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Sample records for wurtzite zns nanorods

  1. Room temperature synthesis of wurtzite phase nanostructured ZnS and accompanied enhancement in dielectric constant

    Science.gov (United States)

    Virpal, Kumar, J.; Singh, G.; Singh, M.; Sharma, S.; Singh, R. C.

    2017-04-01

    We report the room temperature synthesis of ZnS in the wurtzite phase by using ethylenediamine, which acts as a template as well as a capping agent. With the addition of ethylenediamine, structural transformation in ZnS from cubic to wurtzite phase is observed. This is accompanied by an increase in the real permittivity by an order of 2, and reduction in dielectric loss by a factor of 6 as compared to a sample without ethylenediamine. Thus, suggesting that ethylenediamine capped wurtzite ZnS is more suitable for miniaturied capactive devices.

  2. Effect of effective mass and spontaneous polarization on photocatalytic activity of wurtzite and zinc-blende ZnS

    Directory of Open Access Journals (Sweden)

    Ming Dong

    2015-10-01

    Full Text Available Semiconductor zinc sulphide (ZnS has two common phases: hexagonal wurtzite and cubic zinc-blende structures. The crystal structures, energy band structures, density of states (DOS, bond populations, and optical properties of wurtzite and zinc-blende ZnS were investigated by the density functional theory of first-principles. The similar band gaps and DOS of wurtzite and zinc-blende ZnS were found and implied the similarities in crystal structures. However, the distortion of ZnS4 tetrahedron in wurtzite ZnS resulted in the production of spontaneous polarization and internal electric field, which was beneficial for the transfer and separation of photogenerated electrons and holes.

  3. Assembly of three-dimensional hetero-epitaxial ZnO/ZnS core/shell nanorod and single crystalline hollow ZnS nanotube arrays.

    Science.gov (United States)

    Huang, Xing; Wang, Meng; Willinger, Marc-Georg; Shao, Lidong; Su, Dang Sheng; Meng, Xiang-Min

    2012-08-28

    Hetero-epitaxial growth along three-dimensional (3D) interfaces from materials with an intrinsic large lattice mismatch is a key challenge today. In this work we report, for the first time, the controlled synthesis of vertically aligned ZnO/ZnS core/shell nanorod arrays composed of single crystalline wurtzite (WZ) ZnS conformally grown on ZnO rods along 3D interfaces through a simple two-step thermal evaporation method. Structural characterization reveals a "(01-10)(ZnO)//(01-10)(ZnS) and [0001](ZnO)//[0001](ZnS)" epitaxial relationship between the ZnO core and the ZnS shell. It is exciting that arrays of single crystalline hollow ZnS nanotubes are also innovatively obtained by simply etching away the inner ZnO cores. On the basis of systematic structural analysis, a rational growth mechanism for the formation of hetero-epitaxial core/shell nanorods is proposed. Optical properties are also investigated via cathodoluminescence and photoluminescence measurements. Remarkably, the synthesized ZnO/ZnS core/shell heterostructures exhibit a greatly reduced ultraviolet emission and dramatically enhanced green emission compared to the pure ZnO nanorods. The present single-crystalline heterostructure and hollow nanotube arrays are envisaged to be highly promising for applications in novel nanoscale optoelectronic devices, such as UV-A photodetectors, lasers, solar cells, and nanogenerators.

  4. Single crystalline wurtzite ZnO/zinc blende ZnS coaxial heterojunctions and hollow zinc blende ZnS nanotubes: synthesis, structural characterization and optical properties.

    Science.gov (United States)

    Huang, Xing; Willinger, Marc-Georg; Fan, Hua; Xie, Zai-lai; Wang, Lei; Klein-Hoffmann, Achim; Girgsdies, Frank; Lee, Chun-Sing; Meng, Xiang-Min

    2014-08-07

    Synthesis of ZnO/ZnS heterostructures under thermodynamic conditions generally results in the wurtzite (WZ) structure of the ZnS component because its WZ phase is thermodynamically more stable than its zinc blende (ZB) phase. In this report, we demonstrate for the first time the preparation of ZnO/ZnS coaxial nanocables composed of single crystalline ZB structured ZnS epitaxially grown on WZ ZnO via a two-step thermal evaporation method. The deposition temperature is believed to play a crucial role in determining the crystalline phase of ZnS. Through a systematic structural analysis, the ZnO core and the ZnS shell are found to have an orientation relationship of (0002)ZnO(WZ)//(002)ZnS(ZB) and [01-10]ZnO(WZ)//[2-20]ZnS(ZB). Observation of the coaxial nanocables in cross-section reveals the formation of voids between the ZnO core and the ZnS shell during the coating process, which is probably associated with the nanoscale Kirkendall effect known to result in porosity. Furthermore, by immersing the ZnO/ZnS nanocable heterojunctions in an acetic acid solution to etch away the inner ZnO cores, single crystalline ZnS nanotubes orientated along the [001] direction of the ZB structure were also achieved for the first time. Finally, optical properties of the hollow ZnS tubes were investigated and discussed in detail. We believe that our study could provide some insights into the controlled fabrication of one dimensional (1D) semiconductors with desired morphology, structure and composition at the nanoscale, and the synthesized WZ ZnO/ZB ZnS nanocables as well as ZB ZnS nanotubes could be ideal candidates for the study of optoelectronics based on II-VI semiconductors.

  5. Solvothermal Synthesis of Well-Disperse ZnS Nanorods with Efficient Photocatalytic Properties

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    Yun Chen

    2012-01-01

    Full Text Available Well-disperse short-range-ordered ZnS nanorods with efficient photocatalytic property for photodegradation of Rhodamin B have been successfully synthesized through a solvothermal method. Solvent used can be recovered and reused, which makes the route environment-friendly. Dodecylamine was found effective in organizing nanorods to ordered monolayer. Characterization showed that these nanorods were uniform with the diameter of about 3 nm and length of nearly 30 nm. And it is expected that these monodisperse ZnS nanorods have potential applications in electroluminescence materials.

  6. Alternative motif toward high-quality wurtzite MnSe nanorods via subtle sulfur element doping

    Science.gov (United States)

    Zhou, Bo; Yang, Xinyi; Sui, Yongming; Xiao, Guanjun; Wei, Yingjin; Zou, Bo

    2016-04-01

    The manipulated synthesis of high-quality semiconductor nanocrystals (NCs) is of high significance with respect to the exploration of their properties and their corresponding applications. Nevertheless, the preparation of metastable-phase NCs still remains a great challenge due to their high kinetic barriers and harsh synthetic conditions. Herein, we demonstrated the fabrication of high-quality MnSe nanorods with a metastable wurtzite structure via a subtle sulfur-doping strategy. Based on the UV-vis absorption spectra, manganese polysulfide clusters were formed by mixing oleylamine-sulfur and oleylamine-manganese solutions at room temperature. The existence of manganese polysulfide clusters with polymeric sulfur structures makes the system more reactive, inducing fast wurtzite-phase nucleation. This can overcome the natural kinetic barrier of wurtzite MnSe and lead to subsequent growth of targeted NCs. On the other hand, no sulfur doping would produce MnSe NCs in a thermodynamically favorable rock-salt phase. As expected, different doping contents and sulfur sources also resulted in the formation of high-quality wurtzite MnSe nanorods. This success establishes that a facile strategy can be anticipated to synthesize high-quality metal chalcogenide NCs with a metastable phase, especially wurtzite nanorods, for potential applications from spintronics to solar cells.The manipulated synthesis of high-quality semiconductor nanocrystals (NCs) is of high significance with respect to the exploration of their properties and their corresponding applications. Nevertheless, the preparation of metastable-phase NCs still remains a great challenge due to their high kinetic barriers and harsh synthetic conditions. Herein, we demonstrated the fabrication of high-quality MnSe nanorods with a metastable wurtzite structure via a subtle sulfur-doping strategy. Based on the UV-vis absorption spectra, manganese polysulfide clusters were formed by mixing oleylamine-sulfur and oleylamine

  7. Size- and shape-dependent growth of fluorescent ZnS nanorods and nanowires using Ag nanocrystals as seeds.

    Science.gov (United States)

    Shen, Huaibin; Shang, Hangying; Niu, Jinzhong; Xu, Weiwei; Wang, Hongzhe; Li, Lin Song

    2012-10-21

    High-quality, monodisperse, and size-controlled Ag-ZnS nanorods or nanowires have been synthesized successfully using Ag nanocrystals as seeds. Such one-dimensional colloidal Ag-ZnS nanorods or nanowires having a purposefully controlled diameter in the range of 5-9 nm and a length of 18-600 nm were obtained by altering the reaction conditions, such as concentration, reaction time, reaction temperature, and diameter of Ag nanocrystals. The conjunction interface of Ag-ZnS nanorods or nanowires consists of the (200) plane of Ag nanocrystal and (101) plane of ZnS rod or wire, the directions of ZnS nanorods grow preferentially. Based on the photoluminescence and lifetime of Ag-ZnS nanorods, it was found that Ag nanocrystals enhanced the radiative rate eventually, the fluorescence intensity of Ag-ZnS nanorods can be tuned by changing the size of the Ag seeds. The Ag-ZnS nanorods or nanowires showed greatly improved optical properties as compared to ZnS nanocrystals, the maximum emission was around 402 nm and the photoluminescence quantum yield was up to 30% when 5 nm Ag nanocrystals were used as seeds.

  8. Highly Luminescent Water-Dispersible NIR-Emitting Wurtzite CuInS2/ZnS Core/Shell Colloidal Quantum Dots

    Science.gov (United States)

    2017-01-01

    Copper indium sulfide (CIS) quantum dots (QDs) are attractive as labels for biomedical imaging, since they have large absorption coefficients across a broad spectral range, size- and composition-tunable photoluminescence from the visible to the near-infrared, and low toxicity. However, the application of NIR-emitting CIS QDs is still hindered by large size and shape dispersions and low photoluminescence quantum yields (PLQYs). In this work, we develop an efficient pathway to synthesize highly luminescent NIR-emitting wurtzite CIS/ZnS QDs, starting from template Cu2-xS nanocrystals (NCs), which are converted by topotactic partial Cu+ for In3+ exchange into CIS NCs. These NCs are subsequently used as cores for the overgrowth of ZnS shells (≤1 nm thick). The CIS/ZnS core/shell QDs exhibit PL tunability from the first to the second NIR window (750–1100 nm), with PLQYs ranging from 75% (at 820 nm) to 25% (at 1050 nm), and can be readily transferred to water upon exchange of the native ligands for mercaptoundecanoic acid. The resulting water-dispersible CIS/ZnS QDs possess good colloidal stability over at least 6 months and PLQYs ranging from 39% (at 820 nm) to 6% (at 1050 nm). These PLQYs are superior to those of commonly available water-soluble NIR-fluorophores (dyes and QDs), making the hydrophilic CIS/ZnS QDs developed in this work promising candidates for further application as NIR emitters in bioimaging. The hydrophobic CIS/ZnS QDs obtained immediately after the ZnS shelling are also attractive as fluorophores in luminescent solar concentrators. PMID:28638177

  9. The effect of cation doping on the morphology, optical and structural properties of highly oriented wurtzite ZnO-nanorod arrays grown by a hydrothermal method

    Science.gov (United States)

    Hassanpour, A.; Guo, P.; Shen, S.; Bianucci, P.

    2017-10-01

    Undoped and C-doped (C: Mg2+, Ni2+, Mn2+, Co2+, Cu2+, Cr3+) ZnO nanorods were synthesized by a hydrothermal method at temperatures as low as 60 °C. The effect of doping on the morphology of the ZnO nanorods was visualized by taking their cross section and top SEM images. The results show that the size of nanorods was increased in both height and diameter by cation doping. The crystallinity change of the ZnO nanorods due to each doping element was thoroughly investigated by an x-ray diffraction (XRD). The XRD patterns show that the wurtzite crystal structure of ZnO nanorods was maintained after cation addition. The optical Raman-active modes of undoped and cation-doped nanorods were measured with a micro-Raman setup at room temperature. The surface chemistry of samples was investigated by x-ray photoelectron spectroscopy and energy-dispersive x-ray spectroscopy. Finally, the effect of each cation dopant on band-gap shift of the ZnO nanorods was investigated by a photoluminescence setup at room temperature. Although the amount of dopants (Mg2+, Ni2+, and Co2+) was smaller than the amount of Mn2+, Cu2+, and Cr3+ in the nanorods, their effect on the band structure of the ZnO nanorods was profound. The highest band-gap shift was achieved for a Co-doped sample, and the best crystal orientation was for Mn-doped ZnO nanorods. Our results can be used as a comprehensive reference for engineering of the morphological, structural and optical properties of cation-doped ZnO nanorods by using a low-temperature synthesis as an economical mass-production approach.

  10. Shell Layer Thickness-Dependent Photocatalytic Activity of Sputtering Synthesized Hexagonally Structured ZnO-ZnS Composite Nanorods.

    Science.gov (United States)

    Liang, Yuan-Chang; Lo, Ya-Ru; Wang, Chein-Chung; Xu, Nian-Cih

    2018-01-07

    ZnO-ZnS core-shell nanorods are synthesized by combining the hydrothermal method and vacuum sputtering. The core-shell nanorods with variable ZnS shell thickness (7-46 nm) are synthesized by varying ZnS sputtering duration. Structural analyses demonstrated that the as-grown ZnS shell layers are well crystallized with preferring growth direction of ZnS (002). The sputtering-assisted synthesized ZnO-ZnS core-shell nanorods are in a wurtzite structure. Moreover, photoluminance spectral analysis indicated that the introduction of a ZnS shell layer improved the photoexcited electron and hole separation efficiency of the ZnO nanorods. A strong correlation between effective charge separation and the shell thickness aids the photocatalytic behavior of the nanorods and improves their photoresponsive nature. The results of comparative degradation efficiency toward methylene blue showed that the ZnO-ZnS nanorods with the shell thickness of approximately 17 nm have the highest photocatalytic performance than the ZnO-ZnS nanorods with other shell layer thicknesses. The highly reusable catalytic efficiency and superior photocatalytic performance of the ZnO-ZnS nanorods with 17 nm-thick ZnS shell layer supports their potential for environmental applications.

  11. A versatile light-switchable nanorod memory: Wurtzite ZnO on perovskite SrTiO3

    KAUST Repository

    Kumar, Anup Bera

    2013-04-25

    Integrating materials with distinct lattice symmetries and dimensions is an effective design strategy toward realizing novel devices with unprecedented functionalities, but many challenges remain in synthesis and device design. Here, a heterojunction memory made of wurtzite ZnO nanorods grown on perovskite Nb-doped SrTiO3 (NSTO) is reported, the electronic properties of which can be drastically reconfigured by applying a voltage and light. Despite of the distinct lattice structures of ZnO and NSTO, a consistent nature of single crystallinity is achieved in the heterojunctions via the low-temperature solution-based hydrothermal growth. In addition to a high and persistent photoconductivity, the ZnO/NSTO heterojunction diode can be turned into a versatile light-switchable resistive switching memory with highly tunable ON and OFF states. The reversible modification of the effective interfacial energy barrier in the concurrent electronic and ionic processes most likely gives rise to the high susceptibility of the ZnO/NSTO heterojunction to external electric and optical stimuli. Furthermore, this facile synthesis route is promising to be generalized to other novel functional nanodevices integrating materials with diverse structures and properties. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Application of electron crystallography to structure characterization of ZnS nanocrystals

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    Jin-Gyu Kim

    2011-07-01

    Full Text Available We chracterized the structure properties of two types of ZnS nanocrystals by electron crystallography. X-ray diffraction analysis for these ZnS nanocrystals was performed to determine their initial structures. Their crystallite sizes were about 5.9 nm and 8.1 nm and their crystal systems were hexagonal and cubic, respectively. Their atomic structures, however, could not be determined because of the weak diffraction intensities as well as the unexpected intensities from impurty. To overcome these problems, the structures of ZnS nanocrystals were resolved by electron crystallography using EF-EPD (energy-filtered electron powder diffraction and HRTEM (high resolution transmission electron microscopy methods. The structrues determined by Rietveld analysis are P63mc (a = 3.8452 Å, c = 18.5453 Å and F-43m (a = 5.4356 Å, respectively. Their crystallite shapes were nanorods and quasi-nanoparticles and the nanorod crystal were grown along the [001] direction. It was revealed that the phase transformation between the cubic sphalerite to the hexagonal wurtzite structure of ZnS nanocrytals was related to their shapes and growth mechanism. Electron cryststallogrpahy, employing EF-EPD and HRTEM methods together, has advantages for structure analysis and property chracterization of nano-sized materials.

  13. Synthesis of Mn-doped ZnS architectures in ternary solution and their optical properties

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    Wang Xinjuan, E-mail: wangxj@hnu.edu.cn [State Key lab of CBSC, Micronano Research Center, Hunan University, Changsha 410082 (China); Zhang Qinglin [State Key lab of CBSC, Micronano Research Center, Hunan University, Changsha 410082 (China); Zou Bingsuo, E-mail: zoubs@bit.edu.cn [State Key lab of CBSC, Micronano Research Center, Hunan University, Changsha 410082 (China); Micro-nano Technology Center and School of MSE, BIT, Beijing 100081 (China); Lei Aihua; Ren Pinyun [State Key lab of CBSC, Micronano Research Center, Hunan University, Changsha 410082 (China)

    2011-10-01

    Mn-doped ZnS sea urchin-like architectures were fabricated by a one-pot solvothermal route in a ternary solution made of ethylenediamine, ethanolamine and distilled water. The as-prepared products were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and photoluminescence spectra (PL). It was demonstrated that the as-prepared sea urchin-like architectures with diameter of 0.5-1.5 {mu}m were composed of nanorods, possessing a wurtzite structures. The preferred growth orientation of nanorods was found to be the [0 0 2] direction. The PL spectra of the Mn-doped ZnS sea urchin-like architectures show a strong orange emission at 587 nm, indicating the successful doping of Mn{sup 2+} ions into ZnS host. Ethanolamine played the role of oriented-assembly agent in the formation of sea urchin-like architectures. A possible growth mechanism was proposed to explain the formation of sea urchin-like architectures.

  14. An Effective Electrical Throughput from PANI Supplement ZnS Nanorods and PDMS-Based Flexible Piezoelectric Nanogenerator for Power up Portable Electronic Devices: An Alternative of MWCNT Filler.

    Science.gov (United States)

    Sultana, Ayesha; Alam, Md Mehebub; Garain, Samiran; Sinha, Tridib Kumar; Middya, Tapas Ranjan; Mandal, Dipankar

    2015-09-02

    We demonstrate the requirement of electrical poling can be avoided in flexible piezoelectric nanogenerators (FPNGs) made of low-temperature hydrothermally grown wurtzite zinc sulfide nanorods (ZnS-NRs) blended with polydimethylsiloxane (PDMS). It has been found that conductive fillers, such as polyaniline (PANI) and multiwall carbon nanotubes (MWCNTs), can subsequently improve the overall performance of FPNG. A large electrical throughput (open circuit voltage ∼35 V with power density ∼2.43 μW/cm(3)) from PANI supplement added nanogenerator (PZP-FPNG) indicates that it is an effective means to replace the MWCNTs filler. The time constant (τ) estimated from the transient response of the capacitor charging curves signifying that the FPNGs are very much capable to charge the capacitors in very short time span (e.g., 3 V is accomplished in 50 s) and thus expected to be perfectly suitable in portable, wearable and flexible electronics devices. We demonstrate that FPNG can instantly lit up several commercial Light Emitting Diodes (LEDs) (15 red, 25 green, and 55 blue, individually) and power up several portable electronic gadgets, for example, wrist watch, calculator, and LCD screen. Thus, a realization of potential use of PANI in low-temperature-synthesized ZnS-NRs comprising piezoelectric based nanogenerator fabrication is experimentally verified so as to acquire a potential impact in sustainable energy applications. Beside this, wireless piezoelectric signal detection possibility is also worked out where a concept of self-powered smart sensor is introduced.

  15. Excitonic photoluminescence and photoresponse of ZnS nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Dai, Jun, E-mail: daijun@just.edu.cn [Department of Physics, Jiangsu University of Science and Technology, Zhenjiang 212003 (China); Song, Xing [School of Material Science and Engineering, Jiangsu University, Zhenjiang 212003 (China); Zheng, Hongge [Department of Physics, Jiangsu University of Science and Technology, Zhenjiang 212003 (China); Wu, Chunxia, E-mail: chxwu7771@yahoo.com.cn [School of Material Science and Engineering, Jiangsu University, Zhenjiang 212003 (China)

    2016-05-01

    Single crystal ZnS nanowires are fabricated by vapor phase transport method on sapphire substrate in the presence of Au catalyst. The morphology, composition, and crystal structure are characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM). XRD and HRTEM reveal that the ZnS nanowires have perfect single crystal wurtzite structure. The temperature-dependent photoluminescence spectra show that the ZnS nanowires present pure near-bandgap ultraviolet exciton recombination emission at 347 nm. The exciton-related optical properties, including exciton activation energy, temperature-dependent exciton energy and Varshni coefficients describing exciton energy variation, are systematically discussed. In addition, an individual ZnS nanowire-based ultraviolet photodetector is fabricated, which shows good photoresponse ability and fast response rate. The result shows that the ZnS nanowires are particularly suitable for UV photodetectors. - Highlights: • Single crystal ultrathin ZnS nanowires with diameter of 20–100 nm were fabricated by vapor phase transport method. • Exciton-related optical properties were fitted by temperature-dependent photoluminescence spectra. • Single ZnS nanowire ultraviolet photodetector with good photoswitch ability and high photocurrent was demonstrated.

  16. Effect of structure, size and copper doping on the luminescence properties of ZnS

    Energy Technology Data Exchange (ETDEWEB)

    Kamal, Ch. Satya [Crystal Growth and Nanoscience Research Centre, Government College (A), Rajahmundry, Andhra Pradesh 533 105 (India); Mishra, R.K. [Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Patel, Dinesh K. [Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Casali Center for Applied Chemistry, The Hebrew University of Jerusalem, 9190401 (Israel); Rao, K. Ramachandra, E-mail: drkrcr@gmail.com [Crystal Growth and Nanoscience Research Centre, Government College (A), Rajahmundry, Andhra Pradesh 533 105 (India); Sudarsan, V., E-mail: vsudar@barc.gov.in [Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Vatsa, R.K. [Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400085 (India)

    2016-09-15

    Highlights: • Blue and green emission intensity form ZnS is sensitive to crystallographic form. • For ZnS nanoparticles, emission characteristics are not affected by copper doping. • Cu solubility poor in ZnS nanoparticles compared to corresponding bulk. - Abstract: Luminescence properties of wurtzite and cubic forms of bulk ZnS have been investigated in detail and compared with that of ZnS nanoparticles. Blue emission observed in both hexagonal and cubic forms of undoped bulk ZnS is explained based on electron–hole recombination involving electron in conduction band and hole trapped in Zn{sup 2+} vacancies where as green emission arises due to electron hole recombination from Zn{sup 2+} and S{sup 2−} vacancies. Conversion of wurtzite form to cubic form is associated with relative increase in intensity of green emission due to increased defect concentration brought about by high temperature heat treatment. Copper doping in ZnS, initially leads to formation of both Cu{sub Zn} and Cu{sub i} (interstitial copper) centers, and latter to mainly Cu{sub Zn} centers as revealed by variation in relative intensities of blue and green emission from the samples.

  17. Characterization of Sn Doped ZnS thin films synthesized by CBD

    Energy Technology Data Exchange (ETDEWEB)

    Mukherjee, Ayan; Mitra, Partha, E-mail: mitrapartha1@rediffmail.com [Department of Physics, The University of Burdwan, Burdwan (India)

    2017-03-15

    Zinc sulphide (ZnS) thin film were prepared using chemical bath deposition (CBD) process and tin (Sn) doping was successfully carried out in ZnS. Structural, morphological and microstructural characterization was carried out using XRD, TEM, FESEM and EDX. XRD and SAED pattern confirms presence of hexagonal phase. Rietveld analysis using MAUD software was used for particle size estimation. A constantly decreasing trend in particle size was observed with increasing tin incorporation in ZnS film which was due to enhanced microstrain resulting for tin incorporation. The particle size of prepared hexagonal wurtzite ZnS was around 14-18 nm with average size of ~16.5 nm. The bandgap of the film increases from ~ 3.69 eV for ZnS to ~ 3.90 eV for 5% Sn doped ZnS film which might be due to more ordered hexagonal structure as a result of tin incorporation. Band gap tenability property makes Sn doped ZnS suitable for application in different optoelectronics devices. PL study shows variation of intensity with excitation wavelength and a red shift is noticed for increasing excitation wavelength. (author)

  18. Effect of complexing agent and annealing atmosphere on properties of nanocrystalline ZnS thin films.

    Science.gov (United States)

    Shin, Seung Wook; Oh, Hyun Pil; Pawar, S M; Moon, Jong-Ha; Kim, Jin Hyeok

    2010-05-01

    The nanocrystalline Zinc Sulfide (ZnS) thin films were prepared on glass substrates by chemical bath deposition (CBD) method using aqueous solutions of zinc acetate, thiourea and tri-sodium citrate in alkaline medium at 80 degrees C. The tri-sodium citrate acts as a complexing agent. The effects of complexing agent and annealing atmosphere (95%N2 + 5%H2S) on structural, morphological and optical properties of ZnS thin films were studied using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and optical absorption. XRD study revealed that single phase ZnS powder was formed in the solution with tri-sodium citrate, however, ZnS and ZnO mixed phase powder was formed in the solution without tri-sodium citrate. The films deposited with trisodium citrate showed ZnS with hexagonal wurtzite phase. However, annealed film in (N2 + H2S) atmosphere showed cubic (zincblende) phase. FE-SEM images show that grain size of as-deposited and annealed ZnS films are about 20 nm and 50 nm, respectively. Optical absorption study showed that the films have moderate optical transmission from 65% to 75% in the visible region and the optical band gap energy of as-deposited ZnS film is 3.91 eV and it decreases to 3.73 eV after annealing.

  19. Raman selection rule of surface optical phonon in ZnS nanobelts

    KAUST Repository

    Ho, Chih-Hsiang

    2016-02-18

    We report Raman scattering results of high-quality wurtzite ZnS nanobelts (NBs) grown by chemical vapor deposition. In Raman spectrum, the ensembles of ZnS NBs exhibit first order phonon modes at 274 cm-1 and 350 cm-1, corresponding to A1/E1 transverse optical and A1/E1 longitudinal optical phonons, in addition with strong surface optical (SO) phonon mode at 329 cm-1. The existence of SO band is confirmed by its shift with different surrounding dielectric media. Polarization dependent Raman spectrum was performed on a single ZnS NB and for the first time SO phonon band has been detected on a single nanobelt. Different selection rules of SO phonon modeshown from their corresponding E1/A1 phonon modeswere attributed to the anisotropic translational symmetry breaking on the NB surface.

  20. Ferromagnetic and antiferromagnetic orderings in wurtzite diluted magnetic nanostructures

    Science.gov (United States)

    Tronc, P.; Kitaev, Yu. E.; Hayn, R.; Strelchuk, V.; Kolomys, O.

    2017-10-01

    Using a new approach based on symmetry analysis, we have determined the magnetic symmetry groups (Shubnikov groups) of ferro- and antiferromagnetic wurtzite nanostructures doped with magnetic atoms periodically distributed at cation sites as well as the direction of the spontaneous magnetic field. Quantum wells, nanorods (nanowires), nanotubes, and quantum dots have been considered. The direction of the spontaneous magnetic field is determined by magnetic atoms with higher C3v (3m) or Cs (m) site symmetry group (the site symmetry group is defined with respect to the doped nanostructure). When the magnetic-atom distribution becomes more or less disordered (Diluted Magnetic Semiconductors), it seems reasonable to assume that, in most of the cases, the symmetry in regions with a size of some wurtzite unit-cells remains close to that of a periodic one, hence possibly inducing local ferro- or antiferromagnetic properties. The regions can induce overall ferro- or antiferromagnetic states when they have common spontaneous magnetic field direction or, possibly, induce easy-magnetization direction or plane (direction or plane of maximal magnetization intensity for a given external magnetic field strength) when disorder imposes a spread of spontaneous magnetic field direction over the various regions. Of course, such an effect adds itself to magnetic properties eventually induced by grain boundaries, other crystalline phases, and defects such as vacancies, dislocations or interstitial atoms.

  1. Effects of deposition time in chemically deposited ZnS films in acidic solution

    Energy Technology Data Exchange (ETDEWEB)

    Haddad, H.; Chelouche, A., E-mail: azeddinechelouche@gmail.com; Talantikite, D.; Merzouk, H.; Boudjouan, F.; Djouadi, D.

    2015-08-31

    We report an experimental study on the synthesis and characterization of zinc sulfide (ZnS) single layer thin films deposited on glass substrates by chemical bath deposition technique in acidic solution. The effect of deposition time on the microstructure, surface morphology, optical absorption, transmittance, and photoluminescence (PL) was investigated by X-ray diffraction (XRD), scanning electronic microscopy (SEM), UV-Vis–NIR spectrophotometry and photoluminescence (PL) spectroscopy. The results showed that the samples exhibit wurtzite structure and their crystal quality is improved by increasing deposition time. The latter, was found to affect the morphology of the thin films as showed by SEM micrographs. The optical measurements revealed a high transparency in the visible range and a dependence of absorption edge and band gap on deposition time. The room temperature PL spectra indicated that all ZnS grown thin films emit a UV and blue light, while the band intensities are found to be dependent on deposition times. - Highlights: • Single layer ZnS thin films were deposited by CBD in acidic solution at 95 °C. • The effect of deposition time was investigated. • Coexistence of ZnS and ZnO hexagonal structures for time deposition below 2 h • Thicker ZnS films were achieved after monolayer deposition for 5 h. • The highest UV-blue emission observed in thin film deposited at 5 h.

  2. A DFT Study of Structural and Electronic Properties of ZnS Polymorphs and its Pressure-Induced Phase Transitions

    OpenAIRE

    La Porta, Felipe A.; Gracia Edo, Lourdes; Andrés Bort, Juan; Sambrano, Julio Ricardo; Varela, José A.; Longo, Elson

    2014-01-01

    A systematic first-principles investigation, by using the density functional formalism with the nonlocal B3LYP approximation including a long-range dispersion correction, has been performed to calculate the structural and electronic properties and phase transitions under pressure of the three phases of ZnS (cubic zinc blende, ZB, hexagonal wurtzite, W, and cubic rock salt, RS). Numerical and analytical fittings have been carried out to determine the equilibrium unit cell geometry and equation...

  3. Effect of solvent medium on the structural, morphological and optical properties of ZnS nanoparticles synthesized by solvothermal route

    Energy Technology Data Exchange (ETDEWEB)

    Mendil, R., E-mail: radia.mendil@yahoo.fr [Laboratoire de Physique des Matériaux et des Nanomatériaux appliquée à l' Environnement, Université de Gabès, Faculté des Sciences de Gabès, Cité Erriadh Manara Zrig, 6072 Gabès (Tunisia); Ben Ayadi, Z. [Laboratoire de Physique des Matériaux et des Nanomatériaux appliquée à l' Environnement, Université de Gabès, Faculté des Sciences de Gabès, Cité Erriadh Manara Zrig, 6072 Gabès (Tunisia); Djessas, K. [Laboratoire Procédés, Matériaux et Energie Solaire (PROMES-CNRS), TECNOSUD, Rambla de la thermodynamique, 66100 Perpignan (France); Université de Perpignan Via Domitia, 52 avenue Paul Alduy, 68860, Perpignan Cedex9 (France)

    2016-09-05

    Different morphologies of ZnS have been synthesized by a facile solvothermal approach in a mixed solvent made of Ethylenediamine (EN) and distilled water. The effect of solvent medium on the structural, morphological and optical properties of ZnS nanoparticles were investigated. The formation mechanism of different morphologies was proposed based on the experiment results. The as-prepared samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive spectrometer (EDS), Raman spectroscopy and UV-Vis-IR spectrophotometer. The results show that phase transformation is easily induced and there is a strong correlation between morphology and structure of the ZnS nanocrystals by changing the solvent. The results also show that we have successfully produced hexagonal phase ZnS nanorods with mixed solvent. The grain sizes in the range of 17–22 nm were obtained according to elaboration conditions. Raman spectra show the intense peak at 346 cm{sup −1}, which is a typical Raman peak of bulk ZnS crystal, no signature of secondary phases. The band gap of ZnS increased from 3.49 to 3.74 eV with an increase in the EN composition in the solvent, implying that the optical properties of these materials are clearly affected by the synthesis medium. - Highlights: • ZnS was prepared at low temperature using solvothermal method. • The phase transformation and shape evolution processes were studied. • The role of solvent (EN/W) has been discussed for formation of ZnS nanostructures with different morphology. • The properties and growth mechanism of ZnS nanoparticles were investigated. • Optical band gap of ZnS powder were investigated using UV vis spectroscopy.

  4. Study of energy transfer from capping agents to intrinsic vacancies/defects in passivated ZnS nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Manoj, E-mail: manojnarad@gmail.co [Thapar University, School of Physics and Materials Science (India); Kumar, Sunil, E-mail: sunilkumar32@gmail.co [Maharishi Markandeshwar University, Department of Physics (India); Pandey, O. P. [Thapar University, School of Physics and Materials Science (India)

    2010-09-15

    The study of energy transfer mechanism from different capping agents to intrinsic luminescent vacancy centres of zinc sulphide (ZnS) has been reported in the present work. Nanoparticles of capped and uncapped ZnS are prepared by co-precipitation reaction. These nanoparticles are sterically stabilized using organic polymers-poly vinyl pyrrolidone, 2-mercaptoethanol and thioglycerol. Monodispersed nanoparticles were observed under TEM for both capped and uncapped ZnS nanopowders. However, for uncapped ZnS nanopowders, tendency for formation of nanorod like structure exists. Size of ZnS crystallites was calculated from X-ray diffraction pattern. The primary crystallite size estimated from X-ray diffraction pattern is 1.95-2.20 nm for capped nanostructures and 2.2 nm for uncapped nanostructures. FTIR spectra were conducted to confirm capping. Zeta potential measurements have been done to check the stability of dispersed nanoparticles. Band gap measurement was done by UV-visible spectrophotometer. Excitation and emission spectra are also performed in order to compare optical properties in various samples. Increase in emission intensity and band gap has been observed by adding different capping agents in comparison to uncapped ZnS nanoparticles. The results show that in capped ZnS nanoparticles the mechanism of energy transfer from capping layer to photoluminescent vacancy centres is more pronounced.

  5. Synthesis of GaN Nanorods by a Solid-State Reaction

    Directory of Open Access Journals (Sweden)

    Keyan Bao

    2010-01-01

    Full Text Available An atom-economical and eco-friendly chemical synthetic route was developed to synthesize wurtzite GaN nanorods by the reaction of NaNH2 and the as-synthesized orthorhombic GaOOH nanorods in a stainless steel autoclave at 600∘C. The lengths of the GaN nanorods are in the range of 400–600 nm and the diameters are about 80–150 nm. The process of orthorhombic GaOOH nanorods transformation into wurtzite GaN nanorods was investigated by powder X-ray diffraction (XRD and field emission scanning electron microscope (FESEM, indicating that the GaN product retained essentially the same basic topological morphology in contrast to that of the GaOOH precursor. It was found that rhombohedral Ga2O3 was the intermediate between the starting orthorhombic GaOOH precursor and the final wurtzite GaN product. The photoluminescence measurements reveal that the as-prepared wurtzite GaN nanorods showed strong blue emission.

  6. An investigation on the pressure-induced phase transition of nanocrystalline ZnS

    CERN Document Server

    Pan Yue Wu; Dong Shu Shan; Cui Qi Liang; Zhang Wei; LiuXiZhe; LiuJing; Liu Bing Bing; Gao Chun Xi; Zou Guang Tian

    2002-01-01

    An in situ energy dispersive x-ray diffraction study on nanocrystalline ZnS was carried out under high pressure up to 30.8 GPa by using a diamond anvil cell. The phase transition from the wurtzite to the zinc-blende structure occurred at 11.5 GPa, and another obvious transition to a new phase with rock-salt structure also appeared at 16.0 GPa - which was higher than the value for the bulk material. The bulk modulus and the pressure derivative of nanocrystalline ZnS were derived by fitting the Birch-Murnaghan equation. The resulting modulus was higher than that of the corresponding bulk material, indicating that the nanomaterial has higher hardness than the bulk material.

  7. Photoemission studies of wurtzite zinc oxide.

    Science.gov (United States)

    Powell, R. A.; Spicer, W. E.; Mcmenamin, J. C.

    1972-01-01

    The electronic structure of wurtzite zinc oxide, investigated over the widest possible photon energy range by means of photoemission techniques, is described. Of particular interest among the results of the photoemission study are the location of the Zn 3rd core states, the width of the upper valence bands, and structure in the conduction-band and valence-band density of states.

  8. Surface characterization of ZnO nanorods grown by chemical bath deposition

    Energy Technology Data Exchange (ETDEWEB)

    Mbulanga, C.M., E-mail: crispin.mbulanga@nmmu.ac.za [Department of Physics, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031 (South Africa); Urgessa, Z.N.; Tankio Djiokap, S.R.; Botha, J.R. [Department of Physics, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031 (South Africa); Duvenhage, M.M.; Swart, H.C. [Department of Physics, University of the Free State, P.O Box 77000, Bloemfontein ZA9300 (South Africa)

    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.

  9. Surface characterization of ZnO nanorods grown by chemical bath deposition

    Science.gov (United States)

    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.

  10. Surface plasmon resonance in nanostructured Ag incorporated ZnS films

    Energy Technology Data Exchange (ETDEWEB)

    Chalana, S. R.; Mahadevan Pillai, V. P., E-mail: vpmpillai9@gmail.com [Department of Optoelectronics, University of Kerala, Kariavattom, Thiruvananthapuram– 695581, Kerala (India); Ganesan, V. [UGC-DAE Consortium for Scientific Research, Khandwa Road, Indore- 452017, Madhyapradesh (India)

    2015-10-15

    Silver incorporated zinc sulfide thin films are prepared by RF magnetron sputtering technique and the influence of silver incorporation on the structural, optical and luminescence properties is analyzed using techniques like grazing incidence X-Ray diffraction (GIXRD), atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), micro-Raman spectroscopy, UV-Vis spectroscopy and laser photoluminescence spectroscopy. XRD analysis presents hexagonal wurtzite structure for the films. A reduction of crystallinity of the films is observed due to Ag incorporation. The Raman spectral analysis confirms the reduction of crystallinity and increase of strain due to the Ag incorporation. AFM analysis reveals a rough surface morphology for the undoped film and Ag incorporation makes the films uniform, dense and smooth. A blue shift of band gap energy with increase in Ag incorporation is observed due to quantum confinement effect. An absorption band (450-650 nm region) due to surface plasmon resonance of the Ag clusters present in the ZnS matrix is observed for the samples with higher Ag incorporation. The complex dielectric constant, loss factor and distribution of volume and surface energy loss of the ZnS thin films are calculated. Laser photoluminescence measurements gives an intense bluish green emission from the ZnS films and a quenching of the PL emission is observed which can be due to the metal plasmonic absorption and non-radiative energy transfer due to Ag incorporation.

  11. Structural, thermal, magnetic and optical characterization of undoped nanocrystalline ZnS prepared by solid state reaction

    Energy Technology Data Exchange (ETDEWEB)

    Faita, F.L., E-mail: flffisica@yahoo.com.br [Departamento de Física, Universidade Federal de Santa Catarina, Campus Trindade, 88040-900 Florianópolis, SC (Brazil); Ersching, K. [Instituto Federal de Educação, Ciência e Tecnologia Catarinense – Campus Camboriú, 88340-000 Camboriú, SC (Brazil); Poffo, C.M. [Departamento de Física, Universidade Federal do Amazonas, 3000 Japiim, 69077000 Manaus, AM (Brazil); Benetti, L.C. [Departamento de Física, Universidade Federal de Santa Catarina, Campus Trindade, 88040-900 Florianópolis, SC (Brazil); Trichês, D.M.; Souza, S.M. [Departamento de Física, Universidade Federal do Amazonas, 3000 Japiim, 69077000 Manaus, AM (Brazil); Viegas, A.D.C.; Lima, J.C. de [Departamento de Física, Universidade Federal de Santa Catarina, Campus Trindade, 88040-900 Florianópolis, SC (Brazil)

    2014-03-25

    Highlights: • Nanocrystalline zinc blende and wurtzite ZnS phases produced by mechanical alloying. • Sulfur and/or zinc vacancies in the ZnS as-milled. • Magnetic and semiconductor behavior for the as-milled ZnS-10h. • Irreversible demagnetization and Curie temperature above room temperature. • Structural stability after annealing and aged of the ZnS-10h sample. -- Abstract: Nanocrystalline zinc blende and wurtzite ZnS phases with sulfur and/or zinc vacancies were obtained from a mechanically alloyed Zn{sub 50}S{sub 50} powder mixture. Structural, thermal, magnetic, optical and photoacoustic studies were carried out using X-ray diffraction, transmission electron microscopy, differential scanning calorimetry, vibrating sample magnetometer, UV–Vis absorption, photoluminescence and photoacoustic spectroscopy techniques. The cubic zinc blende (ZnS{sup ZB}) and hexagonal wurtzite (ZnS{sup WZ}) phases were nucleated in 3 h of milling and remained until 10 h when the milling process was stopped. The coexistence of these two phases was confirmed by high resolution transmission electron microscopy. X-ray diffraction measurements attested the structural stability of the sample milled for 10 h and aged for eighteen months and of the sample milled 10 h and annealed at 300 °C and 600 °C. Differential scanning calorimetry measurements showed the unreacted sulfur in molecular form (rings and/or chains). Magnetic behavior was observed for as-milled sample and Curie temperature was estimated at 430 °C. Moreover, an irreversible behavior of magnetic properties was observed and correlated with changes on the structural vacancies densities. The UV–Vis absorption spectra and McLean analysis showed an optical band gap around 3.4 eV and 3.9 for ZnS{sup ZB} and ZnS{sup WZ} phases, respectively. The sample milled for 10 h showed low blue photoemission intensity centered at 470 nm and thermal diffusivity around 0.02 cm{sup 2}/s.

  12. Effect of growth durations on the formation of ZnO nanorods prepared using continuous microwave heating technique

    Science.gov (United States)

    Jumali, Mohammad Hafizuddin Hj; Lee, Hock Beng; Abbas, Haidr Abdulzahra

    2017-05-01

    The effect of growth durations on the formation of ZnO nanorods thin film under continuous microwave irradiation was investigated. ZnO nanorods were synthesized using a microwave-assisted seed mediated growth method. ZnO nanoseed layer was prepared on Si substrate using a sol-gel technique. The microwave-assisted seed mediated growth of ZnO nanorods was conducted at different growth durations, namely 15, 20 and 30 min by fixing the irradiation power at 110 W. XRD diffractogram shows that the hexagonal wurtzite crystal structure for all the samples exhibited a preferred growth orientation along the c-axis. FESEM micrographs reveal with increasing heating duration, the average diameter of ZnO nanorods increased considerably and contrarily, the surface density of nanorods reduced. PL analysis suggests that an extended growth duration has resulted in the creation of defects in nanorods films owing to the insufficient supply of precursor ions during growth process.

  13. Polarized Raman scattering of single ZnO nanorod

    Energy Technology Data Exchange (ETDEWEB)

    Yu, J. L., E-mail: jlyu@semi.ac.cn; Lai, Y. F., E-mail: laiyunfeng@gmail.com; Wang, Y. Z.; Cheng, S. Y. [Institute of Micro/Nano Devices and Solar Cells, School of Physics and Information Engineering, Fuzhou University, Fuzhou (China); Chen, Y. H. [Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083 (China)

    2014-01-21

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

  14. Facile in situ synthesis of wurtzite ZnS/ZnO core/shell heterostructure with highly efficient visible-light photocatalytic activity and photostability

    Science.gov (United States)

    Xiao, Jian-Hua; Huang, Wei-Qing; Hu, Yong-sheng; Zeng, Fan; Huang, Qin-Yi; Zhou, Bing-Xin; Pan, Anlian; Li, Kai; Huang, Gui-Fang

    2018-02-01

    High photocatalytic activity and photostability are the pursuit of the goal for designing promising photocatalysts. Herein, using ZnO to encapsulate ZnS nanoparticles is proposed as an effective strategy to enhance photocatalytic activity and anti-photocorrosion. The ZnS/ZnO core/shell heterostructures are obtained via an annealing treatment of ZnS nanoparticles produced by a facile wet chemical approach. Due to its small size, the nascent cubic sphalerite ZnS (s-ZnS) converts into a hexagonal wurtzite ZnS (w-ZnS)/ZnO core/shell structure after annealing treatment. In situ oxidation leads to increasing ZnO, simultaneously decreasing the w-ZnS content in the resultant w-ZnS/ZnO with thermal annealing time. The w-ZnS/ZnO core/shell heterostructures show high photocatalytic activity, demonstrated by the photodegradation rate of methylene blue being up to ten-fold and seven-fold higher than that of s-ZnS under UV and visible light irradiation, respectively, and the high capability of degrading rhodamine B. The enhanced photocatalytic activity may be attributed to the large specific surface and improved charge carrier separation at the core/shell interface. Moreover, it displays high photostability owing to the protection of the ZnO shell, greatly inhibiting the photocorrosion of ZnS. This facile in situ oxidation is effective and easily scalable, providing opportunities for developing novel core/shell structure photocatalysts with high activity and photostability.

  15. Structural and Optical Properties of Eu Doped ZnO Nanorods prepared by Pulsed Laser Deposition

    KAUST Repository

    Alarawi, Abeer

    2014-06-23

    Nano structured wide band gap semiconductors have attracted attention of many researchers due to their potential electronic and optoelectronic applications. In this thesis, we report successful synthesis of well aligned Eu doped ZnO nano-rods prepared, for the first time to our knowledge, by pulsed laser deposition (PLD) without any catalyst. X-ray diffraction (XRD) patterns shows that these Eu doped ZnO nanorods are grown along the c-axis of ZnO wurtzite structure. We have studied the effect of the PLD growth conditions on forming vertically aligned Eu doped ZnO nanorods. The structural properties of the material are investigated using a -scanning electron microscope (SEM). The PLD parameters must be carefully controlled in order to obtain c-axis oriented ZnO nanorods on sapphire substrates, without the use of any catalyst. The experiments conducted in order to identify the optimal growth conditions confirmed that, by adjusting the target-substrate distance, substrate temperature, laser energy and deposition duration, the nanorod size could be successfully controlled. Most importantly, the results indicated that the photoluminescence (PL) properties reflect the quality of the ZnO nanorods. These parameters can change the material’s structure from one-dimensional to two-dimensional however the laser energy and frequency affect the size and the height of the nanorods; the xygen pressure changes the density of the nanorods.

