZnO nanorod coatings significantly reduced the density of Acinetobacter sp. AZ4C and Tetraselmis sp. in comparison to the control (microscope glass substratum without a ZnO coating). High mortality and low settlement of B. neritina larvae was observed on ZnO nanorod coatings subjected to light irradiation. In darkness, neither mortality nor enhanced settlement of larvae was observed. Larvae of B. neritina were not affected by Zn(2+) ions. The AF effect of the ZnO nanorod coatings was thus attributed to the reactive oxygen species (ROS) produced by photocatalysis. It was concluded that ZnO nanorod coatings effectively prevented marine micro and macrofouling in static conditions.

  1. Low-Temperature Solution-Processed Thiophene-Sulfur-Doped Planar ZnO Nanorods as Electron-Transporting Layers for Enhanced Performance of Organic Solar Cells.

    PubMed

    Ambade, Swapnil B; Ambade, Rohan B; Bagde, Sushil S; Eom, Seung Hun; Mane, Rajaram S; Shin, Won Suk; Lee, Soo-Hyoung

    2017-02-01

    1-D ZnO represents a fascinating class of nanostructures that are significant to optoelectronics. In this work, we investigated the use of an eco-friendly, metal free in situ doping through a pure thiophene-sulfur (S) on low temperature processed (<95 °C) and annealed (<170 °C), planar 1-D ZnO nanorods (ZnRs) spin-coated as a hole-blocking and electron transporting layer (ETL) for inverted organic solar cells (iOSCs). The TEM, HRTEM, XPS, FT-IR, EDS and Raman studies clearly reveal that the thiophene-S (Thi-S) atom is incorporated on planar ZnRs. The investigations in electrical properties suggest the enhancement in conductivity after Thi-S doping on 1-D ZnRs. The iOSCs of poly(3-hexylthiophene-2,5-diyl) and phenyl-C61-butyric acid methyl ester (P3HT: PC60BM) photoactive layer containing thiophene-S doped planar ZnRs (Thi-S-PZnRs) as ETL exhibits power conversion efficiency (PCE) of 3.68% under simulated AM 1.5 G, 100 mW cm(-2) illumination. The ∼47% enhancement in PCE compared with pristine planar ZnRs (PCE = 2.38%) ETL is attributed to a combination of desirable energy level alignment, morphological modification, increased conductivity and doping effect. The universality of Thi-S-PZnRs ETL is demonstrated by the highest PCE of 8.15% in contrast to 6.50% exhibited by the iOSCs of ZnRs ETL for the photoactive layer comprising of poly[4,8-bis(5-(2-ethylhexyl)thiophene-2-yl)benzo[1,2-b;4,5-b]dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2-6-diyl)]: phenyl-C71-butyric acid methyl ester (PTB7-Th: PCB71M). This enhancement in PCE is observed to be driven mainly through improved photovoltaic parameters like fill factor (ff) as well as photocurrent density (Jsc), which are assigned to increased conductivity, exciton dissociation, and effective charge extraction, while; better ohmic contact, reduced charge recombination, and low leakage current density resulted in increased Voc.

  2. Work-Function and Surface Energy Tunable Cyanoacrylic Acid Small-Molecule Derivative Interlayer on Planar ZnO Nanorods for Improved Organic Photovoltaic Performance.