  16. Tip-morphology-dependent field emission from ZnO nanorod arrays

    Energy Technology Data Exchange (ETDEWEB)

    Pan Nan; Xue Haizhou; Yu Minghui; Cui Xuefeng; Wang Xiaoping; Hou, J G [Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026 (China); Huang Jianxing; Deng, S Z, E-mail: xpwang@ustc.edu.cn [Guangdong Provincial Key Laboratory of Display Materials and Technology, Sun Yat-Sen University, Guangzhou, Guangdong 510275 (China)

    2010-06-04

    Vertically well-aligned ZnO nanorod arrays with three kinds of tip morphology-abruptly sharpened, tapered and plane-have been controllably fabricated with wafer size uniformity by vapor phase transport and condensation. Except that the tip morphology is distinctly different, all of these nanorods are single crystalline, growing along their wurtzite (0001) axis, with similar diameters, lengths and densities. The field emission properties of these nanorod arrays are comparatively investigated and are found to be strongly affected by the tip morphology. A nanorod with the abruptly sharpened tip possesses the lowest turn-on and threshold electric fields as well as the highest field enhancement factor. Further analysis reveals that the abruptly sharpened tip morphology can reduce the screening effect more efficiently than the others. These results are very helpful for the design, fabrication and optimization of integrated field emitters using 1D nanostructures as the cathode material.

  17. Comparative study of as-implanted and pre-damaged ion-beam-synthesized ZnS nanocrystallites in SiO sub 2

    CERN Document Server

    Gao, K Y; Grosshans, I; Hipp, W; Stritzker, B

    2002-01-01

    The semiconducting ZnS nanocrystallites were synthesized by sequential high dose ion implantation of Zn and S in thermally grown SiO sub 2 on Si(1 0 0) and subsequent rapid thermal annealing (RTA). Some samples were pre-implanted with Ar ions in order to investigate the influence of radiation induced damage on the formation of ZnS nanocrystallites. The crystal structure of the ZnS crystallites, their size distribution and the concentration depth profile were analyzed by X-ray diffraction (XRD), Rutherford backscattering spectroscopy (RBS) and cross-sectional transmission-electron-microscopy (XTEM). The XRD results indicate, that the phase transition from cubic zinc blende to hexagonal wurtzite structure of ZnS nanocrystallites begins at temperatures below 1000 degree sign C. The RBS results show a clear redistribution of Zn and S after RTA annealing. The concentration of Zn is seriously reduced due to strong diffusion towards deeper regions and the surface, while Ar pre-implantation partially suppressed the c...

  18. Transformation from Film to Nanorod via a Sacrifical Layer: Pulsed Laser Deposition of ZnO for Enhancing Photodetector Performance.

    Science.gov (United States)

    Ou, Sin-Liang; Yu, Fei-Peng; Wuu, Dong-Sing

    2017-10-27

    A novel fabrication method for single crystalline ZnO nanorods by pulsed laser deposition (PLD) using a chemical-bath-deposited ZnS seed layer is proposed. For the substrate temperature (Ts) lower than 700 °C, the PLD-ZnO showed a polycrystalline phase and film-type morphology, resulting from the ZnS seed layer with a cubic phase. However, the ZnS film became a sacrifical layer and single crystalline ZnO(002) nanorods can be achieved at Ts of 900 °C, where ZnS was decomposed to zinc metals and sulfur fumes. The transformation from ZnO film to nanorod microstructure was demonstrated with the change of ZnS layer into Zn grains. Enhanced performance of the metal-semiconductor-metal photodetectors were fabricated with ZnO/ZnS samples grown at Ts of 500, 700, and 900 °C. The responsivities (@1 V and 370 nm) of these three devices were 1.71, 6.35, and 98.67 A/W, while their UV-to-visible discrimination ratios were 7.2, 16.5, and 439.1, respectively. Obviously, a higher light-capturing efficiency was obtained in the 900 °C-grown ZnO/ZnS device owing to its one-dimensional nanostructure with high crystal quality. The results indicate PLD combined with a sacrifical nanostructure is a promising method for obtaining high-quality ZnO nanorods, which paves the way for the fabrication of high performance ZnO-based devices.

  19. Strain effects on valence bands of wurtzite ZnO

    Science.gov (United States)

    Qiao, LiPing; Chai, ChangChun; Jin, Zhao; Yang, YinTang; Ma, ZhenYang

    2013-09-01

    Based on the k.p theory of Luttinger-Kohn and Bir-Pikus, analytical E-k solutions for the valence band of strained wurtzite ZnO materials are obtained. Strain effects on valence band edges and hole effective masses in strained wurtzite ZnO materials are also discussed. In comparison with unstrained ZnO materials, apparent movement of valence band edges such as "light hole band", "heavy hole band" and "crystal splitting band" at Γ point is found in strained wurtzite ZnO materials. Moreover, effective masses of "light hole band", "heavy hole band" and "crystal splitting band" for strained wurtzite ZnO materials as the function of stress are given. The analytical results can provide a theoretical foundation for the understanding of physics of strained ZnO materials and its applications with the framework for an effective mass theory.

  20. Room temperature photoluminescence properties of ZnO nanorods grown by hydrothermal reaction

    Energy Technology Data Exchange (ETDEWEB)

    Iwan, S., E-mail: iwan-sugihartono@unj.ac.id [Jurusan Fisika, FMIPA-UNJ, Rawamangun, Jakarta (Indonesia); Prodi Ilmu Material, Departemen Fisika, FMIPA, Universitas Indonesia, Kampus UI Depok (Indonesia); Fauzia, Vivi [Prodi Ilmu Material, Departemen Fisika, FMIPA, Universitas Indonesia, Kampus UI Depok (Indonesia); Umar, A. A. [Institute of Microengineering and Nanoelectronics, Universiti Kebangsaan Malaysia, UKM Bangi, Selangor (Malaysia); Sun, X. W. [School of Electrical & Electronic Engineering, Nanyang Technological University, Nanyang Avenue (Singapore)

    2016-04-19

    Zinc oxide (ZnO) nanorods were fabricated by a hydrothermal reaction on silicon (Si) substrate at 95 °C for 6 hours. The ZnO seed layer was fabricated by depositing ZnO thin films on Si substrates by ultrasonic spray pyrolisis (USP). The annealing effects on crystal structure and optical properties of ZnO nanorods were investigated. The post-annealing treatment was performed at 800 °C with different environments. The annealed of ZnO nanorods were characterized by X-ray diffraction (XRD) and photoluminescence (PL) in order to analyze crystal structure and optical properties, respectively. The results show the orientations of [002], [101], [102], and [103] diffraction peaks were observed and hexagonal wurtzite structure of ZnO nanorods were vertically grown on Si substrates. The room temperature PL spectra show ultra-violet (UV) and visible emissions. The annealed of ZnO nanorods in vacuum condition (3.8 × 10{sup −3} Torr) has dominant UV emission. Meanwhile, non-annealed of ZnO nanorods has dominant visible emission. It was expected that the annealed of ZnO in vacuum condition suppresses the existence of native defects in ZnO nanorods.

  1. Low-temperature growth of ZnO nanorods by chemical bath deposition.

    Science.gov (United States)

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

    2007-09-15

    Aligned ZnO nanorod arrays were synthesized using a chemical bath deposition method at normal atmospheric pressure without any metal catalyst. A simple two-step process was developed for growing ZnO nanorods on a PET substrate at 90-95 degrees C. The ZnO seed precursor was prepared by a sol-gel reaction. ZnO nanorod arrays were fabricated on ZnO-seed-coated substrate. The ZnO seeds were indispensable for the aligned growth of ZnO nanorods. The ZnO nanorods had a length of 400-500 nm and a diameter of 25-50 nm. HR-TEM and XRD analysis confirmed that the ZnO nanorod is a single crystal with a wurtzite structure and its growth direction is [0001] (the c-axis). Photoluminescence measurements of ZnO nanorods revealed an intense ultraviolet peak at 378.3 nm (3.27 eV) at room temperature.

  2. Vertically aligned ZnO nanorods on porous silicon substrates: Effect of growth time

    Directory of Open Access Journals (Sweden)

    R. Shabannia

    2015-04-01

    Full Text Available Vertically aligned ZnO nanorods were successfully grown on porous silicon (PS substrates by chemical bath deposition at a low temperature. X-ray diffraction, field-emission scanning electron microscopy (FESEM, transmission electron microscopy (TEM, and photoluminescence (PL analyses were carried out to investigate the effect of growth duration (2 h to 8 h on the optical and structural properties of the aligned ZnO nanorods. Strong and sharp ZnO (0 0 2 peaks of the ZnO nanorods proved that the aligned ZnO nanorods were preferentially fabricated along the c-axis of the hexagonal wurtzite structure. FESEM images demonstrated that the ZnO nanorod arrays were well aligned along the c-axis and perpendicular to the PS substrates regardless of the growth duration. The TEM image showed that the top surfaces of the ZnO nanorods were round with a smooth curvature. PL spectra demonstrated that the ZnO nanorods grown for 5 h exhibited the sharpest and most intense PL peaks within the ultraviolet range among all samples.

  3. Formation of hexagonal-wurtzite germanium by pulsed laser ablation

    Science.gov (United States)

    Zhang, Y.; Iqbal, Z.; Vijayalakshmi, S.; Qadri, S.; Grebel, H.

    2000-08-01

    A stable phase of relatively large hexagonal-wurtzite germanium (lonsdaleite) crystals (up to 10 μm) was formed when germanium was directly deposited at low pressure using pulsed ultraviolet laser ablation. Films were grown on various substrates at room temperature from a single crystal, cubic germanium target. Crystallites of the hexagonal-wurtzite phase of germanium were clearly identified using selected area electron diffraction. Further characterizations of the films were made using X-ray diffraction and confocal scanning micro-Raman spectroscopy.

  4. Band structure of wurtzite quantum dots with cylindrical symmetry

    Science.gov (United States)

    Voon, Lok Lew Yan; Galeriu, Calin; Lassen, Benny

    2005-03-01

    A six-band k .p theory for wurtzite semiconductor nanostructures with cylindrical symmetry will be presented. Our work extends the formulation of Vahala and Sercel [Phys. Rev. Lett. 65, 239 (1990)] to the Rashba-Sheka-Pikus Hamiltonian for wurtzite semiconductors, without the need for the axial approximation. Results comparing this new formulation for studying the electronic structure of wurzite GaN and CdS cylindrical quantum dots with the conventional formulation will be shown; our formulation is computationally superior. An application to the search for level crossing in the valence band of cylindrical quantum rods as a function of aspect ratio will be given. Supported by NSF CAREER award.

  5. Graded core/shell semiconductor nanorods and nanorod barcodes

    Science.gov (United States)

    Alivisatos, A. Paul; Scher, Erik C.; Manna, Liberato

    2010-12-14

    Graded core/shell semiconductor nanorods and shaped nanorods are disclosed comprising Group II-VI, Group III-V and Group IV semiconductors and methods of making the same. Also disclosed are nanorod barcodes using core/shell nanorods where the core is a semiconductor or metal material, and with or without a shell. Methods of labeling analytes using the nanorod barcodes are also disclosed.

  6. Photoluminescence of Hexagonal ZnO Nanorods Hydrothermally Grown on Zn Foils in KOH Solutions with Different Values of Basicity

    Directory of Open Access Journals (Sweden)

    Nuengruethai Ekthammathat

    2013-01-01

    Full Text Available Aligned hexagonal ZnO nanorods on pure Zn foils were hydrothermally synthesized in 30 mL solutions containing 0.05–0.50 g KOH. The products were characterized by X-ray diffraction (XRD, scanning electron microscopy (SEM, transmission electron microscopy (TEM, and photoluminescence (PL spectroscopy. In this research, wurtzite hexagonal ZnO nanorods grown along the [002] direction with green light emission at 541 nm caused by singly ionized oxygen vacancies inside were detected.

  7. Synthesis, structure and electronic properties of ultranarrow CdS nanorods

    Energy Technology Data Exchange (ETDEWEB)

    Thupakula, Umamahesh; Jena, Amitav; Khan, Ali Hossain; Dalui, Amit; Acharya, Somobrata, E-mail: camsa2@iacs.res.in [Indian Association for the Cultivation of Science, Centre for Advanced Materials (CAM) (India)

    2012-01-15

    We report on the one-step synthesis of ultra narrow wurtzite CdS nanorods using bench top chemical decomposition route. The synthesized CdS nanorods are of 1.8 nm in diameter and show major confinement along the radial dimension, which is well below the exciton Bohr radius of bulk CdS (2.5 nm). Structural and self-assembly properties of nanorods are studied using X-ray Diffraction (XRD) and small angle X-ray scattering (SAXS) measurements, which reveal preferred orientation of the nanorods along <00.2> direction with 2D supercrystalline spatial distribution. The estimated nanorod dimensions from XRD is corroborated with the transmission electron microscopy observations. UV-vis and photoluminescence spectroscopy reveals significant increase in the band gap in comparison to bulk CdS which is further tallied with the simulations using effective mass approximation (EMA). Formation of discrete structure of valence band and conduction band due to strongly quantum confined excitons in the radial direction is evidenced from EMA simulation. Combination of experimental and theoretical approach helps in understanding the structure-property relationship for ultranarrow CdS rods which might lead to nanorod based applications.

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

    Science.gov (United States)

    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.

  9. High-quality vertically aligned ZnO nanorods synthesized by microwave-assisted CBD with ZnO-PVA complex seed layer on Si substrates

    Energy Technology Data Exchange (ETDEWEB)

    Hassan, J.J., E-mail: j1j2h72@yahoo.com [Nano-Optoelectronics Research and Technology Laboratory (N.O.R), School of Physics University Sains Malaysia, Penang 11800 (Malaysia); Hassan, Z.; Abu-Hassan, H. [Nano-Optoelectronics Research and Technology Laboratory (N.O.R), School of Physics University Sains Malaysia, Penang 11800 (Malaysia)

    2011-06-09

    Highlights: > We synthesis high quality ZnO nanorods with low temperature. > We used inorganic-organic nanocomposites ZnO-PVA to prepare good seed layer. > We observed the effect of annealing temperatures of ZnO-PVA seed layer on diameter of produced ZnO nanorods. > We obtained very high photoluminescence from ZnO nanorods synthesis on silicon substrate. - Abstract: We successfully synthesized vertically aligned zinc oxide (ZnO) nanorods on seeded silicon substrates using chemical bath deposition assisted by microwave heating. ZnO nanorods were grown on seed layers of ZnO-polyvinyl alcohol (PVA) nanocomposites spin-coated on p-type Si (1 1 1). The nanorod's diameter was found to be dependent on the annealing temperature of the ZnO-PVA seed layer. We produced ZnO nanorods with diameters in the range of 50-300 nm from five groups of seed layers annealed at 250 deg. C, 350 deg. C, 380 deg. C, 450 deg. C, and 550 deg. C. The nanorods were examined with X-ray diffraction, transmission electron microscopy, and field emission scanning electron microscopy, which revealed hexagonal wurtzite structures perpendicular to the substrate along the z-axis in the direction of (0 0 2). Photoluminescence measurements revealed high UV emission at a high I{sub UV}/I{sub vis} ratio of 175. We also conducted Raman scattering studies on the ZnO nanorods to estimate the lattice vibration modes.

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

    Directory of Open Access Journals (Sweden)

    Omar F. Farhat

    2015-03-01

    Full Text Available 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.

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

    Directory of Open Access Journals (Sweden)

    Zafar Hussain Ibupoto

    2013-08-01

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

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

    Science.gov (United States)

    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.

  13. Study of surface morphology control and investigation of hexagonal indium nitride nanorods grown on GaN/sapphire substrate.

    Science.gov (United States)

    Kuo, Shou-Yi; Chen, Wei-Chun; Lai, Fang-I; Lin, Woei-Tyng; Wang, Han-Yang; Hsiao, Chien-Nan

    2012-02-01

    Heteroepitaxial growth of metal-catalyst-free indium nitride (InN) nanorods on GaN/sapphire substrates by radio-frequency metal-organic molecular beam epitaxy (RF-MOMBE) system was investigated. We found that different N/In flow ratios together with the growth temperatures greatly influenced the surface morphology of InN nanorods and their structural properties. The InN nanorods have been characterized in detail using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM). Optical property was evaluated by photoluminescence (PL) measurements. At lower growth temperatures, InN nanorods were successfully grown. A pronounced two-dimensional growth mode was observed at higher growth temperature of 500 degrees C, and these films showed preferred orientation along the c-axis. XRD patterns and SEM images reveal that InN nanorods has high quality wurtzite structure with FWHM approaching 900 arcsec, and they have uniform diameters of about 150 nm and length of about 800 nm. Meanwhile, no metallic droplet was observed at the end of the nanostructured InN, and this is strong evidence that the nanorods are grown via the self-catalyst process. The PL peak at 0.8 eV is attributed to the quantum confinement and Moss-Burstein effects. These observations provide some valuable insights into the physical-chemical process for manufacturing InN nanorods devices.

  14. ZnO:Ag nanorods as efficient photocatalysts: Sunlight driven photocatalytic degradation of sulforhodamine B

    Science.gov (United States)

    Raji, R.; K. S., Sibi; K. G., Gopchandran

    2018-01-01

    Visible light responsive highly photocatalytic ZnO:Ag nanorods with varying Ag concentration were synthesized via co-precipitation method. X-ray diffraction analysis and high resolution transmission electron microscopy investigations confirmed the hexagonal wurtzite phase for these ZnO:Ag nanorods with preferential growth along the (101) plane. Raman shift and luminescence measurements indicated that the incorporation of Ag influences the lattice vibrational modes; there by causing distortion in lattice, inducing silent vibrational modes and emission behavior by quenching of both the band edge and visible emissions respectively. The photocatalytic performance of these nanorods as catalysts was tested by observing the photodegradation of a representative dye pollutant, viz., sulforhodamine B under sunlight irradiation. Photocatalytic performance was evaluated by determining the rate of reaction kinetics, photodegradation efficiency and mineralization efficiency. A high rate constant of 0.552 min-1, chemical oxygen demand value of 5.8 ppm and a mineralization efficiency of 94% were obtained when ZnO: Ag nanorods with an Ag content of 1.5 at.% were used as catalysts. The observed increase in photocatalytic efficiency with Ag content in ZnO:Ag nanorods is attributed to the electron scavenging action of silver, Schottky barrier between the Ag and ZnO interface and the better utilization of sunlight due to enhanced absorption due to plasmons in the visible region. BET analysis indicated that silver doping causes effective surface area of nanorods to increase, which in turn increases the photocatalytic efficiency. The possible mechanism for degradation of dye under sunlight irradiation is described with a schematic and the photostability of the ZnO:Ag nanorods were also tested through five repetitive cycles. This work suggests that the prepared ZnO:Ag nanorods are excellent reusable photocatalysts for the degradation of toxic organic waste in water, which causes severe

  15. Ferromagnetism in sphalerite and wurtzite CdS nanostructures.

    Science.gov (United States)

    Yang, Zhaolong; Gao, Daqiang; Zhu, Zhonghua; Zhang, Jing; Shi, Zhenhua; Zhang, Zhipeng; Xue, Desheng

    2013-01-07

    Room-temperature ferromagnetism is observed in undoped sphalerite and wurtzite CdS nanostructures which are synthesized by hydrothermal methods. Scanning electron microscopy and transmission electron microscopy results indicate that the sphalerite CdS samples show a spherical-like shape and the wurtzite CdS ones show a flower-like shape, both of which are aggregated by lots of smaller particles. The impurity of the samples has been ruled out by the results of X-ray diffraction, selected-area electron diffraction, and X-ray photoelectron spectroscopy. Magnetization measurements indicate that all the samples exhibit room-temperature ferromagnetism and the saturation magnetization decreases with the increased crystal sizes, revealing that the observed ferromagnetism is defect-related, which is also confirmed by the post-annealing processes. This finding in CdS should be the focus of future electronic and spintronic devices.

  16. The fundamental surface science of wurtzite gallium nitride

    Science.gov (United States)

    Bermudez, V. M.

    2017-09-01

    A review is presented that covers the experimental and theoretical literature relating to the preparation, electronic structure and chemical and physical properties of the surfaces of the wurtzite form of GaN. The discussion includes the adsorption of various chemical elements and of inorganic, organometallic and organic species. The focus is on work that contributes to a microscopic, atomistic understanding of GaN surfaces and interfaces, and the review concludes with an assessment of possible future directions.

  17. Natural zinc enrichment in peatlands: Biogeochemistry of ZnS formation

    Science.gov (United States)

    Yoon, Soh-joung; Yáñez, Carolina; Bruns, Mary Ann; Martínez-Villegas, Nadia; Martínez, Carmen Enid

    2012-05-01

    Peatlands effectively retain heavy metals and prevent stream and watershed contamination. Sulfate reduction is considered the most significant process of metal immobilization in natural wetlands and microbial sulfate reduction is the presumed mechanism that results in the precipitation of metal sulfides. In this study, we examined the biogeochemical mechanisms involved in zinc retention and accumulation in a metalliferous peatland of western New York. In the reducing conditions of these peatlands zinc sulfides occurred as framboidal aggregates of sphalerite and polytypic wurtzite (2nH, n ⩾ 2) nanocrystallites associated with bacterial cells and organic matter. Bacterial cells were co-located with ZnS inside peat particles where the microenvironment remained anoxic. The peat zinc sulfide was depleted in 34S isotopes relative to the sulfate supplied to the peatland by 18-34 per mill, implicating its biological formation. Extraction of microbial community DNA from peat samples yielded diverse PCR amplicons from dissimilatory sulfite reductase (dsrAB) genes, indicating varied bacterial taxa capable of reducing forms of oxidized sulfur. Nanocrystals with distinct structural features were observed in samples containing contrasting dsrAB sequences. The results of this investigation provide clear evidence that microorganisms can influence the chemical forms of heavy metals in peatland environments. Our findings also provide insight into the conditions necessary to promote the immobilization of chalcophile elements in engineered systems for the treatment of acid mine drainage and wastewater effluents.

  18. Electronic and optical properties of 2D graphene-like ZnS: DFT calculations

    Energy Technology Data Exchange (ETDEWEB)

    Lashgari, Hamed [Department of Physics, Science and Research Branch, Islamic Azad University, Tehran (Iran, Islamic Republic of); Boochani, Arash, E-mail: arash_bch@yahoo.com [Department of Physics, Kermanshah Branch, Islamic Azad University, Kermanshah (Iran, Islamic Republic of); Shekaari, Ashkan [Department of Physics, Science and Research Branch, Islamic Azad University, Tehran (Iran, Islamic Republic of); Solaymani, Shahram [Young Researchers and Elite Club, Kermanshah Branch, Islamic Azad University, Kermanshah (Iran, Islamic Republic of); Sartipi, Elmira [Department of Physics, Kermanshah Branch, Islamic Azad University, Kermanshah (Iran, Islamic Republic of); Mendi, Rohollah Taghavi [Department of Physics, Mashhad Branch, Islamic Azad University, Mashhad (Iran, Islamic Republic of)

    2016-04-30

    Graphical abstract: - Highlights: • DFT has been applied to investigate the optical properties of 2D-ZnS and 3D-ZnS. • The electronic and the optical properties of 3D-ZnS and 2D-ZnS are compared. • At visible range of energies the transparency of 2D-ZnS is more than the 3D. - Abstract: Density-functional theory has been applied to investigate the electronic and optical properties of graphene-like two-dimensional ZnS in the (0001) direction of its Wurtzite phase. A comparison with 3D-ZnS has been carried out within the PBE- and EV-GGA. The electronic properties of 2D- and 3D-ZnS have been derived by the examination of the electronic band structures and density of states. The optical properties have been determined through the study of the dielectric function, reflectivity, electron loss function, refractive and extinction indices, the absorption index and optical conductivity. It is found that the transparency of 2D-ZnS is greater than the 3D over the visible range. A thorough study of the dielectric function has been performed so that the peaks and the transition bands have been specified. The electron loss function demonstrates that the plasmonic frequency for 2D- and 3D-ZnS is accrued at 11.22 and 19.93 eV within the PBE-GGA, respectively.

  19. Electrical Properties of Nanoscale ZnS Thin Film Transistor

    Directory of Open Access Journals (Sweden)

    Teresa Oh

    2015-01-01

    Full Text Available To understand the contact mechanism from electrical properties of the ZnS TFTs, ZnS was fabricated on SiOC as a gate insulator on a Si substrate. Ohmic contact without a potential barrier increased the leakage current, but Schottky contact decreased the leakage current because of a Schottky barrier (SB. The ZnS TFTs prepared on SiOC with a Schottky contact improved the stability with respect to the reduction of drain voltages. The structural matching between ZnS and SiOC increased the height of SB such as ZnS annealed at 200°C, which made ZnS become an amorphous structure. ZnS/SiOC films with a low SB increased the capacitance and leakage current. The crystallinity orientation of ZnS localized defect states and the drift current owing to the impurity charge carriers caused the leakage current through low SB near zero voltages. But the increment of diffusion currents in a depletion layer increased the SB and then decreased the leakage current. So the electrical properties of devices were improved by a tunneling effect of diffusion currents.

  20. Fabrication, characterization of ZnO nanorods on the flexible substrate (Kapton tape) via chemical bath deposition for UV photodetector applications

    Science.gov (United States)

    Abdulrahman, Ahmed F.; Ahmed, Sabah M.; Ahmed, Naser M.; Almessiere, Munirah A.

    2017-08-01

    One dimensional ZnO nanorods have been synthesized on flexible substrate. The substrate is Kapton Tape (KT). ZnO Nanorods are produced by using low cost chemical bath deposition method at low temperature. The investigation of the effect of substrate on the morphological, elementary composition, structural characteristics and Raman spectroscopy of ZnO nanorods has been done. Field emission scanning electron microscopy (FESEM), Energy Dispersive analysis (EDX), X-ray diffraction (XRD) and Raman spectroscopy measurements are employed to examine the morphological, compositional and structural characteristics with hexagonal wurtzite structure of the ZnO nanorods arrays. The results found that the average diameter of ZnO nanorods is found to be closely related to the substrate nature. It is concluded that the substrate can effect on the ZnO nanorods growth remarkably and the selective growth of ZnO nanorods is possible through the choice of the substrate. The crystallite size and the lattice constants of the synthesis ZnO nanorods are obtained based on the XRD data. The found results revealed that the increase in the crystallite size is strongly associated with the type of substrate.

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

    Science.gov (United States)

    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.

  2. Structural, morphological, optical and electrical properties of Schottky diodes based on CBD deposited ZnO:Cu nanorods

    Science.gov (United States)

    Mwankemwa, Benard S.; Legodi, Matshisa J.; Mlambo, Mbuso; Nel, Jackie M.; Diale, Mmantsae

    2017-07-01

    Undoped and copper doped zinc oxide (ZnO) nanorods have been synthesized by a simple chemical bath deposition (CBD) method at a temperature of 90 °C. Structural, morphological, optical and electrical properties of the synthesized ZnO nanorods were found to be dependent on the Cu doping percentage. X-ray diffraction (XRD) patterns revealed strong diffraction peaks of hexagonal wurtzite of ZnO, and no impurity phases from metallic zinc or copper. Scanning electron microscopy (SEM) images showed changes in diameter and shape of nanorods, where by those doped with 2 at.% and 3 at.% aggregated and became compact. Selected area electron diffraction (SAED) patterns indicates high quality, single crystalline wurtzite structure ZnO and intensities of bright spots varied with copper doping concentration. UV-visible absorption peaks of ZnO red shifted with increasing copper doping concentration. Raman studies demonstrated among others, strong and sharp E2 (low) and E2 (high) optical phonon peaks confirming crystal structure of ZnO. Current-voltage measurements based on the gold/ZnO nanorods/ITO showed good rectifying behavior of the Schottky diode. The predicted Schottky barrier height of 0.60 eV was obtained which is not far from the theoretical Schottky-Mott value of 0.80 eV.

  3. Enhancing absorption in coated semiconductor nanowire/nanorod core-shell arrays using active host matrices

    Science.gov (United States)

    Jule, Leta; Dejene, Francis; Roro, Kittessa

    2016-12-01

    In the present work, we investigated theoretically and experimentally the interaction of radiation field phenomena interacting with arrays of nanowire/nanorod core-shell embedded in active host matrices. The optical properties of composites are explored including the case when the absorption of propagating wave by dissipative component is completely compensated by amplification in active (lasing) medium. On the basis of more elaborated modeling approach and extended effective medium theory, the effective polarizability and the refractive index of electromagnetic mode dispersion of the core-shell nanowire arrays are derived. ZnS(shell)-coated by sulphidation process on ZnO(shell) nanorod arrays grown on (100) silicon substrate by chemical bath deposition (CBD) has been used for theoretical comparison. Compared with the bare ZnO nanorods, ZnS-coated core/shell nanorods exhibit a strongly reduced ultraviolet (UV) emission and a dramatically enhanced deep level (DL) emission. Obviously, the UV and DL emission peaks are attributed to the emissions of ZnO nanorods within ZnO/ZnS core/shell nanorods. The reduction of UV emission after ZnS coating seems to agree with the charge separation mechanism of type-II band alignment that holes transfer from the core to shell, which would quench the UV emission to a certain extent. Our theoretical calculations and numerical simulation demonstrate that the use of active host (amplifying) medium to compensate absorption at metallic inclusions. Moreover the core-shell nanorod/nanowire arrays create the opportunity for broad band absorption and light harvesting applications.

  4. Enhanced photovoltaic performance of quantum dot-sensitized solar cell fabricated using Al-doped ZnO nanorod electrode

    Science.gov (United States)

    Raja, M.; Muthukumarasamy, N.; Velauthapillai, Dhayalan; Balasundrapraphu, R.; Senthil, T. S.; Agilan, S.

    2015-04-01

    ZnO and Al doped ZnO nanorods have been successfully synthesized on ITO substrate via solgel dip coating method without using any catalyst. The X-ray diffraction studies showed that the Al doped ZnO samples are of hexagonal wurtzite structure. The Al ions were successfully incorporated into the ZnO lattice. Scanning electron microscopy images reveal that the average diameter of ZnO nanorods and Al doped ZnO nanorods are ∼300 nm and ∼200 nm respectively. The energy dispersive X-ray (EDS) analysis confirmed the presence Al in the ZnO thin films. The CdS quantum dot sensitized Al doped ZnO solar cell exhibited a power conversion efficiency of 1.5%.

  5. CONDENSED MATTER: STRUCTURE, MECHANICAL AND THERMAL PROPERTIES: Theoretical Hardness of Wurtzite-Structured Semiconductors

    Science.gov (United States)

    Guo, Xiao-Ju; Xu, Bo; Liu, Zhong-Yuan; Yu, Dong-Li; He, Ju-Long; Guo, Li-Cong

    2008-06-01

    Vickers hardness calculations of eleven wurtzite-structured semiconductors are performed based on the microscopic hardness model. All the parameters are obtained from first-principles calculations. There are two types of chemical bonds in wurtzite-structured crystals. The overlap populations of the two types of chemical bonds in lonsdaleite are chosen as Pc for wurtzite structure. The calculated bond ionicity values of the wurtzite-structured semiconductors are in good agreement with the ionicities from the dielectric definition. When the hardness of wurtzite-structured crystal is higher than 20GPa, our calculated Vickers hardness is within 10% accuracy. Therefore, the hardness of novel wurtzite-structured crystal could be estimated from first-principles calculations.

  6. Effect of annealing temperature on structural, optical and electrical properties of hydrothermal assisted zinc oxide nanorods

    Energy Technology Data Exchange (ETDEWEB)

    Narayanan, Guru Nisha; Sankar Ganesh, R.; Karthigeyan, A., E-mail: karthigeyan.a@ktr.srmuniv.ac.in

    2016-01-01

    Zinc oxide nanorods were grown employing a low cost hydrothermal method on microslide glass substrates pre-coated with ZnO seed layer. The as grown nanorods were annealed in air at 350 °C, 450 °C and 550 °C. The effect of annealing at different temperatures on morphology, structural, optical and electrical properties was investigated using field emission scanning electron microscopic, X-ray diffraction, UV–vis spectral, photoluminescence and electrical studies. The X-ray diffraction pattern of all the samples showed wurtzite structure preferentially oriented along the c-axis (0 0 2) direction. It was found that diameter of the nanorods increased with increasing of annealing temperature. The UV–vis absorption spectra showed a red shift from which it was inferred that the optical bandgap of the material decreases from 3.33 eV to 3.28 eV with increase in annealing temperature. Photoluminescence measurements showed increase in the UV emission intensity with respect to annealing temperature and also produced additional peaks attributed to defects and impurities. Annealing the ZnO nanorod structures at various temperatures evidently showed that the sample annealed at 550 °C acquired the lowest resistivity about 1.62 × 10{sup −4} Ω-cm. - Highlights: • ZnO nanorods were synthesized by hydrothermal method on microslide glass substrates. • Pre-deposited ZnO seeds were used. • Structural, optical and electrical properties of ZnO nanorods were studied. • Crystalline structure of ZnO nanorods was improved with increase in annealing temperature. • Resistivity decrease was observed with increase in the annealing temperature.

  7. Wurtzite CuInS₂ and CuInxGa₁-xS₂ nanoribbons: synthesis, optical and photoelectrical properties.

    Science.gov (United States)

    Li, Qiang; Zhai, Lanlan; Zou, Chao; Huang, Xusheng; Zhang, Lijie; Yang, Yun; Chen, Xi'an; Huang, Shaoming

    2013-02-21

    Single crystalline wurtzite ternary and quaternary semiconductor nanoribbons (CuInS(2), CuIn(x)Ga(1-x)S(2)) were synthesized through a solution-based method. The structure and composition of the nanoribbons were characterized by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), the corresponding fast Fourier transform (FFT) and nanoscale-resolved elemental mapping. Detailed investigation of the growth mechanism by monitoring the structures and morphologies of the nanoribbons during the growth indicates that Cu(1.75)S nanocrystals are formed first and act as a catalyst for the further growth of the nanoribbons. The high mobility of Cu(+) promotes the generation of Cu(+) vacancies in Cu(1.75)S, which will facilitate the diffusion of Cu, In or Ga species from solution into Cu(1.75)S to reach supersaturated states. The supersaturated species in the Cu(1.75)S catalyst, Cu-In-S and Cu-In-Ga-S species, start to condense and crystallize to form wurtzite CuInS(2) or CuIn(x)Ga(1-x)S(2) phases, firstly resulting in two-sided nanoparticles. Successive crystallizations gradually impel the Cu(1.75)S catalyst head forward and prolong the length of the CuInS(2) or CuIn(x)Ga(1-x)S(2) body, forming heterostructured nanorods and thus nanoribbons. The optical band gaps of CuIn(x)Ga(1-x)S(2) nanoribbons can be continuously adjusted between 1.44 eV and 1.91 eV, depending on the Ga concentration in nanoribbons. The successful preparation of those ternary and quaternary semiconductor nanoribbons provide us an opportunity to study their photovoltaic properties. The primary photoresponsive current measurements demonstrate that wurtzite CuIn(x)Ga(1-x)S(2) nanoribbons are excellent photoactive materials. Furthermore, this facile method could open a new way to synthesize other various nano-structured ternary and quaternary semiconductors, such as CuInSe(2) and CuIn(x)Ga(1-x)Se(2), for applications in solar cells and other fields.

  8. Hydrothermal synthesis of wurtzite Zn{sub 1−x}Ni{sub x}S mesoporous nanospheres: With blue–green emissions and ferromagnetic Curie point above room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Amaranatha Reddy, D.; Kim, D.H.; Rhee, S.J.; Jung, C.U.; Lee, B.W.; Liu, Chunli, E-mail: chunliliu@hufs.ac.kr

    2014-03-05

    Highlights: • Wurtzite Zn{sub 1−x}Ni{sub x}S mesoporous nanospheres were synthesized via hydrothermal method. • Structural, band gap, PL and magnetization studies were carried out. • All the doped samples exhibited intrinsic room temperature ferromagnetism. • The maximum PL enhancement was noticed in 2 at.% Ni doped ZnS nanospheres. • Zn{sub 1−x}Ni{sub x}S nanospheres may find applications in luminescent and spintronic devices. -- Abstract: Wurtzite Zn{sub 1−x}Ni{sub x}S (x = 0.00, 0.01, 0.02, 0.03, 0.04 and 0.05) mesoporous nanospheres were successfully synthesized via a versatile hydrothermal method with the assistance of ethylenediamine (EN). The as synthesized nanospheres were uniform, mono-dispersed with a spherical shape. Microstructure investigations revealed that these nanospheres were mesoporous clusters of Zn{sub 1−x}Ni{sub x}S nanoparticles with the size around 5 nm. X-ray Diffraction, X-ray photoelectron spectroscopy, and Energy-dispersive X-ray spectroscopy studies confirmed that the Ni ions substituted into ZnS host lattice without altering the crystal structure. The Fourier-transform infrared spectra confirmed the coupling between the EN molecules and ZnS. The absorption edge in the diffuse reflection spectra shifted towards lower wavelength with increasing Ni concentration, indicating an expansion in the band gap energy that is estimated to be in the range of 3.53–3.60 eV. The photoluminescence spectra of the doped and un-doped samples contained a broad emission band covering the range of 350–650 nm. Room temperature magnetization studies indicated that the undoped ZnS nanospheres yielded only diamagnetism, whereas the doped samples exhibited ferromagnetism that can be attributed to the Ni{sup 2+} dopants. The temperature dependence of magnetization revealed that the Zn{sub 1−x}Ni{sub x}S nanospheres have Curie point above room temperature. The intrinsic ferromagnetism and ferromagnetic Curie point above room temperature

  9. Physical properties of nanorods

    Energy Technology Data Exchange (ETDEWEB)

    Krahne, Roman; George, Chandramohan [Istituto Italiano di Tecnologia, Genoa (Italy). Nanostructures; Manna, Liberato [Istituto Italiano di Tecnologia, Genoa (Italy). Nanochemistry; Morello, Giovanni [CNR, Lecce (Italy). Nanoscience Institute; Figuerola, Albert [Barcelona Univ. (Spain). Inst. de Nanociencia i Nanotecnologia; Deka, Sasanka [Delhi Univ. (India). Dept. of Chemistry

    2013-06-01

    Inorganic nanoparticles are among the most investigated objects nowadays, both in fundamental science and in various technical applications. In this book the physical properties of nanowires formed by nanoparticles with elongated shape, i.e. rod-like or wire-like, are described. The transition in the physical properties is analyzed for nanorods and nanowires consisting of spherical and rod-like nanoparticles. The physical properties of nanowires and elongated inorganic nanoparticles are reviewed too. The optical, electrical, magnetic, mechanical and catalytic properties of nanowires consisting of semiconductors, noble and various other metals, metal oxides properties and metal alloys are presented. The applications of nanorods and nanowires are discussed in the book.

  10. Post-annealing effect on optical absorbance of hydrothermally grown zinc oxide nanorods

    Energy Technology Data Exchange (ETDEWEB)

    Mohar, Rahmat Setiawan; Djuhana, Dede; Imawan, Cuk; Harmoko, Adhi; Fauzia, Vivi, E-mail: vivi@sci.ui.ac.id [Departemen Fisika, FMIPA, Universitas Indonesia, Kampus UI Depok (Indonesia); Iwan, S. [Departemen Fisika, FMIPA, Universitas Indonesia, Kampus UI Depok (Indonesia); Jurusan Fisika, Fakultas MIPA, Universitas Negeri Jakarta, Jl. Pemuda No. 10 Rawamangun, Jakarta 13220 (Indonesia)

    2016-04-19

    In this study, the optical absorbance of zinc oxide (ZnO) nanorods was investigated. The ZnO thin film were deposited on indium tin oxide (ITO) layers using ultrasonic spray pyrolysis (USP) method and then grown by hydrothermal method. In order to improve the optical absorbance, the ZnO nanorods were then post-annealed for one hour at three different of temperatures, namely 250, 400, and 500 °C. The X-ray diffraction (XRD) spectra and FESEM images show that the ZnO nanorods have the hexagonal wurtzite crystal structure and the increasing of post-annealing temperature resulted in the increasing of crystallite size from 38.2 nm to 48.4 nm. The UV-vis spectra shows that all samples of ZnO nanorods exhibited the identical sharp absorption edge at 390 nm indicating that all samples have the same bandgap. The post-annealing process seemed to decrease the optical absorbance in the region of 300-550 nm and increase the optical absorbance in the region of 550-700 nm..

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

    Science.gov (United States)

    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).

  12. Chemical precursors to zinc sulfide: ZnS whisker synthesis

    Science.gov (United States)

    Guiton, T. A.; Czekaj, C. L.; Rau, M. S.; Geoffroy, G. L.; Pantano, C. G.

    1988-07-01

    Currently, Chemical Vapor Deposition (CVD) derived zinc sulfide is one of the most widely used infrared optical window materials. Unfortunately, for numerous applications it does not possess optimum mechanical properties. To fabricate infrared transmitting ZnS/ZnS composites requires the development of high aspect ratio, micron sized ZnS whiskers. Although larger ZnS single crystals and whiskers have been made by a variety of high temperature routes, alternative routes have been sought for greater ZnS whisker morphology control. Low temperature organometallic routes are attractive for this purpose. The precursor compound used in this study is the known pentameric species (EtZn(SBut))5. One of the most successful routes involves the reaction of (EtZn(SBU sup t))5 with hydrogen sulfide at ambient or sub-ambient temperature to yield a precipitate which is subsequently heated under flowing H2S at 500 C to yield a mixture of sub-micron particles and single-crystal ZnS whiskers. Transmission electron micrographs of the (EtZn(SBU sup t))5 products indicate that the ZnS morphology is critically dependent on the rate of H2S reaction. Corresponding X-ray/electron diffraction, electron microscopy, elemental analysis, NMR and infrared spectroscopies have been conducted. A summary of the chemical methods, product characterization results, and proposed synthesis mechanisms are presented.

  13. Structural, Surface Morphology and Optical Properties of ZnS Films by Chemical Bath Deposition at Various Zn/S Molar Ratios

    Directory of Open Access Journals (Sweden)

    Fei-Peng Yu

    2014-01-01

    Full Text Available In this study, ZnS thin films were prepared on glass substrates by chemical bath deposition at various Zn/S molar ratios from 1/50 to 1/150. The effects of Zn/S molar ratio in precursor on the characteristics of ZnS films were demonstrated by X-ray diffraction, scanning electron microscopy, optical transmittance, X-ray photoelectron spectroscopy, and Fourier transform infrared spectrometry. It was found that more voids were formed in the ZnS film prepared using the precursor with Zn/S molar ratio of 1/50, and the other ZnS films showed the denser structure as the molar ratio was decreased from 1/75 to 1/150. From the analyses of chemical bonding states, the ZnS phase was indeed formed in these films. Moreover, the ZnO and Zn(OH2 also appeared due to the water absorption on film surface during deposition. This would be helpful to the junction in cell device. With changing the Zn/S molar ratio from 1/75 to 1/150, the ZnS films demonstrate high transmittance of 75–88% in the visible region, indicating the films are potentially useful in photovoltaic applications.

  14. Unoccupied band structure of wurtzite GaN(0001)

    Energy Technology Data Exchange (ETDEWEB)

    Valla, T.; Johnson, P.D. [Department of Physics, Brookhaven National Laboratory, Upton, New York 11973 (United States); Dhesi, S.S.; Smith, K.E. [Department of Physics, Boston University, Boston, Massachusetts 02215 (United States); Doppalapudi, D.; Moustakas, T.D. [Department of Electrical and Computer Engineering, Boston University, Boston, Massachusetts 02215 (United States); Shirley, E.L. [NIST, PHY B208, Gaithersburg, Maryland 20899 (United States)

    1999-02-01

    We report an inverse photoemission study of the unoccupied states of thin-film {ital n}-type wurtzite GaN. For incident electron energies below 30 eV, free-electron bands do not provide a good description of the initial state. However, using a calculated quasiparticle band structure for the initial state, we can obtain good agreement between our measurements and the calculated low-lying conduction bands. No evidence of unoccupied surface states is observed in the probed part of the Brillouin zone, confirming earlier angle resolved photoemission studies, which identified the surface states on GaN(0001) as occupied dangling bond states, resonant with the valence band. {copyright} {ital 1999} {ital The American Physical Society}

  15. Crystal orientation effects on wurtzite quantum well electromechanical fields

    DEFF Research Database (Denmark)

    Duggen, Lars; Willatzen, Morten

    2010-01-01

    in the literature for semiconductors, is inaccurate for ZnO/MgZnO heterostructures where shear-strain components play an important role. An interesting observation is that a growth direction apart from [1̅ 21̅ 0] exists for which the electric field in the quantum well region becomes zero. This is important for, e......A one-dimensional continuum model for calculating strain and electric field in wurtzite semiconductor heterostructures with arbitrary crystal orientation is presented and applied to GaN/AlGaN and ZnO/MgZnO heterostructure combinations. The model is self-consistent involving feedback couplings...... of spontaneous polarization, strain, and electric field. Significant differences between fully coupled and semicoupled models are found for the longitudinal and shear-strain components as a function of the crystal-growth direction. In particular, we find that the semicoupled model, typically used...

  16. Physics of wurtzite nitrides and oxides passport to devices

    CERN Document Server

    Gil, Bernard

    2014-01-01

    This book gives a survey of the current state of the art of a special class of nitrides semiconductors, Wurtzite Nitride and Oxide Semiconductors. It includes properties, growth and applications. Research in the area of nitrides semiconductors is still booming although some basic materials sciences issues were solved already about 20 years ago. With the advent of modern technologies and the successful growth of nitride substrates, these materials currently experience a second birth. Advanced new applications like light-emitters, including UV operating LEDs, normally on and normally off high frequency operating transistors are expected. With progress in clean room technology, advanced photonic and quantum optic applications are envisioned in a close future. This area of research is fascinating for researchers and students in materials science, electrical engineering, chemistry, electronics, physics and biophysics. This book aims to be the ad-hoc instrument to this active field of research.

  17. Ergonomic Synthesis Suitable for Industrial Production of Silver-Festooned Zinc Oxide Nanorods

    Science.gov (United States)

    Khan, G. R.; Khan, R. A.

    2015-07-01

    For maximizing productivity, minimizing cost, time-boxing process and optimizing human effort, a single-step, cost-effective, ultra-fast and environmentally benign synthesis suitable for industrial production of nanocrystalline ZnO, and Ag-doped ZnO has been reported in this paper. The synthesis based on microwave-supported aqueous solution method used zinc acetate dehydrate and silver nitrate as precursors for fabrication of nanorods. The synthesized products were characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy and UV-Vis-NIR spectroscopy. The undoped and Ag-doped ZnO nanorods crystallized in a hexagonal wurtzite structure having spindle-like morphology. The blue shift occurred at absorption edge of Ag-doped ZnO around 260 nm compared to 365 nm of bulk ZnO. The red shift occurred at Raman peak site of 434 cm-1 compared to characteristic wurtzite phase peak of ZnO (437 cm-1). The bandgap energies were found to be 3.10 eV, 3.11 eV and 3.18 eV for undoped, 1% Ag-doped, and 3% Ag-doped ZnO samples, respectively. The TEM results provided average particle sizes of 17 nm, 15 nm and 13 nm for undoped, and 1% and 3% Ag-doped ZnO samples, respectively.

  18. Richardson-Schottky transport mechanism in ZnS nanoparticles

    Directory of Open Access Journals (Sweden)

    Hassan Ali

    2016-05-01

    Full Text Available We report the synthesis and electrical transport mechanism in ZnS semiconductor nanoparticles. Temperature dependent direct current transport measurements on the compacts of ZnS have been performed to investigate the transport mechanism for temperature ranging from 300 K to 400 K. High frequency dielectric constant has been used to obtain the theoretical values of Richardson-Schottky and Poole-Frenkel barrier lowering coefficients. Experimental value of the barrier lowering coefficient has been calculated from conductance-voltage characteristics. The experimental value of barrier lowering coefficient βexp lies close to the theoretical value of Richardson-Schottky barrier lowering coefficient βth,RS showing Richardson-Schottky emission has been responsible for conduction in ZnS nanoparticles for the temperature range studied.

  19. Richardson-Schottky transport mechanism in ZnS nanoparticles

    Science.gov (United States)

    Ali, Hassan; Khan, Usman; Rafiq, M. A.; Falak, Attia; Narain, Adeela; Jing, Tang; Xu, Xiulai

    2016-05-01

    We report the synthesis and electrical transport mechanism in ZnS semiconductor nanoparticles. Temperature dependent direct current transport measurements on the compacts of ZnS have been performed to investigate the transport mechanism for temperature ranging from 300 K to 400 K. High frequency dielectric constant has been used to obtain the theoretical values of Richardson-Schottky and Poole-Frenkel barrier lowering coefficients. Experimental value of the barrier lowering coefficient has been calculated from conductance-voltage characteristics. The experimental value of barrier lowering coefficient βexp lies close to the theoretical value of Richardson-Schottky barrier lowering coefficient βth,RS showing Richardson-Schottky emission has been responsible for conduction in ZnS nanoparticles for the temperature range studied.

  20. Starch-assisted synthesis and optical properties of ZnS nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Tian, Xiuying, E-mail: xiuyingt@yahoo.com; Wen, Jin; Wang, Shumei; Hu, Jilin; Li, Jing; Peng, Hongxia

    2016-05-15

    Highlights: • ZnS spherical nanostructure was prepared via starch-assisted method. • The crystalline lattice structure, morphologies, chemical and optical properties of ZnS nanoparticles. • The forming mechanism of ZnS nanoparticles. • ZnS spherical nano-structure can show blue emission at 460–500 nm. - Abstract: ZnS nanoparticles are fabricated via starch-assisted method. The effects of different starch amounts on structure and properties of samples are investigated, and the forming mechanism of ZnS nanoparticles is discussed. By X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), ultraviolet–visible (UV–vis) spectroscopy and fluorescence (FL) spectrometer, their phases, crystalline lattice structure, morphologies, chemical and optical properties are characterized. The results show that ZnS has polycrystalline spherical structure with the mean diameter of 130 nm. Sample without starch reveals irregular aggregates with particle size distribution of 0.5–2 μm. The band gap value of ZnS is 3.97 eV. The chemical interaction exists between starch molecules and ZnS nanoparticles by hydrogen bonds. The stronger FL emission peaks of ZnS synthesized with starch, indicate a larger content of sulfur vacancies or defects than ZnS synthesized without starch.

  1. Electrochemical growth of controlled tip shapes of ZnO nanorod arrays on silicon substrate and enhanced photoluminescence emission from nanopyramid arrays compared with flat-head nanorods

    Science.gov (United States)

    Alimanesh, Mahmoud; Hassan, Z.; Zainal, Norzaini

    2017-10-01

    Zinc oxide (ZnO) nanorod arrays (NRAs) with different morphologies such as; perfect hexagon flat-head, pyramidal, compact pencil, nail-shaped, and high-compact ZnO nanorod thin films, were successfully grown on silicon substrates. These NRAs were formed on substrates using a simple low-temperature electrochemical method without adding any catalyst or template via the precursors of zinc nitrate hexahydrate [Zn(NO3)2·6H2O] and hexamethylenetetramine [HMT; C6H12N4] with an equal molar concentration of 0.025 mol/l. The morphologies of the ZnO nanorods (NRs) could be controlled and transformed successfully in to other morphologies by changing the growth conditions, such as; growth temperature and applied current density. Detailed structural investigations reveal that the synthesized various NRs are single crystalline with wurtzite hexagonal phase and preferentially grow along the c-axis direction. The room temperature photoluminescence spectra show that each spectrum consists of an ultraviolet (UV) band and a relative broad visible light emission and infrared emission peak. The enhanced light emission intensity at UV peak (∼375 nm) is observed significantly from ZnO nanopyramid (NP) arrays because of the conical shape of NP. The photoluminescence intensity of the UV peak from the NPs is found to be 1.5-17 times larger than those from the other various NRs.

  2. Tuning photoluminescence of ZnS nanoparticles by silver

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 31; Issue 3. Tuning photoluminescence of ZnS ... Arun Chattopadhyay1 2. Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati 781 039, India; Centre for Nanotechnology, Indian Institute of Technology Guwahati, Guwahati 781 039, India ...

  3. Highly Photoluminescent and Stable Aqueous ZnS Quantum Dots

    Science.gov (United States)

    Li, Hui; Shih, Wan Y.; Shih, Wei-Heng

    2009-01-01

    We report an all-aqueous synthesis of highly photoluminescent and stable ZnS quantum dots (QDs) with water as the medium, i.e. first synthesizing ZnS QDs with 3-mercaptopropionic acid (MPA) as the capping molecule, followed by replacing some of MPA with (3-mercaptopropyl) trimethoxysilane (MPS). The resultant MPS-replaced ZnS QDs were about 5 nm in size with a cubic zinc blende crystalline structure, and had both MPA and MPS on the surface as confirmed by the Fourier Transform Infrared (FTIR) spectroscopy. They exhibited blue trap-state emissions around 415 nm and a quantum yield (QY) of 75% with Rhodamine 101 as the reference, and remained stable for more than 60 days under the ambient conditions. Through the capping molecule replacement procedure, the MPS-replaced ZnS QDs avoided the shortcomings of both the MPA-ZnS QDs and the MPS-ZnS QDs, and acquired the advantages of strong photoluminescence and good stability, which are important to the QDs’ applications especially for bioimaging. PMID:21954321

  4. Tuning photoluminescence of ZnS nanoparticles by silver

    Indian Academy of Sciences (India)

    Wintec

    Tuning photoluminescence of ZnS nanoparticles by silver. A MURUGADOSS. 1 and ARUN CHATTOPADHYAY. 1,2,. *. 1. Department of Chemistry and. 2. Centre for Nanotechnology, Indian Institute of Technology Guwahati,. Guwahati 781 039, India. Abstract. We report the results of investigation of the interaction of silver ...

  5. Dynamic modelling and process control of ZnS precipitation

    NARCIS (Netherlands)

    König, J.; Keesman, K.J.; Veeken, A.H.M.; Lens, P.N.L.

    2006-01-01

    This paper presents the dynamic modelling and design of a control strategy for the ZnS precipitation process. During lab¿scale experiments, the sulfide concentration in a precipitator was controlled at a prespecified pS value by manipulating the flow from a buffer vessel. Batch tests showed that the

  6. Optical Properties of Strained Wurtzite Gallium Phosphide Nanowires

    KAUST Repository

    Greil, J.

    2016-06-08

    Wurtzite gallium phosphide (WZ GaP) has been predicted to exhibit a direct bandgap in the green spectral range. Optical transitions, however, are only weakly allowed by the symmetry of the bands. While efficient luminescence has been experimentally shown, the nature of the transitions is not yet clear. Here we apply tensile strain up to 6% and investigate the evolution of the photoluminescence (PL) spectrum of WZ GaP nanowires (NWs). The pressure and polarization dependence of the emission together with a theoretical analysis of strain effects is employed to establish the nature and symmetry of the transitions. We identify the emission lines to be related to localized states with significant admixture of Γ7c symmetry and not exclusively related to the Γ8c conduction band minimum (CBM). The results emphasize the importance of strongly bound state-related emission in the pseudodirect semiconductor WZ GaP and contribute significantly to the understanding of the optoelectronic properties of this novel material.

  7. Growth of InAs Wurtzite Nanocrosses from Hexagonal and Cubic Basis

    DEFF Research Database (Denmark)

    Krizek, Filip; Kanne, Thomas; Razmadze, Davydas

    2017-01-01

    Epitaxially connected nanowires allow for the design of electron transport experiments and applications beyond the standard two terminal device geometries. In this Letter, we present growth methods of three distinct types of wurtzite structured InAs nanocrosses via the vapor-liquid-solid mechanis...... fabricated junctions in radial nanowire heterostructures.......Epitaxially connected nanowires allow for the design of electron transport experiments and applications beyond the standard two terminal device geometries. In this Letter, we present growth methods of three distinct types of wurtzite structured InAs nanocrosses via the vapor-liquid-solid mechanism....... Two methods use conventional wurtzite nanowire arrays as a 6-fold hexagonal basis for growing single crystal wurtzite nanocrosses. A third method uses the 2-fold cubic symmetry of (100) substrates to form well-defined coherent inclusions of zinc blende in the center of the nanocrosses. We show...

  8. Pre and post annealed low cost ZnO nanorods on seeded substrate

    Science.gov (United States)

    Nordin, M. N.; Kamil, Wan Maryam Wan Ahmad

    2017-05-01

    We wish to report the photonic band gap (where light is confined) in low cost ZnO nanorods created by two-step chemical bath deposition (CBD) method where the glass substrates were pre-treated with two different seeding thicknesses, 100 nm (sample a) and 150 nm (sample b), of ZnO using radio frequency magnetron sputtering. Then the samples were annealed at 600°C for 1 hour in air before and after immersed into the chemical solution for CBD process. To observe the presence of photonic band gap on the sample, UV-Visible-NIR spectrophotometer was utilized and showed that sample a and sample b both achieved wide band gap between 240 nm and 380 nm, within the UV range for typical ZnO, however sample b provided a better light confinement that may be attributed by the difference in average nanorods size. Field Emission Scanning Electron Microscope (FESEM) of the samples revealed better oriented nanorods uniformly scattered across the surface when substrates were coated with 100 nm of seeding layer whilst the 150 nm seeding sample showed a poor distribution of nanorods probably due to defects in the sample. Finally, the crystal structure of the ZnO crystallite is revealed by employing X-ray diffraction and both samples showed polycrystalline with hexagonal wurtzite structure that matched with JCPDS No. 36-1451. The 100 nm pre-seeded samples was recognized to have bigger average crystallite size, however sample b was suggested as having a higher crystalline quality. In conclusion, the sample b is recognized as a better candidate for future photonic applications due to its more apparent of photonic band gap and this may be contributed by more random distribution of the nanorods as observed in FESEM images as well as higher crystalline quality as suggested from XRD measurements.

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

    Directory of Open Access Journals (Sweden)

    Anees A. Ansari

    2013-09-01

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

  10. Zinc oxide nanorods modified indium tin oxide surface for amperometric urea biosensor.

    Science.gov (United States)

    Palomera, Netzahualcóyotl; Balaguera, Marcia; Arya, Sunil K; Hernández, Samuel; Tomar, Maharaj S; Ramírez-Vick, Jaime E; Singh, Surinder P

    2011-08-01

    ZnO nanorods (ZnONR) grown onto indium-tin-oxide (ITO) coated glass surface using zinc nitrate hexahydrate/hexamethylenetetramine (HMT) in aqueous phase has been utilized for urea biosensor. Urease (Urs) was immobilized onto ZnONR/ITO at physiological pH via electrostatic interactions between Urs and ZnO to fabricate Urs/ZnONR/ITO bioelectrode. ZnONR/ITO electrode has been characterized using XRD, FE-SEM techniques and Urs/ZnONR/ITO bioelectrode using electrochemistry. The XRD and FE-SEM measurements confirm the formation of ZnO nanorods in wurtzite structure. Cyclic voltammetric and amperometric measurements on the Urs/ZnONR/ITO biolectrode for urea concentrations in the range of 1-20 mM reveal 0.4 microA mM(-1) sensitivity, with a response time of 3 seconds, and a detection limit of 0.13 mM. The Michaelis-Menten constant (Km) was calculated to be 9.09 mM. Results indicate that ZnO nanorods provide suitable microenvironment for urease immobilization and can be utilized in biosensor design and other biological applications.

  11. Preparation and spectroscopic analysis of zinc oxide nanorod thin films of different thicknesses

    Directory of Open Access Journals (Sweden)

    Mia Nasrul Haque

    2017-10-01

    Full Text Available Zinc oxide thin films with different thicknesses were prepared on microscopic glass slides by sol-gel spin coating method, then hydrothermal process was applied to produce zinc oxide nanorod arrays. The nanorod thin films were characterized by various spectroscopic methods of analysis. From the images of field emission scanning electron microscope (FESEM, it was observed that for the film thickness up to 200 nm the formed nanorods with wurtzite hexagonal structure were uniformly distributed over the entire surface substrate. From X-ray diffraction analysis it was revealed that the thin films had good polycrystalline nature with highly preferred c-axis orientation along (0 0 2 plane. The optical characterization done by UV-Vis spectrometer showed that all the films had high transparency of 83 % to 96 % in the visible region and sharp cut off at ultraviolet region of electromagnetic spectrum. The band gap of the films decreased as their thickness increased. Energy dispersive X-ray spectroscopy (EDS showed the presence of zinc and oxygen elements in the films and Fourier transform infrared spectroscopy (FT-IR revealed the chemical composition of ZnO in the film.

  12. Gold-Catalyzed Growth of Aluminium-Doped Zinc Oxide Nanorods by Sputtering Method

    Directory of Open Access Journals (Sweden)

    A. B. Rosli

    2014-01-01

    Full Text Available Aluminium-doped zinc oxide (AZO nanorods thin films were grown by RF magnetron sputtering on gold (Au metal catalyst. The Au catalyst layers with 5, 10, and 15 nm thickness were deposited on glass substrates by sputtering method followed by annealing for 15 min at 500°C to form Au nanostructures on the glass substrate. The AZO thin films were then deposited on the Au catalyst at different deposition temperature varying from 200 to 500°C. Postdeposition annealing processes of the Au catalyst resulted in different morphologies of the Au catalyst layers depending on their thicknesses. This in turn gave different AZO morphologies which suggest that the Au catalyst layer thickness and the deposition temperature contribute to the growth mechanism of the AZO nanostructures. AZO nanorods thin films having hexagonal wurtzite structure with individual nanorods on the film surface were obtained from the samples deposited on 5 and 10 nm thick Au catalyst with the deposition temperature of 300°C.

  13. Partial Ion Exchange Derived 2D Cu-Zn-In-S Nanosheets as Sensitizers of 1D TiO2 Nanorods for Boosting Solar Water Splitting.

    Science.gov (United States)

    Liu, Qiong; Cao, Fengren; Wu, Fangli; Chen, Shimou; Xiong, Jie; Li, Liang

    2016-10-05

    A facile route for the fabrication of a novel ZnS shell/Cu-Zn-In-S nanosheets/TiO2 nanorods heterojunction was reported in this work. Especially, the quaternary Cu-Zn-In-S nanosheets were synthesized creatively from the ternary ZnIn2S4 nanosheets by partial exchange reaction, leading to substantial enhancement on the light absorbance. Such heterojunction could increase the surface area and accelerate the charge transfer resulting from its hierarchical 2D/1D structure and favorable energy bands. Moreover, the ZnS coating acted as a passivation layer as well as a potential barrier, significantly suppressing the interface recombination. The above synergistic effects resulted in the largely increased photocurrent density from 0.34 mA cm-2 for the pristine TiO2 to 0.81 mA cm-2 for the heterojunction at 0.8 V vs RHE.

  14. Effect of growth time on Ti-doped ZnO nanorods prepared by low-temperature chemical bath deposition

    Science.gov (United States)

    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.

  15. Photovoltaic performance of dye-sensitized solar cell low temperature growth of ZnO nanorods using chemical bath deposition.

    Science.gov (United States)

    Lee, Jeong-Gwan; Choi, Young-Cheol; Lee, Do-Kyung; Ahn, Kwang-Soon; Kim, Jae Hong

    2012-04-01

    Nanostructured ZnO photoelectrodes were synthesized on fluorine-doped tin oxide (FTO) glass substrates that were spin-coated with a sol-gel based ZnO seed layer via a chemical bath deposition (CBD) method at varying times of 1, 2, 4, and 8 h. Then, TiO2 nanoparticulate electrodes were prepared on ZnO nanorods using the doctor blade technique. The uniformly grown ZnO nanorod layer had a length of approximately 710 nm on the FTO glass substrate with wurtzite structures which was confirmed through X-ray diffraction patterns. The length and diameter of the ZnO nanorods increased with an increase in the deposition time. The DSSCs fabricated with TiO2 nanoparticulate/grown ZnO nanorods and grown for 8 h showed the maximum efficiency (5.51%) with a short circuit current density (J(sc)) of 12.21 mA/cm2 and an open circuit voltage (V(oc)) of 0.70 at 100 mW/cm2 light intensity.

  16. Evaluation of undoped ZnS single crystal materials for x-ray imaging applications

    Science.gov (United States)

    Saleh, Muad; Lynn, Kelvin G.; McCloy, John S.

    2017-05-01

    ZnS-based materials have a long history of use as x-ray luminescent materials. ZnS was one of the first discovered scintillators and is reported to have one of the highest scintillator efficiencies. The use of ZnS for high energy luminescence has been thus far limited to thin powder screens, such as ZnS:Ag which is used for detecting alpha radiation, due to opacity to its scintillation light, primarily due to scattering. ZnS in bulk form (chemical vapor deposited, powder processed, and single crystal) has high transmission and low scattering compared to powder screens. In this paper, the performance of single crystalline ZnS is evaluated for low energy x-ray (PLE) of several undoped ZnS single crystals is compared to their Radioluminescence (RL) spectra. It was found that the ZnS emission wavelength varies on the excitation source energy.

  17. Microstructural, chemical and textural characterization of ZnO nanorods synthesized by aerosol assisted chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Sáenz-Trevizo, A.; Amézaga-Madrid, P.; Fuentes-Cobas, L.; Pizá-Ruiz, P.; Antúnez-Flores, W.; Ornelas-Gutiérrez, C. [Centro de Investigación en Materiales Avanzados, S.C., Chihuahua, Chihuahua 31109 (Mexico); Pérez-García, S.A. [Centro de Investigación en Materiales Avanzados, S.C., Unidad Monterrey, Apodaca, Nuevo León 66600 (Mexico); Miki-Yoshida, M., E-mail: mario.miki@cimav.edu.mx [Centro de Investigación en Materiales Avanzados, S.C., Chihuahua, Chihuahua 31109 (Mexico)

    2014-12-15

    ZnO nanorods were synthesized by aerosol assisted chemical vapor deposition onto TiO{sub 2} covered borosilicate glass substrates. Deposition parameters were optimized and kept constant. Solely the effect of different nozzle velocities on the growth of ZnO nanorods was evaluated in order to develop a dense and uniform structure. The crystalline structure was characterized by conventional X-ray diffraction in grazing incidence and Bragg–Brentano configurations. In addition, two-dimensional grazing incidence synchrotron radiation diffraction was employed to determine the preferred growth direction of the nanorods. Morphology and growth characteristics analyzed by electron microscopy were correlated with diffraction outcomes. Chemical composition was established by X-ray photoelectron spectroscopy. X-ray diffraction results and X-ray photoelectron spectroscopy showed the presence of wurtzite ZnO and anatase TiO{sub 2} phases. Morphological changes noticed when the deposition velocity was lowered to the minimum, indicated the formation of relatively vertically oriented nanorods evenly distributed onto the TiO{sub 2} buffer film. By coupling two-dimensional X-ray diffraction and computational modeling with ANAELU it was proved that a successful texture determination was achieved and confirmed by scanning electron microscopy analysis. Texture analysis led to the conclusion of a preferred growth direction in [001] having a distribution width Ω = 20° ± 2°. - Highlights: • Uniform and pure single-crystal ZnO nanorods were obtained by AACVD technique. • Longitudinal and transversal axis parallel to the [001] and [110] directions, respectively. • Texture was determined by 2D synchrotron diffraction and electron microscopy analysis. • Nanorods have its [001] direction distributed close to the normal of the substrate. • Angular spread about the preferred orientation is 20° ± 2°.

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

    Directory of Open Access Journals (Sweden)

    Chan Oeurn Chey

    2014-01-01

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

  19. Microwave assisted chemical bath deposition of vertically aligned ZnO nanorods on a variety of substrates seeded by PVA-Zn(OH){sub 2} nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Hassan, J.J., E-mail: j1j2h72@yahoo.com [Nano-Optoelectronics Research and Technology Laboratory (N.O.R.), School of Physics Universiti Sains Malaysia, Penang 11800 (Malaysia); Department of Physics, College of Science, University of Basrah, Basrah (Iraq); Mahdi, M.A. [Nano-Optoelectronics Research and Technology Laboratory (N.O.R.), School of Physics Universiti Sains Malaysia, Penang 11800 (Malaysia); Department of Physics, College of Science, University of Basrah, Basrah (Iraq); Chin, C.W.; Hassan, Z.; Abu-Hassan, H. [Nano-Optoelectronics Research and Technology Laboratory (N.O.R.), School of Physics Universiti Sains Malaysia, Penang 11800 (Malaysia)

    2012-03-01

    Vertically aligned zinc oxide (ZnO) nanorods were synthesized successfully on p-type GaN, c-lattice Al{sub 2}O{sub 3}, ITO glass, and quartz single crystal substrates using the microwave-assisted chemical bath deposition method. All substrates were seeded with a PVA-Zn(OH){sub 2} nanocomposites layer prior to nanorods growth. The effect of substrate type on the vertically alignment and morphology of the zinc oxide nanorods was studied. The diameter of the grown ZnO nanorods ranged from 30 to 170 nm. Their structural quality and morphology were determined by X-ray diffraction (XRD) and scanning electron microscopy (SEM), which revealed hexagonal wurtzite structures perpendicular to the substrate along the z-axis in the direction of (0 0 2) plane. Photoluminescence (PL) measurements of the grown ZnO nanorods on all substrates exhibited high UV peak intensity compared to broad visible peak. Raman scattering studies were conducted to estimate the lattice vibration modes.

  20. Cathodoluminescence spectra of gallium nitride nanorods.

    Science.gov (United States)

    Tsai, Chia-Chang; Li, Guan-Hua; Lin, Yuan-Ting; Chang, Ching-Wen; Wadekar, Paritosh; Chen, Quark Yung-Sung; Rigutti, Lorenzo; Tchernycheva, Maria; Julien, François Henri; Tu, Li-Wei

    2011-12-14

    Gallium nitride [GaN] nanorods grown on a Si(111) substrate at 720°C via plasma-assisted molecular beam epitaxy were studied by field-emission electron microscopy and cathodoluminescence [CL]. The surface topography and optical properties of the GaN nanorod cluster and single GaN nanorod were measured and discussed. The defect-related CL spectra of GaN nanorods and their dependence on temperature were investigated. The CL spectra along the length of the individual GaN nanorod were also studied. The results reveal that the 3.2-eV peak comes from the structural defect at the interface between the GaN nanorod and Si substrate. The surface state emission of the single GaN nanorod is stronger as the diameter of the GaN nanorod becomes smaller due to an increased surface-to-volume ratio.

  1. [Preparation and spectrum properties of ZnS : Ag nanocrystals].

    Science.gov (United States)

    Qu, Hua; Cao, Li-Xin; Su, Ge; Liu, Wei; Jiang, Dai-Xun; Dong, Bo-Hua; Sun, Yuan-Guang

    2009-02-01

    In the present paper, ZnS : Ag nanoparticles were prepared with simple chemicals by hydrothermal method. XRD patterns indicated that the products have cubic zinc blende crystal structure. The particle diameters were calculated using the Scherer's formula, and the particle size showed a nonlinear increase with the rise of reaction temperature. TEM images demonstrated the approximate sphere shapes of products, and the crystal sizes approached the estimated ones respectively. The luminescence properties were investigated with PL and PLE spectra. Emission peaks were at about 450 nm. This emission was ascribed to the recombination between the sulfur vacancy-related electron trap donor having an energy level just below the conduction band and the Ag-related hole trap acceptor above the valence band. Excitation peaks were at about 333 nm, and the excitation was attributed to the near-band-edge absorption of ZnS matrix. The luminescence intensity was strongly influenced by the reaction temperatures and time. It increased, decreased, and then increased again with the rise of reaction temperature, and increased then decreased with the increase in reaction time. ZnS : Ag nanoparticles synthesized at 200 degrees C for 6 hours have a well luminescence intensity.

  2. Measurement of the Euler Angles of Wurtzitic ZnO by Raman Spectroscopy

    Directory of Open Access Journals (Sweden)

    Wu Liu

    2017-01-01

    Full Text Available A Raman spectroscopy-based step-by-step measuring method of Euler angles φ,θ,and  ψ was presented for the wurtzitic crystal orientation on a microscopic scale. Based on the polarization selection rule and coordinate transformation theory, a series of analytic expressions for the Euler angle measurement using Raman spectroscopy were derived. Specific experimental measurement processes were presented, and the measurement of Raman tensor elements and Euler angles of the ZnO crystal were implemented. It is deduced that there is a trigonometric functional relationship between the intensity of each Raman bands of wurtzite crystal and Euler angle ψ, the polarization direction of incident light under different polarization configurations, which can be used to measure the Euler angles. The experimental results show that the proposed method can realize the measurement of Euler angles for wurtzite crystal effectively.

  3. Growth of InAs Wurtzite Nanocrosses from Hexagonal and Cubic Basis.

    Science.gov (United States)

    Krizek, Filip; Kanne, Thomas; Razmadze, Davydas; Johnson, Erik; Nygård, Jesper; Marcus, Charles M; Krogstrup, Peter

    2017-10-11

    Epitaxially connected nanowires allow for the design of electron transport experiments and applications beyond the standard two terminal device geometries. In this Letter, we present growth methods of three distinct types of wurtzite structured InAs nanocrosses via the vapor-liquid-solid mechanism. Two methods use conventional wurtzite nanowire arrays as a 6-fold hexagonal basis for growing single crystal wurtzite nanocrosses. A third method uses the 2-fold cubic symmetry of (100) substrates to form well-defined coherent inclusions of zinc blende in the center of the nanocrosses. We show that all three types of nanocrosses can be transferred undamaged to arbitrary substrates, which allows for structural, compositional, and electrical characterization. We further demonstrate the potential for synthesis of as-grown nanowire networks and for using nanowires as shadow masks for in situ fabricated junctions in radial nanowire heterostructures.

  4. Pressure dependence of the refractive index in wurtzite and rocksalt indium nitride

    Energy Technology Data Exchange (ETDEWEB)

    Oliva, R. [Institut Jaume Almera, Consell Superior d' Investigacions Científiques (CSIC), Lluís Solé i Sabarís s.n., 08028 Barcelona, Catalonia (Spain); MALTA-Consolider Team, Departament de Física Aplicada, ICMUV, Universitat de València, c/Dr. Moliner 50, 46100 Burjassot, València (Spain); Segura, A. [MALTA-Consolider Team, Departament de Física Aplicada, ICMUV, Universitat de València, c/Dr. Moliner 50, 46100 Burjassot, València (Spain); Ibáñez, J., E-mail: jibanez@ictja.csic.es; Artús, L. [Institut Jaume Almera, Consell Superior d' Investigacions Científiques (CSIC), Lluís Solé i Sabarís s.n., 08028 Barcelona, Catalonia (Spain); Yamaguchi, T.; Nanishi, Y. [Faculty of Science and Engineering, Ritsumeikan University, Shiga 525-8577 (Japan)

    2014-12-08

    We have performed high-pressure Fourier transform infrared reflectance measurements on a freestanding InN thin film to determine the refractive index of wurtzite InN and its high-pressure rocksalt phase as a function of hydrostatic pressure. From a fit to the experimental refractive-index curves including the effect of the high-energy optical gaps, phonons, free carriers, and the direct (fundamental) band-gap in the case of wurtzite InN, we obtain pressure coefficients for the low-frequency (electronic) dielectric constant ε{sub ∞}. Negative pressure coefficients of −8.8 × 10{sup −2 }GPa{sup −1} and −14.8 × 10{sup −2 }GPa{sup −1} are obtained for the wurtzite and rocksalt phases, respectively. The results are discussed in terms of the electronic band structure and the compressibility of both phases.

  5. 100-nm thick single-phase wurtzite BAlN films with boron contents over 10%

    KAUST Repository

    Li, Xiaohang

    2017-01-11

    Growing thicker BAlN films while maintaining single-phase wurtzite structure and boron content over 10% has been challenging. In this study, we report on the growth of 100 nm-thick single-phase wurtzite BAlN films with boron contents up to 14.4% by MOCVD. Flow-modulated epitaxy was employed to increase diffusion length of group-III atoms and reduce parasitic reactions between the metalorganics and NH3. A large growth efficiency of ∼2000 μm mol−1 was achieved as a result. Small B/III ratios up to 17% in conjunction with high temperatures up to 1010 °C were utilized to prevent formation of the cubic phase and maintain wurtzite structure.

  6. Fast production of ZnO nanorods by arc discharge in de-ionized water and applications in dye-sensitized solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Sönmezoğlu, S., E-mail: svssonmezoglu@kmu.edu.tr [Department of Materials Science and Engineering, Karamanoğlu Mehmetbey University, Karaman (Turkey); Eskizeybek, V. [Department of Materials Science and Engineering, Çanakkale Onsekiz Mart University, Çanakkale (Turkey); Toumiat, A. [Department of Physics, Constantine Ceramics Lab., Mentouri University (Algeria); Avcı, A. [Department of Mechanical Engineering, Selçuk University, Konya (Turkey)

    2014-02-15

    Highlights: • Fast production of ZnO nanorods was synthesized by bottom up approach using arc discharge in de-ionized water method. • A dye-sensitized solar cell based on ZnO nanorod displayed the most efficient solar to electricity conversion efficiency of the N719 dyes with a maximum η value of 6.96%. • We focused on the morphology, photocatalytical and optical properties of the ZnO nanorods. -- Abstract: Fast production of the ZnO nanorods by bottom up approach using arc discharge method in de-ionized water was carried out. Structural analysis showed that the obtained ZnO powder exhibits crystallize in the hexagonal wurtzite structure with (1 0 1) preferential orientation. Furthermore, transmission electron microscopy observations showed that rod-like structure is the abundant form with a bimodial grain size distribution around 10 and 30 nm. Optical characterization of the as-synthesized ZnO nanorods revealed the existence of the two absorption and photoluminescence (PL) bands both located at UV spectral region attributed to the two grain size distributions. In addition, the two additional visible bands PL spectrum located at 430 and 492 nm are attributed the interstitial zinc and oxygen vacancies; respectively. Dye sensitized solar cells (DSSCs) were successfully produced via different ruthenium based dyes and ferrocene liquid electrolyte by using of as synthesized ZnO nanorods modified photoanodes. It has been found that DSSCs made with N719 dye is the most efficient with photoconversion of approximately 7% compared to the other dyes. Such nanorod form of the ZnO nanostructures with ruthenium dyes resulted in significant improvements of the device performance in terms of electron transportation and UV light absorption. This work would explore feasible routes to synthesize efficient metal-oxide nanostructures for opto-electronic or other related applications.

  7. Si/ZnO nanorods/Ag/AZO structures as promising photovoltaic plasmonic cells

    Energy Technology Data Exchange (ETDEWEB)

    Placzek-Popko, E., E-mail: ewa.popko@pwr.edu.pl; Gwozdz, K.; Gumienny, Z.; Zielony, E.; Jacak, W. [Faculty of Fundamental Problems of Technology, Institute of Physics, Wroclaw University of Technology, Wybrzeze Wyspianskiego 27, 50-370 Wroclaw (Poland); Pietruszka, R.; Witkowski, B. S.; Wachnicki, Ł.; Gieraltowska, S. [Institute of Physics, Polish Academy of Sciences, al. Lotnikow 32/46, 02-668 Warsaw (Poland); Godlewski, M. [Institute of Physics, Polish Academy of Sciences, al. Lotnikow 32/46, 02-668 Warsaw (Poland); Department of Mathematics and Natural Sciences College of Science, Cardinal Stefan Wyszynski University, Dewajtis 5, 01-815 Warsaw (Poland); Chang, Liann-Be [Department of Electronic Engineering and Green Technology Research Center, Chang-Gung University, Taoyuan, Taiwan (China)

    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.

  8. Investigation on structural properties of Al-substituted ZnS particle prepared from wet chemical synthetic route

    Directory of Open Access Journals (Sweden)

    Yingyot Infahsaeng

    Full Text Available ZnS, a wide energy band gap semiconductor, is the potential candidates as a buffer layer for solar cells application. Here, ZnS and Al-substituted ZnS were prepared by simply chemical synthetic route with various high concentration of Al dopant from 0 at% to 40 at%. The structures of ZnS and Al-substituted ZnS powder are all in cubic zinc blende phase. Interestingly, the crystallite size slightly decreases with increasing of Al concentration. A presence of Al content is related with the absence of Zn atom indicate that aluminum is partially substituted into ZnS structure. However, the crystalline structure and morphology of Al-substituted ZnS are not dramatically affected by the aluminum dopant concentration. The band gap energy of the bulk ZnS is approximately at 3.62 eV and slightly increase with increasing of Al dopant. The photoluminescence of Al-substituted ZnS were slightly red-shift and broaden from that of bare ZnS. Keywords: ZnS, Al-substituted ZnS, Photoluminescence, Morphology

  9. Scintillation and luminescence in transparent colorless single and polycrystalline bulk ceramic ZnS

    Energy Technology Data Exchange (ETDEWEB)

    McCloy, John S., E-mail: john.mccloy@wsu.edu [School of Mechanical and Materials Engineering, Washington State University, P.O. Box 642920, Pullman, WA 99164 (United States); Materials Science and Engineering Program, Washington State University, PO Box 641030, Pullman, WA 99164 (United States); Bliss, Mary; Miller, Brian; Wang, Zheming; Stave, Sean [Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA 99352 (United States)

    2015-01-15

    ZnS:Ag is a well-known, extremely bright scintillator used in powder form for α-particle detection and, mixed with powdered LiF, for thermal neutron detection. Recently, we discovered some colorless and transparent commercial bulk single-crystal and polycrystalline (chemical vapor-deposited) ZnS forms that scintillate in response to α-particles. The scintillation light transmits through the sample thickness (millimeters), challenging the commonly held assumption that ZnS is opaque to its own scintillation light. Individual α-particle events were imaged in space and time using a charged-particle camera originally developed for medical imaging applications. Photoluminescence (PL) and PL excitation show that scintillating bulk ZnS likely depends on different electronic defects than commercial ZnS powder scintillators. These defects, associated with copper and oxygen, are discussed in relation to PL results and extensive literature assessment. Commercial transparent ZnS is routinely produced by chemical vapor deposition to sizes larger than square meters, enabling potentially novel radiation detection applications requiring large, thick apertures. - Highlights: • Colorless transparent chemical vapor deposited ZnS shows α-particle scintillation. • Scintillation in CVD ZnS has been imaged spatially and temporally. • Scintillation light transmitted through 1 to 5 mm thick samples. • Photoluminescence data suggests origin of scintillation behavior. • Copper and oxygen impurities likely linked to scintillation in CVD ZnS.

  10. Hydrothermal Synthesis of Nanoclusters of ZnS Comprised on Nanowires

    Directory of Open Access Journals (Sweden)

    Magnus Willander

    2013-09-01

    Full Text Available Cetyltrimethyl ammonium bromide cationic (CTAB surfactant was used as template for the synthesis of nanoclusters of ZnS composed of nanowires, by hydrothermal method. The structural and morphological studies were performed by using X-ray diffraction (XRD, scanning electron microscopy (SEM and high resolution transmission electron microscopy (HRTEM techniques. The synthesized ZnS nanoclusters are composed of nanowires and high yield on the substrate was observed. The ZnS nanocrystalline consists of hexagonal phase and polycrystalline in nature. The chemical composition of ZnS nanoclusters composed of nanowires was studied by X-ray photo electron microscopy (XPS. This investigation has shown that the ZnS nanoclusters are composed of Zn and S atoms.

  11. Synthesis of ZnS thin films from aqueous caustic of trisodium citrate and their properties

    Directory of Open Access Journals (Sweden)

    Martyn A. Sozanskyi

    2015-12-01

    Full Text Available Zinc sulfide (ZnS thin films due to their properties are widely used in various electronic optical devices. They are produced by several methods, among which – vacuum sublimation, high frequency sputtering method, quasiclosed volume method, sol-gel method, electrodeposition. These methods have high energy consumption which increases the price of ZnS thin films. Aim: The aim of this work is to establish the optimal parameters of the synthesis of ZnS thin films of the aqueous caustic and the correlation between content of zinc in the synthesized films determined by the method of stripping voltammetry and thickness, structural, morphological and optical parameters. Materials and Methods: The ZnS thin films were obtained from aqueous caustics of zinc-containing salt using chemical deposition. Fresh solution of zinc-containing salt, trisodium citrate (Na3C6H5O7 as a complexing agent, thiourea ((NH22CS and ammonium hydroxide (NH4OH was used for the synthesis of ZnS films by chemical deposition. The deposition was performed on prepared glass substrates with the area of 5,76 cm2. Results: The phase mixture of the films has been determined. It showed the presence of ZnS compounds in the cubic modification (sphalerite. Stripping voltammetry was used to determine the mass of zinc in the ZnS films on various conditions of synthesis, namely on the concentration of the initial zinc-containing salt, trisodium citrate, thiourea, deposition time and temperature. The surface morphology, optical properties, the thickness of the ZnS resulting films have been studied. Conclusions: The optimal conditions for the synthesis of ZnS films were found based on these data. Three-dimensional surface morphology of ZnS film studies showed its smoothness, uniformity, integrity and confirmed the correctness of determining the optimal synthesis parameters.

  12. Microstructure analysis of chemically synthesized wurtzite-type CdS ...

    Indian Academy of Sciences (India)

    Abstract. Microstructure of chemically synthesized wurtzite-type CdS nanocrystals have been investigated by X-ray diffraction (XRD) peak profile analysis by applying different forms of. Williamson–Hall (WH) method viz., uniform deformation model (UDM), uniform stress deforma- tion model (USDM) and uniform deformation ...

  13. Acousto-optical phonon excitation in piezoelectric wurtzite slabs and crystal growth orientation effects

    DEFF Research Database (Denmark)

    Duggen, Lars; Willatzen, Morten

    2017-01-01

    This paper presents a theoretical investigation of phonon dispersion in piezoelectric slabs of hexagonal crystal symmetry (wurtzite). Specifically we solve the fully coupled dispersion relations in a GaN free standing quantum well by varying the crystal growth direction from the [001] axis...

  14. Facile one-pot synthesis of polytypic (wurtzite-chalcopyrite) CuGaS2

    Science.gov (United States)

    Vahidshad, Yaser; Mirkazemi, Seyed Mohammad; Tahir, Muhammad Nawaz; Zad, Azam Iraji; Ghasemzadeh, Reza; Tremel, Wolfgang

    2016-03-01

    In this investigation, monodisperse CuGaS2 nanoparticles intended for use as visible-light-absorbing materials were synthesized using a facile one-step heating method that involved dissolving the precursors copper chloride, gallium acetylacetonate, and thiourea in a solvent consisting of either oleylamine alone or a combination of oleylamine, oleic acid, and 1-octadecene. The shapes of the resulting nanoparticles were either elongated, polygonal, or a mixture of both, depending on whether the crystal structure of the nanoparticles was predominantly wurtzite, predominantly chalcopyrite, or a more balanced mixture of both wurtzite and chalcopyrite (i.e., the nanoparticles were polytypic: both wurtzite and chalcopyrite phases were present). The crystal structure of the synthesized nanoparticles was found to be influenced by the temperature and the solvent applied during synthesis. X-ray diffraction data for the nanoparticles indicated that applying a temperature of 270 °C or using oleylamine, oleic acid solvent, and 1-octadecene during synthesis tended to yield a chalcopyrite phase, whereas applying a somewhat lower temperature (210 °C) or using oleylamine alone during synthesis tended to result in a wurtzite phase. The chemical states of the compounds obtained at different temperatures and using various solvents, as well as their crystal structures, morphologies, and optical properties were characterized via X-ray photoelectron spectroscopy, X-ray diffraction, transmission electron microscopy, ultraviolet-visible spectroscopy, and photoluminescence.

  15. from Anatase to Rutile Nanorods

    African Journals Online (AJOL)

    NJD

    occurred in two steps (rate constants 0.046 ± 0.025 min–1 and 0.0013 ± 0.0002 min–1). The first step entailed a relatively rapid reaction corresponding to the conversion of anatase nanoparticles to rutile nanoparticles, while the second slower reaction converted the remaining anatase material into rutile titania nanorod ...

  16. Emission characteristics of SPAN-80 activated ZnS nanocolloids

    Energy Technology Data Exchange (ETDEWEB)

    Ngo, Thu Huong; Bui, Hong Van; Pham, Van Ben; Tran, Thi Hong; Ngac, An Bang [Faculty of Physics, HUS, Vietnam National University, Hanoi, 334 Nguyen Trai, Thanh Xuan, Ha Noi (Viet Nam); Hoang, Nam Nhat, E-mail: namnhat@gmail.com [Faculty of Technical Physics and Nanotechnology, UET, Vietnam National University, Hanoi, 144 Xuan Thuy, Cau Giay, Ha Noi (Viet Nam)

    2012-08-15

    Quantum surface effects (new emission bands, blueshifts, intensity enhancement) were observed in SPAN-80 activated ZnS nanocolloids and explained in terms of time-dependent density functional theory. The experimental evidences were demonstrated for both undoped and Cu, Mn-doped colloidal phases. The photoluminescence spectra of these materials showed a new green band at 520 nm (ZnS:Cu) and a yellow-orange band at 576 nm (ZnS:Mn) besides a blue band at 465 nm. All bands lie in the visible region and are blueshifted, show sharp emissions with narrow widths and have approximately 20-times stronger intensities in comparison with those of the bulk samples. The time-resolved luminescence spectra showed that the life-times of free electrons were 0.12 {mu}s and 1.9 ms in ZnS:Cu and ZnS:Mn correspondingly. - Highlights: Black-Right-Pointing-Pointer Novel SPAN-80 activated ZnS nanocolloids with new observables. Black-Right-Pointing-Pointer Enhanced emission intensity of colloidal systems activated by SPAN-80. Black-Right-Pointing-Pointer Quantum surface effects explained on basis of time-dependent density functional theory.

  17. Growth of Multipod ZnO Architectures Made by Accumulation of Hexagonal Nanorods for Dye Sensitized Solar Cell (DSSC) Application.

    Science.gov (United States)

    Umar, Ahmad

    2015-09-01

    Well-crystalline multipod ZnO architectures made by accumulation of hexagonal nanorods were synthesized, characterized and used as efficient anode material for the fabrication of dye-sensitized solar cell (DSSC). The multipod ZnO architectures were synthesized by simple and facile hydrothermal process and characterized by several techniques to examine the structural, morphological, optical and photovoltaic properties. The morphological characterizations revealed that the synthesized multipod ZnO architectures were made of several hexagonal shaped ZnO nanorods which are originated from a single centre. The structural and compositional properties revealed that the nanorods are pure ZnO and possessing well crystallinity and wurtzite hexagonal phase. The assynthesized multipods ZnO architectures were utilized as potential anode materials for the fabrication of dye-sensitized solar cell (DSSC). The dye sensitized solar cells fabricated with multipods ZnO architectures photoanode attained a reasonable solar to electricity energy conversion efficiency of -1.9% with a photocurrent density i.e., short circuit current (J(sc)) of 4.59 mA/cm2.

  18. Structural, magnetic and optical properties of ZnO nanostructures converted from ZnS nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Patel, Prayas Chandra; Ghosh, Surajit; Srivastava, P.C., E-mail: pcsrivastava50@gmail.com

    2016-09-15

    Graphical abstract: The phase conversion of ZnS to highly crystalline hexagonal ZnO was done by heat treatment. - Highlights: • Phase change of cubic ZnS to hexagonal ZnO via heat treatment. • Band gap was found to decrease with increasing calcinations temperature. • ZnO samples have higher magnetic moment than ZnS. • Blocking Temperature of the samples is well above room temperature. • Maximum negative%MR with saturation value ∼38% was found for sample calcined at 600° C. - Abstract: The present work concentrates on the synthesis of cubic ZnS and hexagonal ZnO semiconducting nanoparticle from same precursor via co-precipitation method. The phase conversion of ZnS to highly crystalline hexagonal ZnO was done by heat treatment. From the analysis of influence of calcination temperature on the structural, optical and vibrational properties of the samples, an optimum temperature was found for the total conversion of ZnS nanoparticles to ZnO. Role of quantum confinement due to finite size is evident from the blue shift of the fundamental absorption in UV–vis spectra only in the ZnS nanoparticles. The semiconducting nature of the prepared samples is confirmed from the UV–vis, PL study and transport study. From the magnetic and transport studies, pure ZnO phase was found to be more prone to magnetic field.