    PubMed

    Ambade, Swapnil B; Ambade, Rohan B; Bagde, Sushil S; Lee, Soo-Hyoung

    2016-12-28

    The issue of work-function and surface energy is fundamental to "decode" the critical inorganic/organic interface in hybrid organic photovoltaics, which influences important photovoltaic events like exciton dissociation, charge transfer, photocurrent (Jsc), open-circuit voltage (Voc), etc. We demonstrate that by incorporating an interlayer of cyanoacrylic acid small molecular layer (SML) on solution-processed, spin-coated, planar ZnO nanorods (P-ZnO NRs), higher photovoltaic (PV) performances were achieved in both inverted organic photovoltaic (iOPV) and hybrid organic photovoltaic (HOPV) devices, where ZnO acts as an "electron-transporting layer" and as an "electron acceptor", respectively. For the tuned range of surface energy from 52.5 to 33 mN/m, the power conversion efficiency (PCE) in bulk heterojunction (BHJ) iOPVs based on poly(3-hexylthiophene) (P3HT) and phenyl-C60-butyric acid methyl ester (PC60BM) increases from 3.16% to 3.68%, and that based on poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5b']dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene)-2-carboxylate-2-6-diyl)] (PTB7:Th):[6,6]-phenyl C71 butyric acid methyl ester (PC71BM) photoactive BHJ increases from 6.55% to 8.0%, respectively. The improved PV performance in iOPV devices is majorly attributed to enhanced photocurrents achieved as a result of reduced surface energy and greater electron affinity from the covalent attachment of the strong electron-withdrawing cyano moiety, while that in HOPV devices, where PCE increases from 0.21% to 0.79% for SML-modified devices, is ascribed to a large increase in Voc benefitted due to reduced work function effected from the presence of strong dipole moment in SML that points away from P-ZnO NRs.

  3. Effect of solution concentration on the functional properties of ZnO nanostructures: Role of Hexamethylenetetramine

    NASA Astrophysics Data System (ADS)

    Heo, Si Nae; Park, Keun Young; Seo, Yong Jun; Ahmed, Faheem; Anwar, M. S.; Koo, Bon Heun

    2013-05-01

    In this research, ZnO nanorods have been successfully synthesized via wet chemical method. XRD results revealed the single phase nature with the wurtzite structure of the as prepared ZnO nanorods. By only varying the concentration of Hexamethylenetetramine (HMT) in the solution, morphology of ZnO changed from hexagonal facet nanorods to pencil like nanorods and size of nanorods also changed. The band gap of as-synthesized ZnO nanorods was found to increase with increasing the concentration of HMT in the solution. The narrow full-width at half-maximum (FWHM) of the UV emission of PL spectra indicated that the grown ZnO nanorods have high crystal quality and is well matched with the obtained XRD results. These results revealed that the concentration of Hexamethylenetetramine plays a vital role to control the properties of ZnO nanorods.

  4. Photocatalytic paper using zinc oxide nanorods

    NASA Astrophysics Data System (ADS)

    Baruah, Sunandan; Jaisai, Mayuree; Imani, Reza; Nazhad, Mousa M.; Dutta, Joydeep

    2010-10-01

    Zinc oxide (ZnO) nanorods were grown on a paper support prepared from soft wood pulp. The photocatalytic activity of a sheet of paper with ZnO nanorods embedded in its porous matrix has been studied. ZnO nanorods were firmly attached to cellulose fibers and the photocatalytic paper samples were reused several times with nominal decrease in efficiency. Photodegradation of up to 93% was observed for methylene blue in the presence of paper filled with ZnO nanorods upon irradiation with visible light at 963 Wm-2 for 120 min. Under similar conditions, photodegradation of approximately 35% was observed for methyl orange. Antibacterial tests revealed that the photocatalytic paper inhibits the growth of Escherichia coli under room lighting conditions.

  5. Photocatalytic paper using zinc oxide nanorods

    PubMed Central

    Baruah, Sunandan; Jaisai, Mayuree; Imani, Reza; Nazhad, Mousa M; Dutta, Joydeep

    2010-01-01

    Zinc oxide (ZnO) nanorods were grown on a paper support prepared from soft wood pulp. The photocatalytic activity of a sheet of paper with ZnO nanorods embedded in its porous matrix has been studied. ZnO nanorods were firmly attached to cellulose fibers and the photocatalytic paper samples were reused several times with nominal decrease in efficiency. Photodegradation of up to 93% was observed for methylene blue in the presence of paper filled with ZnO nanorods upon irradiation with visible light at 963 Wm–2 for 120 min. Under similar conditions, photodegradation of approximately 35% was observed for methyl orange. Antibacterial tests revealed that the photocatalytic paper inhibits the growth of Escherichia coli under room lighting conditions. PMID:27877367

  6. Effects of electrical and optical properties of thickness condition of ZnO nanorod array layer for efficient electrochemical luminescence cell device

    NASA Astrophysics Data System (ADS)