  19. Magnetic properties of NI-doped ZnS: First-principles study

    Science.gov (United States)

    Xie, Hai-Qing; Tang, Li-Jun; Tang, Jun-Long; Peng, Ping

    2015-03-01

    A systematic investigation on magnetism and spin-resolved electronic properties in Ni-doped ZnS systems was performed by using the first principle plane-wave pseudo potential method. The formation energy calculation implied that Ni-doped ZnS could be realized experimentally at room temperature and ferromagnetic state was ground state in Ni-doped ZnS. Electronic structures showed Ni-doped ZnS supercell was p-type half-metallic ferromagnetic (FM) semiconductor with a total magnetic moment of 2.0 μB per Ni. Due to the neighboring S atoms around doped Ni atoms mediating the magnetic coupling by p-d hybridization, the long distance FM coupling in Ni-doped ZnS was achieved. Furthermore, high dopant concentration and not obvious clustering effect could be obtained in Ni-doped ZnS. These results imply that Ni-doped ZnS could be a promising dilute magnetic semiconductor for application in spintronic devices.

  20. Interface-mediated synthesis of monodisperse ZnS nanoparticles with sulfate-reducing bacterium culture.

    Science.gov (United States)

    Liang, Zhanguo; Mu, Jun; Mu, Ying; Shi, Jiaming; Hao, Wenjing; Dong, Xuewei; Yu, Hongquan

    2013-12-01

    We have created a new method of ZnS nanospheres synthesis. By interface-mediated precipitation method (IMPM), monodisperse ZnS nanoparticles was synthesized on the particle surface of sulfate-reducing bacterium nutritious agar culture. Sulfate-reducing bacterium (SRB) was used as a sulfide producer because of its dissimilatory sulfate reduction capability, meanwhile produced a variety of amino acids acting as templates for nanomaterials synthesis. Then zinc acetate was dispersed into nutritious agar plate. Subsequently agar plate was broken into particles bearing much external surface, which successfully mediated the synthesis of monodisperse ZnS nanoparticles. The morphology of monodisperse ZnS nanospheres and SRB were examined by scanning electron microscopy (SEM), and the microstructure was investigated by X-ray diffraction (XRD). The thermostability of ZnS nanoparticles was determined by thermo gravimetric-differential thermo gravimetric (TG-DTG). The maximum absorption wavelengh was analysed with an ultraviolet-visible spectrophotometer within a range of 199-700 nm. As a result, monodisperse ZnS nanoparticles were successfully synthesized, with an average diameter of 80 nm. Maximum absorption wavelengh was 228 nm, and heat decomposed temperature of monodisperse ZnS nanoparticles was 596°C. Copyright © 2013 The Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

  1. In-Doped ZnO Hexagonal Stepped Nanorods and Nanodisks as Potential Scaffold for Highly-Sensitive Phenyl Hydrazine Chemical Sensors

    Directory of Open Access Journals (Sweden)

    Ahmad Umar

    2017-11-01

    Full Text Available Herein, we report the growth of In-doped ZnO (IZO nanomaterials, i.e., stepped hexagonal nanorods and nanodisks by the thermal evaporation process using metallic zinc and indium powders in the presence of oxygen. The as-grown IZO nanomaterials were investigated by several techniques in order to examine their morphological, structural, compositional and optical properties. The detailed investigations confirmed that the grown nanomaterials, i.e., nanorods and nanodisks possess well-crystallinity with wurtzite hexagonal phase and grown in high density. The room-temperature PL spectra exhibited a suppressed UV emissions with strong green emissions for both In-doped ZnO nanomaterials, i.e., nanorods and nanodisks. From an application point of view, the grown IZO nanomaterials were used as a potential scaffold to fabricate sensitive phenyl hydrazine chemical sensors based on the I–V technique. The observed sensitivities of the fabricated sensors based on IZO nanorods and nanodisks were 70.43 μA·mM−1·cm−2 and 130.18 μA·mM−1·cm−2, respectively. For both the fabricated sensors, the experimental detection limit was 0.5 μM, while the linear range was 0.5 μM–5.0 mM. The observed results revealed that the simply grown IZO nanomaterials could efficiently be used to fabricate highly sensitive chemical sensors.

  2. In-Doped ZnO Hexagonal Stepped Nanorods and Nanodisks as Potential Scaffold for Highly-Sensitive Phenyl Hydrazine Chemical Sensors.

    Science.gov (United States)

    Umar, Ahmad; Kim, Sang Hoon; Kumar, Rajesh; Al-Assiri, Mohammad S; Al-Salami, A E; Ibrahim, Ahmed A; Baskoutas, Sotirios

    2017-11-21

    Herein, we report the growth of In-doped ZnO (IZO) nanomaterials, i.e., stepped hexagonal nanorods and nanodisks by the thermal evaporation process using metallic zinc and indium powders in the presence of oxygen. The as-grown IZO nanomaterials were investigated by several techniques in order to examine their morphological, structural, compositional and optical properties. The detailed investigations confirmed that the grown nanomaterials, i.e., nanorods and nanodisks possess well-crystallinity with wurtzite hexagonal phase and grown in high density. The room-temperature PL spectra exhibited a suppressed UV emissions with strong green emissions for both In-doped ZnO nanomaterials, i.e., nanorods and nanodisks. From an application point of view, the grown IZO nanomaterials were used as a potential scaffold to fabricate sensitive phenyl hydrazine chemical sensors based on the I-V technique. The observed sensitivities of the fabricated sensors based on IZO nanorods and nanodisks were 70.43 μA·mM-1 cm-2 and 130.18 μA·mM-1 cm-2, respectively. For both the fabricated sensors, the experimental detection limit was 0.5 μM, while the linear range was 0.5 μM-5.0 mM. The observed results revealed that the simply grown IZO nanomaterials could efficiently be used to fabricate highly sensitive chemical sensors.

  3. A Comparative Study on Structural and Optical Properties of ZnO Micro-Nanorod Arrays Grown on Seed Layers Using Chemical Bath Deposition and Spin Coating Methods

    Directory of Open Access Journals (Sweden)

    Sibel MORKOÇ KARADENİZ

    2016-11-01

    Full Text Available In this study, Zinc Oxide (ZnO seed layers were prepared on Indium Tin Oxide (ITO substrates by using Chemical Bath Deposition (CBD method and Sol-gel Spin Coating (SC method. ZnO micro-nanorod arrays were grown on ZnO seed layers by using Hydrothermal Synthesis method. Seed layer effects of structural and optical properties of ZnO arrays were characterized. X-ray diffractometer (XRD, Scanning Electron Microscopy (SEM and Ultraviolet Visible (UV-Vis Spectrometer were used for analyses. ZnO micro-nanorod arrays consisted of a single crystalline wurtzite ZnO structure for each seed layer. Besides, ZnO rod arrays were grown smoothly and vertically on SC seed layer, while ZnO rod arrays were grown randomly and flower like structures on CBD seed layer. The optical absorbance peaks found at 422 nm wavelength in the visible region for both ZnO arrays. Optical bandgap values were determined by using UV-Vis measurements at 3.12 and 3.15 eV for ZnO micro-nanorod arrays on CBD seed layer and for ZnO micro-nanorod arrays on SC-seed layer respectively.DOI: http://dx.doi.org/10.5755/j01.ms.22.4.13443

  4. Aqueous chemical growth of free standing vertical ZnO nanoprisms, nanorods and nanodiskettes with improved texture co-efficient and tunable size uniformity

    Energy Technology Data Exchange (ETDEWEB)

    Ram, S.D.G. [Bharath Niketan Engineering College, Department of Physics, Aundipatti (India); Ravi, G.; Mahalingam, T. [Alagappa University, Department of Physics, Karaikudi (India); Athimoolam, A. [Fatima Michael College of Engineering and Technology, Department of Physics, Madurai (India); Kulandainathan, M.A. [Central Electro Chemical Research Institute, Karaikudi (India)

    2011-12-15

    Tuning the morphology, size and aspect ratio of free standing ZnO nanostructured arrays by a simple hydrothermal method is reported. Pre-coated ZnO seed layers of two different thicknesses ({approx}350 nm or 550 nm) were used as substrates to grow ZnO nanostructures for the study. Various parameters such as chemical ambience, pH of the solution, strength of the Zn{sup 2+} atoms and thickness of seed bed are varied to analyze their effects on the resultant ZnO nanostructures. Vertically oriented hexagonal nanorods, multi-angular nanorods, hexagonal diskette and popcorn-like nanostructures are obtained by altering the experimental parameters. All the produced nanostructures were analysed by X-ray powder diffraction analysis and found to be grown in the (002) orientation of wurtzite ZnO. The texture co-efficient of ZnO layer was improved by combining a thick seed layer with higher cationic strength. Surface morphological studies reveal various nanostructures such as nanorods, diskettes and popcorn-like structures based on various preparation conditions. The optical property of the closest packed nanorods array was recorded by UV-VIS spectrometry, and the band gap value simulated from the results reflect the near characteristic band gap of ZnO. The surface roughness profile taken from the Atomic Force Microscopy reveals a roughness of less than 320 nm. (orig.)

  5. Physiological investigation of gold nanorods toward watermelon.

    Science.gov (United States)

    Wan, Yujie; Li, Junli; Ren, Hongxuan; Huang, Jin; Yuan, Hong

    2014-08-01

    The objective of the present study was to evaluate the phytotoxicity and oxidant stress of the gold nanorods toward watermelon, and hence give a quantitative risk assessment of both seeds and plants phase. The seed germination, the activity of antioxidant enzymes, and the contents of soluble protein and malondialdehyde (MDA) have been measured while the plant roots were observed by transmission electron microscopy (TEM). It was found that the gold nanorods significantly promoted the root elongation. Furthermore, the results on the enzymes activities of plant indicated that oxidative stress happened in the plant treated with gold nanorods. However, the gold nanorods resulted in the phytotoxicity toward plant especially at high concentration. The TEM images of the plant roots with and without the treatment of gold nanorods showed the significant different size of starch granules. In conclusion, significant physiological changes of plant occurred after treatment with the gold nanorods.

  6. Solid solutions of gadolinium doped zinc oxide nanorods by combined microwave-ultrasonic irradiation assisted crystallization

    Science.gov (United States)

    Kiani, Armin; Dastafkan, Kamran; Obeydavi, Ali; Rahimi, Mohammad

    2017-12-01

    Nanocrystalline solid solutions consisting of un-doped and gadolinium doped zinc oxide nanorods were fabricated by a modified sol-gel process utilizing combined ultrasonic-microwave irradiations. Polyvinylpyrrolidone, diethylene glycol, and triethylenetetramine respectively as capping, structure directing, and complexing agents were used under ultrasound dynamic aging and microwave heating to obtain crystalline nanorods. Crystalline phase monitoring, lattice parameters and variation, morphology and shape, elemental analysis, functional groups, reducibility, and the oxidation state of emerged species were examined by PXRD, FESEM, TEM, EDX, FTIR, micro Raman, H2-TPR, and EPR techniques. Results have verified that irradiation mechanism of gelation and crystallization reduces the reaction time, augments the crystal quality, and formation of hexagonal close pack structure of Wurtzite morphology. Besides, dissolution of gadolinium within host lattice involves lattice deformation, unit cell distortion, and angular position variation. Structure related shape and growth along with compositional purity were observed through microscopic and spectroscopic surveys. Furthermore, TPR and EPR studies elucidated more detailed behavior upon exposure to the exerted irradiations and subsequent air-annealing including the formed oxidation states and electron trapping centers, presence of gadolinium, zinc, and oxygen disarrays and defects, as well as alteration in the host unit cell via gadolinium addition.

  7. Synthesis, characterization, and applications of zinc oxide nanoparticles and nanorods in acetone gas detection

    Science.gov (United States)

    Nauman Ali, Rai; Diao, Kaidi; Naz, Hina; Cui, Xudong; Xiang, Bin

    2017-09-01

    In this paper, we report an enhanced gas sensing performance of ZnO by changing the ZnO configuration from one dimension (1D) to zero dimension (0D). The structural and optical properties of the as-synthesized samples have been investigated by transmission electron microscopy (TEM), x-ray diffraction (XRD), UV-visible near infrared and photoluminescence spectroscopies (PL). TEM results confirm the non-agglomerated crystalline morphology of 0D ZnO nanoparticles as well as the 1D nanorods. All the representative peaks observed in the XRD spectrum confirm the hexagonal wurtzite structure. The UV-visible absorption and PL emission spectra for 0D ZnO nanoparticles indicate an obvious blue shift compared to the 1D nanorods because of its lower dimension size. Our dynamic response-recovery characterizations reveal that the 0D ZnO exhibits better acetone-gas sensing performance compared to 1D ZnO under an optimum operating temperature of 250 °C.

  8. Growth of Well-Aligned ZnO Nanorod Arrays and Their Application for Photovoltaic Devices

    Science.gov (United States)

    Yuan, Zhaolin; Yao, Juncai

    2017-11-01

    We have fabricated well-aligned ZnO nanorod arrays (ZNRAs) on indium tin oxide-coated glass substrates by a facile chemical bath deposition method. We used field-emission scanning electron microscope, x-ray diffraction and UV-Vis absorption spectroscopy to study the morphology, crystalline structure and optical absorption of the fabricated ZNRAs, respectively. The results showed that ZnO nanorods stood almost perpendicularly on the substrate, were about 30-50 nm in diameter and 800-900 nm in length, and were wurtzite-structured (hexagonal) ZnO. In addition, well-aligned ZNRAs exhibited a weak absorption in the visible region and had an optical band gap value of 3.28 eV. Furthermore, a hybrid ZNRAs/polymer photovoltaic device was made, under 1 sun AM 1.5 illumination (light intensity, ˜100 mW/cm2), and the device showed an open circuit voltage ( V oc) of 0.32 V, a short circuit current density ( J sc) of 7.67 mA/cm2, and a fill factor ( FF) of 0.37, yielding an overall power conversion efficiency of 0.91%. Also, the exciton dissociation and transportation processes of charge carriers in the device under illumination were explained according to its current density-voltage ( J- V) curve and the energy level diagram.

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

    Science.gov (United States)

    Pal, Partha P.; Manam, J.

    2014-07-01

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

  10. Surface Passivation and Photoluminescence of Mn-Doped ZnS Nanocrystals

    OpenAIRE

    Ping Yang; Michael Bredol

    2008-01-01

    Enhanced photoluminescence (PL) is reported from Mn-doped ZnS nanocrystals (NCs) capped with ZnS (ZnS:Mn/ZnS core-shell NCs) and thioglycolic acid (TGA) (ZnS:Mn/ZnS core-shell NCs dispersed in an alkaline TGA solution). The NCs were prepared using a reverse micelle route. Comparing with initial ZnS:Mn core NCs, the ZnS:Mn/ZnS core-shell NCs exhibit much stronger orange PL (~580 nm). This is presumably the result of effective passivation of quenching ZnS:Mn NCs surface states by a pure ZnS sh...

  11. Magnetophoresis of Fe3O4 Nanorods

    Science.gov (United States)

    Tan, David; Lim, Jitkang; Lanni, Caitlin; Lanni, Frederick; Tilton, Robert; Majetich, Sara

    2009-03-01

    The magnetophoretic motion of a nanorod is quite different from that of a nanosphere. In large particles, motion is predicted from the balance of magnetic and viscous drag forces, but for nanoparticles random thermal forces lead to Brownian motion as well. Due to magnetic and diffusive anisotropy, a nanorod has advantages over a nanosphere for the single particle guidance and tracking, which would be important for studies within living cells. We have investigated the magnetophoretic behavior of nanorods and nanospheres both theoretically and experimentally. Peclet number analysis shows that 300 nm x 20 nm nanorods are more likely to be in the convective than diffusive regime than nanospheres of equal volume, for the same field and field gradient. Experimental studies of nanorod motion were made using Fe3O4 nanorods coated with poly (diallyldimethylammonium chloride) and fluorescein-5-isothiocyanate (FITC) tagged bovine serum albumin (BSA) and dispersed in saline solution. The motion of the nanorods was observed with and without magnetic field gradients using fluorescence microscopy. Fluorescence micrograph showed the nanorods undergo magnetophoretic motion toward the higher field gradient region with a velocity of about 28μm/sec. The controlled motion of magnetic nanorods within HeLa cancer cells has been demonstrated.

  12. Single and multi-layered core-shell structures based on ZnO nanorods obtained by aerosol assisted chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Sáenz-Trevizo, A.; Amézaga-Madrid, P.; Pizá-Ruiz, P.; Antúnez-Flores, W.; Ornelas-Gutiérrez, C.; Miki-Yoshida, M., E-mail: mario.miki@cimav.edu.mx

    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

  13. On the transition from the wurtzite to the NaCl type.

    Science.gov (United States)

    Sowa, H

    2001-03-01

    A crystallographic interpretation of a possible transition mechanism from the wurtzite to the NaCl type is given. For this purpose, different atoms in the structures of both types are replaced by like ones, resulting in lonsdaleite-type configurations and in cubic primitive lattices, respectively. The atomic arrangements of both types correspond to homogeneous sphere packings. It is shown that a lonsdaleite configuration may be deformed into a cubic primitive lattice within the Wyckoff position Cmcm 8(f) m. 0,y,z. Such a transition is displacive since no bonds have to be broken. The corresponding phase transformation from the wurtzite to the NaCl type can be described as a deformation of a heterogeneous sphere packing. The intermediate structure would have the symmetry Cmc2(1).

  14. Crystal and electronic structure study of Mn doped wurtzite ZnO nanoparticles

    Directory of Open Access Journals (Sweden)

    O.M. Ozkendir

    2016-08-01

    Full Text Available The change in the crystal and electronic structure properties of wurtzite ZnO nanoparticles was studied according to Mn doping in the powder samples. The investigations were conducted by X-ray Absorption Fine Structure Spectroscopy (XAFS technique for the samples prepared with different heating and doping processes. Electronic analysis was carried out by the collected data from the X-ray Absorption Near-Edge Structure Spectroscopy (XANES measurements. Additional crystal structure properties were studied by Extended-XAFS (EXAFS analysis. Longer heating periods for the undoped wurtzite ZnO samples were determined to own stable crystal geometries. However, for some doped samples, the distortions in the crystal were observed as a result of the low doping amounts of Mn which was treated as an impurity. Besides, the changes in oxygen locations were determined to create defects and distortions in the samples.

  15. DC conductivity studies of ZnS and Ag nanoparticles doped P3HT thin films

    National Research Council Canada - National Science Library

    T Abdul Kareem

    2016-01-01

    Interest in the P3HT: ZnS nanocomposites are increased due to their applicability as an active layer for bulk heterojunction solar cells of high open circuit voltage and charge transport in this type of solar cells...

  16. A facile synthesis of ZnS nanocrystallites by pyrolysis of single ...

    Indian Academy of Sciences (India)

    )2 and ZnCl2 (cinnamtsczH)2 (cinnamtsczH = cinnamaldehyde thiosemicarbazone) as single source precursors. The prepared ZnS nanocrystallites were characterized by powder X-ray diffraction (XRD), transmission electron microscopy ...

  17. Photoluminescence of doped ZnS nanoparticles under hydrostatic pressure

    Energy Technology Data Exchange (ETDEWEB)

    Li, G.H.; Su, F.H.; Ma, B.S.; Ding, K. [National Laboratory for Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083 (China); Xu, S.J. [Department of Physics and HKU-CAS Joint Laboratory on New Materials, The University of Hong Kong, Pokfulam Road, Hong Kong (China); Chen, W. [Nomadics, Inc., 1024 South Innovation Way, Stillwater, OK 74074 (United States)

    2004-11-01

    The pressure dependence of the photoluminescence from ZnS:Mn{sup 2+}, ZnS:Cu{sup 2+}, and ZnS:Eu{sup 2+} nanoparticles were investigated under hydrostatic pressure up to 6 GPa at room temperature. Both the orange emission from the {sup 4}T{sub 1}-{sup 6}A{sub 1} transition of Mn{sup 2+} ions and the blue emission from the DA pair transition in the ZnS host were observed in the Mn-doped samples. The measured pressure coefficients are -34.3(8) meV/GPa for the Mn-related emission and -3(3) meV/GPa for the DA band, respectively. The emission corresponding to the 4f{sup 6}5d{sup 1}-4f{sup 7} transition of Eu{sup 2+} ions and the emission related to the transition from the conduction band of ZnS to the t{sub 2} level of Cu{sup 2+} ions were observed in the Eu- and Cu-doped samples, respectively. The pressure coefficient of the Eu-related emission was found to be 24.1(5) meV/GPa, while that of the Cu-related emission is 63.2(9) meV/GPa. The size dependence of the pressure coefficients for the Mn-related emission was also investigated. The Mn emission shifts to lower energies with increasing pressure and the shift rate (the absolute value of the pressure coefficient) is larger in the ZnS:Mn{sup 2+} nanoparticles than in bulk. Moreover, the absolute pressure coefficient increases with the decrease of the particle size. The pressure coefficients calculated based on the crystal field theory are in agreement with the experimental results. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  18. Elastic and piezoelectric properties of zincblende and wurtzite crystalline nanowire heterostructures.

    Science.gov (United States)

    Boxberg, Fredrik; Søndergaard, Niels; Xu, H Q

    2012-09-04

    The elastic and piezoelectric properties of zincblende and wurtzite crystalline InAs/InP nanowire heterostructures have been studied using electro-elastically coupled continuum elasticity theory. A comprehensive comparison of strains, piezoelectric potentials and piezoelectric fields in the two crystal types of nanowire heterostructures is presented. For each crystal type, three different forms of heterostructures-core-shell, axial superlattice, and quantum dot nanowire heterostructures-are considered. In the studied nanowire heterostructures, the principal strains are found to be insensitive to the change in the crystal structure. However, the shear strains in the zincblende and wurtzite nanowire heterostructures can be very different. All the studied nanowire heterostructures are found to exhibit a piezoelectric field along the nanowire axis. The piezoelectric field is in general much stronger in a wurtzite nanowire heterostructure than in its corresponding zincblende heterostructure. Our results are expected to be particularly important for analyzing and understanding the properties of epitaxially grown nanowire heterostructures and for applications in nanowire electronics, optoelectronics, and biochemical sensing. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Elastic and piezoelectric properties of zincblende and wurtzite crystalline nanowire heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Boxberg, Fredrik [Division of Solid State Physics, Lund University (Sweden); Soendergaard, Niels [Division of Mathematical Physics, Lund University (Sweden); Xu, H.Q. [Department of Electronics and Key Laboratory for the Physics and Chemistry of Nanodevices, Peking University, Beijing (China); Division of Solid State Physics, Lund University (Sweden)

    2012-09-04

    The elastic and piezoelectric properties of zincblende and wurtzite crystalline InAs/InP nanowire heterostructures have been studied using electro-elastically coupled continuum elasticity theory. A comprehensive comparison of strains, piezoelectric potentials and piezoelectric fields in the two crystal types of nanowire heterostructures is presented. For each crystal type, three different forms of heterostructures - core-shell, axial superlattice, and quantum dot nanowire heterostructures - are considered. In the studied nanowire heterostructures, the principal strains are found to be insensitive to the change in the crystal structure. However, the shear strains in the zincblende and wurtzite nanowire heterostructures can be very different. All the studied nanowire heterostructures are found to exhibit a piezoelectric field along the nanowire axis. The piezoelectric field is in general much stronger in a wurtzite nanowire heterostructure than in its corresponding zincblende heterostructure. Our results are expected to be particularly important for analyzing and understanding the properties of epitaxially grown nanowire heterostructures and for applications in nanowire electronics, optoelectronics, and biochemical sensing. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  20. Room temperature ferromagnetism and half metallicity in nickel doped ZnS: Experimental and DFT studies

    Energy Technology Data Exchange (ETDEWEB)

    Akhtar, Muhammad Saeed [School of Materials, The University of Manchester, Oxford Road, Manchester M13 9PL (United Kingdom); Centre of Excellence in Solid State Physics, University of the Punjab, Lahore 54590 (Pakistan); Malik, Mohammad Azad, E-mail: Azad.malik@manchester.ac.uk [School of Materials, The University of Manchester, Oxford Road, Manchester M13 9PL (United Kingdom); Riaz, Saira; Naseem, Shahzad [Centre of Excellence in Solid State Physics, University of the Punjab, Lahore 54590 (Pakistan)

    2015-06-15

    The nickel doped nanocrystalline ZnS thin films were deposited onto glass substrates by chemical bath deposition (CBD). Also ZnS:Ni nanoparticles were synthesized by CBD/co-precipitation method. Powder X-ray diffraction (p-XRD) studies demonstrate that both thin films and nanoparticles correspond to sphalerite (cubic) phase of ZnS with slight shift towards higher 2θ values due to incorporation of nickel in the ZnS lattice. The crystallite sizes estimated by Scherrer equation were 4 and 2.6 nm for ZnNiS thin films and nanoparticles, respectively. Scanning Electron Microscopy (SEM) images reveal that the morphology of thin films is based on quasi-spherical particles with nano scale dimensions. Energy Dispersive X-ray (EDX) spectroscopy confirms that the as-deposited thin films have a stoichiometry consistent with the nickel doped ZnS. Full-potential linearized augmented plane wave (FP-L/APW) method based on spin-polarized density functional theory (DFT) was employed to investigate the electronic and magnetic properties of ZnNiS for the doping concentration. Exchange-correlation functional was studied using generalized gradient approximation (GGA + U) method. Electronic band structures and density of states (DOS) demonstrate 100% spin polarization (half metallicity) with ferromagnetic exchange interactions. Superconducting quantum interference device (SQUID) analysis confirms the theoretical observation of ferromagnetism in nickel doped ZnS. These ZnS based half metallic ferromagnets seem to have virtuous applications in future spintronic devices. - Highlights: • ZnS.Ni thin films and nanoparticles were deposited onto glass substrates by CBD. • p-XRD correspond to sphalerite (cubic) phase of ZnS with slight shift in peaks. • DFT was employed to investigate the properties of ZnS.Ni. • DOS demonstrate 100% spin polarization with ferromagnetic exchange interactions. • SQUID analysis confirms the theoretical observations of nickel doped ZnS.

  1. Photoluminescence study of Mn doped ZnS nanoparticles prepared by co-precipitation method

    Energy Technology Data Exchange (ETDEWEB)

    Deshpande, M. P., E-mail: vishwadeshpande@yahoo.co.in; Patel, Kamakshi, E-mail: kamphysics@gmail.com; Gujarati, Vivek P.; Chaki, S. H. [Department of Physics, Sardar Patel University, VallabhVidyanagr-388120,Anand, Gujarat, India. (India)

    2016-05-06

    ZnS nanoparticles co-doped with different concentration (5,10,15%) of Mn were synthesized using polyvinylpyrrolidone (PVP) as a capping agent under microwave irradiation. We confirmed doping of Mn in the host ZnS by EDAX whereas powder X-ray diffractogram showed the cubic zinc blende structure of all these samples. TEM images did showed agglomeration of particles and SAED pattern obtained indicated polycrystalline nature. From SAED pattern we calculated lattice parameter of the samples which have close resemblance from that obtained from XRD pattern. The band gap values of pure and doped ZnS nanoparticles were calculated from UV-Visible absorption spectra. ZnS itself is a luminescence material but when we dope it with transition metal ion such as Mn, Co, and Cu they exhibits strong and intense luminescence in the particular region. The photoluminescence spectra of pure ZnS nanoparticles showed an emission at 421 and 485nm which is blue emission which was originated from the defect sites of ZnS itself and also sulfur deficiency and when doped with Mn{sup 2+} an extra peak with high intensity was observed at 530nm which is nearly yellow-orange emission which isrelated to the presence of Mn in the host lattice.

  2. ZnS nanosheets: Egg albumin and microwave-assisted synthesis and optical properties

    Science.gov (United States)

    Tian, Xiuying; Wen, Jin; Hu, Jilin; Chen, Zhanjun; Wang, Shumei; Peng, Hongxia; Li, Jing

    2016-09-01

    ZnS nanosheets were prepared via egg albumin and microwave-assisted method. The phases, crystalline lattice structures, morphologies, chemical and optical properties were characterized by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), field-emission scanning electron microscope(FE-SEM), selected area electron diffraction (SAED), Fourier transform infrared (FTIR) spectroscopy, ultraviolet-visible (UV-Vis) spectroscopy and fluorescence(FL) spectrometer and growth mechanism of ZnS nanosheets was investigated. The results showed that all samples were pure cubic zinc blende with polycrystalline structure. The width of ZnS nanosheets with a rectangular nanostructure was in the range of 450-750 nm. The chemical interaction existed between egg albumin molecules and ZnS nanoparticles via the amide/carboxylate group. The band gap value calculated was 3.72 eV. The band at around 440 nm was attributed to the sulfur vacancies of the ZnS nanosheets. With increasing volumes of egg albumin, the photoluminescence (PL) intensity of ZnS samples firstly increased and then decreased, attributed to concentration quenching.

  3. Tuning of deep level emission in highly oriented electrodeposited ZnO nanorods by post growth annealing treatments

    Science.gov (United States)

    Simimol, A.; Manikandanath, N. T.; Anappara, Aji A.; Chowdhury, Prasanta; Barshilia, Harish C.

    2014-08-01

    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 (TA = 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 (VO), zinc interstitial (Zni), and oxygen interstitial (Oi) 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 TA greater than the optimized values for the respective environments due to the introduction of various defect centers. For example, for TA ≥ 450 °C in the oxygen and air environments, the density of Oi defects increased, whereas, the green emission associated with VO is dominant in the vacuum annealed (TA = 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.

  4. Facile synthesis of water-soluble ZnS quantum dots with strong luminescent emission and biocompatibility

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Rui; Liu, Yingbo, E-mail: liuyingbo6666@126.com; Sun, Shuqing

    2013-10-01

    ZnS quantum dots (QDs) are among the most promising emerging fluorescent materials for biolabeling. High-quality colloidal ZnS QDs were synthesized via a new facile chemical precipitation method using the mixture of ethylene glycol (EG) and water as the solvent. The phase structure and morphology of the ZnS QDs were characterized by X-ray powder diffraction and high resolution transmission electron microscopy. The synthesized ZnS QDs have a cubic zinc blende structure with monodispered and small particles. ZnS QDs easily dispersed in water to form stable and clear colloids and the strong tunable trap state emissions from 452 to 516 nm were achieved by varying the reaction time. The hemolysis assay was performed to evaluate the biocompatibility of the ZnS QDs.

  5. Differential spectral imaging with gold nanorod light scattering labels

    Science.gov (United States)

    Qiu, Le; Vitkin, Edward; Guo, Lianyu; Hanlon, Eugene B.; Itzkan, Irving; Perelman, Lev T.

    2011-01-01

    Gold nanorods have the potential to be employed as extremely bright molecular marker labels. However, samples containing a large number of gold nanorods usually exhibit relatively wide spectral lines. This linewidth limits the use of the nanorods since it would be rather difficult to image several types of nanorod markers simultaneously. We measured native scattering spectra of single gold nanorods with the CLASS microscope and found that single gold nanorods have a narrow spectrum as predicted by the theory. That suggests that nanorod-based molecular markers with controlled narrow aspect ratios should provide spectral lines sufficiently narrow for effective biomedical imaging.

  6. [The preparation and characterization of 1-D orderly ZnO nanorod arrarys].

    Science.gov (United States)

    Liu, Ran; Zhang, Ting; Zhao, Su-ling; Xu, Zheng; Zhang, Fu-jun; Yuan, Guang-cai; Xu, Xu-rong

    2008-10-01

    Improving on the sealing and high pressure conditions of traditional hydrothermal method, vertical ZnO nanorod arrays were synthesized on indium tin oxide substrate by employing Zn(NO3)2 x 6H2O, (CH2)4N6 as the starting materials in the presence of polyethylenimine(PEI) at ambient pressure and low temperature (92 degrees). Between the substrate and the nanorods, a layer of ZnO flim was prepared as buffer layer and seed layer. The ZnO film was gained by spin-coating zinc acetate solution on indium tin oxide substrate, then annealed at 350 degrees C for 20 min, which can make zinc acetate decompose into zinc oxide. The zinc acetate spin-coating and decomposition procedure was carried out twice to ensure a complete and uniform coverage of ZnO seeds. The second layer was annealed at 500 degrees C for 30 mini Different spin-coating speeds were adopted, one was 2500 r x min(-1), and the other was 5000 r x min(-1). XRD result indicated that the seed layer with 5000 r x min(-1) has better alignment than the layer with 2500 r x min(-1). The aligned seeds with 5000 r x min(-1) show only a (002) reflection, indicating their complete c-axis texturing, whereas the spin-coated seeds give a powder pattern because they rest at all angles on the substrate. SEM result shows that the layer is made up of grains with an the average size of about 30 nm. Well-aligned ZnO nanorod arrays were synthesized by putting the substrate with ZnO seeds into the precursor solutions vertically for one hour. The nanorod arrays were taken out and rinsed with clean ethanol and pure-water for several times, blown dry with a stream of nitrogen, then annealed at 400 degrees C for 30 min in order to wipe off the organic solvent. At room-temperature, the SEM and XRD were measured. SEM results indicate that the crystal structure of most of ZnO nanorods is hexagonal wurtzite crystallographic phase structure, mainly vertical to the substrate. ZnO nanorods have good crystallization, the diameter of the rods is

  7. Resonator-based detection in nanorods

    Science.gov (United States)

    Morassi, A.; Fernández-Sáez, J.; Zaera, R.; Loya, J. A.

    2017-09-01

    In this paper the axial vibrational behavior of nanorods with an attached point-mass is studied, using the modified strain energy theory. The natural frequencies of the nanorod with the concentrated mass are obtained for different boundary conditions. The effects of the concentrated mass intensity, mass location, as well as the value of scale parameters have been analysed. For the case of small intensity of the concentrated mass, the natural frequencies of the nanorod can be estimated using a first order perturbative solution. These approximate results are compared with those corresponding to the exact solution. For this case, from the properties of the eigenvalue perturbative theory, the identification of single point mass in uniform nanorods (mass intensity and position) is addressed. The results obtained encourage the use of axial vibrations of nanorods as a very precise sensing technique.

  8. Synthesis, characterization and enhanced photocatalytic performance of Ag{sub 2}S-coupled ZnO/ZnS core/shell nanorods

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Shan [Tianjin Key Laboratory of Applied Catalysis Science and Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Wang, Xitao, E-mail: wangxt@tju.edu.cn [Tianjin Key Laboratory of Applied Catalysis Science and Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Zhao, Wenxi [Tianjin Academy of Environmental Sciences, Tianjin 300191 (China); Wang, Kang [Tianjin Key Laboratory of Applied Catalysis Science and Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Sang, Huanxin [Tianjin Academy of Environmental Sciences, Tianjin 300191 (China); He, Zhong [Department of Chemical, Biological and Pharmaceutical Engineering, New Jersey Institute of Technology, Newark, NJ 07102 (United States)

    2013-08-15

    Highlights: •A new route was developed to synthetize Ag{sub 2}S-coupled ZnO/ZnS core/shell nanorods. •ZnO/ZnS–Ag{sub 2}S nanorods display enhanced photocatalytic activity for H{sub 2} evolution. •Dilute solution of glycerol is used as sacrificial reagent. •Ag{sub 2}S/ZnS molar ratio on the shell affects obviously the photocatalytic performance. -- Abstract: A series of composite photocatalysts comprised of ZnO nanorods core and ZnS–Ag{sub 2}S heterostructural shell layer with different Ag{sub 2}S/ZnS molar ratios have been synthesized via the combination of a low-temperature hydrothermal growth and cation exchange technique. The core/shell nanorods, with the diameters of about 150 nm and the lengths of ranging from a few 100 nm to several micrometers, were fabricated by coating the ZnO nanorods with a layer of ZnS and Ag{sub 2}S composite shell mainly consisting of nanocrystals with the diameters of about 5–8 nm. The characterization from SEM, TEM, EDX, XPS, and UV–Vis DRS reveals that the molar ratio of Ag{sub 2}S/ZnS in shell layer strongly affects the morphologies, distribution of components, photo absorption, and photocatalytic performance of the ZnO/ZnS–Ag{sub 2}S core/shell nanorods. Due to the coupling with low bandgap material Ag{sub 2}S, the ZnO/ZnS–Ag{sub 2}S nanorods have a much higher solar-simulated light absorption capability than that of ZnO/ZnS. As a result, the as-prepared ZnO/ZnS–Ag{sub 2}S nanocomposites exhibited much higher catalytic efficiency for the hydrogen production from glycerol aqueous solution. The superior photo absorption properties and photocatalytic performance of the ZnO/ZnS–Ag{sub 2}S core/shell nanorods may be ascribed to the heterostructure, which enhanced the separation of photo-induced electron–hole pairs.

  9. Gd doping induced weak ferromagnetic ordering in ZnS nanoparticles synthesized by low temperature co-precipitation technique

    Energy Technology Data Exchange (ETDEWEB)

    Kaur, Palvinder [Department of Physics, Punjabi University, Patiala, Punjab, 147002 (India); Kumar, Sanjeev, E-mail: sanjeev04101977@gmail.com [Applied Science Department, PEC University of Technology, Chandigarh, 160012 (India); Chen, Chi-Liang, E-mail: chen.cl@nsrrc.org.tw [National Synchrotron Radiation Research Center (NSRRC), Hsinchu, 30076, Taiwan (China); Yang, Kai-Siang [National Synchrotron Radiation Research Center (NSRRC), Hsinchu, 30076, Taiwan (China); Department of Mechanical Engineering, National Taipei University of Technology, Taipei, Taiwan (China); Wei, Da-Hua [Department of Mechanical Engineering, National Taipei University of Technology, Taipei, Taiwan (China); Dong, Chung-Li [Department of Physics, Tamkang University, Tamsui, Taiwan (China); Srivastava, C. [Materials Engineering Department, Indian Institute of Science, Bangalore, 560012 (India); Rao, S.M. [Department of Physics, Punjabi University, Patiala, Punjab, 147002 (India); Institute of Physics, Academia Sinica, Taipei, 11529, Taiwan (China)

    2017-01-15

    Zn{sub 1−x}Gd{sub x}S nanoparticles with Gd concentration x = 0.00, 0.02 and 0.04 were synthesized by the chemical co-precipitation technique using thioglycerol as capping agent. X-ray diffraction (XRD), transmission electron microscopy (TEM), photoluminescence (PL) spectroscopy, X-ray absorption near-edge structure (XANES) and vibrating sample magnetometer (VSM) were employed to characterize the as synthesized Gd doped ZnS nanoparticles. XRD and TEM studies show the formation of cubic ZnS nanoparticles with an average size in the range 5–10 nm. The doping did not alter the phase of the ZnS. The PL spectra of doped ZnS nanoparticles showed the presence of sulphur vacancies in the lattice. XANES of Gd doped ZnS nanoparticles depicts spectral changes may arise from charge transfer between host Zn and dopant Gd ions. A VSM study shows that the weak ferromagnetic behaviour increases with increase in Gd doping ZnS nanoparticles. - Highlights: • Gd doped ZnS nanoparticles synthesized using co-precipitation technique. • PL studies depict sulphur and zinc vacancies in Gd doped ZnS nanoparticles. • XANES studies depict the charge transfer between host Zn and dopant Gd ions. • Room temperature weak ferromagnetism is observed in Gd doped ZnS nanoparticles.

  10. Quantification and Control of Inhomogeneity in Wurtzite (GaN) 1-x(ZnO)x Semiconductors for Visible Light Absorption

    Science.gov (United States)

    Reinert, Alexandra Audrey

    Semiconductors must absorb energy from solar photons and subsequently transport photogenerated electrons and holes to surfaces in order to drive the H2 and O2 formation half-reactions of solar water splitting. The hexagonal wurtzite (GaN)1-x(ZnO)x semiconductor solid solution has produced promising results for visible light solar water splitting, but has yet to achieve an efficiency high enough for practical applications, and the origin of the efficiency limit remains unknown. In this work, a detailed investigation of the average and local structure of these materials has been conducted in order to gain insights into how to improve water splitting efficiencies. Our analysis of (GaN)1-x(ZnO)x samples up to x ~ 0.67, has led to the discovery of previously unrecognized types of compositional and structural defects. A new high zinc content Ga2O3(ZnO)16 (2:16) precursor, was developed to prepare higher zinc content oxynitrides. The use of this precursor results in the production of arrays of nanorods with favorable diameters and band gaps for visible light solar water splitting. Optical measurements of these 2:16 precursor samples have shown to be sensitive to small amounts of free carriers whose presence is indicative of compositional defects. Complementary quantitative phase analysis by thermogravimetric analysis, on nanorod samples ranging from xv = 0.08 - 0.52, suggests a substantial quantity of cation vacancies (~3%) may be present. A structural defect in the form of a common zinc-blende (cubic) intergrowth was discovered from transmission electron microscopy measurements. This defect was found to have a uniform size throughout many particles. The abundance of this defect is dependent on both the precursor used during synthesis and the overall zinc content. Further supporting evidence for this cubic intergrowth phase is provided by 14N solid state NMR experiments. Samples synthesized from the novel Ga2O3(ZnO)16 precursor show no evidence of cubic intergrowths

  11. Extended photoresponse and multi-band luminescence of ZnO/ZnSe core/shell nanorods.

    Science.gov (United States)

    Yang, Qin; Cai, Hua; Hu, Zhigao; Duan, Zhihua; Yang, Xu; Sun, Jian; Xu, Ning; Wu, Jiada

    2014-01-15

    Aligned ZnO/ZnSe core/shell nanorods (NRs) with type-II energy band alignment were fabricated by pulsed laser deposition of ZnSe on the surfaces of hydrothermally grown ZnO NRs. The obtained ZnO/ZnSe core/shell NRs are composed of wurtzite ZnO cores and zinc blende ZnSe shells. The bare ZnO NRs are capable of emitting strong ultraviolet (UV) near band edge (NBE) emission at 325-nm light excitation, while the ZnSe shells greatly suppress the emission from the ZnO cores. High-temperature processing results in an improvement in the structures of the ZnO cores and the ZnSe shells and significant changes in the optical properties of ZnO/ZnSe core/shell NRs. The fabricated ZnO/ZnSe core/shell NRs show optical properties corresponding to the two excitonic band gaps of wurtzite ZnO and zinc blende ZnSe and the effective band gap between the conduction band minimum of ZnO and the valence band maximum ZnSe. An extended photoresponse much wider than those of the constituting ZnO and ZnSe and a multi-band photoluminescence including the UV NBE emission of ZnO and the blue NBE emission of ZnSe are observed.

  12. Extended photoresponse and multi-band luminescence of ZnO/ZnSe core/shell nanorods

    Science.gov (United States)

    2014-01-01

    Aligned ZnO/ZnSe core/shell nanorods (NRs) with type-II energy band alignment were fabricated by pulsed laser deposition of ZnSe on the surfaces of hydrothermally grown ZnO NRs. The obtained ZnO/ZnSe core/shell NRs are composed of wurtzite ZnO cores and zinc blende ZnSe shells. The bare ZnO NRs are capable of emitting strong ultraviolet (UV) near band edge (NBE) emission at 325-nm light excitation, while the ZnSe shells greatly suppress the emission from the ZnO cores. High-temperature processing results in an improvement in the structures of the ZnO cores and the ZnSe shells and significant changes in the optical properties of ZnO/ZnSe core/shell NRs. The fabricated ZnO/ZnSe core/shell NRs show optical properties corresponding to the two excitonic band gaps of wurtzite ZnO and zinc blende ZnSe and the effective band gap between the conduction band minimum of ZnO and the valence band maximum ZnSe. An extended photoresponse much wider than those of the constituting ZnO and ZnSe and a multi-band photoluminescence including the UV NBE emission of ZnO and the blue NBE emission of ZnSe are observed. PMID:24428949

  13. [Influence of parameters of ZnS film on the organic/inorganic composite luminescence devices].

    Science.gov (United States)

    Song, Ling-Yun; Cai, Chun-Feng; Liu, Bo-Zhi; Hu, Lian; Zhang, Bing-Po; Wu, Jian-Zhong; Bi, Gang; Wu, Hui-Zhen

    2014-04-01

    In the present paper, to fabricate electroluminescent devices CdSe QDs were used as active materials, TPD (N,N'-biphenyl-N,N'-bis-(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine) was used as a hole transport layer, and ZnS was used as an electron transport layer. The electroluminescent properties of the organic/inorganic composite ITO/TPD/CdSe QDs/ZnS/Ag light emitting devices were studied. Both TPD and CdSe QDs thin films were spin-coated and ZnS thin films were deposited by magnetron sputtering. The surfaces of the devices are smooth. The luminescence (EL) peak of the CdSe QDs is at 580 nm which is assigned to the band-edge exciton emission. Compared to the previous EL device of ITO/ZnS/CdSe QDs/ZnS/Ag, it is seen that the new devices do not display surface state related emission peaks and EL intensity is about 10 folds that of the previous device. The enhancement of luminescence efficiency is attributed to both of the excitation of CdSe QDs by accelerated electron collision and carriers injection into QDs: (1) electrons are accelerated by the ZnS layer and collide with CdSe QDs, which excites electrons in QDs to excited states and allows them to emit photons; (2) the holes injected into QDs recombine with some of electrons excited in the QDs. The authors further studied the influence of thickness variation of ZnS on the luminescent properties. ZnS thin films are of 80, 120, and 160 nm thickness, respectively. It was found that as the thickness of ZnS increases the threshold voltage rises and EL intensity increases, but breakdown voltage decreases. The EL peak position blue shifts when the thickness of ZnS decreases. The explanation of underlying mechanism is given.

  14. Quasi-particle energies and optical excitations of ZnS monolayer honeycomb structure

    Energy Technology Data Exchange (ETDEWEB)

    Shahrokhi, Masoud, E-mail: shahrokhimasoud37@gmail.com

    2016-12-30

    Highlights: • The electronic and optical properties of ZnS honeycomb sheet are investigated. • The electronic properties were analyzed at three levels of GW approach. • The optical properties of these materials are investigated using the BSE approach. • Optical properties of ZnS sheet strongly dominated by excitonic effects. • Spectrum is dominated by strongly bound Frenkel excitons. - Abstract: Using ab-initio density functional theory calculations combined with many-body perturbation formalism we carried out the electronic structure and optical properties of 2D graphene-like ZnS structure. The electronic properties were analyzed at three levels of many-body GW approach (G{sub 0}W{sub 0}, GW{sub 0} and GW) constructed over a Generalized Gradient Approximation functional. Our results indicate that ZnS sheet has a direct band gap at the Γ-point. Also it is seen that inclusion of electron–electron interaction does not change the sort of direct semiconducting band gap in ZnS sheet. The optical properties and excitonic effects of these materials are investigated using the Bethe-Salpeter equation (BSE) approach. The formation of first exciton peaks at 3.86, 4.26, and 4.57 eV with large binding energy of 0.36, 0.49 and 0.73 eV using G{sub 0}W{sub 0} + BSE, GW{sub 0} + BSE and GW + BSE, respectively, was observed. We show that the optical absorption spectrum of 2D ZnS structure is dominated by strongly bound Frenkel excitons. The enhanced excitonic effects in the ZnS monolayer sheet can be useful in designing optoelectronic applications.

  15. Photoluminescence of ZnS: Mn quantum dot by hydrothermal method

    Directory of Open Access Journals (Sweden)

    Yun Hu

    2018-01-01

    Full Text Available ZnS: Mn quantum dots (QDs with the average grain size from 4.2 to 7.2 nm were synthesized by a hydrothermal method. All samples were cubic zinc blende structure (β-ZnS measured using X-ray diffraction (XRD. And the main diffraction peaks of ZnS: Mn shifted slightly towards higher angle in comparison with the intrinsic ZnS because of the substitution of Mn2+ for Zn2+. Due to the small grain size (4-7 nm effect, the poor dispersion and serious reunion phenomenon for the samples were observed from transmission electron microscopy (TEM. ZnS: Mn QDs had four peaks centered at 466, 495, 522, and 554 nm, respectively, in the photoluminescence (PL spectra, in which the band at 554 nm absent in the intrinsic ZnS: Mn is attributed to the doping of Mn2+ in the lattice sites. As the concentration of Mn2+ increasing from 0% to 0.6 at%, the intensity of the PL emission also increased. But the concentration reached 0.9 at%, quenching of PL emission occurred. The peak in ZnS: Mn QDs observed at 490 cm-1 was originated from the stretching vibration of the Mn–O bonds in the Fourier transform infrared (FTIR spectra. And the small changes about this peak compared with the previous reports at 500 cm-1 can be attributed to the formation of quantum dots. This method we utilized to synthesize ZnS: Mn QDs is very simple, low cost, and applicable for other semiconductor QD materials.

  16. High quality antireflective ZnS thin films prepared by chemical bath deposition

    Energy Technology Data Exchange (ETDEWEB)

    Tec-Yam, S.; Rojas, J.; Rejon, V. [Centro de Investigacion y de Estudios Avanzados del IPN, Unidad Merida, Departamento de Fisica Aplicada, Km. 6 Antigua Carretera a Progreso, AP 73-Cordemex, 97310 Merida Yucatan (Mexico); Oliva, A.I., E-mail: oliva@mda.cinvestav.mx [Centro de Investigacion y de Estudios Avanzados del IPN, Unidad Merida, Departamento de Fisica Aplicada, Km. 6 Antigua Carretera a Progreso, AP 73-Cordemex, 97310 Merida Yucatan (Mexico)

    2012-10-15

    Zinc sulfide (ZnS) thin films for antireflective applications were deposited on glass substrates by chemical bath deposition (CBD). Chemical analysis of the soluble species permits to predict the optimal pH conditions to obtain high quality ZnS films. For the CBD, the ZnCl{sub 2}, NH{sub 4}NO{sub 3}, and CS(NH{sub 2}){sub 2} were fixed components, whereas the KOH concentration was varied from 0.8 to 1.4 M. Groups of samples with deposition times from 60 to 120 min were prepared in a bath with magnetic agitation and heated at 90 Degree-Sign C. ZnS films obtained from optimal KOH concentrations of 0.9 M and 1.0 M exhibited high transparency, homogeneity, adherence, and crystalline. The ZnS films presented a band gap energy of 3.84 eV, an atomic Zn:S stoichiometry ratio of 49:51, a transmittance above 85% in the 300-800 nm wavelength range, and a reflectance below 25% in the UV-Vis range. X-ray diffraction analysis revealed a cubic structure in the (111) orientation for the films. The thickness of the films was tuned between 60 nm and 135 nm by controlling the deposition time and KOH concentration. The incorporation of the CBD-ZnS films into ITO/ZnS/CdS/CdTe and glass/Mo/ZnS heterostructures as antireflective layer confirms their high optical quality. -- Highlights: Black-Right-Pointing-Pointer High quality ZnS thin films were prepared by chemical bath deposition (CBD). Black-Right-Pointing-Pointer Better CBD-ZnS films were achieved by using 0.9 M-KOH concentration. Black-Right-Pointing-Pointer Reduction in the reflectance was obtained for ZnS films used as buffer layers.

  17. Enhancement of efficiency by embedding ZnS and Mn-doped ZnS nanoparticles in P3HT:PCBM hybrid solid state solar cells

    Science.gov (United States)

    Jabeen, Uzma; Adhikari, Tham; Shah, Syed Mujtaba; Nunzi, Jean-Michel; Badshah, Amin; Ahmad, Iqbal

    2017-06-01

    Zinc sulphide (ZnS) and Mn-doped ZnS nanoparticles were synthesized by wet chemical method. The synthesized nanoparticles were characterized by UV-visible, fluorescence, X-ray diffraction (XRD), fourier transform infra-red (FTIR) spectrometer, field emission scanning electron microscope (FESEM) and high resolution transmission electron microscope (HRTEM). Scanning electron microscope (SEM) was used to find particle size while chemical composition of the synthesized materials was investigated by EDAX. UV-visible absorption spectrum of Mn-doped ZnS was slightly shifted to lower wavelength with respect to the un-doped zinc sulphide with decrease in the size of nanoparticles. Consequently, the band gap was tuned from 3.04 to 3.13 eV. The photoluminescence (PL) emission positioned at 597 nm was ascribed to 4T1 → 6A1 transition within the 3d shell of Mn2+. X-ray diffraction (XRD) analysis revealed that the synthesized nanomaterials existed in cubic crystalline state. The effect of embedding un-doped and doped ZnS nanoparticles in the active layer and changing the ratio of PCBM ([6, 6]-phenyl-C61-butyric acid methyl ester) to nanoparticles on the performance of hybrid solar cell was studied. The device with active layer consisting of poly(3-hexylthiophene) (P3HT), [6, 6]-phenyl-C61-butyric acid methyl ester (PCBM), and un-doped ZnS nanoparticles combined in the ratio of (1:0.5:0.5) attained an efficiency of 2.42% which was found 71% higher than the reference device under the same conditions but not containing nanoparticles. Replacing ZnS nanoparticles with Mn-doped ZnS had a little effect on the enhancement of efficiency. The packing behavior and morphology of blend of nanoparticles with P3HT:PCBM were examined using atomic force microscope (AFM) and XRD. Contribution to the topical issue "Materials for Energy harvesting, conversion and storage II (ICOME 2016)", edited by Jean-Michel Nunzi, Rachid Bennacer and Mohammed El Ganaoui

  18. Ferromagnetism in α-Mn nanorods

    Science.gov (United States)

    Tiwary, Chandra Sekhar; Bhowmick, Somnath; Prakash, Abhinav; Chakrabarti, Ramananda; Biswas, Krishanu; Chattopadhyay, Kamanio

    2017-02-01

    The present investigation reports the first experimental evidence of ferromagnetism in the cryomilled pure α-Mn nano-rods. Cryomilling of Mn powder at liquid nitrogen temperature leads to the formation of long nanorods of α-Mn. The detailed electron microscopy reveals that the nanorods grow along [ 1 1 ¯ 2 ] directions with surfaces bounded by {110} planes of FCC α-Mn. The magnetic measurements indicate ferromagnetic hysteresis loops, suggesting typical ferromagnetic order. The ab-initio density functional theory calculations indicate that the ferromagnetic response originates from the under coordinated surface atoms.

  19. Electronic structure and photocatalytic activity of wurtzite Cu–Ga–S nanocrystals and their Zn substitution

    KAUST Repository

    Kandiel, Tarek

    2015-03-23

    Stoichiometric and gallium-rich wurtzite Cu-Ga-S ternary nanocrystals were synthesized via a facile solution-based hot injection method using 1-dodecanethiol as a sulfur source. The use of 1-dodecanethiol was found to be essential not only as a sulfur source but also as a structure-directing reagent to form a metastable wurtzite structure. In addition, the substitution of zinc in the wurtzite gallium-rich Cu-Ga-S nanocrystals was also investigated. The obtained nanocrystals were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), diffuse reflectance spectroscopy (DRS), photoluminescence (PL), and inductively coupled plasma atomic emission spectroscopy (ICP-OES). Electronic structures of pristine and the Zn-substituted Cu-Ga-S system were investigated using density functional theory (DFT) with HSE06 exchange-correlation functional. The calculated bandgaps accurately reflect the measured ones. The allowed electronic transitions occur upon the photon absorption from the (Cu + S) band towards the (Ga + S) one. The Zn substitution was found not to contribute to the band edge structure and hence altered the bandgaps only slightly, the direct transition nature remaining unchanged with the Zn substitution. The photocatalytic activities of H2 evolution from an aqueous Na2S/Na2SO3 solution under visible-light illumination on the synthesized nanocrystals were investigated. While the stoichiometric CuGaS2 exhibited negligible activity, the gallium-rich Cu-Ga-S ternary nanocrystals displayed reasonable activity. The optimum Zn substitution in the gallium-rich Cu-Ga-S ternary nanocrystals enhanced the H2 evolution rate, achieving an apparent quantum efficiency of >6% at 400 nm. © 2015 The Royal Society of Chemistry.

  20. Ab-initio investigations of the electronic properties of bulk wurtzite Beryllia and its derived nanofilms

    KAUST Repository

    Goumri-Said, Souraya

    2010-08-01

    In this Letter we investigate the electronic properties of the bulk and the nanofilm BeO in wurtzite structure. We performed a first-principles pseudo-potential method within the generalized gradient approximation. We will give more importance to the changes in band structure and density of states between the bulk structure and its derived nanofilms. The bonding characterization will be investigated via the analysis Mulliken population and charge density contours. It is found that the nanofilm retains the same properties as its bulk structure with slight changes in electronic properties and band structure which may offer some unusual transport properties. © 2010 Elsevier B.V. All rights reserved.

  1. Optical forces in nanorod metamaterial.

    Science.gov (United States)

    Bogdanov, Andrey A; Shalin, Alexander S; Ginzburg, Pavel

    2015-10-30

    Optomechanical manipulation of micro and nano-scale objects with laser beams finds use in a large span of multidisciplinary applications. Auxiliary nanostructuring could substantially improve performances of classical optical tweezers by means of spatial localization of objects and intensity required for trapping. Here we investigate a three-dimensional nanorod metamaterial platform, serving as an auxiliary tool for the optical manipulation, able to support and control near-field interactions and generate both steep and flat optical potential profiles. It was shown that the 'topological transition' from the elliptic to hyperbolic dispersion regime of the metamaterial, usually having a significant impact on various light-matter interaction processes, does not strongly affect the distribution of optical forces in the metamaterial. This effect is explained by the predominant near-fields contributions of the nanostructure to optomechanical interactions. Semi-analytical model, approximating the finite size nanoparticle by a point dipole and neglecting the mutual re-scattering between the particle and nanorod array, was found to be in a good agreement with full-wave numerical simulation. In-plane (perpendicular to the rods) trapping regime, saddle equilibrium points and optical puling forces (directed along the rods towards the light source), acting on a particle situated inside or at the nearby the metamaterial, were found.

  2. Zn vacancy ferromagnetism in ZnS nanocrystals

    Science.gov (United States)

    Proshchenko, Vitaly; Dahnovsky, Yuri

    2017-12-01

    To explain three order of magnitude discrepancy between the experimental and calculated magnetic moments due to Zn vacancies in ZnS nanocrystals we study the effect of Zn vacancy distribution in a nanocrystal (NC). We consider small, intermediate, and large quantum dots. For the latter we employ the surface-bulk model. To study Zn vacancy distributions we choose aggregates and uniformly distributed gas in an NC core, on a surface, and both core + surface. From the investigation we find that the uniform distribution of vacancies on a surface is the most favorable configuration for quantum dots of all sizes. Then we investigate the detailed vacancy arrangement on an NC surface. We find that the most likely arrangement if the vacancies are placed along the diagonal of the unit cell square rather than along the square side. The former has the zero magnetic moment what explains the huge reduction in the total magnetization. The small nonvanishing magnetization is probably due to the presence of a small amount of Zn vacancies in the side configuration in a metastable state.

  3. Synthesis and influence of ultrasonic treatment on luminescence of Mn incorporated ZnS nanoparticles

    Science.gov (United States)

    Cadis, A.-I.; Muresan, L. E.; Perhaita, I.; Munteanu, V.; Karabulut, Y.; Garcia Guinea, J.; Canimoglu, A.; Ayvacikli, M.; Can, N.

    2017-10-01

    Manganese (Mn) doping of ZnS phosphors was achieved by precipitation method using different ultrasound (US) maturation times. The structural and luminescence properties of the samples were carried out by means of X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), photoluminescence (PL), and cathodoluminescence (CL). The real amount of manganese incorporated in ZnS lattice was calculated based on ICP-OES results. According with XRD patterns, the phase structure of ZnS:Mn samples is cubic. EDS spectra reveal deviations of the Mn dopant concentration from the target composition. Both 300 K PL and CL emission spectra of the Mn doped ZnS phosphors display intense orange emission at 590 and 600 nm, respectively, which is characteristic emission of Mn ion corresponding to a 4T1→6A1 transition. Both PL and CL spectra confirmed manganese is substitutionally incorporated into the ZnS host as Mn2+. However, it is suggested that the origin of broad blue emission around 400 nm appeared in CL is due to the radiative recombination at deep level defect states in the ZnS. The ultrasound treatment at first enhances the luminescent intensity by ∼3 times in comparison with samples prepared by classical way. This study gives rise to an optimization guideline, which is extremely demanded for the development of new luminescent materials.

  4. Infrared Radiation Assisted Stokes’ Law Based Synthesis and Optical Characterization of ZnS Nanoparticles

    Directory of Open Access Journals (Sweden)

    Beer Pal Singh

    2016-01-01

    Full Text Available The strategy and technique exploited in the synthesis of nanostructure materials have an explicit effect on the nucleation, growth, and properties of product materials. Nanoparticles of zinc sulfide (ZnS have been synthesized by new infrared radiation (IR assisted and Stokes’ law based controlled bottom-up approach without using any capping agent and stirring. IR has been used for heating the reaction surface designed in accordance with the well-known Stokes law for a free body falling in a quiescent fluid for the synthesis of ZnS nanoparticles. The desired concentration of aqueous solutions of zinc nitrate (Zn(NO32·4H2O and thioacetamide (CH3CSNH2 was reacted in a controlled manner by IR radiation heating at the reaction area (top layer of reactants solution of the solution which results in the formation of ZnS nanoparticles at ambient conditions following Stokes’ law for a free body falling in a quiescent fluid. The phase, crystal structure, and particle size of as-synthesized nanoparticles were studied by X-ray diffraction (XRD. The optical properties of as-synthesized ZnS nanoparticles were studied by means of optical absorption spectroscopic measurements. The optical energy band gap and the nature of transition have been studied using the well-known Tauc relation with the help of absorption spectra of as-synthesized ZnS nanoparticles.

  5. Size dependent photocatalytic activity of ZnS nanostructures prepared by a facile precipitation method

    Energy Technology Data Exchange (ETDEWEB)

    Yin, Lixiong, E-mail: ylx@sust.edu.com; Zhang, Dongdong; Wang, Dan; Kong, Xingang; Huang, Jianfeng, E-mail: huangjfsust@126.com; Wang, Feifei; Wu, Yabo

    2016-06-15

    Highlights: • Size-controlled ZnS crystallites were achieved by adjusting the reaction pH. • The formation mechanism of ZnS prepared at different pH was discussed. • Size-related photocatalytic properties of ZnS were shown. - Abstract: Size-controlled ZnS nanostructures have been synthesized successfully with different reaction pH via a facile homogeneous precipitation method. These samples were characterized by X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM), N{sub 2}-sorption BET surface area, Raman spectra and UV–vis spectroscopy for their structures, morphologies, specific surface area and band gaps values (E{sub g}). Results show that the size of the prepared nanospheres can be controllably tuned by adjusting pH value. Moreover, the size-related mechanism of different samples was also discussed. The degradation of methyl orange (MO) under UV light irradiation was carried out to study the effects of the size on the photocatalytic activity of the prepared samples. It was found that the sample obtained at pH = 7 exhibited the higher photocatalytic activity, which degradation efficiency reaches 99.5% under UV irradiation for 30 min. The big specific surface area of ZnS nanostructures are believed to greatly affect the final degradation efficiency of MO in our research. Moreover, the mechanism of enhanced photocatalytic activity was also investigated and the ·O{sup 2−} plays a dominant role during degradation process.

  6. Investigation of thioglycerol stabilized ZnS quantum dots in electroluminescent device performance

    Energy Technology Data Exchange (ETDEWEB)

    Ethiraj, Anita Sagadevan, E-mail: anita.ethiraj@vit.ac.in [Department of Physics, Sungkyunkwan University,Suwon 440-746 (Korea, Republic of); Center for Nanotechnology Research, VIT University, Vellore, TamilNadu-632014 (India); Rhen, Dani; Kang, Dae Joon [Department of Physics, Sungkyunkwan University,Suwon 440-746 (Korea, Republic of); Lee, D. H. [School of Chemical Engineering Novel Materials Lab, Natural Sciences Campus, 300 Cheoncheon-dong, jangan-gu, Suwon, Gyeonggi-do 440-746 (Korea, Republic of); Kulkarni, S. K. [Physics Department, Indian Institute of Science Education & Research, Sutarwadi, Pune-411021 (India)

    2016-05-06

    The present work is focused on the investigation of thioglycerol (TG) stabilized Zinc Sulfide Quantum dots (ZnS QDs) in the hybrid electroluminescence (EL) device. Optical absorption spectroscopy clearly indicates the formation of narrow size distributed ZnS in the quantum confinement regime. X-ray Diffraction (XRD), Photoluminescence (PL), Energy Dispersive X-ray Spectroscopy (EDS) data supports the same. The hybrid EL device with structure of ITO (indium tin oxide)//PEDOT:PSS ((poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate)//HTL (α NPD- N,N′-diphenyl-N,N′-bis(1-naphthyl)-(1,1′-phenyl)-4,4′-diamine// PVK:ZnS QDs//ETL(PBD- 2-tert-butylphenyl- 5-biphenyl-1,3,4-oxadiazole)//LiF:Al (Device 1) was fabricated. Reference device without the ZnS QDs were also prepared (Device 2). The results show that the ZnS QDs based device exhibited bright electroluminescence emission of 24 cd/m{sup 2} at a driving voltage of 16 Volts under the forward bias conditions as compared to the reference device without the ZnS QDs, which showed 6 cd/m{sup 2} at ∼22 Volts.

  7. Study of ZnS Nanostructures Based Electrochemical and Photoelectrochemical Biosensors for Uric Acid Detection

    Directory of Open Access Journals (Sweden)

    Yao Zhao

    2017-05-01

    Full Text Available Uric acid (UA is a kind of purine metabolism product and important in clinical diagnosis. In this work, we present a study of ZnS nanostructures-based electrochemical and photoelectrochemical biosensors for UA detection. Through a simple hydrothermal method and varying the ratio of reaction solvents, we obtained ZnS nanomaterials of one-dimensional to three-dimensional morphologies and they were characterized using field emission scanning electron microscopy (FESEM and X-ray diffraction (XRD. To fabricate the UA biosensor and study the effect of material morphology on its performance, ZnS nanomaterials were deposited on indium tin oxide (ITO conducting glass and then coated with uricase by physical absorption. Three kinds of working electrodes were characterized by cyclic voltammetry method. The effect of material morphology on performance of UA detection was investigated via amperometric response based electrochemical method based on enzymatic reaction. The ZnS urchin-like nanostructures electrode shows better sensitivity compared with those made of nanoparticles and nanoflakes because of its high surface-area-to-volume ratio. The photoelectrochemical method for detection of UA was also studied. The sensitivity was increased 5 times after irradiation of 300 nm UV light. These results indicate that ZnS nanostructures are good candidate materials for developing enzyme-based UA biosensors.

  8. Study of ZnS Nanostructures Based Electrochemical and Photoelectrochemical Biosensors for Uric Acid Detection.

    Science.gov (United States)

    Zhao, Yao; Wei, Xueyong; Peng, Niancai; Wang, Jiuhong; Jiang, Zhuangde

    2017-05-28

    Uric acid (UA) is a kind of purine metabolism product and important in clinical diagnosis. In this work, we present a study of ZnS nanostructures-based electrochemical and photoelectrochemical biosensors for UA detection. Through a simple hydrothermal method and varying the ratio of reaction solvents, we obtained ZnS nanomaterials of one-dimensional to three-dimensional morphologies and they were characterized using field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD). To fabricate the UA biosensor and study the effect of material morphology on its performance, ZnS nanomaterials were deposited on indium tin oxide (ITO) conducting glass and then coated with uricase by physical absorption. Three kinds of working electrodes were characterized by cyclic voltammetry method. The effect of material morphology on performance of UA detection was investigated via amperometric response based electrochemical method based on enzymatic reaction. The ZnS urchin-like nanostructures electrode shows better sensitivity compared with those made of nanoparticles and nanoflakes because of its high surface-area-to-volume ratio. The photoelectrochemical method for detection of UA was also studied. The sensitivity was increased 5 times after irradiation of 300 nm UV light. These results indicate that ZnS nanostructures are good candidate materials for developing enzyme-based UA biosensors.

  9. Scintillation and luminescence in transparent colorless single and polycrystalline bulk ceramic ZnS

    Energy Technology Data Exchange (ETDEWEB)

    McCloy, John S.; Bliss, Mary; Miller, Brian W.; Wang, Zheming; Stave, Sean C.

    2015-01-01

    ZnS:Ag is a well-known extremely bright scintillator used in powder form for α-particle detection and, mixed with powdered LiF, for thermal neutron detection. Recently, we discovered some commercial bulk colorless and transparent, single-crystal and polycrystalline (chemical vapor-deposited) ZnS forms that scintillate in response to α-particles. The scintillation light transmits through the sample thickness (mm), challenging the commonly held assumption that ZnS is opaque to its own scintillation light. Individual α-particle events were imaged in space and time using a charged-particle camera originally developed for medical imaging applications. Photoluminescence (PL) and PL excitation show that scintillating bulk ZnS likely depends on different electronic defects than commercial ZnS powder scintillators. These defects, associated with copper and oxygen, are discussed in relation to PL results and extensive literature assessment. Commercial transparent ZnS is routinely produced by chemical vapor deposition to sizes larger than square meters, enabling potentially novel radiation detection applications requiring large, thick apertures.

  10. Surface Passivation and Photoluminescence of Mn-Doped ZnS Nanocrystals

    Directory of Open Access Journals (Sweden)

    Ping Yang

    2008-01-01

    Full Text Available Enhanced photoluminescence (PL is reported from Mn-doped ZnS nanocrystals (NCs capped with ZnS (ZnS:Mn/ZnS core-shell NCs and thioglycolic acid (TGA (ZnS:Mn/ZnS core-shell NCs dispersed in an alkaline TGA solution. The NCs were prepared using a reverse micelle route. Comparing with initial ZnS:Mn core NCs, the ZnS:Mn/ZnS core-shell NCs exhibit much stronger orange PL (~580 nm. This is presumably the result of effective passivation of quenching ZnS:Mn NCs surface states by a pure ZnS shell. As for TGA-capped ZnS:Mn/ZnS core-shell NCs, the parallel decrease of a defect-related emission of ZnS is associated with the formation of a shell surface layer of TGA-Zn complexes. In summary, the combination of ZnS shells with TGA ligands was demonstrated to yield ZnS:Mn NCs with narrow size distribution and intense PL.

  11. ZnO nanorod arrays prepared by chemical bath deposition combined with rapid thermal annealing: structural, photoluminescence and field emission characteristics

    Science.gov (United States)

    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.

  12. A study of the effects of aligned vertically growth time on ZnO nanorods deposited for the first time on Teflon substrate

    Science.gov (United States)

    Farhat, O. F.; Halim, M. M.; Ahmed, Naser M.; Oglat, Ammar A.; Abuelsamen, A. A.; Bououdina, M.; Qaeed, M. A.

    2017-12-01

    In this study, ZnO nanorods (NRs) were well deposited on Teflon substrates (PTFE) via a chemical bath deposition (CBD) method at low temperature. The consequences of growth time (1 h-4 h) on the structural and optical properties of the aligned ZnO (NRs) were investigated through X-ray diffraction, field-emission scanning electron microscopy (FESEM), and photoluminescence (PL) analyses. The results show that the ZnO (NRs) were preferred to grew aligned along the c-axis as hexagonal wurtzite structure as proved by the sharp and strong ZnO (002) peaks of the ZnO (NRs). Irrespective of the growth continuation, FESEM photos confirmed that the ZnO nanorods arrays were fit to be aligned along the c-axis and perpendicular to (PTFE) substrates. The ZnO nanorods that exhibited the sharper stand most intense PL peaks among the sample were grown for 3hs as demonstrated by PL spectra. The device further showed a sensitivity of 4068 to low-power (1.25 mW/cm2) 375 nm light pulses without an external bias. The measurements of photoresponse demonstrated the highly reproducible characteristics of the fabricated UV detector with rapid response and baseline recovery times of 48.05 ms. Thus, this work introduced a simple, low-cost method of fabricating rapid-response, and highly photosensitive UV detectors with zero power consumption on Teflon substrates.

  13. Lasing action in gallium nitride quasicrystal nanorod arrays.

    Science.gov (United States)

    Chang, Shih-Pang; Sou, Kuok-Pan; Chen, Chieh-Han; Cheng, Yuh-Jen; Huang, Ji-Kai; Lin, Chung-Hsiang; Kuo, Hao-Chung; Chang, Chun-Yen; Hsieh, Wen-Feng

    2012-05-21

    We report the observation of lasing action from an optically pumped gallium nitride quasicrystal nanorod arrays. The nanorods were fabricated from a GaN substrate by patterned etching, followed by epitaxial regrowth. The nanorods were arranged in a 12-fold symmetric quasicrystal pattern. The regrowth grew hexagonal crystalline facets and core-shell multiple quantum wells (MQWs) on nanorods. Under optical pumping, multiple lasing peaks resembling random lasing were observed. The lasing was identified to be from the emission of MQWs on the nanorod sidewalls. The resonant spectrum and mode field of the 12-fold symmetric photonic quasicrystal nanorod arrays is discussed.

  14. Effect of Eu2+ doping on structural, optical, magnetic and photovoltaic properties of ZnS quantum dots

    Science.gov (United States)

    Horoz, Sabit

    2017-11-01

    ZnS and Eu2+: ZnS QDs with different doping concentrations were prepared by co-precipitation method at room temperature. It was observed that all samples form in cubic structure. The Eu2+ (0.1%): ZnS, Eu2+ (0.3%): ZnS and Eu2+ (0.5%): ZnS QDs display broad photoluminescence emission peaks at 513.5 nm, 511. 7 nm and 510.6 nm, respectively, are related to the Eu2+ intra-ion transition of 4f6d1 - 4f7. The M-H measurements indicated that unlike ZnS QDs, Eu2+: ZnS QDs with different doping concentrations indicates ferromagnetic behavior at room temperature. The incident photon to electron conversion efficiency (IPCE) is improved with the Eu2+ doping, which proposes the QD solar cell efficiency is able to be boosted by Eu2+ doping by reason of broadened absorption spectra. Accordingly, the data point out that Eu2+: ZnS QDs with different doping concentrations are able to be appropriate materials for photovoltaic and spintronic applications.

  15. Microwave Assisted Growth of ZnO Nanorods and Nanopolypods Nanostructure Thin Films for Gas and Explosives Sensing

    Directory of Open Access Journals (Sweden)

    A. K. Singh

    2013-01-01

    Full Text Available The growth of uniformly distributed and densely packed array of zinc oxide (ZnO nanorods (NRs and nanorods (NRs/nanopolypods (NPPs was successfully achieved through microwave-assisted chemical route at low temperature. The ZnO NRs and NRs/NPPs were characterized using X-ray diffraction (XRD, scanning electron microscope (SEM, energy dispersive X-ray analysis (EDX, and UV-Vis absorption spectroscopy. The ZnO NRs were of 100–150 nm diameter and 0.5–1 μm length, while the NPPs were of diameter about 150–200 nm and 1.5–2 μm pod length. The prepared films are polycrystalline in nature and highly oriented along (002 plane with a hexagonal wurtzite structure. These films were studied for the sensing properties of liquefied petroleum gas (LPG, oxygen, and hazardous explosives, that is, 2,4,6-trinitrotoluene (TNT and cyclotrimethylenetrinitramines (RDX, in the temperature ranges of 25–425 °C and 100–200 °C, respectively. The grown nanostructure films showed reliable stable response to several on-off cycles, and reduction in sensor recovery time was found with the increase in temperature. ZnO NRs and NRs/NPPs showed better sensitivity and recovery time for both LPG and oxygen, as compared to the literature-reported results for ZnO thin films.

  16. Synthesis and characterization of visible light absorbing (GaN)(1-x)(ZnO)x semiconductor nanorods.

    Science.gov (United States)

    Reinert, Alexandra A; Payne, Candace; Wang, Limin; Ciston, James; Zhu, Yimei; Khalifah, Peter G

    2013-08-05

    Although the (GaN)(1-x)(ZnO)x solid solution is one of the most effective systems for driving overall solar water splitting with visible light, its quantum yield for overall water splitting using visible light photons has not yet reached ten percent. Understanding and controlling the nanoscale morphology of this system may allow its overall conversion efficiency to be raised to technologically relevant levels. We describe the use a Ga2O3(ZnO)16 precursor phase in the synthesis of this phase which naturally results in the production of arrays of nanorods with favorable diameters (∼100 nm) and band gaps (∼2.5 eV). Substantial absorption within the band gap is observed, part of which is found to follow the E(-3) scaling characteristic of free carriers scattered by ionized impurity sites. Compositional analysis suggests that a substantial quantity of cation vacancies (∼3%) may be present in some samples. The typical nanorod growth direction and dominant {1011} facet for powders in this system have been identified through electron microscopy methods, leading to the conclusion that polarity may play an important role in the high photoactivity of this family of wurtzite semiconductors.

  17. Structural refinement, photoluminescence and Raman spectroscopy of wurtzite Mn-doped Zn O pellets

    Energy Technology Data Exchange (ETDEWEB)

    Marquina, J.; Martin, J.; Luengo, J.; Vera, F.; Roa, L. [Centro de Estudios Avanzados en Optica, Universidad de los Andes, Merida 5101 (Venezuela, Bolivarian Republic of); Gonzalez, J. [Centro de Estudios de Semiconductores, Universidad de los Andes, Merida 5101 (Venezuela, Bolivarian Republic of); Rodriguez, F.; Renero L, C.; Valiente, R. [Malta-Consolider Team, CITIMAC, Facultad de Ciencias, Universidad de Cantabria, Santander 69005 (Spain); Delgado, G. E., E-mail: marquinajesus@gmail.com [Laboratorio de Cristalografia, Facultad de Ciencias, Universidad de los Andes, Merida 5101 (Venezuela, Bolivarian Republic of)

    2017-11-01

    We report the results of the Rietveld refinement, photoluminescence and Raman spectroscopy of Mn-doped Zn O ceramic pellets. Rietveld refinement shows that samples crystallize in the wurtzite structure and for the Mn-doped sample indicated that the Mn atoms substitute the Zn tetrahedral crystallographic sites in the Zn O host lattice. The emission and absorption spectra of Mn-doped Zn O have been investigated in the visible-UV region and the data have been interpreted in terms of the wurtzite Zn O electronic structure. Two broad bands, one due to superposition between donor bound excitons (DX) and free excitons (FX) and other due free-to bond excitonic recombination (FB) dominates the low-temperature photoluminescence spectra of Mn-doped Zn O bulk. In the Raman spectrum, an extra mode at ∼520 cm{sup -1} has been observed in agreement with earlier works, and it is an indicator for the incorporation of Mn{sup +2} ions into the Zn O host matrix since it is not is observed in Zn O pristine. Rietveld refinement of the X-ray diffraction patterns, energy-dispersive X-ray spectroscopy (EDS) technique, and Raman spectroscopies were performed to study these effects. (Author)

  18. Mechanism of polarization switching in wurtzite-structured zinc oxide thin films

    Energy Technology Data Exchange (ETDEWEB)

    Konishi, Ayako; Ogawa, Takafumi; Fisher, Craig A. J.; Kuwabara, Akihide; Moriwake, Hiroki, E-mail: moriwake@jfcc.or.jp [Nanostructures Research Laboratory, Japan Fine Ceramics Center, Nagoya 456-8587 (Japan); Shimizu, Takao; Yasui, Shintaro; Itoh, Mitsuru [Materials and Structures Laboratory, Tokyo Institute Technology, Yokohama 226-8503 (Japan)

    2016-09-05

    The properties of a potentially new class of ferroelectric materials based on wurtzite-structured ZnO thin films are examined using the first-principles calculations. Theoretical P-E hysteresis loops were calculated using the fixed-D method for both unstrained and (biaxially) strained single crystals. Ferroelectric polarization switching in ZnO (S.G. P6{sub 3}mc) is shown to occur via an intermediate non-polar structure with centrosymmetric P6{sub 3}/mmc symmetry by displacement of cations relative to anions in the long-axis direction. The calculated coercive electric field (E{sub c}) for polarization switching was estimated to be 7.2 MV/cm for defect-free monocrystalline ZnO. During switching, the short- and long-axis lattice parameters expand and contract, respectively. The large structural distortion required for switching may explain why ferroelectricity in this compound has not been reported experimentally for pure ZnO. Applying an epitaxial tensile strain parallel to the basal plane is shown to be effective in lowering E{sub c} during polarization, with a 5% biaxial expansion resulting in a decrease of E{sub c} to 3.5 MV/cm. Comparison with calculated values for conventional ferroelectric materials suggests that the ferroelectric polarization switching of wurtzite-structured ZnO may be achievable by preparing high-quality ZnO thin films with suitable strain levels and low defect concentrations.

  19. Spin-relaxation time in the impurity band of wurtzite semiconductors

    Science.gov (United States)

    Tamborenea, Pablo I.; Wellens, Thomas; Weinmann, Dietmar; Jalabert, Rodolfo A.

    2017-09-01

    The spin-relaxation time for electrons in the impurity band of semiconductors with wurtzite crystal structure is determined. The effective Dresselhaus spin-orbit interaction Hamiltonian is taken as the source of the spin relaxation at low temperature and for doping densities corresponding to the metallic side of the metal-insulator transition. The spin-flip hopping matrix elements between impurity states are calculated and used to set up a tight-binding Hamiltonian that incorporates the symmetries of wurtzite semiconductors. The spin-relaxation time is obtained from a semiclassical model of spin diffusion, as well as from a microscopic self-consistent diagrammatic theory of spin and charge diffusion in doped semiconductors. Estimates are provided for particularly important materials. The theoretical spin-relaxation times compare favorably with the corresponding low-temperature measurements in GaN and ZnO. For InN and AlN we predict that tuning of the spin-orbit coupling constant induced by an external potential leads to a potentially dramatic increase of the spin-relaxation time related to the mechanism under study.

  20. Raman study of phase transformation from diamond structure to wurtzite structure in the silicon nanowires

    Science.gov (United States)

    Shukla, A. K.; Dixit, Saurabh

    2016-07-01

    Hexagonal silicon has emerged as an exciting material due to its novel vibrational and electronic properties. Synthesis of the wurtzite silicon nanowires (w-SiNWs) is studied here using metal assisted chemical etching (MACE) technique. Stress induced in the SiNWs during wet chemical etching is attributed to formation of the w-SiNWs. Presence of the w-SiNWs is revealed by first-order and second-order Raman spectra. The effect of variation of deposition time of silver (catalyst) is explicitly studied for growth of w-SiNWs. The deposition time enhances the density of SiNWs in an island of vertically aligned SiNWs. Absorption coefficient studies of the w-SiNWs are also conducted using UV-vis spectroscopy as a function of deposition time. Increase in the absorption coefficient in SiNWs is noticed with increasing deposition time. The prominent quantum confinement along with stress and porosity is shown to be mainly responsible for the transformation from diamond structure to wurtzite structure in the silicon nanowires.

  1. Uniaxial strain effects on the band structure and effective masses of wurtzite GaAs

    Science.gov (United States)

    Cheiwchanchamnangij, Tawinan; Lambrecht, Walter

    2010-03-01

    While GaAs in bulk form has the zincblende structure, recent interest in the wurtzite form of GaAs arises in the context of nanowires. The band structure of wurtzite GaAs is calculated using the full-potential (FP) linearized muffin-tin orbital (LMTO) method within the local density approximation. The relativistic and spin-orbit coupling effects are included when obtaining the conduction and valence band effective mass tensors and related Rashba-Sheka-Pikus Hamiltonian parameters. The effects of c-axis uniaxial strain on the band structure is investigated and used to determine the relevant strain deformation potentials. It is found that under increasing uniaxial strain, a crossing of the γ5 and γ1 valence band levels occurs first, followed at higher strain by an additional crossing of the γ3 and γ1 conduction bands.. The latter is related to a corresponding direct to indirect (γ-L) crossing under uniaxial strain in zinblende.

  2. Optical characterization of InAs quantum wells and dots grown radially on wurtzite InP nanowires.

    Science.gov (United States)

    Lindgren, David; Kawaguchi, Kenichi; Heurlin, Magnus; Borgström, Magnus T; Pistol, Mats-Erik; Samuelson, Lars; Gustafsson, Anders

    2013-06-07

    Correlated micro-photoluminescence (μPL) and cathodoluminescence (CL) measurements are reported for single core-shell InP-InAs wurtzite nanowires grown using metal-organic vapor phase epitaxy. Samples covering a radial InAs shell thickness of 1-12 ML were investigated. The effective masses for the wurtzite material were determined from the transition energy dependence of the InAs shell thickness, using a model based on linear deformation potential theory. InP cores with segments of mixed zincblende and wurtzite, on which quantum dots nucleated selectively, were also investigated. Narrow peaks were observed by μPL and the spatial origin of the emission was identified with CL imaging.

  3. Band structure parameters of wurtzite and zinc-blende GaAs under strain in the GW approximation

    Science.gov (United States)

    Cheiwchanchamnangij, Tawinan; Lambrecht, Walter R. L.

    2011-07-01

    Quasiparticle self-consistent GW calculations are used to study the band structure in wurtzite and zinc-blende GaAs. The band-gap change between wurtzite and zinc blende is found to be sensitive to lattice constant and k-point convergence of the GW self-energy. Furthermore, the conduction-band minimum can switch between Γ1 and Γ3 character as a function of strain and the valence-band maximum can cross over from Γ5 to Γ1 under compressive uniaxial strain. The Kohn-Luttinger and Rashba-Sheka-Pikus effective Hamiltonian band structure parameters of zinc-blende and wurtzite GaAs, respectively, are determined from these first-principles band structure calculations. The uniaxial and homogeneous strain dependence of the band structure are studied and summarized in the appropriate strain deformation potential parameters.

  4. Synthesis of Cu doped ZnS nanostructures on flexible substrate using low cost chemical method

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Nitin, E-mail: nitinmishra97@gmail.com; Purohit, L. P., E-mail: lppurohit@gmail.com [Gurukula Kangari University, Haridwar UK (India); Goswami, Y. C., E-mail: y-goswami@yahoo.com [ITM University, Turari, Gwalior, MP (India)

    2015-08-28

    Flexible electronics is one of the emerging area of this era. In this paper we have reported synthesis of Cu doped Zinc sulphide nanostructures on filter paper flexible substrates. Zinc chloride and Thio urea were used as a precursor for Zinc and Sulphur. The structures were characterized by XRD, FE-SEM and UV visible spectrometer. All the peaks identified for cubic structure of ZnS. Appearance of small Cu peaks indicates incorporation of Cu into ZnS lattice. Zns nanostructures assembled as nanobelts and nanofibers as shown in FE-SEM micrographs. Compound Structures provide the reasonable electrical conductivity on filter paper. Absorption in UV region makes them suitable for flexible electronic devices.

  5. Ultraviolet optical properties of ZnS quantum-dots synthesized in ethanol

    Science.gov (United States)

    Kuang, Wen-Jian; Li, Qing; Liu, Xiang; Chen, Jing; Su, Jing; Tolner, Harm

    2017-12-01

    We investigated the UV optical properties of 2.2 to 2.5 nm colloidal ZnS quantum dots (QDs) that were synthesized using a one-step solution-processed method. X-ray diffraction patterns and transmission electron microscopy images show clear cubic zinc-blende ZnS structure. Photoluminescence results show defect-related light emission with a peak wavelength that can be tuned from 400 to 389 nm by changing the particle size of the ZnS QDs. As judged from absorption spectroscopy, the optical bandgaps of the QD suspensions then change from 4.0 to 4.2 eV and for the QD films from 3.9 to 4.0 eV, showing clear quantum confinement. The excitation spectra show excitation maxima at the exciton energy, changing from 3.89 eV (319 nm) down to 4.07 eV (305 nm).

  6. Measurement of XUV-absorption spectra of ZnS radiatively heated foils

    CERN Document Server

    Kontogiannopoulmos, Nikolaos; Thais, Frédéric; Chenais-Popovics, Claude; Sauvan, Pascal; Schott, R; Fölsner, Wolfgang; Arnault, Philippe; Poirier, Michel; Blenski, Thomas

    2008-01-01

    Time-resolved absorption of zinc sulfide (ZnS) and aluminum in the XUV-range has been measured. Thin foils in conditions close to local thermodynamic equilibrium were heated by radiation from laser-irradiated gold spherical cavities. Analysis of the aluminum foil radiative hydrodynamic expansion, based on the detailed atomic calculations of its absorption spectra, showed that the cavity emitted flux that heated the absorption foils corresponds to a radiation temperature in the range 55 60 eV. Comparison of the ZnS absorption spectra with calculations based on a superconfiguration approach identified the presence of species Zn6+ - Zn8+ and S5+ - S6+. Based on the validation of the radiative source simulations, experimental spectra were then compared to calculations performed by post-processing the radiative hydrodynamic simulations of ZnS. Satisfying agreement is found when temperature gradients are accounted for.

  7. Kinetics of oxygen adsorption on ZnS nanoparticles synthesized by precipitation process

    Directory of Open Access Journals (Sweden)

    Ahmadi Reza

    2016-06-01

    Full Text Available ZnS nanoparticles were synthesized through a one-step precipitation process. Effect of time and temperature on the formation reaction was investigated. The synthesized samples were characterized by X-ray diffraction (XRD, ultraviolet (UV visible absorption and photoluminescence (PL spectrophotometry. Based on XRD and UV-Vis data, the particles produced at 70 °C had a mean particle size of about 5 nm. Increasing time and temperature of the synthesis reaction resulted in photoluminescence intensification. PL spectroscopy helped understanding the adsorption kinetics of oxygen on ZnS nanoparticles during the precipitation synthesis process. Fabrication of ZnS structures with appropriate oxygen adsorption capacity was suggested as a means of PL emission intensity control.

  8. Synthesis and characterization of ZnS doped with metallic impurities.

    Science.gov (United States)

    Gomez, Estela; Sanchez-Mora, Enrique; Silva, Rutilo; Perez-Hernandez, Leticia; Lopez-Garcia, Cesar; Lozada-Dircio, Victor

    2007-03-01

    Zinc sulfide (ZnS) is a wide band gap and direct transition semiconductor. It is an important material for detection emission and modulation of visible and ultraviolet light, and for electroluminescent devices among other applications. The object of this work was to deposit by the sol-gel method/deep coating, ZnS, ZnS:Mn and ZnS:Sm films (5 coatings) on glass substrate. The samples were characterized to study the surface morphology, composition and some optical properties. SEM micrographs show a porous surface morphology with agglomerate type defects. FTIR spectra show the presence of surface O-H and S-O groups. By AES it was determined the composition of the films, and UV-Vis spectra confirmed the ZnS compound formation. This work has been partially supported by VIEP-BUAP, Project No. 11/EXC/06/G.

  9. Efficient Carrier Multiplication in Colloidal Silicon Nanorods.

    Science.gov (United States)

    Stolle, Carl Jackson; Lu, Xiaotang; Yu, Yixuan; Schaller, Richard D; Korgel, Brian A

    2017-09-13

    Auger recombination lifetimes, absorption cross sections, and the quantum yields of carrier multiplication (CM), or multiexciton generation (MEG), were determined for solvent-dispersed silicon (Si) nanorods using transient absorption spectroscopy (TAS). Nanorods with an average diameter of 7.5 nm and aspect ratios of 6.1, 19.3, and 33.2 were examined. Colloidal Si nanocrystals of similar diameters were also studied for comparison. The nanocrystals and nanorods were passivated with organic ligands by hydrosilylation to prevent surface oxidation and limit the effects of surface trapping of photoexcited carriers. All samples used in the study exhibited relatively efficient photoluminescence. The Auger lifetimes increased with nanorod length, and the nanorods exhibited higher CM quantum yield and efficiency than the nanocrystals with a similar band gap energy E g . Beyond a critical length, the CM quantum yield decreases. Nanorods with the aspect ratio of 19.3 had the highest CM quantum yield of 1.6 ± 0.2 at 2.9E g , which corresponded to a multiexciton yield that was twice as high as observed for the spherical nanocrystals.