    Choi, Hye Su; Chansri, Pakpoom; Sung, Youl Moon

    2016-02-01

    In this paper, we report on electrochemical luminescence (ECL) cells with a ZnO nanorod (ZNR) layer. The investigated ECL cells were composed of F-doped SnO2 (FTO) glass/Ru(II)/ZNRs/FTO glass, which used a ZNR layer as an electrode and the Ru(II) complex [Ru(bpy)32+] as a light-emitting material. The ECL cells were fabricated by changing the thickness of ZNRs from 5 to 12.5 µm. The luminescence property of the ECL cells was strongly affected by the variation in the thickness of the ZNR layer. The threshold voltage for the light emission from the ECL cells was 2 V for 10 µm thick ZNRs, which was lower than that of the thickness of the ECL cells without a ZNR layer. Also, the intensity of luminance from the ECL cells with ZNRs was much higher than that from the ECL cells without ZNRs at the same operating voltage. The efficiency of the ECL cells without ZNRs measured at 3 V was 0.0049 lm/W, while those of the ECL cells with ZNRs were 0.0121, 0.0157, 0.0354, and 0.024 lm/W for the ZNRs layer thicknesses 5, 7.5, 10, and 12.5 µm, respectively. However, the peak light intensity at the wavelength was 623 nm which had not affected the all ZNRs thicknesses. The best lifetime of the ECL cells with these thicknesses was 40 min for ZNRs 10 µm. The use of the ZNR layer in the ECL cells significantly improves the luminescence performance.

  7. Application of ZnO nanorods loaded on activated carbon for ultrasonic assisted dyes removal: Experimental design and derivative spectrophotometry method.

    PubMed

    Ansari, Fatemeh; Ghaedi, Mehrorang; Taghdiri, Mehdi; Asfaram, Arash

    2016-11-01

    A method based on application of ZnO nanorods loaded on activated carbon (ZnO-NRs-AC) for adsorption of Bromocresol Green (BCG) and Eosin Y (EY) accelerated by ultrasound was described. The present material was synthesized under ultrasound assisted wet-chemical method and subsequently was characterized by FE-SEM, TEM, BET and XRD analysis. The extent of contribution of conventional variables like pH (2.0-10.0), BCG concentration (4-20mgL(-1)), EY concentration (3-23mgL(-1)), adsorbent dosage (0.01-0.03g), sonication time (1-5min) and centrifuge time (2-6min) as main and interaction part were investigated by central composite design under response surface methodology. Analysis of variance (ANOVA) was adapted to experimental data and guide the best operational conditions mass by set at 6.0, 9mgL(-1), 10mgL(-1), 0.02g, 4 and 4min for pH, BCG concentration, EY concentration, adsorbent dosage, sonication and centrifuge time, respectively. At these specified conditions dye adsorption efficiency was higher than 99.5%. The suitability and well prediction of optimum point was tested by conducting five experiments and respective results revel that RSD% was lower than 3% and high quality of fitting was confirmed by t-test. The experimental data were best fitted in Langmuir isotherm equation and the removal followed pseudo second order kinetics. The experimentally obtained maximum adsorption capacities were estimated as 57.80 and 61.73mgg(-1) of ZnO-NRs-AC for BCG and EY respectively from binary dye solutions. The mechanism of removal was explained by boundary layer diffusion via intraparticle diffusion.

  8. Si/ZnO nanorods/Ag/AZO structures as promising photovoltaic plasmonic cells

    NASA Astrophysics Data System (ADS)

    Placzek-Popko, E.; Gwozdz, K.; Gumienny, Z.; Zielony, E.; Pietruszka, R.; Witkowski, B. S.; Wachnicki, Ł.; Gieraltowska, S.; Godlewski, M.; Jacak, W.; Chang, Liann-Be