  10. Effects of ZnS layer on the performance improvement of the photosensitive ZnO nanowire arrays solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Javed, Hafiz Muhammad Asif [Electronic Materials Research Laboratory, International Center for Dielectric Research, Key Laboratory of the Ministry of Education, Xi' an Jiaotong University, Xi' an, 710049 (China); Que, Wenxiu, E-mail: wxque@mail.xjtu.edu.cn [Electronic Materials Research Laboratory, International Center for Dielectric Research, Key Laboratory of the Ministry of Education, Xi' an Jiaotong University, Xi' an, 710049 (China); Gao, Yanping; Xing, Yonglei [Electronic Materials Research Laboratory, International Center for Dielectric Research, Key Laboratory of the Ministry of Education, Xi' an Jiaotong University, Xi' an, 710049 (China); Kong, Ling Bing, E-mail: ELBKong@ntu.edu.sg [School of Materials Science and Engineering, Nanyang Technological University, Nanyang Avenue, 639798 (Singapore)

    2016-08-01

    The impact of ZnS layer as an interface modification on the photosensitive ZnO nanowire arrays solar cells was studied. CdS, CdSe and ZnS were deposited on ZnO nanowire arrays by SILAR method. When a ZnS layer was deposited, the quantum dot barrier was indirectly become in contact with the electrolyte, which thus restrained the flow of electrons. The CdS sensitized solar cells has an efficiency of 0.55% with the deposition of the ZnS(3) layer, that is, with a deposition of three times, whereas the CdS/CdSe co-sensitized solar cells has an efficiency of 2.03% with the deposition of the ZnS(1) layer. It was also noted that as the thickness of the of ZnS layer was increased, V{sub oc}, I{sub sc} and efficiencies of both the solar cells were first increased and then decreased. In addition, the CdS/N719 solar cells has an efficiency of 0.75% with the deposition of the ZnS(2) layer. - Highlights: • The impact of ZnS layer on the photosensitive ZnO nanowire solar cells was studied. • ZnS layer restrained the flow of electrons to the electrolyte. • CdS/CdSe co-sensitized solar cells have higher efficiency than CdS solar cells. • When ZnS layer was increased, V{sub oc} and I{sub sc} firstly increased and then decreased.

  11. Surfactant and template free synthesis of porous ZnS nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Akhtar, Muhammad Saeed [Division of Science and Technology, University of Education, College Road Township, Lahore (Pakistan); Schools of Materials, The University of Manchester, Oxford Road, Manchester M13 9PL (United Kingdom); Riaz, Saira [Centre of Excellence in Solid State Physics, University of the Punjab, Lahore-54590 (Pakistan); Mehmood, Rana Farhat [University of Education, Lahore, D.G. Khan Campus, Kangan Road, Dera Ghazi Khan (Pakistan); Ahmad, Khuram Shahzad [Environmental Sciences Department, Fatima Jinnah Women University, The Mall, Rawalpindi (Pakistan); Alghamdi, Yousef [Department of Chemistry, Faculty of Science & Art –Rabigh, King Abdulaziz University, Jeddah (Saudi Arabia); Malik, Mohammad Azad, E-mail: Azad.malik@manchester.ac.uk [Schools of Materials, The University of Manchester, Oxford Road, Manchester M13 9PL (United Kingdom); Department of Chemistry, University of Zululand, Private Bag X1001, Kwa-Dlangezwa, 3886 (South Africa); Naseem, Shahzad [Centre of Excellence in Solid State Physics, University of the Punjab, Lahore-54590 (Pakistan)

    2017-03-01

    ZnS thin films composed of porous nanoparticles have been deposited on to glass substrates by combining three simple synthesis methodologies i.e. chemical bath deposition, co-precipitation and spin coating. The XRD results reveal the cubic phase of ZnS thin films crystallized at nano scale. The crystallite size estimated by Scherrer formula was 3.4 nm. The morphology of the samples was analyzed through scanning electron microscopy (SEM) and is evident that thin films are composed of porous nanoparticles with an average size of 150 nm and pores of 40 nm on almost every grain. Crystallinity, phase and morphology were further confirmed via transmission electron microscopy (TEM). The stoichiometry and phase purity of thin films were determined by energy dispersive X-ray (EDX) spectrum and X-ray photoelectron spectroscopy (XPS) analysis, respectively. The surface topography and homogeneity of thin films were analyzed by atomic force microscopy (AFM) and obtained root mean square roughness (4.0326 nm) reveals the morphologically homogeneous growth of ZnS on glass substrates. The UV–Vis spectroscopy and photoluminescence (PL) were carried out to estimate the band gap and observe the emission spectra in order to speculate the viability of ZnS porous nanoparticles in optoelectronic devices and sensors. - Highlights: • ZnS thin films composed of porous nanoparticles have been deposited. • Methodology is based on a combination of three techniques. • Cubic phase ZnS nanoparticles deposited onto glass substrates. • Films characterized by UV/Vis, PL, XRD, SEM, TEM, AFM and XPS.

  12. Oxidation dynamics of aluminum nanorods

    Energy Technology Data Exchange (ETDEWEB)

    Li, Ying [Argonne Leadership Computing Facility, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Kalia, Rajiv K.; Nakano, Aiichiro; Vashishta, Priya [Collaboratory for Advanced Computing and Simulations, Department of Physics and Astronomy, Department of Chemical Engineering and Materials Science, Department of Computer Science, University of Southern California, Los Angeles, California 90089-0242 (United States)

    2015-02-23

    Aluminum nanorods (Al-NRs) are promising fuels for pyrotechnics due to the high contact areas with oxidizers, but their oxidation mechanisms are largely unknown. Here, reactive molecular dynamics simulations are performed to study thermally initiated burning of oxide-coated Al-NRs with different diameters (D = 26, 36, and 46 nm) in oxygen environment. We found that thinner Al-NRs burn faster due to the larger surface-to-volume ratio. The reaction initiates with the dissolution of the alumina shell into the molten Al core to generate heat. This is followed by the incorporation of environmental oxygen atoms into the resulting Al-rich shell, thereby accelerating the heat release. These results reveal an unexpectedly active role of the alumina shell as a “nanoreactor” for oxidation.

  13. Synthesis and Photophysical Properties of ZnS Colloidal Particles Doped with Silver.

    Science.gov (United States)

    Hao; Sun; Yang; Zhang; Liu; Shen

    1998-08-15

    The synthesis and photophysical characterization of ZnS:Ag colloid are reported. The presence of mercaptoacetic acid has an important effect not only on the formation of doped and undoped ZnS but also on the photophysical properties. ZnS colloid doped with silver shows a strong green emission upon ultraviolet excitation, the intensity of which was enhanced significantly compared with that of the undoped colloid. The green emission was ascribed to a transition from a donor level such as anion vacancy to the levels of the Ag impurities. Copyright 1998 Academic Press.

  14. In vitro toxicity studies of polymer-coated gold nanorods

    NARCIS (Netherlands)

    Rayavarapu, R.G.; Petersen, Wilhelmina; Hartsuiker, Liesbeth; Chin, Patrick; Janssen, Hans; van Leeuwen, F.W.B.; Otto, Cornelis; Manohar, Srirang; van Leeuwen, Ton

    2010-01-01

    We evaluated cellular responses to polymer-treated gold nanorods, which were synthesized using the standard wet-chemistry method that utilizes hexadecyltrimethylammonium bromide (CTAB). The nanorod dispersions were coated with either polystyrene sulfonate (PSS) or polyethylene glycol (PEG). Two

  15. Effect of Postannealing Treatment on Structural and Optical Properties of ZnO Nanorods Prepared Using Chemical Bath Deposition

    Science.gov (United States)

    Bidier, Shaker A.; Hashim, M. R.; Aldiabat, Ahmad M.

    2017-07-01

    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.

  16. Growth and characterization of n-ZnO/p-GaN nanorods on silicon for the fabrication of heterojunction diodes

    Energy Technology Data Exchange (ETDEWEB)

    Guan-Hung Shen [Department of Chemical Engineering, National Cheng Kung University, Tainan 70101, Taiwan (China); Hong, Franklin Chau-Nan, E-mail: hong@mail.ncku.edu.tw [Department of Chemical Engineering, National Cheng Kung University, Tainan 70101, Taiwan (China); Advanced Optoelectronic Technology Center, National Cheng Kung University, Tainan 70101, Taiwan (China); Center for Micro/Nano Science and Technology, National Cheng Kung University, Tainan 70101, Taiwan (China); NCKU Research Center for Energy Technology and Strategy, National Cheng Kung University, Tainan 70101, Taiwan (China)

    2014-11-03

    A heterojunction n-ZnO/p-GaN diode device was fabricated and characterized on Si (111) substrate. Vertically-aligned Mg-doped GaN nanorods (NRs) were grown on Si (111) by plasma assisted chemical vapor deposition. Intrinsic n-type ZnO was subsequently grown on top of p-GaN nanorods by hydrothermal method at low temperature. The effects of precursor concentrations on the morphology and optical properties of ZnO nanostructures were investigated. Various ZnO nanostructures could be synthesized to obtain different heterojunction nanostructures. The high resolution transmission electron microscopy and selected area electron diffraction results further verified that the GaN NRs were single crystals with the growth orientation along [0001], and the epitaxial wurtzite ZnO films were grown on GaN NRs. The n-ZnO film/p-GaN NR heterojunction diodes were thus fabricated. Diode-like rectifying behavior was actually observed with a leakage current of less than 2.0 × 10{sup −4} A at − 20 V bias, a forward current of 7.2 × 10{sup −3} A at 20 V bias, and the turn-on voltage at around 5.6 V. - Highlights: • High-quality zinc oxide layer was epitaxially grown on gallium nitride nanorods. • The morphology of zinc oxide can be controlled by varying the growth conditions. • The n-zinc oxide/p-gallium nitride diodes with rectifying behavior were fabricated.

  17. New trend for synthesizing of magnetic nanorods with titanomaghemite structure

    Energy Technology Data Exchange (ETDEWEB)

    Saber, Osama, E-mail: osmohamed@kfu.edu.sa [Faculty of Science, King Faisal University, P.O. Box 400, Al-Hassa 31982 (Saudi Arabia); Egyptian Petroleum Research Institute, Nasr City, P.O. Box 11727, Cairo (Egypt)

    2016-07-15

    This research aims at developing magnetic and optical materials through fabrication of uniform nanorods by facile and novel technique. In this trend, titanium and iron were successfully combined together forming nanorods without template or high temperature by urea hydrolysis. TEM images showed uniform and homogeneous nanorods with dimensions; 10 nm in width and 50 nm in length. In the same time, fine nanoparticles were observed around the nanorods. With further treatment for the nanorods at high temperature and pressure, FESEM images revealed that the dimensions of the rods slightly increased to be 70 nm in length and 12 nm in width with a complete disappearance of the nanoparticles. Using X-ray diffraction, thermal analyses and infrared spectra in addition to the results of the electron microscopy, the oriented attachment mechanism was suggested for the formation of titanium iron oxides nanorods. The magnetic measurements revealed that the prepared nanorods possess ferromagnetic behavior and exhibit high saturation magnetization. Also, the optical properties showed that the nanorods have high absorption in the visible region and possess low band gap energy. Finally, we concluded that it is probably the first time to prepare nanorods by urea hydrolysis. The advanced optical and magnetic properties give the prepared nanorods relevance to use as building blocks in functional nanoscale devices. - Graphical abstract: The present study has a dual aim for developing new and facile method for fabrication of nanorods containing titanomaghemite structure and improving their optical and magnetic properties - Highlights: • Synthesis of titanium iron oxides nanorods with titanomaghemite structure. • Using urea hydrolysis for preparation of nanorods. • Studying of the effect of pressure and temperature on the nanorods. • Enhancement of the magnetic properties of the nanorods in comparison with the nanoparticles. • Improvement of the optical properties of the nanorods

  18. Hydrothermal synthesis of CdWO 4 nanorods and their ...

    African Journals Online (AJOL)

    The pH value impacts on crystallinity of the products. The PL properties of the CdWO4 nanorods prepared under different conditions were studied. The intensity of the PL emissions of the samples increases with crystallinity and aspect ratio of the CdWO4 nanorods. Keywords: CdWO4 nanorods, photoluminescence, ...

  19. One-step synthesis of graphitic-C 3 N 4 /ZnS composites for enhanced supercapacitor performance

    KAUST Repository

    Wei, Binbin

    2017-11-24

    A series of graphitic-C3N4/ZnS (g-C3N4/ZnS) supercapacitor electrode materials have been prepared via a one-step calcination process of zinc acetate/thiourea with different mass ratios under nitrogen atmosphere. The optimized g-C3N4/ZnS composite shows a highest specific capacitance of 497.7 F/g at 1 A/g and good cycling stability with capacitance retention of 80.4% at 5 A/g after 1000 cycles. Moreover, g-C3N4/ZnS composites display an improved supercapacitor performance in terms of specific capacitance compared to the pure g-C3N4 and ZnS. In addition, our designed symmetric supercapacitor device based on g-C3N4/ZnS composite electrodes can exhibit an energy density of 10.4 Wh/kg at a power density of 187.3 W/kg. As a result, g-C3N4/ZnS composites are expected to be a prospective material for supercapacitors and other energy storage applications.

  20. Harder than Diamond: Superior Indentation Strength of Wurtzite BN and Lonsdaleite

    Science.gov (United States)

    Pan, Zicheng; Sun, Hong; Zhang, Yi; Chen, Changfeng

    2009-02-01

    Recent indentation experiments indicate that wurtzite BN (w-BN) exhibits surprisingly high hardness that rivals that of diamond. Here we unveil a novel two-stage shear deformation mechanism responsible for this unexpected result. We show by first-principles calculations that large normal compressive pressures under indenters can compel w-BN into a stronger structure through a volume-conserving bond-flipping structural phase transformation during indentation which produces significant enhancement in its strength, propelling it above diamond’s. We further demonstrate that the same mechanism also works in lonsdaleite (hexagonal diamond) and produces superior indentation strength that is 58% higher than the corresponding value of diamond, setting a new record.

  1. Al4SiC4 wurtzite crystal: Structural, optoelectronic, elastic, and piezoelectric properties

    Directory of Open Access Journals (Sweden)

    L. Pedesseau

    2015-12-01

    Full Text Available New experimental results supported by theoretical analyses are proposed for aluminum silicon carbide (Al4SiC4. A state of the art implementation of the density functional theory is used to analyze the experimental crystal structure, the Born charges, the elastic properties, and the piezoelectric properties. The Born charge tensor is correlated to the local bonding environment for each atom. The electronic band structure is computed including self-consistent many-body corrections. Al4SiC4 material properties are compared to other wide band gap wurtzite materials. From a comparison between an ellipsometry study of the optical properties and theoretical results, we conclude that the Al4SiC4 material has indirect and direct band gap energies of about 2.5 eV and 3.2 eV, respectively.

  2. Electron LO-phonon interaction in wurtzite GaN quantum wells under a magnetic field

    Science.gov (United States)

    Cao, J. C.; Lü, J. T.; Guo, Qixin

    2008-08-01

    We calculate the electron-LO-phonon relaxation rates in wurtzite GaN quantum wells in the presence of a magnetic field parallel to the growth direction. Using the dielectric continuum model (DCM), we are able to include contributions from both the interface and the quasi-confined phonon modes. The relaxation rate expression takes the phonon dispersion into account, and is applicable to all phonon modes. We find that the relaxation rates show strong oscillations as a function of the applied magnetic field. In relatively wide (8 nm) quantum wells, the inclusion of interface phonon mode decreases this oscillation amplitude. But in thin wells (5 nm), the interface phonon mode is of the same importance as the quasi-confined mode, and it strongly modifies the oscillation behavior.

  3. In-situ x-ray characterization of wurtzite formation in GaAs nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Krogstrup, Peter; Hannibal Madsen, Morten; Nygaard, Jesper; Feidenhans' l, Robert [Nano-Science Center, Niels Bohr Institute, University of Copenhagen, Copenhagen (Denmark); Hu Wen [Quantum Beam Science Directorate, Japan Atomic Energy Agency, 1-1-1 Koto, Sayo, Hyogo 679-5148 (Japan); Kozu, Miwa; Nakata, Yuka [University of Hyogo, 3-2-1 Koto, Kamigori, Hyogo 678-1297 (Japan); Takahasi, Masamitu [Quantum Beam Science Directorate, Japan Atomic Energy Agency, 1-1-1 Koto, Sayo, Hyogo 679-5148 (Japan); University of Hyogo, 3-2-1 Koto, Kamigori, Hyogo 678-1297 (Japan)

    2012-02-27

    In-situ monitoring of the crystal structure formation during Ga-assisted GaAs nanowire growth on Si(111) substrates has been performed in a combined molecular beam epitaxy growth and x-ray characterization experiment. Under Ga rich conditions, we show that an increase in the V/III ratio increases the formation rate of the wurtzite structure. Moreover, the response time for changes in the structural phase formation to changes in the beam fluxes is observed to be much longer than predicted time scales of adatom kinetics and liquid diffusion. This suggests that the morphology of the growth interface plays the key role for the relative growth structure formation rates.

  4. Raman spectroscopy of wurtzite and zinc-blende GaAs nanowires: Polarization dependence, selection rules, and strain effects

    Science.gov (United States)

    Zardo, I.; Conesa-Boj, S.; Peiro, F.; Morante, J. R.; Arbiol, J.; Uccelli, E.; Abstreiter, G.; Fontcuberta I Morral, A.

    2009-12-01

    Polarization-dependent Raman scattering experiments realized on single GaAs nanowires with different percentages of zinc-blende and wurtzite structure are presented. The selection rules for the special case of nanowires are found and discussed. In the case of zinc-blende, the transversal optical mode E1 (TO) at 267cm-1 exhibits the highest intensity when the incident and analyzed polarization are parallel to the nanowire axis. This is a consequence of the nanowire geometry and dielectric mismatch with the environment, and in quite good agreement with the Raman selection rules. We also find a consistent splitting of 1cm-1 of the E1 (TO). The transversal optical mode related to the wurtzite structure, E2H , is measured between 254 and 256cm-1 , depending on the wurtzite content. The azimuthal dependence of E2H indicates that the mode is excited with the highest efficiency when the incident and analyzed polarization are perpendicular to the nanowire axis, in agreement with the selection rules. The presence of strain between wurtzite and zinc-blende is analyzed by the relative shift of the E1 (TO) and E2H modes. Finally, the influence of the surface roughness in the intensity of the longitudinal optical mode on {110} facets is presented.

  5. Detailed Structures of Hexagonal Diamond (lonsdaleite) and Wurtzite-type BN

    Science.gov (United States)

    Yoshiasa, Akira; Murai, Yu; Ohtaka, Osamu; Katsura, Tomoo

    2003-04-01

    Hexagonal diamond (hDIA) and wurtzite-type BN (wBN) powders were synthesized using a Kawai-type high-pressure apparatus and the essential details of their structures were examined by Reitveld refinements in order to investigate their thermodynamic stability and transition mechanism. X-ray diffraction profiles of the products were well explained by a mixture of hDIA and cubic diamond (cDIA) with stacking faults. The mass fraction of hDIA and cDIA was 50:50 for the products annealed between 800 and 1400°C and it became 20:80 for the product annealed at 1600°C. Temperatures higher than 1600°C seem to favor the formation of cDIA or to induce the conversion from hDIA to cDIA. Structure refinement revealed that a decrease and an increase in the basal and apical distances of C-C and B-N bonds in hDIA and wBN, respectively, are introduced by lowering the symmetry from cubic to hexagonal. Since the relative stability of wurtzite-type compounds largely depends on the distortion of the tetrahedral bond angle, the deviation from the ideal tetrahedron in both hDIA and wBN was refined to discuss their stability. The transition mechanism from graphite and graphite-like BN to hDIA and wBN is discussed by comparing the present results and those of previous simulation studies. Based on analogous features observed in the synthetic hDIA and lonsdaleite (natural hDIA found in meteorites), the formation mechanism of hDIA in meteorites is proposed.

  6. The electronic structures of AlN and InN wurtzite nanowires

    Science.gov (United States)

    Xiong, Wen; Li, Dong-Xiao

    2017-07-01

    We derive the relations between the analogous seven Luttinger-Kohn parameters and six Rashba-Sheka-Pikus parameters for wurtzite semiconductors, which can be used to investigate the electronic structures of some wurtzite semiconductors such as AlN and InN materials, including their low-dimensional structures. As an example, the electronic structures of AlN and InN nanowires are calculated by using the derived relations and six-band effective-mass k · p theory. Interestingly, it is found that the ground hole state of AlN nanowires is always a pure S state whether the radius R is small (1 nm) or large (6 nm), and the ground hole state only contains | Z > Bloch orbital component. Therefore, AlN nanowires is the ideal low-dimensional material for the production of purely linearly polarized π light, unlike ZnO nanowires, which emits plane-polarized σ light. However, the ground hole state of InN nanowires can be tuned from a pure S state to a mixed P state when the radius R is larger than 2.6 nm, which will make the polarized properties of the lowest optical transition changes from linearly polarized π light to plane-polarized σ light. Meanwhile, the valence band structures of InN nanowires will present strong band-crossings when the radius R increases to 6 nm, and through the detail analysis of possible transitions of InN nanowires at the Γ point, we find some of the neighbor optical transitions are almost degenerate, because the spin-orbit splitting energy of InN material is only 0.001 eV. Therefore, it is concluded that the electronic structures and optical properties of InN nanowires present great differences with that of AlN nanowires.

  7. Synthesis and characterization of sol–gel derived ZnS: Mn 2 ...

    Indian Academy of Sciences (India)

    Synthesis and characterization of undoped and Mn2+ doped ZnS nanocrystallites (radius 2–3 nm) embedded in a partially densified silica gel matrix are presented. Optical transmittance, photoluminescence (PL), ellipsometric and electron spin resonance measurements revealed manifestation of quantum size effect.

  8. First principles results of structural and electronic properties of ZnS ...

    Indian Academy of Sciences (India)

    http://www.ias.ac.in/article/fulltext/boms/035/07/1055-1062. Keywords. Projector augmented wave method; fragmentation paths; HOMO–LUMO gap. Abstract. We present results of the study of ZnS (1 ≤ ≤ 9) clusters, using the density functional formalism and projector augmented wave method within the generalized ...

  9. Anisotropic optical properties of ZnS thin films with zigzag structure

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 40; Issue 5. Anisotropic optical properties of ... ZnS sculptured thin films produced by thermal evaporation method using the glancing angle deposition techniqueat different deposition angles (0, 30, 60, 70 and 80 ∘ ) are reported. The structural and optical properties of ...

  10. Preparation and characterization of ZnS nanoparticles prepared by hydrothermal method

    Science.gov (United States)

    Wang, Caifeng; Li, Qingshan; Hu, Bo

    2017-07-01

    ZnS nanoparticles were prepared by hydrothermal method using zinc nitrate [Zn(NO3)2 ṡ 6H2O] and thiourea [SC(NH2)2] as sources of Zn2+ and S2- ions and cetyltrimethyl ammonium bromide [CH3(CH2)15N+(CH3)3 ṡ Br-; CTAB] as a surface active agent. The structural, surface morphology and optical properties of ZnS nanoparticles as a function of growth temperature were investigated. The studies show that ZnS nanoparticles have high transmittance over 70% in the visible light range of 400-800 nm, and it has a strong green emission band at about 520 nm which originates from the recombination of electrons from the energy level of sulfur vacancies with the holes from the energy level of zinc vacancies. With the increase of the growth temperature, the XRD peak intensity and the size of ZnS nanoparticles increase, while the green emission intensity firstly increases and then decreases.

  11. Scalable production of microbially-mediated ZnS nanoparticles and application to functional thin films

    Energy Technology Data Exchange (ETDEWEB)

    Moon, Ji Won [ORNL; Ivanov, Ilia N [ORNL; Joshi, Pooran C [ORNL; Armstrong, Beth L [ORNL; Wang, Wei [ORNL; Jung, Hyunsung [ORNL; Rondinone, Adam Justin [ORNL; Jellison Jr, Gerald Earle [ORNL; Meyer III, Harry M [ORNL; Jang, Gyoung Gug [Oak Ridge National Laboratory (ORNL); Meisner, Roberta [Oak Ridge National Laboratory (ORNL); Duty, Chad E [ORNL; Phelps, Tommy Joe [ORNL

    2014-01-01

    A series of semiconducting zinc sulfide (ZnS) nanoparticles were scalably, reproducibly, controllably, and economically synthesized with anaerobic metal-reducing Thermoanaerobacter species. They reduced partially oxidized sulfur sources to sulfides that extracellularly and thermodynamically incorporated with zinc ions to produce sparingly soluble ZnS nanoparticles with ~5 nm crystallites at yields of ~5 g l 1 month 1. A predominant sphalerite formation was facilitated by rapid precipitation kinetics, low cation/anion ratio, higher zinc concentration, water stabilization, or some combination of the four. The sphalerite ZnS nanoparticles exhibited narrow size distribution, high emission intensity, and few native defects. Scale-up and emission tunability using copper-doping were confirmed spectroscopically. Surface characterization was determined using Fourier transform infrared and X-ray photoelectron spectroscopies, which confirmed amine and carboxylic acid not only maintaining a nano-dimensional average crystallite size, but also increasing aggregation. Application of ZnS nanoparticle ink to a functional thin film was successfully tested for potential future applications.

  12. Chitosan-encapsulated ZnS: M (M: Fe 3 or Mn 2) quantum dots for ...

    Indian Academy of Sciences (India)

    ... TEM which substantiated UV–Vis and XRD results. Photoluminescence spectroscopy detected the bacteria attachment to the QDs by showing significant blue shift in bacteria conjugated ZnS QDs. Fluorescence microscopy confirmed the fluorescent labelling of QDs to Thiobacillus novellus bacteria cells making them ideal ...

  13. Synthesis and investigation of optical properties of ZnS nanostructures

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 34; Issue 2. Synthesis and investigation of optical properties of ZnS nanostructures. Neslihan Üzar M Çetin Arikan. Volume 34 Issue ... Spectral dependence of photoluminescence (PL) was also carried out for optical characterization. PL results indicate that the bandgap ...

  14. Studies on Characterization, Optical Absorption, and Photoluminescence of Yttrium Doped ZnS Nanoparticles

    Directory of Open Access Journals (Sweden)

    Ranganaik Viswanath

    2014-01-01

    Full Text Available Pure ZnS and ZnS:Y nanoparticles were synthesized by a chemical coprecipitation route using EDTA-ethylenediamine as a stabilizing agent. X-ray diffraction (XRD, high resolution transmission electron microscopy (HRTEM, field emission scanning electron microscopy (FE-SEM, Fourier transform infrared spectrometry (FTIR, thermogravimetric-differential scanning calorimetry (TG-DSC, and UV-visible and photoluminescence (PL spectroscopy were employed to characterize the as-synthesized ZnS and ZnS:Y nanoparticles, respectively. XRD and TEM studies show the formation of cubic ZnS:Y particles with an average size of ~4.5 nm. The doping did not alter the phase of the zinc sulphide, as a result the sample showed cubic zincblende structure. The UV-visible spectra of ZnS and ZnS:Y nanoparticles showed a band gap energy value, 3.85 eV and 3.73 eV, which corresponds to a semiconductor material. A luminescence characteristics such as strong and stable visible-light emissions in the orange region alone with the blue emission peaks were observed for doped ZnS nanoparticles at room temperature. The PL intensity of orange emission peak was found to be increased with an increase in yttrium ions concentration by suppressing blue emission peaks. These results strongly propose that yttrium doped zinc sulphide nanoparticles form a new class of luminescent material.

  15. Enhanced photovoltaic performance of bulk heterojunction based on ZnS quantum dots-grafted graphene

    Science.gov (United States)

    Jindal, Shikha; Giripunje, Sushama M.

    2016-12-01

    ZnS quantum dots (QDs) and ZnS:graphene QDs were synthesized successfully via simple sonochemical method. X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM) analysis revealed the average size of ZnS and ZnS:graphene QDs of the order of 3.7 nm and 8.4 nm, respectively. The band gap of ZnS:graphene QDs was tuned to 4.9 eV. Fourier transform infrared (FTIR) analysis confirms the formation of single phase ZnS QDs. The significant increase in conductivity of the order of 104 S/cm was observed in ZnS:graphene QDs. The bulk heterojunction devices ITO/PEDOT:PSS/P3HT:ZnSQDs/Al and ITO/PEDOT:PSS/P3HT:(ZnS:graphene)QDs/Al were fabricated. Here we demonstrate the increase in current density (from 2.44 μA/cm2 to 98.4 μA/cm2), alongwith the lower turn on voltage (decrease from 0.40 V to 0.12 V) by using the ZnS:graphene QDs as compared to pristine ZnS QDs in the active layer. Furthermore, this enhancement in current density shows that the ZnS:graphene QDs have a great potential for active layer in photovoltaic devices.

  16. The effect of ZnS thin film's electrical conductivity on electromagnetic ...

    African Journals Online (AJOL)

    The effect of electrical conductivity on an electromagnetic wave propagating through ZnS thin film is analyzed using electromagnetic wave equation with relevant boundary condition. The solution of this equation enabled us to obtain a parameter known as the skin depth that relates to the conductivity of the thin film. This was ...

  17. Observation of two-photon absorption at UV radiation in ZnS ...

    Indian Academy of Sciences (India)

    2014-02-12

    YAG laser radiation having pulsed duration of 10 ns with the repetition rate of 10 Hz. The measured experimental data have been analysed by using analytical models and two-photon absorption coefficients of the ZnS QDs at ...

  18. Prism coupling into ZnS waveguides: a classic example of a nonlinear coupler.

    Science.gov (United States)

    Assanto, G; Svensson, B; Kuchibhatla, D; Gibson, U J; Seaton, C T; Stegeman, G I

    1986-10-01

    Prism coupling of an argon laser into a nonlinear ZnS waveguide was investigated for power slew rates much less than the nonlinearity relaxation time. The angular variation in coupling efficiency becomes progressively more asymmetric with increasing power until switching occurs on one side of the curve. For large detunings on the switching side, increasing absorption bistability was observed.

  19. Photo physical studies of PVP arrested ZnS quantum dots

    Science.gov (United States)

    Shahi, Ashutosh Kumar; Pandey, Bishnu Kumar; Singh, Bheeshma Pratap; Gupta, Bipin Kumar; Singh, Sukhvir; Gopal, Ram

    2017-03-01

    Monodispersed polyvinylpyrrolidone (PVP) arrested ZnS quantum dots (QDs) having diameter in range 2-5 nm are synthesized by a colloidal precipitation method using PVP as the stabilizing agent. X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), selective area electron diffraction (SAED) and Fourier transform infrared (FT-IR) spectroscopy are probed to investigate the structural information. The optical properties are studied using diffuse UV-visible reflectance and photoluminescence (PL) spectroscopy techniques. TEM images as well as XRD reflection peak broadening indicate the nanometer size particles formation with cubic (sphalerite) phase within the polymer matrix. Optical absorbance studies reveal an excitonic peak at around 310 nm dictates the effect of quantum confinement effect in the ZnS QDs. PL emission spectra for ZnS QDs in PVP exhibit four emission peaks at 382 nm, 414 nm, 480 nm and 527 nm are observed. These excitonic emissions from ZnS QDs are caused by the interstitial sulfur/Zn vacancies and surface states.

  20. Growth process for gallium nitride porous nanorods

    Science.gov (United States)

    Wildeson, Isaac Harshman; Sands, Timothy David

    2015-03-24

    A GaN nanorod and formation method. Formation includes providing a substrate having a GaN film, depositing SiN.sub.x on the GaN film, etching a growth opening through the SiN.sub.x and into the GaN film, growing a GaN nanorod through the growth opening, the nanorod having a nanopore running substantially through its centerline. Focused ion beam etching can be used. The growing can be done using organometallic vapor phase epitaxy. The nanopore diameter can be controlled using the growth opening diameter or the growing step duration. The GaN nanorods can be removed from the substrate. The SiN.sub.x layer can be removed after the growing step. A SiO.sub.x template can be formed on the GaN film and the GaN can be grown to cover the SiO.sub.x template before depositing SiN.sub.x on the GaN film. The SiO.sub.x template can be removed after growing the nanorods.

  1. Hydroquinone Based Synthesis of Gold Nanorods.

    Science.gov (United States)

    Picciolini, Silvia; Mehn, Dora; Ojea-Jiménez, Isaac; Gramatica, Furio; Morasso, Carlo

    2016-08-10

    Gold nanorods are an important kind of nanoparticles characterized by peculiar plasmonic properties. Despite their widespread use in nanotechnology, the synthetic methods for the preparation of gold nanorods are still not fully optimized. In this paper we describe a new, highly efficient, two-step protocol based on the use of hydroquinone as a mild reducing agent. Our approach allows the preparation of nanorods with a good control of size and aspect ratio (AR) simply by varying the amount of hexadecyl trimethylammonium bromide (CTAB) and silver ions (Ag(+)) present in the "growth solution". By using this method, it is possible to markedly reduce the amount of CTAB, an expensive and cytotoxic reagent, necessary to obtain the elongated shape. Gold nanorods with an aspect ratio of about 3 can be obtained in the presence of just 50 mM of CTAB (versus 100 mM used in the standard protocol based on the use of ascorbic acid), while shorter gold nanorods are obtained using a concentration as low as 10 mM.

  2. Two-step synthesis of luminescent MoS2-ZnS hybrid quantum dots

    Science.gov (United States)

    Clark, Rhiannon M.; Carey, Benjamin J.; Daeneke, Torben; Atkin, Paul; Bhaskaran, Madhu; Latham, Kay; Cole, Ivan S.; Kalantar-Zadeh, Kourosh

    2015-10-01

    A surfactant assisted technique has been used to promote the exfoliation of molybdenum disulphide (MoS2) in a water-ethanol mixture, to avoid the use of harsh organic solvents, whilst still producing sufficient concentration of MoS2 in suspension. The exfoliated flakes are converted into MoS2 quantum dots (QDs), through a hydrothermal procedure. Alternatively, when the flakes are processed with precursors for zinc sulphide (ZnS) synthesis, a simultaneous break-down and composite growth is achieved. The products are separated by centrifugation, into large ZnS spheres (200-300 nm) and small MoS2-ZnS hybrid QD materials (photoluminescent (PL) peaks are seen at 380 and 450 nm, which are assigned to MoS2 and ZnS components of QDs, respectively. The PL emission from MoS2-ZnS QDs is of high energy and is more intense than the bare MoS2 flakes or QDs, with a quantum yield as high as 1.96%. The emission wavelength is independent from the excitation wavelength and does not change over time. Due to such properties, the developed hybrid QDs are potentially suitable for imaging and sensing applications.A surfactant assisted technique has been used to promote the exfoliation of molybdenum disulphide (MoS2) in a water-ethanol mixture, to avoid the use of harsh organic solvents, whilst still producing sufficient concentration of MoS2 in suspension. The exfoliated flakes are converted into MoS2 quantum dots (QDs), through a hydrothermal procedure. Alternatively, when the flakes are processed with precursors for zinc sulphide (ZnS) synthesis, a simultaneous break-down and composite growth is achieved. The products are separated by centrifugation, into large ZnS spheres (200-300 nm) and small MoS2-ZnS hybrid QD materials (photoluminescent (PL) peaks are seen at 380 and 450 nm, which are assigned to MoS2 and ZnS components of QDs, respectively. The PL emission from MoS2-ZnS QDs is of high energy and is more intense than the bare MoS2 flakes or QDs, with a quantum yield as high as 1

  3. Nature of inhomogeneities and luminescence centers in low-resistance Al-doped ZnS single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Morosova, N.K.; Filipova, V.A.; Galstyan, V.G.; Malyshev, A.A.; Muratova, V.I.

    1985-12-01

    The authors study low-resistance Al-doped ZnS single crytals and find that they exhibit a banding nonuniformity, which is explained by the nonuniform distribution of aluminum and oxygen impurities in them. The intense blue emission of the crystals is caused by the high-resistance layer, in which oxygen concentrates, while aluminum is completely bound to the oxygen. The emission is caused by the annihilation of localized excitons. The low-resistance layers with the weak blue luminescence are intercalations of oxygen-depleted Al-doped ZnS. ZnS crystals containing Al and O in equal concentrations are stable.

  4. Preparation and characterization of ZnS thin films by the chemical bath deposition method (Conference Presentation)

    Science.gov (United States)

    Ando, Shizutoshi; Iwashita, Taisuke

    2017-06-01

    Nowadays, the conversion efficiency of Cu(In・Ga)Se2 (CIGS)-based solar cell already reached over 20%. CdS thin films prepared by chemical bath deposition (CBD) method are used for CIGS-based thin film solar cells as the buffer layer. Over the past several years, a considerable number of studies have been conducted on ZnS buffer layer prepared by CBD in order to improve in conversion efficiency of CIGS-based solar cells. In addition, application to CIGS-based solar cell of ZnS buffer layer is expected as an eco-friendly solar cell by cadmium-free. However, it was found that ZnS thin films prepared by CBD included ZnO or Zn(OH)2 as different phase [1]. Nakata et. al reported that the conversion efficiency of CIGS-based solar cell using ZnS buffer layer (CBD-ZnS/CIGS) reached over 18% [2]. The problem which we have to consider next is improvement in crystallinity of ZnS thin films prepared by CBD. In this work, we prepared ZnS thin films on quarts (Si02) and SnO2/glass substrates by CBD with the self-catalysis growth process in order to improve crystallinity and quality of CBD-ZnS thin films. The solution to use for CBD were prepared by mixture of 0.2M ZnI2 or ZnSO4, 0.6M (NH2)2CS and 8.0M NH3 aq. In the first, we prepared the particles of ZnS on Si02 or SnO2/glass substrates by CBD at 80° for 20 min as initial nucleus (1st step ). After that, the particles of ZnS on Si02 or SnO2/glass substrates grew up to be ZnS thin films by CBD method at 80° for 40 min again (2nd step). We found that the surface of ZnS thin films by CBD with the self-catalyst growth process was flat and smooth. Consequently, we concluded that the CBD technique with self-catalyst growth process in order to prepare the particles of ZnS as initial nucleus layer was useful for improvement of crystallinity of ZnS thin films on SnO2/glass. [1] J.Vidal et,al., Thin Solid Films 419 (2002) 118. [2] T.Nakata et.al., Jpn. J. Appl. Phys. 41(2B), L165-L167 (2002)

  5. Controlled synthesis of Eu2+ and Eu3+ doped ZnS quantum dots and their photovoltaic and magnetic properties

    OpenAIRE

    Sabit Horoz; Baichhabi Yakami; Uma Poudyal; Jon M. Pikal; Wenyong Wang; Jinke Tang

    2016-01-01

    Eu-doped ZnS quantum dots (QDs) have been synthesized by wet-chemical method and found to form in zinc blende (cubic) structure. Both Eu2+ and Eu3+ doped ZnS can be controllably synthesized. The Eu2+ doped ZnS QDs show broad photoluminescence emission peak around 512 nm, which is from the Eu2+ intra-ion transition of 4f6d1 – 4f7, while the Eu3+ doped samples exhibit narrow emission lines characteristic of transitions between the 4f levels. The investigation of the magnetic properties shows th...

  6. Extended photo-response of ZnO/CdS core/shell nanorods fabricated by hydrothermal reaction and pulsed laser deposition.

    Science.gov (United States)

    Yang, Qin; Li, Yanli; Hu, Zhigao; Duan, Zhihua; Liang, Peipei; Sun, Jian; Xu, Ning; Wu, Jiada

    2014-04-07

    Heterogenous nanostructures shaped with CdS covered ZnO (ZnO/CdS) core/shell nanorods (NRs) are fabricated on indium-tin-oxide by pulsed laser deposition of CdS on hydrothermally grown ZnO NRs and characterized through morphology examination, structure characterization, photoluminescence and optical absorption measurements. Both the ZnO cores and the CdS shells are hexagonal wurtzite in structure. Compared with bare ZnO NRs, the fabricated ZnO/CdS core/shell NRs present an extended photo-response and have optical properties corresponding to the two excitonic band-gaps of ZnO and CdS as well as the effective band-gap formed between the conduction band minimum of ZnO and the valence band maximum of CdS.

  7. Enhanced thermal stability of Ag nanorods through capping

    Energy Technology Data Exchange (ETDEWEB)

    Bachenheimer, Lou; Elliott, Paul [Department of Mechanical Engineering, University of Connecticut, Storrs, Connecticut 06269 (United States); Stagon, Stephen [Department of Mechanical Engineering, University of North Florida, Jacksonville, Florida 32224 (United States); Huang, Hanchen, E-mail: h.huang@neu.edu [Department of Mechanical and Industrial Engineering, Northeastern University, Boston, Massachusetts 02115 (United States)

    2014-11-24

    Ag nanorods may serve as sensors in the detection of trace amounts of chemical agents, even single molecules, through surface enhanced Raman spectroscopy (SERS). However, thermal coarsening of Ag nanorods near room temperature limits their applications. This letter proposes the use of a thin oxide capping layer to enhance the thermal stability of Ag nanorods beyond 100 °C. Using electron microscopy characterization and SERS tests, the authors show that the proposed method is effective in stabilizing both morphology and sensitivity of Ag nanorods. The results of this work extend the applicability of Ag nanorods as chemical sensors to higher temperatures.

  8. Nanocrystal formation and luminescence properties of ZnS based doped nanophosphors.

    Science.gov (United States)

    Karar, N; Chander, Harish

    2005-09-01

    There is an ongoing interest on the photoluminescence (PL) and related properties of doped nano ZnS since there is a large change in their PL properties with particle size reduction. Such PL properties are theoretically predicted to be much enhanced with ZnS particle sizes below the Bohr radius, i.e., in ZnS for particle sizes less than 5 nm or so. We start this discussion by first suggesting some nanoparticle formation mechanisms. The type of capping mechanism used dictates the temporal PL stability under different ambient conditions and other post-processing device requirements. We then describe results on PL of our different doped nanocrystalline ZnS and compare our interpretation of results with those available in literature. We have used 3-D plots featuring the effect of different excitation wavelengths on the PL emission profile and its intensity variation on nanocrystalline ZnS doped with different ions. Reported results and our own data suggests that the nanoparticle formation leads to drastic change in PL emission peaks-such that they are often greatly different from those of similar bulk samples. These features are seen in cases where PL is due to electron recombination from dopant and codopant sites, e.g., during Cu and Ag doping. Such results are explained due to greatly modified band structure with nanoparticle formation and bandgap enhancement where dopant and codopant levels have also greatly changed. However, in nanocrystalline samples where the PL mechanism is due to intraion transitions of dopants (e.g., in Mn doping), the luminescence properties remain similar to those of the bulk--this is because as long as the host material and its related crystal field is the same, such electron transition levels remain similar.

  9. Fast imaging of eccrine latent fingerprints with nontoxic Mn-doped ZnS QDs.

    Science.gov (United States)

    Xu, Chaoying; Zhou, Ronghui; He, Wenwei; Wu, Lan; Wu, Peng; Hou, Xiandeng

    2014-04-01

    Fingerprints are unique characteristics of an individual, and their imaging and recognition is a top-priority task in forensic science. Fast LFP (latent fingerprint) acquirement can greatly help policemen in screening the potential criminal scenes and capturing fingerprint clues. Of the two major latent fingerprints (LFP), eccrine is expected to be more representative than sebaceous in LFP identification. Here we explored the heavy metal-free Mn-doped ZnS quantum dots (QDs) as a new imaging moiety for eccrine LFPs. To study the effects of different ligands on the LFP image quality, we prepared Mn-doped ZnS QDs with various surface-capping ligands using QDs synthesized in high-temperature organic media as starting material. The orange fluorescence emission from Mn-doped ZnS QDs clearly revealed the optical images of eccrine LFPs. Interestingly, N-acetyl-cysteine-capped Mn-doped ZnS QDs could stain the eccrine LFPs in as fast as 5 s. Meanwhile, the levels 2 and 3 substructures of the fingerprints could also be simultaneously and clearly identified. While in the absence of QDs or without rubbing and stamping the finger onto foil, no fluorescent fingerprint images could be visualized. Besides fresh fingerprint, aged (5, 10, and 50 days), incomplete eccrine LFPs could also be successfully stained with N-acetyl-cysteine-capped Mn-doped ZnS QDs, demonstrating the analytical potential of this method in real world applications. The method was also robust for imaging of eccrine LFPs on a series of nonporous surfaces, such as aluminum foil, compact discs, glass, and black plastic bags.

  10. Collective alignment of nanorods in thin Newtonian films

    Science.gov (United States)

    Gu, Yu; Burtovyy, Ruslan; Townsend, James; Owens, Jeffery; Luzinov, Igor; Kornev, Konstantin

    2013-11-01

    We provide a complete analytical description of the alignment kinetics of magnetic nanorods in magnetic field. Nickel nanorods were formed by template electrochemical deposition in alumina membranes from a dispersion in a water-glycerol mixture. To ensure uniformity of the dispersion, the surface of the nickel nanorods was covered with polyvinylpyrrolidone (PVP). A 40-70 nm coating prevented aggregation of nanoroda. These modifications allowed us to control alignment of the nanorods in a magnetic field and test the proposed theory. An orientational distribution function of nanorods was introduced. We demonstrated that the 0.04% volume fraction of nanorods in the glycerol-water mixture behaves as a system of non-interacting particles. However, the kinetics of alignment of a nanorod assembly does not follow the predictions of the single-nanorod theory. The distribution function theory explains the kinetics of alignment of a nanorod assembly and shows the significance of the initial distribution of nanorods in the film. It can be used to develop an experimental protocol for controlled ordering of magnetic nanorods in thin films. This work was supported by the Air Force Office of Scientific Research, Grant numbers FA9550-12-1-0459 and FA8650-09-D-507 5900.

  11. A facile arrested precipitation method for synthesis of pure wurtzite Cu{sub 2}ZnSnS{sub 4} nanocrystals using thiourea as a sulfur source

    Energy Technology Data Exchange (ETDEWEB)

    Li, Chunya [Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong Special Administrative Region (Hong Kong); Key Laboratory of Analytical Chemistry of the State Ethnic Affairs Commission, College of Chemistry and Materials Science, South-Central University for Nationalities, Wuhan 430074 (China); Ha, Enna; Wong, Wing-Leung [Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong Special Administrative Region (Hong Kong); Li, Cuiling [Key Laboratory of Analytical Chemistry of the State Ethnic Affairs Commission, College of Chemistry and Materials Science, South-Central University for Nationalities, Wuhan 430074 (China); Ho, Kam-Piu [Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong Special Administrative Region (Hong Kong); Wong, Kwok-Yin, E-mail: bckywong@polyu.edu.hk [Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong Special Administrative Region (Hong Kong)

    2012-11-15

    Graphical abstract: High-resolution TEM image of wurtzite Cu{sub 2}ZnSnS{sub 4} nanocrystals. Highlights: ► Wurtzite Cu{sub 2}ZnSnS{sub 4} nanocrystals were synthesized by arrested precipitation method. ► XRD, EDX, TEM demonstrate that the CZTS nanocrystals are purely wurtzite structure. ► The average diameter of the bulk CZTS products is found to be 10 ± 1.1 nm. ► The estimated direct bandgap energy is 1.56 eV for wurtzite CZTS nanocrystals. ► The electrical resistivity of the wurtzite CZTS nanocrystals is low. -- Abstract: A facile route for the synthesis of wurtzite Cu{sub 2}ZnSnS{sub 4} (CZTS) nanocrystals was developed by an arrested precipitation method at 240 °C under simple reaction conditions with diethanolamine as the solvent and thiourea as sulfur source. The structure and morphology of the CZTS nanocrystals were characterized by X-ray diffraction and transmission electron microscopy. Control experiments demonstrated that CZTS nanocrystals which are purely wurtzite structure are readily obtained. The average diameter of the bulk CZTS products is found to be 10 ± 1.1 nm. The estimated direct bandgap energy is 1.56 eV, which indicates that the CZTS nanocrystals produced by this method possess promising applications in photovoltaic devices.

  12. Single-layer ZnS supported on Au(111): A combined XPS, LEED, STM and DFT study

    Science.gov (United States)

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

    2017-04-01

    Single-layer of ZnS, consisting of one atomic layer of ZnS(111) plane, has been grown on Au(111) and characterized using X-ray photoelectron spectroscopy (XPS), low energy electron diffraction (LEED) and scanning tunneling microscopy (STM). While the LEED measurement indicates a coincidence structure of ZnS-(3×3)/Au(111)-(4×4), high resolution STM images reveal hexagonal unit cells of 6.7×6.7 Å2 and 11.6×11.6 Å2, corresponding to √3 and 3 times the unit cell of the ideal zincblende ZnS-(1×1), respectively, depending on the tunneling conditions. Calculations based on density functional theory (DFT) indicate a significantly reconstructed non-planar structure of ZnS single-layer on Au(111) with 2/3 of the S anions being located nearly in the plane of the Zn cations and the rest 1/3 of the S anions protruding above the Zn plane. The calculated STM image shows similar characteristics to those of the experimental STM image. Additionally, the DFT calculations reveal the different bonding nature of the S anions in ZnS single-layer supported on Au(111).

  13. Magic sized ZnS quantum dots as a highly sensitive and selective fluorescence sensor probe for Ag+ ions.

    Science.gov (United States)

    Mandal, Abhijit; Dandapat, Anirban; De, Goutam

    2012-02-07

    A green and simple chemical synthesis of magic sized water soluble blue-emitting ZnS quantum dots (QDs) has been accomplished by reacting anhydrous Zn acetate, sodium sulfide and thiolactic acid (TLA) at room temperature in aqueous solution. Refluxing of this mixture in open air yielded ZnS clusters of about 3.5 nm in diameter showing very strong and narrow photoluminescence properties with long stability. Refluxing did not cause any noticeable size increment of the clusters. As a result, the QDs obtained after different refluxing conditions showed similar absorption and photoluminescence (PL) features. Use of TLA as a capping agent effectively yielded such stable and magic sized QDs. The as-synthesized and 0.5 h refluxed ZnS QDs were used as a fluorescence sensor for Ag(+) ions. It has been observed that after addition of Ag(+) ions of concentration 0.5-1 μM the strong fluorescence of ZnS QDs was almost quenched. The quenched fluorescence can be recovered by adding ethylenediamine to form a complex with Ag(+) ions. The other metal ions (K(+), Ca(2+), Au(3+), Cu(2+), Fe(3+), Mn(2+), Mg(2+), Co(2+)) showed little or no effect on the fluorescence of ZnS QDs when tested individually or as a mixture. In the presence of all these ions, Ag(+) responded well and therefore ZnS QDs reported in this work can be used as a Ag(+) ion fluorescence sensor.

  14. Effect of Cationic Surfactant Head Groups on Synthesis, Growth and Agglomeration Behavior of ZnS Nanoparticles

    Directory of Open Access Journals (Sweden)

    Mehta SK

    2009-01-01

    Full Text Available Abstract Colloidal nanodispersions of ZnS have been prepared using aqueous micellar solution of two cationic surfactants of trimethylammonium/pyridinium series with different head groups i.e., cetyltrimethylammonium chloride (CTAC and cetyltrimethylpyridinium chloride (CPyC. The role of these surfactants in controlling size, agglomeration behavior and photophysical properties of ZnS nanoparticles has been discussed. UV–visible spectroscopy has been carried out for determination of optical band gap and size of ZnS nanoparticles. Transmission electron microscopy and dynamic light scattering were used to measure sizes and size distribution of ZnS nanoparticles. Powder X-ray analysis (Powder XRD reveals the cubic structure of nanocrystallite in powdered sample. The photoluminescence emission band exhibits red shift for ZnS nanoparticles in CTAC compared to those in CPyC. The aggregation behavior in two surfactants has been compared using turbidity measurements after redispersing the nanoparticles in water. In situ evolution and growth of ZnS nanoparticles in two different surfactants have been compared through time-dependent absorption behavior and UV irradiation studies. Electrical conductivity measurements reveal that CPyC micelles better stabilize the nanoparticles than that of CTAC.

  15. Effect of Cationic Surfactant Head Groups on Synthesis, Growth and Agglomeration Behavior of ZnS Nanoparticles

    Science.gov (United States)

    2009-01-01

    Colloidal nanodispersions of ZnS have been prepared using aqueous micellar solution of two cationic surfactants of trimethylammonium/pyridinium series with different head groups i.e., cetyltrimethylammonium chloride (CTAC) and cetyltrimethylpyridinium chloride (CPyC). The role of these surfactants in controlling size, agglomeration behavior and photophysical properties of ZnS nanoparticles has been discussed. UV–visible spectroscopy has been carried out for determination of optical band gap and size of ZnS nanoparticles. Transmission electron microscopy and dynamic light scattering were used to measure sizes and size distribution of ZnS nanoparticles. Powder X-ray analysis (Powder XRD) reveals the cubic structure of nanocrystallite in powdered sample. The photoluminescence emission band exhibits red shift for ZnS nanoparticles in CTAC compared to those in CPyC. The aggregation behavior in two surfactants has been compared using turbidity measurements after redispersing the nanoparticles in water. In situ evolution and growth of ZnS nanoparticles in two different surfactants have been compared through time-dependent absorption behavior and UV irradiation studies. Electrical conductivity measurements reveal that CPyC micelles better stabilize the nanoparticles than that of CTAC. PMID:20596462

  16. Synthesis of in-situ luminescent ZnS nanoparticles facile with CTAB micelles and their properties study

    Energy Technology Data Exchange (ETDEWEB)

    Shukla, Vaishali [Centre for Nanoscience, Central University of Gujarat, Gandhinagar (India); Singh, Man [School of Chemical Sciences, Central University of Gujarat, Gandhinagar, India Telephone: 079-23260210, fax: 079-23260076 (India)

    2016-04-13

    Currently, the development of micelles route is thrust area of research in nanoscience for the control particle size and remarkable properties through chemical co-precipitation method. A 0.9 mM aqueous CTAB micellar solution plays a role as capping agent in the homogeneous solution of 0.5 M ZnSO{sub 4} and 0.5 M Na{sub 2}S for synthesis, further precipitates purified with centrifugation in cold ethanol and millipore water to remove unreacted reagents and ionic salt particles. A resultant, white colored luminescent ZnS nanoparticle out with ∼95% yield is reported. The ZnS nanoparticles have been examined by their luminescence properties, optical properties and crystal structure. The mean particle size of ZnS nanoparticles is found to be ∼10 nm in various technical results and UV-absorption was 80 nm blue shifts moved from 345 nm (bulk material) to 265 nm, showing a quantum size impact. The X-ray diffraction (XRD) pattern shows the immaculate cubic phase. Photoluminescence (PL) investigates the recombination mechanism with blue emission from shallow electron traps at 490 nm in ZnS nanoparticles. An FTIR spectrum and Thermal gravimetric analysis (TGA) gives confirmation of CTAB – cationic surfactant on surface of ZnS nanoparticle as capping agent as well thermal stability of CTAB capped ZnS nanoparticles with respect to temperature.

  17. Carrier Transport Mechanism and Band Offsets at the Interface of ZnS/ n-Si (111) Heterojunctions Fabricated by Vacuum Thermal Evaporation

    Science.gov (United States)

    Li, Ya-Peng; Li, Ying-Feng; Wang, Jian-Yuan; Zhang, Yong-Hong; Xu, Feng

    2017-11-01

    The electrical properties and band offset of ZnS/ n-Si(111) heterojunctions with and without annealing were analyzed. The result showed that the rectifying characteristics of ZnS/ n-Si(111) heterojunctions became better and the leakage current increased after annealing. This phenomenon is mostly due to the volatilization of S atoms of ZnS films and leads to defect levels appearing at the interface of the ZnS/ n-Si(111) hetrojunctions. The valence band offset (Δ E V) of the ZnS/ n-Si(111) heterojunctions can be calculated to be -0.7 ± 0.15 eV by means of photoelectron spectroscopy, indicating that the band offsets of ZnS/ n-Si(111) heterojunctions show a type-II band alignment.

  18. Metal oxide nanorod arrays on monolithic substrates

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Pu-Xian; Guo, Yanbing; Ren, Zheng

    2018-01-02

    A metal oxide nanorod array structure according to embodiments disclosed herein includes a monolithic substrate having a surface and multiple channels, an interface layer bonded to the surface of the substrate, and a metal oxide nanorod array coupled to the substrate surface via the interface layer. The metal oxide can include ceria, zinc oxide, tin oxide, alumina, zirconia, cobalt oxide, and gallium oxide. The substrate can include a glass substrate, a plastic substrate, a silicon substrate, a ceramic monolith, and a stainless steel monolith. The ceramic can include cordierite, alumina, tin oxide, and titania. The nanorod array structure can include a perovskite shell, such as a lanthanum-based transition metal oxide, or a metal oxide shell, such as ceria, zinc oxide, tin oxide, alumina, zirconia, cobalt oxide, and gallium oxide, or a coating of metal particles, such as platinum, gold, palladium, rhodium, and ruthenium, over each metal oxide nanorod. Structures can be bonded to the surface of a substrate and resist erosion if exposed to high velocity flow rates.

  19. Nanorods and nanotubes for solar cells.

    Science.gov (United States)

    Kislyuk, V V; Dimitriev, O P

    2008-01-01

    Nanorods and nanotubes as photoactive materials as well as electrodes in photovoltaic cells have been launched a few years ago, and the literature in this field started to appear only recently. The first steps have shown both advantages and disadvantages of their application, and the main expectation associated with their effective charge transport has not been realized completely. This article aims to review both the first and the recent tendencies in the development and application of nanorod and nanotube materials in photovoltaic cells. Two basic techniques of synthesis of crystalline nanorod structures are described, the top-down and bottom-up approaches, respectively. Design and photovoltaic performance of solar cells based on various semiconductor nanorod materials, such as TiO2, ZnO, CdS, CdSe, CdTe, CuO, Si are presented and compared with respective solar cells based on semiconductor nanoparticles. Specific of synthesis and application of carbon nanotubes in photovoltaic devices is also reviewed.

  20. GaN based nanorods for solid state lighting

    Energy Technology Data Exchange (ETDEWEB)

    Li Shunfeng; Waag, Andreas [Institute of Semiconductor Technology, Braunschweig University of Technology, 38106 Braunschweig (Germany)

    2012-04-01

    In recent years, GaN nanorods are emerging as a very promising novel route toward devices for nano-optoelectronics and nano-photonics. In particular, core-shell light emitting devices are thought to be a breakthrough development in solid state lighting, nanorod based LEDs have many potential advantages as compared to their 2 D thin film counterparts. In this paper, we review the recent developments of GaN nanorod growth, characterization, and related device applications based on GaN nanorods. The initial work on GaN nanorod growth focused on catalyst-assisted and catalyst-free statistical growth. The growth condition and growth mechanisms were extensively investigated and discussed. Doping of GaN nanorods, especially p-doping, was found to significantly influence the morphology of GaN nanorods. The large surface of 3 D GaN nanorods induces new optical and electrical properties, which normally can be neglected in layered structures. Recently, more controlled selective area growth of GaN nanorods was realized using patterned substrates both by metalorganic chemical vapor deposition (MOCVD) and by molecular beam epitaxy (MBE). Advanced structures, for example, photonic crystals and DBRs are meanwhile integrated in GaN nanorod structures. Based on the work of growth and characterization of GaN nanorods, GaN nanoLEDs were reported by several groups with different growth and processing methods. Core/shell nanoLED structures were also demonstrated, which could be potentially useful for future high efficient LED structures. In this paper, we will discuss recent developments in GaN nanorod technology, focusing on the potential advantages, but also discussing problems and open questions, which may impose obstacles during the future development of a GaN nanorod based LED technology.

  1. Ultraclean emission from InAsP quantum dots in defect-free wurtzite InP nanowires.

    Science.gov (United States)

    Dalacu, Dan; Mnaymneh, Khaled; Lapointe, Jean; Wu, Xiaohua; Poole, Philip J; Bulgarini, Gabriele; Zwiller, Val; Reimer, Michael E

    2012-11-14

    We report on the ultraclean emission from single quantum dots embedded in pure wurtzite nanowires. Using a two-step growth process combining selective-area and vapor-liquid-solid epitaxy, we grow defect-free wurtzite InP nanowires with embedded InAsP quantum dots, which are clad to diameters sufficient for waveguiding at λ ~ 950 nm. The absence of nearby traps, at both the nanowire surface and along its length in the vicinity of the quantum dot, manifests in excitonic transitions of high spectral purity. Narrow emission line widths (30 μeV) and very-pure single photon emission with a probability of multiphoton emission below 1% are achieved, both of which were not possible in previous work where stacking fault densities were significantly higher.

  2. Surface and bulk electronic structure of thin-film wurtzite GaN

    Energy Technology Data Exchange (ETDEWEB)

    Dhesi, S.S.; Stagarescu, C.B.; Smith, K.E. [Department of Physics, Boston University, Boston, Massachusetts 02215 (United States); Doppalapudi, D.; Singh, R.; Moustakas, T.D. [Department of Electrical and Computer Engineering, Boston University, Boston, Massachusetts 02215 (United States)

    1997-10-01

    The bulk and surface valence-band electronic structure of thin-wurtzite GaN has been studied using angle-resolved photoemission spectroscopy. The bulk band dispersion along the {Gamma}{Delta}A, {Gamma}{Sigma}M, and {Gamma}TK directions of the bulk Brillouin zone was measured. Our results indicate the local-density approximation band-structure calculations using partial-core corrections for the Ga 3d states predict the relative dispersion of many of the observed bands with a high degree of accuracy. Furthermore, a nondispersive feature was identified near the valence-band maximum in a region of k space devoid of bulk states. This feature is identified as emission from a surface state on GaN(0001)-(1{times}1). The symmetry of this surface state is even with respect to the mirror planes of the surface and polarization measurements indicate that it is of sp{sub z} character, consistent with a dangling-bond state. {copyright} {ital 1997} {ital The American Physical Society}

  3. Structural and electronic properties of wurtzite Bx Al1-x N from first-principles calculations

    KAUST Repository

    Zhang, Muwei

    2017-06-14

    The structural and electronic properties of wurtzite BAlN (0≤x≤1) are studied using density functional theory. The change of lattice parameters with increased B composition shows small bowing parameters and thus slightly nonlinearity. The bandgap exhibits strong dependence on the B composition, where transition from direct to indirect bandgap occurs at a relatively low B composition (x∼0.12) is observed, above which the bandgap of BAlN maintained indirect, thus desirable for low-absorption optical structures. The Γ-A and Γ-K indirect bandgaps are dominant at lower and higher B compositions, respectively. Density of states (DOS) of the valence band is susceptible to the B incorporation. Strong hybridization of Al, B, and N in p-states leads to high DOS near the valence band maximum. The hybridization of Al and B in s-states at lower B compositions and p-states of B at higher B compositions give rise to high DOS near lower end of the upper valence band. Charge density analysis reveals the B-N chemical bond is more covalent than the Al-N bond. This will lead to more covalent crystal with increasing B composition. Dramatic change of the heavy hole effective mass is found due to significant curvature increase of the band by minor B incorporation.

  4. Optical study of the band structure of wurtzite GaP nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Assali, S., E-mail: simone.assali@polymtl.ca; Greil, J.; Zardo, I.; Moor, M. W. A. de; Koelling, S.; Koenraad, P. M.; Haverkort, J. E. M. [Department of Applied Physics, Eindhoven University of Technology, 5600 MB Eindhoven (Netherlands); Belabbes, A.; Bechstedt, F. [Institut für Festkörpertheorie und -optik, Friedrich-Schiller-Universitat, Max-Wien-Platz 1, D-07743 Jena (Germany); Bakkers, E. P. A. M. [Department of Applied Physics, Eindhoven University of Technology, 5600 MB Eindhoven (Netherlands); Kavli Institute of Nanoscience, Delft University of Technology, 2600 GA Delft (Netherlands)

    2016-07-28

    We investigated the optical properties of wurtzite (WZ) GaP nanowires by performing photoluminescence (PL) and time-resolved PL measurements in the temperature range from 4 K to 300 K, together with atom probe tomography to identify residual impurities in the nanowires. At low temperature, the WZ GaP luminescence shows donor-acceptor pair emission at 2.115 eV and 2.088 eV, and Burstein-Moss band-filling continuum between 2.180 and 2.253 eV, resulting in a direct band gap above 2.170 eV. Sharp exciton α-β-γ lines are observed at 2.140–2.164–2.252 eV, respectively, showing clear differences in lifetime, presence of phonon replicas, and temperature-dependence. The excitonic nature of those peaks is critically discussed, leading to a direct band gap of ∼2.190 eV and to a resonant state associated with the γ-line ∼80 meV above the Γ{sub 8C} conduction band edge.

  5. Wurtzite BAlN and BGaN alloys for heterointerface polarization engineering

    KAUST Repository

    Liu, Kaikai

    2017-11-30

    The spontaneous polarization (SP) and piezoelectric (PZ) constants of BxAl1-xN and BxGa1-xN (0 ≤ x ≤ 1) ternary alloys were calculated with the hexagonal structure as reference. The SP constants show moderate nonlinearity due to the volume deformation and the dipole moment difference between the hexagonal and wurtzite structures. The PZ constants exhibit significant bowing because of the large lattice difference between binary alloys. Furthermore, the PZ constants of BxAl1-xN and BxGa1-xN become zero at boron compositions of ∼87% and ∼74%, respectively, indicating non-piezoelectricity. The large range of SP and PZ constants of BxAl1-xN (BAlN) and BxGa1-xN (BGaN) can be beneficial for the compound semiconductor device development. For instance, zero heterointerface polarization ΔP can be formed for BAlN and BGaN based heterojunctions with proper B compositions, potentially eliminating the quantum-confined Stark effect for c-plane optical devices and thus removing the need of non-polar layers and substrates. Besides, large heterointerface polarization ΔP is available that is desirable for electronic devices.

  6. Wurtzite BAlN and BGaN alloys for heterointerface polarization engineering

    Science.gov (United States)

    Liu, Kaikai; Sun, Haiding; AlQatari, Feras; Guo, Wenzhe; Liu, Xinwei; Li, Jingtao; Torres Castanedo, Carlos G.; Li, Xiaohang

    2017-11-01

    The spontaneous polarization (SP) and piezoelectric (PZ) constants of BxAl1-xN and BxGa1-xN (0 ≤ x ≤ 1) ternary alloys were calculated with the hexagonal structure as reference. The SP constants show moderate nonlinearity due to the volume deformation and the dipole moment difference between the hexagonal and wurtzite structures. The PZ constants exhibit significant bowing because of the large lattice difference between binary alloys. Furthermore, the PZ constants of BxAl1-xN and BxGa1-xN become zero at boron compositions of ˜87% and ˜74%, respectively, indicating non-piezoelectricity. The large range of SP and PZ constants of BxAl1-xN (BAlN) and BxGa1-xN (BGaN) can be beneficial for the compound semiconductor device development. For instance, zero heterointerface polarization Δ P can be formed for BAlN and BGaN based heterojunctions with proper B compositions, potentially eliminating the quantum-confined Stark effect for c-plane optical devices and thus removing the need of non-polar layers and substrates. Besides, large heterointerface polarization Δ P is available that is desirable for electronic devices.

  7. Resistivity, photoresistivity and magnetoresistance in sharp zincblende-wurtzite phase transition in CdS nanoparticles

    Science.gov (United States)

    Marquez-Marín, J.; Torres-Castanedo, C. G.; Torres-Delgado, G.; Castanedo-Pérez, R.; Zelaya-Ángel, O.

    2017-11-01

    Cadmium sulfide nanoparticles were deposited by microwaves assisted chemical bath synthesis on glass substrates at bath temperatures (Tb) in the range 60 ≤ Tb ≤ 97 °C. The films are formed of nanocrystals with a size of 6-20 nm. The crystalline phase depends on Tb, for 60 °C ≤ Tb ≤ 93 °C the lattice is cubic zinc blende and for Tb ≥ 95 °C hexagonal wurtzite. The critical temperature of phase transition is Tbc = 94 °C. Interplanar spacing calculated values, along the preferred orientation of growth, indicate that the lattice experiences a uniaxial contraction in the vicinity of Tbc, which is reflected in the thickness of the films. In this work, the electrical properties of these films are discussed and correlated with their structural ones for the whole temperature range. The electrical resistivity decreases as the nanoparticle size increases. Majority carrier density, mobility, and magnetoresistance experience strong variations around Tbc, similar to the behavior of the film thickness. As well as, resistivity measurements as function of (1/kT) show a change in the activation energy at Tbc.

  8. Raman study of zinc blende and wurtzite CdSe/CdS heteronanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Biermann, Amelie; Lange, Holger; Thomsen, Christian [TU Berlin, Institut fuer Festkoerperphysik, EW5-4, 10623 Berlin (Germany); Gomes, Raquel; Hens, Zeger [University of Ghent, Physics and Chemistry of Nanostructures, Krijgslaan 281-S3, Ghent, B-9000 (Belgium)

    2012-07-01

    CdSe based heteronanocrystals offer a wide range of potential applications in the field of optoelectronics. Especially colloidal CdSe-CdS core-shell nanocrystals are currently of high interest because they offer new technics of application, e.g. printing of devices from a solution. The possibility to synthesize defined nanocrystals with a precise control over their size enables the use in systems like biological sensors, LEDs, lasers and solar cells. The magnitude of the coupling of excited carriers to phonons in the CdSe core contributes to the time scales of different photophysical processes of high significance for those applications. These processes include for example carrier multiplication rates, and relaxation times and are strongly influenced by the states in the interface region of core and shell. In our contribution we present a systematic Raman study of wurtzite and zinc blende CdSe/CdS core-shell structures, revealing the structural details of the sample as well as the exciton-phonon coupling strength via the Huang-Rhys factor.

  9. Optical study of the band structure of wurtzite GaP nanowires

    KAUST Repository

    Assali, S.

    2016-07-25

    We investigated the optical properties of wurtzite (WZ) GaP nanowires by performing photoluminescence (PL) and time-resolved PL measurements in the temperature range from 4 K to 300 K, together with atom probe tomography to identify residual impurities in the nanowires. At low temperature, the WZ GaP luminescence shows donor-acceptor pair emission at 2.115 eV and 2.088 eV, and Burstein-Moss band-filling continuum between 2.180 and 2.253 eV, resulting in a direct band gap above 2.170 eV. Sharp exciton α-β-γ lines are observed at 2.140–2.164–2.252 eV, respectively, showing clear differences in lifetime, presence of phonon replicas, and temperature-dependence. The excitonic nature of those peaks is critically discussed, leading to a direct band gap of ∼2.190 eV and to a resonant state associated with the γ-line ∼80 meV above the Γ8C conduction band edge.

  10. A transition path for the pressure-induced wurtzite- to NaCl-type transformation described in Pna2[1

    Science.gov (United States)

    Sowa, H.

    2005-05-01

    For the transition from the wurtzite to the NaCl type, a new transition path is presented that is based on the deformation of a lonsdaleite configuration into a cubic primitive lattice cP using symmetry Pnma.

  11. Fabrication and Characterization of Thin Film Solar Cell Made from CuIn0.75Ga0.25S2 Wurtzite Nanoparticles

    Directory of Open Access Journals (Sweden)

    Fengyan Zhang

    2013-01-01

    Full Text Available CuIn0.75Ga0.25S2 (CIGS thin film solar cells have been successfully fabricated using CIGS Wurtzite phase nanoparticles for the first time. The structure of the cell is Glass/Mo/CIGS/CdS/ZnO/ZnO:Al/Ag. The light absorption layer is made from CIGS Wurtzite phase nanoparticles that are formed from single-source precursors through a microwave irradiation. The Wurtzite phase nanoparticles were converted to Chalcopyrite phase film through a single-step annealing process in the presence of argon and sulfur at 450°C. The solar cell made from Wurtzite phase nanoparticles showed 1.6% efficiency and 0.42 fill factor.

  12. High-resolution three-photon biomedical imaging using doped ZnS nanocrystals.

    Science.gov (United States)

    Yu, Jung Ho; Kwon, Seung-Hae; Petrášek, Zdeněk; Park, Ok Kyu; Jun, Samuel Woojoo; Shin, Kwangsoo; Choi, Moonkee; Park, Yong Il; Park, Kyeongsoon; Na, Hyon Bin; Lee, Nohyun; Lee, Dong Won; Kim, Jeong Hyun; Schwille, Petra; Hyeon, Taeghwan

    2013-04-01

    Three-photon excitation is a process that occurs when three photons are simultaneously absorbed within a luminophore for photo-excitation through virtual states. Although the imaging application of this process was proposed decades ago, three-photon biomedical imaging has not been realized yet owing to its intrinsic low quantum efficiency. We herein report on high-resolution in vitro and in vivo imaging by combining three-photon excitation of ZnS nanocrystals and visible emission from Mn(2+) dopants. The large three-photon cross-section of the nanocrystals enabled targeted cellular imaging under high spatial resolution, approaching the theoretical limit of three-photon excitation. Owing to the enhanced Stokes shift achieved through nanocrystal doping, the three-photon process was successfully applied to high-resolution in vivo tumour-targeted imaging. Furthermore, the biocompatibility of ZnS nanocrystals offers great potential for clinical applications of three-photon imaging.

  13. Minimizing artifact formation in magnetorheological finishing of chemical vapor deposition ZnS flats

    Science.gov (United States)

    Kozhinova, Irina A.; Romanofsky, Henry J.; Maltsev, Alexander; Jacobs, Stephen D.; Kordonski, William I.; Gorodkin, Sergei R.

    2005-08-01

    The polishing performance of magnetorheological (MR) fluids prepared with a variety of magnetic and nonmagnetic ingredients was studied on four types of initial surface for chemical vapor deposition (CVD) ZnS flats from domestic and foreign sources. The results showed that it was possible to greatly improve smoothing performance of magnetorheological finishing (MRF) by altering the fluid composition, with the best results obtained for nanoalumina abrasive used with soft carbonyl iron and altered MR fluid chemistry. Surface roughness did not exceed 20 nm peak to valley and 2 nm rms after removal of 2 μm of material. The formation of orange peel and the exposure of a pebblelike structure inherent in ZnS from the CVD process were suppressed.

  14. 2D double-layer-tube-shaped structure Bi{sub 2}S{sub 3}/ZnS heterojunction with enhanced photocatalytic activities

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Xiaoming, E-mail: dawn1026@163.com [Department of Chemistry and Chemical Engineering, Shaanxi Key Laboratory of Chemical Reaction Engineering, Yan' an University, Yanan, Shaanxi 716000 (China); Wang, Zihang; Fu, Feng [Department of Chemistry and Chemical Engineering, Shaanxi Key Laboratory of Chemical Reaction Engineering, Yan' an University, Yanan, Shaanxi 716000 (China); Li, Xiang [Department of Chemistry and Chemical Engineering, Shaanxi Key Laboratory of Chemical Reaction Engineering, Yan' an University, Yanan, Shaanxi 716000 (China); Department of Chemical Engineering, Northwest University, Xian, Shaanxi 710069 (China); Li, Wenhong [Department of Chemical Engineering, Northwest University, Xian, Shaanxi 710069 (China)

    2015-10-01

    Bi{sub 2}S{sub 3}/ZnS heterojunction with 2D double-layer-tube-shaped structures was prepared by the facile synthesis method. The corresponding relationship was obtained among loaded content to phase, morphology, and optical absorption property of Bi{sub 2}S{sub 3}/ZnS composite. The results shown that Bi{sub 2}S{sub 3} loaded could evidently change the crystallinity of ZnS, enhance the optical absorption ability for visible light of ZnS, and improve the morphologies and microstructure of ZnS. The photocatalytic activities of the Bi{sub 2}S{sub 3}/ZnS sample were evaluated for the photodegradation of phenol and desulfurization of thiophene under visible light irradiation. The results showed that Bi{sub 2}S{sub 3} loaded greatly improved the photocatalytic activity of ZnS, and the content of loaded Bi{sub 2}S{sub 3} had an impact on the catalytic activity of ZnS. Moreover, the mechanism of enhanced photocatalytic activity was also investigated by analysis of relative band positions of Bi{sub 2}S{sub 3} and ZnS, and photo-generated hole was main active radicals during photocatalytic oxidation process.

  15. Understanding the mechanism of enhanced charge separation and visible light photocatalytic activity of modified wurtzite ZnO with nanoclusters of ZnS and graphene oxide: from a hybrid density functional study

    CSIR Research Space (South Africa)

    Opoku, F

    2017-01-01

    Full Text Available A first principles study of the Titania is done as used in photo-catalysis to generate charge carries. Models of titania, silica, graphene, epoxy graphene monoxide, single wall Carbon nanotubes and their respective layer were studied in order...

  16. Electron lucky-drift impact ionization coefficients of ZnS: Mn

    Indian Academy of Sciences (India)

    Fit of the experimental data of ZnS: Mn by a modified lucky-drift formula has been performed using the least square algorithm. The fit agrees well with the experimental data only at high field. The best fitting parameters at high field are the mean free path of order 102.74 Å and Keldysh factor, 0 = 0.0138. A generalized ...

  17. Microphysics of KCl and ZnS Clouds on GJ 1214 b

    Science.gov (United States)

    Gao, Peter; Benneke, Björn

    2016-10-01

    Clouds are ubiquitous in the atmospheres of exoplanets. However, as most of these planets have temperatures between 600 and 2000 K, their clouds are likely composed of exotic condensates such as salts, sulfides, silicates, and metals. Treatment of these clouds in current exoplanet atmosphere models do not consider the microphysical processes that govern their formation, evolution, and distribution, such as nucleation and condensation/evaporation, thus creating a gulf between the cloud properties retrieved from observations and the cloud composition predictions from condensation equilibrium models. In this work, we apply a 1D microphysical cloud model to GJ 1214 b and investigate the properties of potassium chloride (KCl) and zinc sulfide (ZnS) clouds as a function of atmospheric metallicity, the intensity of vertical mixing, and the mode of nucleation. Our cloud model has been widely applied to planets in our own Solar System, and as such our work bridges a gap between planetary science and exoplanets. Using model background atmospheres calculated by the SCARLET code, we find that (1) the cloud distribution is not significantly affected by metallicity unless [Fe/H] > 2, (2) higher intensities of vertical mixing leads to more extended cloud decks, more cloud particles at all altitudes, and smaller mean particle radii, (3) the high surface energy of solid ZnS prevents the homogeneous nucleation of pure ZnS cloud particles, such that KCl clouds dominate; solid ZnS can only manifest by nucleating onto pre-existing surfaces (heterogeneous nucleation), such as KCl cloud particles, resulting in mixed clouds, and (4) formation of KCl clouds results in a KCl vapor abundance above the cloud deck ~5 orders of magnitude less than that calculated from equilibrium chemistry. We also examine the transmission spectra that would result from these different cases. Extension of this model to other planets and condensates will shed light on the observed continuum in the "cloudiness

  18. Mechanisms of polymer-templated nanoparticle synthesis: contrasting ZnS and Au

    OpenAIRE

    Podhorska, L; Delcassian, D; Goode, AE; Agyei, M; Mccomb, DW; Ryan, MP; Dunlop, IE

    2016-01-01

    We combine solution small-angle X-ray scattering (SAXS) and high-resolution analytical transmission electron microscopy (ATEM) to gain a full mechanistic understanding of substructure formation in nanoparticles templated by block copolymer reverse micelles, specifically poly(styrene)-block-poly(2-vinyl pyridine). We report a novel substructure for micelle-templated ZnS nanoparticles, in which small crystallites (~4 nm) exist within a larger (~20 nm) amorphous organic-inorganic hybrid matrix. ...

  19. Synthesis and investigation of optical properties of ZnS nanostructures

    Indian Academy of Sciences (India)

    Ar gas to eliminate any O2 in the tube and the furnace was started to heat. When the furnace reached the process tem- perature (1100. ◦. C), the terminal opposite to the gas flow sys- tem opened and was kept open during the process for the gas to flow out. Then the quartz boat containing ZnS pow- der was transferred from ...

  20. TEM characterization of Cr-doped ZnS Thin Films for Solar Cell applications

    OpenAIRE

    Seim, Eivind

    2014-01-01

    The morphology of three Cr-doped zinc sulfide thin films, one deposited by molec-ular beam epitaxy (MBE) and two by pulsed laser deposition (PLD), have beenstudied by transmission electron microscopy (TEM). Investigations of the poly-morphic crystal structure of ZnS have been done by analysis of diffraction, brightfield and high resolution images. Both similarities and differences in morphologybetween the three samples have been discovered. An unambiguous determinationof the crystal structure...

  1. Synthesis, characterization and optical properties of polymer-based ZnS nanocomposites.

    Science.gov (United States)

    Tiwari, A; Khan, S A; Kher, R S; Dhoble, S J; Chandel, A L S

    2016-03-01

    Nanostructured polymer-semiconductor hybrid materials such as ZnS-poly(vinyl alcohol) (ZnS-PVA), ZnS-starch and ZnS-hydroxypropylmethyl cellulose (Zns-HPMC) are synthesized by a facile aqueous route. The obtained nanocomposites are characterized using various techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), UV/vis spectroscopy and photoluminescence (PL). XRD studies confirm the zinc blende phase of the nanocomposites and indicate the high purity of the samples. SEM studies indicate small nanoparticles clinging to the surface of a bigger particle. The Energy Dispersive Analysis by X-rays (EDAX) spectrum reveals that the elemental composition of the nanocomposites consists primarily of Zn:S. FTIR studies indicate that the polymer matrix is closely associated with ZnS nanoparticles. The large number of hydroxyl groups in the polymer matrix facilitates the complexation of metal ions. The absorption spectra of the specimens show a blue shift in the absorption edge. The spectrum reveals an absorption edge at 320, 310 and 325 nm, respectively. PL of nanocomposites shows broad peaks in the violet-blue region (420-450 nm). The emission intensity changes with the nature of capping agent. The PL intensity of ZnS-HPMC nanocomposites is found to be highest among the studied nanocomposites. The results clearly indicate that hydroxyl-functionalized HPMC is much more effective at nucleating and stabilizing colloidal ZnS nanoparticles in aqueous suspensions compared with PVA and starch. Copyright © 2015 John Wiley & Sons, Ltd.

  2. Aqueous route to color-tunable Mn-doped ZnS quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Labiadh, Houcine; Chaabane, Tahar Ben [Unité de Recherche UR11ES30 de Synthèse et Structures de Nanomatériaux, Faculté des Sciences de Bizerte, 7021 Jarzouna (Tunisia); Piatkowski, David; Mackowski, Sebastian [Optics of Hybrid Nanostructures Group, Institute of Physics, Nicolaus Copernicus University, Grudziadzka 5/7, 87-100 Torun (Poland); Lalevée, Jacques [Institut de Science des Matériaux de Mulhouse (IS2M), LRC 7228, 15 rue Jean Starcky, 68093 Mulhouse (France); Ghanbaja, Jaafar [Université de Lorraine, Institut Jean Lamour (IJL), UMR 7198, CNRS, BP 70239, 54506 Vandoeuvre-lès-Nancy Cedex (France); Aldeek, Fadi [Université de Lorraine, Laboratoire Réactions et Génie des Procédés (LRGP), UMR 7274, CNRS, 1 rue Grandville, BP 20451, 54001 Nancy Cedex (France); Schneider, Raphaël, E-mail: raphael.schneider@univ-lorraine.fr [Université de Lorraine, Laboratoire Réactions et Génie des Procédés (LRGP), UMR 7274, CNRS, 1 rue Grandville, BP 20451, 54001 Nancy Cedex (France)

    2013-07-15

    Mn-doped zinc sulfide (Mn:ZnS) quantum dots stabilized by 3-mercaptopropionic acid (MPA) were synthesized at 100 °C in basic aqueous solution using the nucleation-doping strategy. The optical properties and structure of the obtained Mn:ZnS QDs have been characterized by UV–vis, photoluminescence (PL) and time-resolved PL spectroscopies, transmission electron microscopy (TEM), X-ray diffraction (XRD), and electron spin resonance (ESR). The obtained nearly monodisperse Mn:ZnS@MPA QDs have an average diameter of ca. 2.5 nm and a zinc-blende crystal structure. By varying the base (LiOH, NaOH, KOH, CsOH) used to deprotonate the MPA ligand and adjust the pH of the aqueous solution to 11, the PL emission wavelengths can be tuned within a relatively large optical window, from 567 to 594 nm. The variations of charge density near the surface of the QDs obtained by changing the cation associated to the MPA ligand and of the dopant location in the ZnS host are at the origin of the PL shifts observed. In order to improve the PL emission efficiency, a ZnS shell was subsequently overcoated around the Mn:ZnS core nanocrystals. With ZnS shell growth, the PL emission wavelength was restricted between 570 and 583 nm but PL quantum efficiency of Mn:ZnS/ZnS core/shell QDs increased up to 18.4%. - Graphical abstract: Display Omitted - Highlights: • An aqueous route to color-tunable Mn-doped ZnS QDs was developed. • PL emission can be tuned from 567 to 594 nm by changing the base. • Variations of charge at the surface of the QDs and dopant location are responsible of the PL shifts.

  3. ZnS semiconductor quantum dots production by an endophytic fungus Aspergillus flavus

    Energy Technology Data Exchange (ETDEWEB)

    Uddandarao, Priyanka, E-mail: uddandaraopriyanka@gmail.com; B, Raj Mohan, E-mail: rajmohanbala@gmail.com

    2016-05-15

    Graphical abstract: - Highlights: • Endophytic fungus Aspergillus flavus isolated from a medicinal plant Nothapodytes foetida was used for the synthesis of quantum dots. • Morris-Weber kinetic model and Lagergren's pseudo-first-order rate equation were used to study the biosorption kinetics. • Polycrystalline ZnS quantum dots of 18 nm and 58.9 nm from TEM and DLS, respectively. - Abstract: The development of reliable and eco-friendly processes for the synthesis of metal sulphide quantum dots has been considered as a major challenge in the field of nanotechnology. In the present study, polycrystalline ZnS quantum dots were synthesized from an endophytic fungus Aspergillus flavus. It is noteworthy that apart from being rich sources of bioactive compounds, endophytic fungus also has the ability to mediate the synthesis of nanoparticles. TEM and DLS revealed the formation of spherical particles with an average diameter of about 18 nm and 58.9 nm, respectively. The ZnS quantum dots were further characterized using SEM, EDAX, XRD, UV–visible spectroscopy and FTIR. The obtained results confirmed the synthesis of polycrystalline ZnS quantum dots and these quantum dots are used for studying ROS activity. In addition this paper explains kinetics of metal sorption to study the role of biosorption in synthesis of quantum dots by applying Morris-Weber kinetic model. Since Aspergillus flavus is isolated from a medicinal plant Nothapodytes foetida, quantum dots synthesized from this fungus may have great potential in broad environmental and medical applications.

  4. A novel drug delivery of 5-fluorouracil device based on TiO{sub 2}/ZnS nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Mendonça Faria, Henrique Antonio, E-mail: henrique.fisica@ifsc.usp.br [Institute of Physics and Chemistry, Federal University of Itajubá (UNIFEI), Av. BPS, 1303, Pinheirinho, Itajubá, MG, PO Box 50, CEP: 37500-903 (Brazil); Nanomedicine and Nanotoxicology Laboratory, São Carlos Institute of Physics, University of São Paulo. Av. Trabalhador São-carlense, 400, Arnold Schimidt, São Carlos, SP CEP: 13566-590 (Brazil); Alencar de Queiroz, Alvaro Antonio, E-mail: alencar@unifei.edu.br [Institute of Physics and Chemistry, Federal University of Itajubá (UNIFEI), Av. BPS, 1303, Pinheirinho, Itajubá, MG, PO Box 50, CEP: 37500-903 (Brazil)

    2015-11-01

    The structural and electronic properties of titanium oxide nanotubes (TiO{sub 2}) have attracted considerable attention for the development of therapeutic devices and imaging probes for nanomedicine. However, the fluorescence response of TiO{sub 2} has typically been within ultraviolet spectrum. In this study, the surface modification of TiO{sub 2} nanotubes with ZnS quantum dots was found to produce a red shift in the ultra violet emission band. The TiO{sub 2} nanotubes used in this work were obtained by sol–gel template synthesis. The ZnS quantum dots were deposited onto TiO{sub 2} nanotube surface by a micelle-template inducing reaction. The structure and morphology of the resulting hybrid TiO{sub 2}/ZnS nanotubes were investigated by scanning electron microscopy, transmission electron microscopy and X-ray diffraction techniques. According to the results of fluorescence spectroscopy, pure TiO{sub 2} nanotubes exhibited a high emission at 380 nm (3.26 eV), whereas TiO{sub 2}/ZnS exhibited an emission at 410 nm (3.02 eV). The TiO{sub 2}/ZnS nanotubes demonstrated good bio-imaging ability on sycamore cultured plant cells. The biocompatibility against mammalian cells (Chinese Hamster Ovarian Cells—CHO) suggesting that TiO{sub 2}/ZnS may also have suitable optical properties for use as biological markers in diagnostic medicine. The drug release characteristic of TiO{sub 2}/ZnS nanotubes was explored using 5-fluorouracil (5-FU), an anticancer drug used in photodynamic therapy. The results show that the TiO{sub 2}/ZnS nanotubes are a promising candidate for anticancer drug delivery systems. - Highlights: • TiO{sub 2}/ZnS nanotubes showed a redshift in fluorescence spectrum. • Cytotoxicity against mammalian cells revealed biocompatibility of the nanotubes. • TiO{sub 2}/ZnS proved an efficient delivery system for anti-tumor 5-fluorouracil.

  5. Control of ruthenium oxide nanorod length in reactive sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Cross, Michael W [School of Engineering, Electrical Engineering Program, University of Vermont, Burlington, VT 05405 (United States); Varhue, Walter J [School of Engineering, Electrical Engineering Program, University of Vermont, Burlington, VT 05405 (United States); Hitt, Darren L [School of Engineering, Mechanical Engineering Program, University of Vermont, Burlington, VT 05405 (United States); Adams, Edward [IBM Microelectronics, Essex Junction, VT 05452 (United States)

    2008-01-30

    Ruthenium oxide nanorods have been grown on Si wafer substrates under a variety of pre-existing surface conditions by reactive radio frequency sputtering in an electron cyclotron resonant plasma process. Nanorod formation by this method is fast relative to that observed in other processes reported in the literature, with nucleation being the rate determining step. Growth in the axial direction is limited by the availability of ruthenium precursors which competes with their consumption in the lateral growth of the nanorods. The availability of Ru precursors at the top of the nanorods can be controlled by surface diffusion and therefore substrate temperature. The ultimate length of the nanorods is determined by the mole fraction of oxygen used in the reactor ambient through the production of mobile Ru hyperoxide precursors. The results of this investigation show the way to develop a process for producing a high density field of nanorods with a specified length.

  6. High rate flame synthesis of highly crystalline iron oxide nanorods

    Science.gov (United States)

    Merchan-Merchan, W.; Saveliev, A. V.; Taylor, A. M.

    2008-03-01

    Single-step flame synthesis of iron oxide nanorods is performed using iron probes inserted into an opposed-flow methane oxy-flame. The high temperature reacting environment of the flame tends to convert elemental iron into a high density layer of iron oxide nanorods. The diameters of the iron oxide nanorods vary from 10 to 100 nm with a typical length of a few microns. The structural characterization performed shows that nanorods possess a highly ordered crystalline structure with parameters corresponding to cubic magnetite (Fe3O4) with the [100] direction oriented along the nanorod axis. Structural variations of straight nanorods such as bends, and T-branched and Y-branched shapes are frequently observed within the nanomaterials formed, opening pathways for synthesis of multidimensional, interconnected networks.

  7. Fabrication of 3D rotor-like ZnO nanostructure from 1D ZnO nanorods and their morphology dependent photoluminescence property

    Science.gov (United States)

    Rai, Prabhakar; Jo, Jin-Nyeong; Lee, In-Hwan; Yu, Yeon-Tae

    2010-10-01

    A facile and eco-friendly sonochemical route to fabricate well-defined dentritic (rotor-like) ZnO nanostructures from 1D ZnO nanorods without alloying elements, templates and surfactants has been reported. Phase and structural analysis has been carried out by X-ray diffraction (XRD) and Fourier Transform Infra-Red (FTIR) spectroscopy, showed the formation of hexagonal wurtzite structure of ZnO. Scanning electron microscopic (SEM) study showed the formation of rotor-like ZnO nanostructure having a central core which is surrounded by side branches nanocones. Transmission electron microscopic (TEM) study showed that these nanocones grow along [0001] direction on the six {01-10} planes of central core ZnO nanorods. A plausible formation mechanism of rotor-like ZnO nanostructures was studied by SEM which indicates that the size and morphology of side branches can be controlled by adjusting the concentration of OH - ions and time duration of growth. The photoluminescence (PL) spectrum of the synthesized rotor-like ZnO nanostructures exhibited a weak ultraviolet emission at 400 nm and a strong green emission at 532 nm recorded at room temperature. The influence of morphology on the origin of green emission was discussed in detail. The results suggested a positive relationship among polar plane, oxygen vacancy and green emission.