    2015-05-01

    The test structures for photovoltaic (PV) applications based on zinc oxide nanorods (NRs) that were grown using a low-temperature hydrothermal method on p-type silicon substrates (100) covered with Ag nanoparticles (NPs) were studied. The NPs of three different diameters, i.e., 5-10 nm, 20-30 nm, and 50-60 nm, were deposited using a sputtering method. The morphology and crystallinity of the structures were confirmed by scanning electron microscopy and Raman spectroscopy. It was found that the nanorods have a hexagonal wurtzite structure. An analysis of the Raman and photoluminescence spectra permitted the identification of the surface modes at 476 cm-1 and 561 cm-1. The presence of these modes is evidence of nanorods oriented along the wurtzite c-axis. The NRs with Ag NPs were covered with a ZnO:Al (AZO) layer that was grown using the low-temperature atomic layer deposition technique. The AZO layer served as a transparent ohmic contact to the ZnO nanorods. The applicability of the AZO layer for this purpose and the influence of the Ag nanoparticles on the effectiveness of light acquisition by such prepared PV cells were checked by reflectance and transmittance measurements of the AZO/glass and AZO/NPs/glass reference structures. Based on these studies, the high-energy transmittance edge was assigned to the ZnO energy gap, although it is blueshifted with respect to the bulk ZnO energy gap because of Al doping. It was also shown that the most optimal PV performance is obtained from a structure containing Ag nanoparticles with a diameter of 20-30 nm. This result is confirmed by the current-voltage measurements performed with 1-sun illumination. The structures show a plasmonic effect within the short wavelength range: the PV response for the structure with Ag nanoparticles is twice that of the structure without the nanoparticles. However, the influence of the Ag nanoparticle diameters on the plasmonic effect is ambiguous.

  9. Si/ZnO nanorods/Ag/AZO structures as promising photovoltaic plasmonic cells

    SciTech Connect

    Placzek-Popko, E. Gwozdz, K.; Gumienny, Z.; Zielony, E.; Jacak, W.; Pietruszka, R.; Witkowski, B. S.; Wachnicki, Ł.; Gieraltowska, S.; Chang, Liann-Be

    2015-05-21

    The test structures for photovoltaic (PV) applications based on zinc oxide nanorods (NRs) that were grown using a low-temperature hydrothermal method on p-type silicon substrates (100) covered with Ag nanoparticles (NPs) were studied. The NPs of three different diameters, i.e., 5–10 nm, 20-30 nm, and 50–60 nm, were deposited using a sputtering method. The morphology and crystallinity of the structures were confirmed by scanning electron microscopy and Raman spectroscopy. It was found that the nanorods have a hexagonal wurtzite structure. An analysis of the Raman and photoluminescence spectra permitted the identification of the surface modes at 476 cm{sup −1} and 561 cm{sup −1}. The presence of these modes is evidence of nanorods oriented along the wurtzite c-axis. The NRs with Ag NPs were covered with a ZnO:Al (AZO) layer that was grown using the low-temperature atomic layer deposition technique. The AZO layer served as a transparent ohmic contact to the ZnO nanorods. The applicability of the AZO layer for this purpose and the influence of the Ag nanoparticles on the effectiveness of light acquisition by such prepared PV cells were checked by reflectance and transmittance measurements of the AZO/glass and AZO/NPs/glass reference structures. Based on these studies, the high-energy transmittance edge was assigned to the ZnO energy gap, although it is blueshifted with respect to the bulk ZnO energy gap because of Al doping. It was also shown that the most optimal PV performance is obtained from a structure containing Ag nanoparticles with a diameter of 20–30 nm. This result is confirmed by the current-voltage measurements performed with 1-sun illumination. The structures show a plasmonic effect within the short wavelength range: the PV response for the structure with Ag nanoparticles is twice that of the structure without the nanoparticles. However, the influence of the Ag nanoparticle diameters on the plasmonic effect is ambiguous.

  10. Incorporating β-cyclodextrin with ZnO nanorods: a potentiometric strategy for selectivity and detection of dopamine.

    PubMed

    Elhag, Sami; Ibupoto, Zafar Hussain; Nur, Omer; Willander, Magnus

    2014-01-17

    We describe a chemical sensor based on a simple synthesis of zinc oxide nanorods (ZNRs) for the detection of dopamine molecules by a potentiometric approach. The polar nature of dopamine leads to a change of surface charges on the ZNR surface via metal ligand bond formation which results in a measurable electrical signal. ZNRs were grown on a gold-coated glass substrate by a low temperature aqueous chemical growth (ACG) method. Polymeric membranes incorporating β-cyclodextrin (β-CD) and potassium tetrakis (4-chlorophenyl) borate was immobilized on the ZNR surface. The fabricated electrodes were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The grown ZNRs were well aligned and exhibited good crystal quality. The present sensor system displays a stable potential response for the detection of dopamine in 10(-2) mol·L(-1) acetic acid/sodium acetate buffer solution at pH 5.45 within a wide concentration range of 1 × 10(-6) M(-1) × 10(-1) M, with sensitivity of 49 mV/decade. The electrode shows a good response time (less than 10 s) and excellent repeatability. This finding can contribute to routine analysis in laboratories studying the neuropharmacology of catecholamines. Moreover, the metal-ligand bonds can be further exploited to detect DA receptors, and for bio-imaging applications.

  11. Improved Photoresponse of Hybrid ZnO/P3HT Bilayered Photodetector Obtained Through Oriented Growth of ZnO Nanorod Arrays and the Use of Hole Injection Layer

    NASA Astrophysics Data System (ADS)

    Bilgaiyan, Anubha; Dixit, Tejendra; Palani, I. A.; Singh, Vipul

    2015-08-01

    We report highly oriented one-dimensional (1-D) growth of zinc oxide (ZnO) nanorod arrays (NRA) which were later utilized to fabricate hybrid photodiodes having the typical photodiode configuration of indium tin oxide (ITO)/ZnO/poly(3-hexylthiophene) (P3HT)/Ag. These functional hybrid bilayered photodiodes were found to have high rectification ratio under dark conditions and demonstrated enhanced responsivity under light illumination. Further, we studied the effect of an intermediate electron blocking layer of poly(ethylenedioxythiophene) doped with polystyrene sulfonate (PEDOT:PSS) on the photodiode characteristics and demonstrated ITO/ZnO/P3HT/PEDOT:PSS/Ag photodiodes, reporting very high rectification ratio and responsivity in this bilayered configuration. The observed results are explained on the basis of the increased surface area of contact between the ZnO nanorods and the P3HT, and also the efficient hole injection into the P3HT layer from the top Ag electrode.

  12. Self-organized ZnO nanorod with photooxidative cell membrane perforation enables large-scale cell manipulation.

    PubMed

    Saito, Takashi K; Seki, Munetoshi; Tabata, Hitoshi

    2008-08-01

    Various devices have been developed for verification and application of cellular functions in recent years. In our previous study, we found that local oxidation reactions in the cell membrane could produce submicron sizes of reversible membrane perforations in cells, while more than 80% of treated cells were viable even after perforations; therefore, to date, we have attempted some applications of this mechanism and analyzed their feasibility. In the present study, we developed a rod-shaped device in which the function of membrane perforation is added by utilizing a photosensitizer and, using the device, we have attempted to produce membrane perforations in a large number of cells. Zinc oxide nanorods were synthesized on the basis of the vapor-liquid-solid mechanism and alpha-terthienyl (photosensitizer) was adsorbed onto gold at the top of the rods to add a membrane perforation function. We studied the effect of the oxidation catalytic ability of the rods on rat PC12 cells after pressing and making the rods' growth side come into contact with the base plate pressed onto the cells in a culture plate followed by photoexcitation of the photosensitizer for a certain period of time. It was revealed that water-soluble fluorescent marker molecules added extracellularly were taken up by the cells when the rods were applied at a pressure of 70 g/cm(2), with a light intensity of 0.82 W/cm(2), and with light irradiation for 30 s, as found in the case of the conventional photochemical cell membrane perforation method targeted at a single cell. These results suggest that cell membrane perforation can be successfully achieved in a large number of cells at a time.

  13. The Kinetic Study of The Hydrothermal Growth of Zno Nanorod Array Films / Zno Nanostieņu Kopu Pārklājuma Hidrotermālās Augšanas Kinētikas Izpēte

    NASA Astrophysics Data System (ADS)

    Gerbreders, V.; Sarajevs, P.; Mihailova, I.; Tamanis, E.

    2015-10-01

    The simple analysis method has been introduced for the kinetic analysis of the hydrothermal growth. The zinc oxide nanorod arrays have been synthesized via a hydrothermal process. Zinc nitrate hexahydrate (Zn(NO3)2 · 6H2O) has been used as the precursor in the presence of hexamethylenetetramine (C6H12N4) for the formation of ZnO nanostructures. Long-term isothermal growth kinetics of ZnO nano