  8. Controlled growth of high-density CdS and CdSe nanorod arrays on selective facets of two-dimensional semiconductor nanoplates.

    Science.gov (United States)

    Wu, Xue-Jun; Chen, Junze; Tan, Chaoliang; Zhu, Yihan; Han, Yu; Zhang, Hua

    2016-05-01

    The rational synthesis of hierarchical three-dimensional nanostructures with specific compositions, morphologies and functionalities is important for applications in a variety of fields ranging from energy conversion and electronics to biotechnology. Here, we report a seeded growth approach for the controlled epitaxial growth of three types of hierarchical one-dimensional (1D)/two-dimensional (2D) nanostructures, where nanorod arrays of II-VI semiconductor CdS or CdSe are grown on the selective facets of hexagonal-shaped nanoplates, either on the two basal facets of the nanoplate, or on one basal facet, or on the two basal facets and six side facets. The seed engineering of 2D hexagonal-shaped nanoplates is the key factor for growth of the three resulting types of 1D/2D nanostructures. The wurtzite- and zinc-blende-type polymorphs of semiconductors are used to determine the facet-selective epitaxial growth of 1D nanorod arrays, resulting in the formation of different hierarchical three-dimensional (3D) nanostructures.

  9. Controlled growth of high-density CdS and CdSe nanorod arrays on selective facets of two-dimensional semiconductor nanoplates

    KAUST Repository

    Wu, Xue-Jun

    2016-03-14

    The rational synthesis of hierarchical three-dimensional nanostructures with specific compositions, morphologies and functionalities is important for applications in a variety of fields ranging from energy conversion and electronics to biotechnology. Here, we report a seeded growth approach for the controlled epitaxial growth of three types of hierarchical one-dimensional (1D)/two-dimensional (2D) nanostructures, where nanorod arrays of II-VI semiconductor CdS or CdSe are grown on the selective facets of hexagonal-shaped nanoplates, either on the two basal facets of the nanoplate, or on one basal facet, or on the two basal facets and six side facets. The seed engineering of 2D hexagonal-shaped nanoplates is the key factor for growth of the three resulting types of 1D/2D nanostructures. The wurtzite- and zinc-blende-type polymorphs of semiconductors are used to determine the facet-selective epitaxial growth of 1D nanorod arrays, resulting in the formation of different hierarchical three-dimensional (3D) nanostructures. © 2016 Macmillan Publishers Limited. All rights reserved.

  10. Low-Temperature Growth of Well-Aligned ZnO Nanorod Arrays by Chemical Bath Deposition for Schottky Diode Application

    Science.gov (United States)

    Yuan, Zhaolin

    2015-04-01

    A well-aligned ZnO nanorod array (ZNRA) was successfully grown on an indium tin oxide (ITO) substrate by chemical bath deposition at low temperature. The morphology, crystalline structure, transmittance spectrum and photoluminescence spectrum of as-grown ZNRA were investigated by field emission scanning electron microscopy, x-ray diffraction, ultraviolet-visible spectroscopy and spectrophotometer, respectively. The results of these measurements showed that the ZNRA contained densely packed, aligned nanorods with diameters from 30 nm to 40 nm and a wurtzite structure. The ZNRA exhibited good optical transparency within the visible spectral range, with >80% transmission. Gold (Au) was deposited on top of the ZNRA, and the current-voltage characteristics of the resulting ITO/ZNRA/Au device in the dark were evaluated in detail. The ITO/ZNRA/Au device acted as a Schottky barrier diode with rectifying behaviour, low turn-on voltage (0.6 V), small reverse-bias saturation current (3.73 × 10-6 A), a high ideality factor (3.75), and a reasonable barrier height (0.65 V) between the ZNRA and Au.

  11. Detection of Femtomolar Proteins by Non-Fluorescent ZnS Nanocrystal Clusters

    Science.gov (United States)

    Yao, Jingjing; Han, Xiaogang; Zeng, Shang; Zhong, Wenwan

    2012-01-01

    Cation exchange (CX) in the non-fluorescent ZnS nanocrystal clusters (NCCs) was employed to detect trace biomolecules with immunoassays. The NCCs were porous, and allowed fast cation exchange reaction to release an ultra-large number of Zn2+ from each cluster that turned on the Zn-responsive dyes for fluorescence detection. The ZnS NCCs were highly stable in biological buffers and more biocompatible than quantum dots. Zn2+ release efficiency and target binding by NCCs with average diameters of 44 nm, 86 nm, and 144 nm were investigated. The smallest NCCs exhibited the highest CX efficiency because of its larger surface area and bigger pores inside the cluster structure, and 71.0% of the enclosed Zn2+ were freed by CX with 2-minute microwave irradiation. They also experienced the least space hindrance and the fastest rate when binding to target molecules immobilized on surface. When the 44-nm NCCs were used to detect IgE in a sandwich assay, the limit of detection (LOD) was 5 pg/mL (33 fM), 1,000 times better than that of ELISA. Our results well demonstrate that CX in the ZnS NCCs is superior to the conventional signaling strategies in its high amplification efficiency, robustness, and biocompatibility. PMID:22243488

  12. Synthesis and study of optical properties of transition metals doped ZnS nanoparticles.

    Science.gov (United States)

    Ramasamy, V; Praba, K; Murugadoss, G

    2012-10-01

    ZnS and transition metal (Mn, Co, Ni, Cu, Ag and Cd) doped ZnS were synthesized using chemical precipitation method in an air atmosphere. The structural and optical properties were studied using various techniques. The X-ray diffraction (XRD) analysis show that the particles are in cubic structure. The mean size of the nanoparticles calculated through Scherrer equation is in the range of 4-6.1 nm. Elemental dispersive (EDX) analysis of doped samples reveals the presence of doping ions. The scanning electron microscopic (SEM) and transmission electron microscopic (TEM) studies show that the synthesized particles are in spherical shape. Optical characterization of both undoped and doped samples was carried out by ultraviolet-visible (UV-Vis) and photoluminescence (PL) spectroscopy. The absorption spectra of all the samples are blue shifted from the bulk ZnS. An optimum doping level of the transition metals for enhanced PL properties are found through optical study. Copyright © 2012 Elsevier B.V. All rights reserved.

  13. Interaction of insulin with colloidal ZnS quantum dots functionalized by various surface capping agents.

    Science.gov (United States)

    Hosseinzadeh, Ghader; Maghari, Ali; Farniya, Seyed Morteza Famil; Keihan, Amir Homayoun; Moosavi-Movahedi, Ali A

    2017-08-01

    Interaction of quantum dots (QDs) and proteins strongly influenced by the surface characteristics of the QDs at the protein-QD interface. For a precise control of these surface-related interactions, it is necessary to improve our understanding in this field. In this regard, in the present work, the interaction between the insulin and differently functionalized ZnS quantum dots (QDs) were studied. The ZnS QDs were functionalized with various functional groups of hydroxyl (OH), carboxyl (COOH), amine (NH2), and amino acid (COOH and NH2). The effect of surface hydrophobicity was also studied by changing the alkyl-chain lengths of mercaptocarboxylic acid capping agents. The interaction between insulin and the ZnS QDs were investigated by fluorescence quenching, synchronous fluorescence, circular dichroism (CD), and thermal aggregation techniques. The results reveal that among the studied QDs, mercaptosuccinic acid functionalized QDs has the strongest interaction (∆G°=-51.50kJ/mol at 310K) with insulin, mercaptoethanol functionalized QDs destabilize insulin by increasing the beta-sheet contents, and only cysteine functionalized QDs improves the insulin stability by increasing the alpha-helix contents of the protein, and. Our results also indicate that by increasing the alkyl-chain length of capping agents, due to an increase in hydrophobicity of the QDs surface, the beta-sheet contents of insulin increase which results in the enhancement of insulin instability. Copyright © 2017 Elsevier B.V. All rights reserved.

  14. Low temperature method for synthesis of ZnS quantum dots and its luminescence characterization studies

    Energy Technology Data Exchange (ETDEWEB)

    Senthilkumar, K., E-mail: senovi2007@gmail.com [Department of Physics, AMET University, Chennai 603112 (India); Department of Physics, SRM University, Chennai 603203 (India); Kalaivani, T. [Department of Physics, SRM University, Chennai 603203 (India); Kanagesan, S. [Materials Synthesis and Characterization Laboratory (MSCL), Institute of Advanced Technology, Universiti Putra Malaysia, Serdang 43400, Selangor (Malaysia); Balasubramanian, V. [Department of Chemistry, AMET University, Chennai 603112 (India)

    2013-01-01

    Highlights: Black-Right-Pointing-Pointer We prepared zinc sulfide (ZnS) quantum dots of sizes 2.68-4.8 nm. Black-Right-Pointing-Pointer It is embedded on polyvinyl alcohol (PVA) matrix, have been synthesized at 70 Degree-Sign C by wet chemical method. Black-Right-Pointing-Pointer Optical absorption spectra showed strong blue shift, which is an indication of strong quantum confinement. Black-Right-Pointing-Pointer ZnS quantum dots exhibit strong quantum confinement effect as the optical band gap increases significantly, from 3.96 eV to 4.06 eV, compared to bulk value 3.68 eV. - Abstract: Zinc Sulfide (ZnS) quantum dots of sizes 2.68-4.8 nm, embedded on polyvinyl alcohol (PVA) matrix, have been synthesized at 70 Degree-Sign C by wet chemical method. X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), UV-vis spectroscopy and photoluminescence (PL) Spectroscopy has been adopted for sample characterization. Optical absorption spectra showed strong blue shift, which is an indication of strong quantum confinement. Photoluminescence spectra of the sample have been recorded at room temperature and observed two peaks centred around 415 nm and 440 nm. We have assigned the first peak due to band gap transitions while the later due to sulfur vacancy in the sample.

  15. Mechano-chemical synthesis and optical properties of ZnS nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Pathak, C.S., E-mail: chandrashekharpathak09@gmail.com [Department of Physics, Bharat Institute of Technology, Meerut, UP 250103 (India); Agarwala, V. [Department of Metallurgical and Materials Engineering, Indian Institute of Technology, Roorkee 247667 (India); Mandal, M.K. [Department of Physics, National Institute of Technology, Durgapur 713209 (India)

    2012-09-01

    In the present work, we report the synthesis and optical properties of ZnS nanoparticles produced by the mechano-chemical route. We used zinc acetate and sodium sulphide as source materials in a high energy planetary ball mill at rotation speed of 300 rpm and vial rotation speed of 600 rpm with ball to powder (BPR or charge ratio CR) 5:1 for 30 and 90 min. The milled powders were washed with methanol to remove impurity and dried at 300 Degree-Sign C for 1 h. The prepared nanoparticles have been characterized using X-ray diffraction (XRD), Field emission scanning electron microscope (FESEM), UV-vis-NIR spectrophotometer and Fluorescence spectroscopy. The crystallite size of the synthesized ZnS nanoparticles is found to be in the range 7-8 nm which was calculated using Debye-Scherer's formula. The value of optical band gap has been found to be in the range 3.80-4.15 eV. Room temperature photoluminescence (PL) spectrum of ZnS samples exhibit a blue emission peaked at 466 nm under UV excitation.

  16. Latex-mediated synthesis of ZnS nanoparticles: green synthesis approach

    Energy Technology Data Exchange (ETDEWEB)

    Hudlikar, Manish; Joglekar, Shreeram [University of Pune, Division of Biochemistry, Department of Chemistry (India); Dhaygude, Mayur [National Chemical Laboratory, Polymer Science and Engineering Division (India); Kodam, Kisan, E-mail: kodam@chem.unipune.ac.in [University of Pune, Division of Biochemistry, Department of Chemistry (India)

    2012-05-15

    A low-cost, green synthesis of ZnS nanoparticles is reported using 0.3 % latex solution prepared from Jatropha curcas L. ZnS nanoparticles were characterized by X-ray diffraction, selected area electron diffraction, transmission electron microscopy, energy dispersive analysis of X-rays, UV-vis optical absorption and photoluminescence techniques. Fourier Transform Infrared Spectroscopy was performed to find the role of cyclic peptides namely curcacycline A (an octapeptide), curcacycline B (a nonapeptide) and curcain (an enzyme) as a possible reducing and stabilizing agents present in the latex of J. curcas L. The average size of ZnS nanoparticles was found to be 10 nm. Latex of J. curcas L. itself acts as a source of sulphide (S{sup -2}) ions that are donated to Zn ions under present experimental conditions. Source of sulphide (S{sup -2}) ions is still unclear, but we speculate that cysteine or thiol residues present in enzyme curcain may be donating these sulphide (S{sup -2}) ions.

  17. Latex-mediated synthesis of ZnS nanoparticles: green synthesis approach

    Science.gov (United States)

    Hudlikar, Manish; Joglekar, Shreeram; Dhaygude, Mayur; Kodam, Kisan

    2012-05-01

    A low-cost, green synthesis of ZnS nanoparticles is reported using 0.3 % latex solution prepared from Jatropha curcas L. ZnS nanoparticles were characterized by X-ray diffraction, selected area electron diffraction, transmission electron microscopy, energy dispersive analysis of X-rays, UV-vis optical absorption and photoluminescence techniques. Fourier Transform Infrared Spectroscopy was performed to find the role of cyclic peptides namely curcacycline A (an octapeptide), curcacycline B (a nonapeptide) and curcain (an enzyme) as a possible reducing and stabilizing agents present in the latex of J. curcas L. The average size of ZnS nanoparticles was found to be 10 nm. Latex of J. curcas L. itself acts as a source of sulphide (S-2) ions that are donated to Zn ions under present experimental conditions. Source of sulphide (S-2) ions is still unclear, but we speculate that cysteine or thiol residues present in enzyme curcain may be donating these sulphide (S-2) ions.

  18. Synthesis and characterization of metal oxide nanorod brushes

    Indian Academy of Sciences (India)

    Nanorod brushes of -Al2O3, MoO3 and ZnO have been synthesized using amorphous carbon nanotube (-CNT) brushes as the starting material. The brushes of -Al2O3 and MoO3 are made up of single crystalline nanorods. In the case of ZnO brushes, the nanorod bristles are made by the fusion of 15–25 nm size ...

  19. Proton Dynamics in ZnO Nanorods Quantified by In Situ Solid-State 1H Nuclear Magnetic Resonance

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Li Q.; Zhou, Xiao Dong; Exarhos, Gregory J.; Pederson, Larry R.; Wang, Chong M.; Windisch, Charles F.; Yao, Chunhua

    2007-10-22

    Zinc oxide (ZnO) adopts wurtzite structure and possesses a direct wide band gap (Eg ~ 3.3 eV at 300 K), similar to that of GaN (Eg ~ 3.4 eV at 300 K), which enables ZnO as an alternative candidate to replace GaN for use in optoelectronic devices. The present controversy is centered at the microscopic origin of the “native donors”, particularly after ab initio calculations by Van de Walle, which indicate that hydrogen is soluble in ZnO at the interstitial sites, effectively forming a donor level just below the conduction band in ZnO. Hence, the origin of n type conductivity in ZnO is proposed due to the presence of hydrogen. Electron paramagnetic resonance and spectroscopic observations of muons provide experimental evidence of hydrogen presence in ZnO. Whereas, Look et al. suggests that the complex of zinc interstitial and nitrogen defect is a stronger candidate for donor than hydrogen interstitials under N ambient. Hydrogen-oxygen complex is claimed to be stable even at T > 1000°C in the hydrothermally synthesized ZnO. Therefore, the thermodynamic nature of hydrogen characteristics remains controversial, particularly its role on resident defects. In this letter, in situ temperature dependent solid state 1H magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy is employed to probe the local chemical environments of hydrogen in ZnO nanorods. To best knowledge of ours, this is the first time that the presence of hydrogen, its concentration, and local transport dynamics are directly chemically determined. Moreover, in situ NMR allows a new approach to investigate the absorption and desorption of protons from different sites on the ZnO nanorods, thus study of site-specific proton dynamics in ZnO becomes feasible.

  20. Photoluminescence and thermoluminescence studies of Tb{sup 3+} doped ZnO nanorods

    Energy Technology Data Exchange (ETDEWEB)

    Pal, Partha P., E-mail: phys.ppal@gmail.com [Department of Applied Physics, Indian School of Mines, Dhanbad 826004 (India); Manam, Jairam [Department of Applied Physics, Indian School of Mines, Dhanbad 826004 (India)

    2013-04-20

    Highlights: ► Tb{sup 3+} doped ZnO nanorods were prepared by precipitation method. ► No change in XRD peak pattern observed after Tb{sup 3+} incorporation. ► PL spectra indicate efficient energy transfer from ZnO host to Tb{sup 3+}. ► Tb{sup 3+} related glow peak at 255 °C obey first order kinetics. ► Tb{sup 3+} related glow peak is 1.5 times more intense than that of undoped sample. -- Abstract: Here in, the synthesis of the terbium doped zinc oxide (ZnO:Tb{sup 3+}) nanorods via room temperature chemical co-precipitation was explored and their structural, photoluminescence (PL) and thermoluminescence (TL) studies were investigated in detail. The present samples were found to have pure hexagonal wurtzite crystal structure. The as obtained samples were broadly composed of nanoflakes while the highly crystalline nanorods have been formed due to low temperature annealing of the as synthesized samples. The diameters of the nanoflakes are found to be in the range 50–60 nm whereas the nanorods have diameter 60–90 nm and length 700–900 nm. FTIR study shows Zn-O stretching band at 475 cm{sup −1} showing improved crystal quality with annealing. The bands at 1545 and 1431 cm{sup −1} are attributed to asymmetric and symmetric C=O stretching vibration modes. The diffuse reflectance spectra show band edge emission near 390 nm and a blue shift of the absorption edge with higher concentration of Tb doping. The PL spectra of the Tb{sup 3+}-doped sample exhibited bright bluish green and green emissions at 490 nm ({sup 5}D{sub 4} → {sup 7}F{sub 6}) and 544 nm ({sup 5}D{sub 4} → {sup 7}F{sub 5}) respectively which is much more intense then the blue (450 nm), bluish green (472 nm) and broad green emission (532 nm) for the undoped sample. An efficient energy transfer process from ZnO host to Tb{sup 3+} is observed in PL emission and excitation spectra of Tb{sup 3+}-doped ZnO ions. The doped sample exhibits a strong TL glow peak at 255 °C compared to the

  1. Electrical contacts to nanorod networks at different length scales: From macroscale ensembles to single nanorod chains

    KAUST Repository

    Lavieville, Romain

    2013-11-01

    The nature of metal-semiconductor interfaces at the nanoscale is an important issue in micro- and nanoelectronic engineering. The study of charge transport through chains of CdSe semiconductor nanorods linked by Au particles represents an ideal model system for this matter, because the metal semiconductor interface is an intrinsic feature of the nanosystem. Here we show the controlled fabrication of all-inorganic hybrid metal-semiconductor networks with different size, in which the semiconductor nanorods are linked by Au domains at their tips. We demonstrate different approaches to selectively contact the networks and single nanorod chains with planar electrodes, and we investigate their charge transport at room temperature. © 2013 Elsevier B.V. All rights reserved.

  2. Gold nanorod vaccine for respiratory syncytial virus

    Science.gov (United States)

    Stone, John W.; Thornburg, Natalie J.; Blum, David L.; Kuhn, Sam J.; Wright, David W.; Crowe, James E., Jr.

    2013-07-01

    Respiratory syncytial virus (RSV) is a major cause of pneumonia and wheezing in infants and the elderly, but to date there is no licensed vaccine. We developed a gold nanorod construct that displayed the major protective antigen of the virus, the fusion protein (F). Nanorods conjugated to RSV F were formulated as a candidate vaccine preparation by covalent attachment of viral protein using a layer-by-layer approach. In vitro studies using ELISA, electron microscopy and circular dichroism revealed that conformation-dependent epitopes were maintained during conjugation, and transmission electron microscopy studies showed that a dispersed population of particles could be achieved. Human dendritic cells treated with the vaccine induced immune responses in primary human T cells. These results suggest that this vaccine approach may be a potent method for immunizing against viruses such as RSV with surface glycoproteins that are targets for the human immune response.

  3. Influence of Structural Defects on Biomineralized ZnS Nanoparticle Dissolution: An In-Situ Electron Microscopy Study.

    Science.gov (United States)

    Eskelsen, Jeremy R; Xu, Jie; Chiu, Michelle Y; Moon, Ji-Won; Wilkins, Branford O; Graham, David E; Gu, Baohua; Pierce, Eric M

    2017-12-19

    The dissolution of metal sulfides, such as ZnS, is an important biogeochemical process affecting fate and transport of trace metals in the environment. However, currently studies of in-situ dissolution of metal sulfides and the effects of structural defects on dissolution are lacking. Here we have examined the dissolution behavior of ZnS nanoparticles synthesized via several abiotic and biological pathways. Specifically, the biogenic ZnS nanoparticles were produced by an anaerobic, metal-reducing bacterium Thermoanaerobacter sp. X513 in a Zn-amended, thiosulfate-containing growth medium either in the presence or absence of silver (Ag), whereas the abiogenic ZnS nanoparticles were produced by mixing an aqueous Zn solution with either H2S-rich gas or Na2S solution. The size distribution, crystal structure, aggregation behavior, and internal defects of the synthesized ZnS nanoparticles were examined using high-resolution transmission electron microscopy (TEM) coupled with X-ray energy dispersive spectroscopy. The characterization results show that both the biogenic and abiogenic samples were dominantly composed of sphalerite. In the absence of Ag, the biogenic ZnS nanoparticles were significantly larger (i.e., ~10 nm) than the abiogenic ones (i.e., ~3-5 nm) and contained structural defects (e.g., twins and stacking faults). The presence of trace Ag showed a restraining effect on the particle size of the biogenic ZnS, resulting in quantum-dot-sized nanoparticles (i.e., ~3 nm). In situ dissolution experiments for the synthesized ZnS were conducted with a liquid-cell TEM (LCTEM), and the primary factors (i.e., the presence or absence structural defects) were evaluated for their effects on the dissolution behavior using the biogenic and abiogenic ZnS nanoparticle samples with the largest average particle size. Analysis of the dissolution results (i.e., change in particle radius with time) using the Kelvin equation shows that the defect-bearing biogenic ZnS nanoparticles

  4. Tensile properties of a ZnS nanowire determined with a nano-manipulator and force sensor

    Science.gov (United States)

    Jang, Hoon-Sik; Nahm, Seung Hoon; Lee, Hak Joo; Kim, Jung Han; Oh, Kyu Hwan

    2012-08-01

    Tensile tests of an individual ZnS nanowire with a cubic structure were performed with a nano-manipulator inside a scanning electron microscope (SEM). To perform the tensile test of ZnS nanowires, a mechanical testing system was installed in the SEM. A nano-manipulator was set up in the SEM, and a cantilever force sensor was mounted on the nano-manipulator. The force sensor could be controlled with the nano-manipulator. The ZnS nanowires were dispersed on the transmission electron microscope (TEM) grid; then, the ends of the ZnS nanowires were welded to the TEM grid and the tip of force sensor by exposing them to the E-beam of the SEM. The tensile tests of the ZnS nanowires were performed by controlling the nano-manipulator in the SEM. The load response during the tensile tests was obtained with a force sensor. The strain-stress curve was obtained from the tensile load-displacement curve after the tensile test. The tensile strengths for nanowires 1, 2, and 3 were 364.7 ± 5.2, 146.2 ± 5.2, and 234.4 ± 5.2 MPa, respectively, and the elastic moduli for nanowires 1, 2, and 3 were 39 ± 5.2, 33.4 ± 5.2, and 37.4 ± 5.2 GPa, respectively.

  5. Chemical bath deposited ZnS buffer layer for Cu(In,Ga)Se2 thin film solar cell

    Science.gov (United States)

    Hong, Jiyeon; Lim, Donghwan; Eo, Young-Joo; Choi, Changhwan

    2018-02-01

    The dependence of Zn precursors using zinc sulfate (ZnSO4), zinc acetate (Zn(CH3COO)2), and zinc chloride (ZnCl2) on the characteristics of the chemical bath deposited ZnS thin film used as a buffer layer of Cu(In,Ga)Se2 (CIGS) thin film solar cell was studied. It is found that the ZnS film deposition rate increases with higher stability constant during decomplexation reaction of zinc ligands, which affects the crack formation and the amount of sulfur and oxygen contents within the film. The band gap energies of all deposited films are in the range of 3.40-3.49 eV, which is lower than that of the bulk ZnS film due to oxygen contents within the films. Among the CIGS solar cells having ZnS buffer layers prepared by different Zn precursors, the best cell efficiency with 9.4% was attained using Zn(CH3COO)2 precursor due to increased Voc mainly. This result suggests that [Zn(NH3)4]2+ complex formation should be well controlled to attain the high quality ZnS thin films.

  6. Attomolar DNA detection with chiral nanorod assemblies

    Science.gov (United States)

    Ma, Wei; Kuang, Hua; Xu, Liguang; Ding, Li; Xu, Chuanlai; Wang, Libing; Kotov, Nicholas A.

    2013-10-01

    Nanoscale plasmonic assemblies display exceptionally strong chiral optical activity. So far, their structural design was primarily driven by challenges related to metamaterials whose practical applications are remote. Here we demonstrate that gold nanorods assembled by the polymerase chain reaction into DNA-bridged chiral systems have promising analytical applications. The chiroplasmonic activity of side-by-side assembled patterns is attributed to a 7-9 degree twist between the nanorod axes. This results in a strong polarization rotation that matches theoretical expectations. The amplitude of the bisignate ‘wave’ in the circular dichroism spectra of side-by-side assemblies demonstrates excellent linearity with the amount of target DNA. The limit of detection for DNA using side-by-side assemblies is as low as 3.7 aM. This chiroplasmonic method may be particularly useful for biological analytes larger than 2-5 nm which are difficult to detect by methods based on plasmon coupling and ‘hot spots’. Circular polarization increases for inter-nanorod gaps between 2 and 20 nm when plasmonic coupling rapidly decreases. Reaching the attomolar limit of detection for simple and reliable bioanalysis of oligonucleotides may have a crucial role in DNA biomarker detection for early diagnostics of different diseases, forensics and environmental monitoring.

  7. Optically stimulated luminescence of ZnO obtained by thermal treatment of ZnS chemically synthesized; Luminiscencia opticamente estimulada de ZnO obtenido por tratamiento termico de ZnS sintetizado quimicamente

    Energy Technology Data Exchange (ETDEWEB)

    Cruz V, C.; Burruel I, S.E.; Orante B, V.R.; Grijalva M, H.; Perez S, R.; Bernal, R. [Universidad de Sonora, A.P. 130, Hermosillo (Mexico)

    2005-07-01

    In this work, we report the optically stimulated luminescence (OSL) dosimetry of new nano phosphors of ZnO obtained by thermal annealing of chemically synthesized ZnS powder. The synthesized ZnS nano powder was compressed in order to form pellet shaped pellets, which were afterwards subjected to a thermal annealing at 700 C during 24 h under air atmosphere. X-ray diffraction (XRD) patterns and energy-disperse X-ray Spectrometry (EDS) analyses confirmed the transformation of ZnS to ZnO. Samples were exposed to several doses of beta radiation up to 600 Gy, and the optically stimulated luminescence with 470 nm wavelength light was recorded as a function of dose. The intensity of the OSL signal increases by increasing dose, for what it is concluded that these new phosphor materials are suitable to be used in optically stimulated luminescence dosimetry. (Author)

  8. Effect of Reaction Parameters on Morphology and Photoluminescence of Intrinsic and Mn-doped ZnS Microspheres Synthesized by Hydrothermal Method

    Science.gov (United States)

    Chanu, T. Inakhunbi; Samanta, Dhrubajyoti; Tiwari, Archana; Chatterjee, Somenath

    2017-11-01

    Intrinsic and Manganese (Mn)-doped ZnS microspheres have been synthesized by hydrothermal method. Thiourea and amino acid, and uc(l)-histidine have been used as sulfur source and capping agent, respectively. The synthesized materials have been characterized using x-ray diffraction, field emission scanning electron microscopy, photoluminescence (PL) and UV-Vis spectroscopy. The above-said characterizations conveyed the information regarding the crystallinity, existence of microspheres, size and optical properties of synthesized ZnS and Mn-doped ZnS samples. Formation of microspheres of intrinsic and Mn-doped ZnS has been observed when the reaction parameters are kept at 150 °C for 4 h, and similarly, the micropores have been noticed when reaction parameters are kept at 150 °C for 8 h. The PL of ZnS microspheres shows multiple defect emissions. The nature of PL for pure ZnS has been regulated based on reaction parameters. Doping of Mn in the ZnS enhances the PL emission. This study reveals the role of reaction parameters and effect of Mn doping on tuning the morphology and emission behavior of ZnS microspheres.

  9. Porphyrin-phthalocyanine nanorods (P-PcNR) formed by ...

    African Journals Online (AJOL)

    ... tetra {2,(3)-(2-mercaptopyridine) phthalocyaninato}(MTSPyPc). The transmission electron microscope (TEM) images of the colloid suspension of the aggregate confirmed formation of nanorods while their electron spectra showed that the molecules formed J-aggregation. Keywords: Porphyrin, Phthalocyanine, Nanorods, ...

  10. Covalently stabilized self-assembled chlorophyll nanorods by olefin metathesis.

    Science.gov (United States)

    Sengupta, Sanchita; Würthner, Frank

    2012-06-11

    A new chlorophyll derivative with peripheral olefinic chains has been synthesised and its self-assembly properties have been studied, revealing formation of well-defined nanorods. These nanorods were stabilized and rigidified by olefin metathesis reaction as confirmed by spectroscopic and microscopic methods.

  11. Dielectric Nanorod Scattering and its Influence on Material Interfaces.

    Science.gov (United States)

    Mangalgiri, Gauri M; Manley, Phillip; Riedel, Wiebke; Schmid, Martina

    2017-06-27

    This work elaborates on the high scattering which dielectric nanorods exhibit and how it can be exploited to control light propagation across material interfaces. A detailed overview of how dielectric nanorods interact with light through a combination of dipolar scattering and leaky modes is performed via outward power flux calculations. We establish and account for design parameters that best result in light magnification owing to resonant behavior of nanorods. Impact of material parameters on scattering and their dispersion have been calculated to establish that low loss dielectric oxides like ZnO when nanostructured show excellent antenna like resonances which can be used to control light coupling and propagation. Interfacial scattering calculations demonstrate the high forward directivity of nanorods for various dielectric interfaces. A systematic analysis for different configurations of single and periodic nanorods on air dielectric interface emphasizes the light coupling tendencies exhibited by nanorods to and from a dielectric. Spatial characteristics of the localized field enhancement of the nanorod array on an air dielectric interface show focusing attributes of the nanorod array. We give a detailed account to tailor and selectively increase light propagation across an interface with good spectral and spatial control.

  12. Superior photocatalytic, electrocatalytic, and self-cleaning applications of Fly ash supported ZnO nanorods

    Energy Technology Data Exchange (ETDEWEB)

    Thirumalai, Kuppulingam; Balachandran, Subramanian [Department of Chemistry, Annamalai University, Annamalainagar, 608 002, Tamil Nadu (India); Swaminathan, Meenakshisundaram, E-mail: chemres50@gmail.com [Department of Chemistry, Annamalai University, Annamalainagar, 608 002, Tamil Nadu (India); Nanomaterials Laboratory, International Research Centre, Kalasalingam Universty, Krihnankoil, 626126 (India)

    2016-11-01

    Ever growing research on modified semiconductor oxides made a significant progress in catalytic functional materials. In this article, we report the modification of ZnO photocatalyst by a simple hydrothermal decomposition method utilizing the cheaply available industrial waste fly ash. This modified Fly ash-ZnO photocatalyst was characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS), high resolution transmission electron microscopy (HR-TEM), Atomic force microscopy (AFM), photoluminescence spectroscopy (PL) and diffuse reflectance spectroscopy (DRS). The XRD pattern indicates the presence of fly ash components and the hexagonal wurtzite structured ZnO. TEM images reveal well defined nanorod like structure. Reduction of photoluminescence intensity of Fly ash-ZnO at 418 nm, when compared to, prepared ZnO, indicates the suppression of recombination of the photogenerated electron–hole pair by loaded Fly ash on ZnO. Fly ash-ZnO exhibits enhanced photocatalytic activity for the degradation of azo dyes Reactive Orange 4, Rhodamine-B and Trypan Blue. This catalyst shows higher electrocatalytic activity than ZnO in the oxidation of methanol. Significant hydrophobicity of Fly ash-ZnO reveals its self cleaning property. - Highlights: • The degradation efficiency of Fly ash-ZnO under UV and Solar irradiation is greater than prepared ZnO and TiO{sub 2}‒P25. • Electrocatalytic activity of Fly ash-ZnO exhibits enhanced current production by methanol oxidation. • Fly ash-ZnO shows the high hydrophobicity than ZnO, it can be used as a self cleaning material for industrial applications.

  13. Facile fabrication of controllable zinc oxide nanorod clusters on polyacrylonitrile nanofibers via repeatedly alternating immersion method

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Ying; Li, Xia; Yu, Hou-Yong, E-mail: phdyu@zstu.edu.cn [Zhejiang Sci-Tech University, The Key Laboratory of Advanced Textile Materials and Manufacturing Technology of Ministry of Education, College of Materials and Textiles (China); Hu, Guo-Liang; Yao, Ju-Ming, E-mail: yaoj@zstu.edu.cn [Zhejiang Sci-Tech University, National Engineering Lab for Textile Fiber Materials and Processing Technology (China)

    2016-12-15

    Polyacrylonitrile/zinc oxide (PAN/ZnO) composite nanofiber membranes with different ZnO morphologies were fabricated by repeatedly alternating hot–cold immersion and single alternating hot–cold immersion methods. The influence of the PAN/ZnCl{sub 2} ratio and different immersion methods on the morphology, microstructure, and properties of the nanofiber membranes was investigated by using field-emission scanning electron microscopy (FE-SEM), Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) analysis, thermogravimetric analysis (TGA), and ultraviolet–visible (UV–Vis) spectroscopy. A possible mechanism for different morphologies of PAN/ZnO nanofiber membranes with different PAN/ZnCl{sub 2} ratio through different immersion processes was presented, and well-dispersed ZnO nanorod clusters with smallest average dimeter of 115 nm and hexagonal wurtzite structure were successfully anchored onto the PAN nanofiber surface for R-7/1 nanofiber membrane. Compared to S-5/1 prepared by single alternating hot–cold immersion method, the PAN/ZnO nanofiber membrane fabricated by repeatedly alternating hot–cold immersion method (especially for R-7/1) showed improved thermal stability and high photocatalytic activity for methylene blue (MB). Compared to S-5/1, decomposition temperature at 5% weight loss (T{sub 5%}) was increased by 43 °C from 282 to 325 °C for R-7/1; meanwhile, R-7/1 showed higher photocatalytic degradation ratio of approximately 100% (after UV light irradiation for 8 h) than 65% for S-5/1 even after irradiation for 14 h. Moreover, the degradation efficiency of R-7/1 with good reuse stability remained above 94% after 3 cycles.

  14. CdSe nanorod/TiO2 nanoparticle heterojunctions with enhanced solar- and visible-light photocatalytic activity

    Directory of Open Access Journals (Sweden)

    Fakher Laatar

    2017-12-01

    Full Text Available CdSe nanorods (NRs with an average length of ≈120 nm were prepared by a solvothermal process and associated to TiO2 nanoparticles (Aeroxide® P25 by annealing at 300 °C for 1 h. The content of CdSe NRs in CdSe/TiO2 composites was varied from 0.5 to 5 wt %. The CdSe/TiO2 heterostructured materials were characterized by XRD, TEM, SEM, XPS, UV–visible spectroscopy and Raman spectroscopy. TEM images and XRD patterns show that CdSe NRs with wurtzite structure are associated to TiO2 particles. The UV–visible spectra demonstrate that the narrow bandgap of CdSe NRs serves to increase the photoresponse of CdSe/TiO2 composites until ≈725 nm. The CdSe (2 wt %/TiO2 composite exhibits the highest photocatalytic activity for the degradation of rhodamine B in aqueous solution under simulated sunlight or visible light irradiation. The enhancement in photocatalytic activity likely originates from CdSe sensitization of TiO2 and the heterojunction between these materials which facilitates electron transfer from CdSe to TiO2. Due to its high stability (up to ten reuses without any significant loss in activity, the CdSe/TiO2 heterostructured catalysts show high potential for real water decontamination.

  15. Theoretical study of the low-lying electronic states of ZnO and ZnS

    Science.gov (United States)

    Bauschlicher, C. W., Jr.; Langhoff, S. R.

    1986-01-01

    Theoretical spectroscopic constants and dipole moments are determined for the 1 Sigma(+), 1,3 Pi, and 3 Sigma(+) states of ZnO and ZnS, using extended Gaussian basis sets and incorporating correlation using both configuration-interaction and coupled pair (CPF) methods. Relativistic corrections (Darwin plus mass velocity), included using first-order perturbation theory, are relatively small. At the CPF level, both ZnO and ZnS have 1 Sigma(+) ground states, with the 3 Pi state lying 209 and 2075/cm higher, respectively. The 3 Sigma(+) state lies about 1.5 eV higher in ZnO and 2.1 eV higher in ZnS. The 1,3 Pi states are relatively close together since the exchange splitting is small with the sigma electron localized on Zn and the pi electron on oxygen (or sulfur).

  16. Investigation of intrinsic defect magnetic properties in wurtzite ZnO materials

    Science.gov (United States)

    Fedorov, A. S.; Visotin, M. A.; Kholtobina, A. S.; Kuzubov, A. A.; Mikhaleva, N. S.; Hsu, Hua Shu

    2017-10-01

    Theoretical and experimental investigations of the ferromagnetism induced by intrinsic defects inside wurtzite zinc oxide structures are performed using magnetic field-dependent circular dichroism (MCD-H), direct magnetization measurement (M-H) by superconducting quantum interference device (SQUID) as well as by generalized gradient density functional theory (GGA-DFT). To investigate localized magnetic moments of bulk material intrinsic defects - vacancies, interstitial atoms and Frenkel defects, various-size periodic supercells are calculated. It is shown that oxygen interstitial atoms (Oi) or zinc vacancies (Znv) generate magnetic moments of 1,98 и 1,26 μB respectively, however, the magnitudes are significantly reduced when the distance between defects increases. At the same time, the magnetic moments of oxygen Frenkel defects are large ( 1.5-1.8 μB) and do not depend on the distance between the defects. It is shown that the origin of the induced ferromagnetism in bulk ZnO is the extra spin density on the oxygen atoms nearest to the defect. Also dependence of the magnetization of ZnO (10 1 ̅ 0) and (0001) thin films on the positions of Oi and Znv in subsurface layers were investigated and it is shown that the magnetic moments of both defects are significantly different from the values inside bulk material. In order to check theoretical results regarding the defect induced ferromagnetism in ZnO, two thin films doped by carbon (C) and having Zn interstitials and oxygen vacancies were prepared and annealed in vacuum and air, respectively. According to the MCD-H and M-H measurements, the film, which was annealed in air, exhibits a ferromagnetic behavior, while the other does not. One can assume annealing of ZnO in vacuum should create oxygen vacancies or Zn interstitial atoms. At that annealing of the second C:ZnO film in air leads to essential magnetization, probably by annihilation of oxygen vacancies, formation of interstitial oxygen atoms or zinc vacancies

  17. Critical Temperature for the Conversion from Wurtzite to Zincblende of the Optical Emission of InAs Nanowires

    KAUST Repository

    Rota, Michele B.

    2017-07-12

    One hour annealing at 300 degrees C changes the optical emission characteristics of InAs nanowires (NWs) from the wurtzite (WZ) phase into that of zincblende (ZB). These results are accounted for by the conversion of a small fraction of the NW WZ metastable structure into the stable ZB structure. Several paths toward the polytype transformation in the configuration space are also demonstrated using first-principles calculations. For lower annealing temperatures, emission which is likely related to WZ polytypes is observed at energies that agree with theoretical predictions. These results demonstrate severe constraints on thermal processes to which devices made from InAs WZ NWs can be exposed.

  18. Structural Phase Transitions in High-Pressure Wurtzite to Rocksalt Phase in GaN and SiC

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, H. Y.; Gao, Fei; Wang, Lumin M.; Zu, Xiaotao T.; Zhang, Yanwen; Weber, William J.

    2008-06-16

    Ab initio molecular dynamics simulations are employed to study the atomistic mechanisms and pathways of high-pressure phase transformation in GaN and SiC. Our simulations bring a fundamental level of understanding of the wurtzite to rocksalt phase transformation that undergoes inhomogeneous displacements via a tetragonal atomic configuration, and suggest that the transition path may be independent of the presence of d electrons on the cation in GaN. The discrepancies between experimental and theoretical studies of transition paths are discussed.

  19. Brain metastases from malignant melanoma; ZNS-Metastasen beim malignen Melanom

    Energy Technology Data Exchange (ETDEWEB)

    Willner, J. [Wuerzburg Univ. (Germany). Klinik und Poliklinik fuer Strahlentherapie; Bohndorf, W. [Wuerzburg Univ. (Germany). Klinik und Poliklinik fuer Strahlentherapie

    1995-03-01

    Between 1985 and 1993 30 patients underwent radiation therapy for brain metastases from malignant melanoma. In 9 patients they had been surgically resected. All except 1 patient received whole brain irradiation with a total dose of 20 to 46 Gy/2 to 5 weeks using daily fractions of 2,0 to 4,0 Gy. In 5 patients a local boost of 20 to 25 Gy/2 weeks was administered. Survival rates were compared using the Cox-method. Univariate and multivariate analyses were performed to define prognostic subgroups. In 6/30 patients (20%) brain metastases were diagnosed at the time of primary manifestation of melanoma. In 83% of patients brain metastases developed during the first 5 years following primary diagnosis. Late manifestation was observed (18 years). Overall survival rate of the whole group was 39% at 6 months and 23% at 1 year. Univariate analysis revealed that age at diagnosis of brain metastases, time to manifestation, number of intracranial metastases and existence of extracerebral distant metastases had significant influence on survival. Sex was not found to influence survival rate. Multivariate analysis identified the existence of extracerebral distant metastases at the time of diagnosis of brain metastases as the most important prognostic factor for survival, followed by age and surgical resection. The role of fractionation was studied separately in a subgroup of patients receiving whole brain irradiation to a total dose of 39 to 42 Gy. Survival rates deteriorated when overall treatment time exceeded 3 weeks. (orig./MG) [Deutsch] Zwischen 1985 und 1993 wurden 30 Patienten mit ZNS-Metastasen bei malignem Melanom einer strahlentherapeutischen Behandlung unterzogen. Bei neun Patienten war eine operative Metastasenresektion vorausgegangen. Alle bis auf einen Patienten erhielten eine Ganzschaedelbestrahlung mit 20 bis 46 Gy in zwei bis fuenf Wochen bei Einzeldosen von 2,0 bis 4,0 Gy. In fuenf Faellen erfolgte eine lokale Aufsaettigung mit 20 bis 25 Gy/2 Wochen. Die

  20. Structural, electronic and magnetic properties of transition metal atom-doped ZnS dilute magnetic semiconductors: A first-principles study

    Energy Technology Data Exchange (ETDEWEB)

    Yin, Zhu-Hua [College of Physics and Information Technology, Shaanxi Normal University, Xian, 710119, Shaanxi (China); Zhang, Jian-Min, E-mail: jmzhang@snnu.edu.cn [College of Physics and Information Technology, Shaanxi Normal University, Xian, 710119, Shaanxi (China); Xu, Ke-Wei [State Key Laboratory for Mechanical Behavior of Materials, Xian Jiaotong University, Xian, 710049, Shaanxi (China)

    2016-11-01

    The spin-polarized first-principles calculations are performed to study the structural, electronic and magnetic properties of a single and two identical transition metal (TM) atoms X (X = V, Cr, Mn, Fe, Co and Ni) doped ZnS dilute magnetic semiconductors (DMS). The single V-, Cr-, Fe- and Ni-doped ZnS systems exhibit the magnetic half-metallic (HM) characters, while Mn- and Co-doped ZnS systems display magnetic semiconducting characters. For two identical TM atoms doped ZnS systems, the two identical V, Cr and Ni atoms are in a ferromagnetic (FM) coupling under the double-exchange (DE) mechanism, leading V-, Cr- and Ni-doped ZnS systems to be HM with FM coupling. While two identical Mn- and Co-doped ZnS systems are semiconductors with antiferromagnetic (AFM) coupling consisting with the superexchange (SE) mechanism. Specifically, two identical Fe atoms display a competition between the SE and DE mechanisms. The Zn{sub 70}Fe{sub 2}S{sub 72} system is metal with AFM coupling at the nearest separation of two Fe atoms while HM with FM coupling at the farther separations of two Fe atoms. - Graphical abstract: The 3 × 2 × 3 supercell containing 72 formula units of zincblende ZnS. Red (Green) balls represent the S (Zn) atoms. One TM atom or two identical TM atoms X (X = V, Cr, Mn, Fe, Co or Ni) to substitute for one Zn atom at position 0 or two Zn atoms at positions 0 and i (i = 1, 2, 3 or 4). - Highlights: • A single V, Cr, Fe or Ni (Mn or Co) atoms doped ZnS are magnetic HM (magnetic semiconductor). • Two V, Cr or Ni (two Mn or Co) atoms doped ZnS are FM HM (AFM semiconductor). • Two Fe atoms doped ZnS are AFM metal (FM HM) at the nearest (farther) separations.

  1. Controlled extracellular biosynthesis of ZnS quantum dots by sulphate reduction bacteria in the presence of hydroxypropyl starch as a mediator

    Science.gov (United States)

    Qi, Shiyue; Zhang, Mi; Guo, Xingming; Yue, Lei; Wang, Jia; Shao, Ziqiang; Xin, Baoping

    2017-06-01

    Metal sulphide quantum dots (QDs) have broad applications. Sulphate-reducing bacteria (SRB) have been recognized as synthesizers of metal sulphides, with the characteristics of a high-production efficiency and easy product harvest. However, SRB are incapable of synthesizing metal sulphide QDs. In the present study, cheap hydroxypropyl starch (HPS) was used to assist SRB in manufacturing the ZnS QDs. The results exhibited that the HPS accelerated the growth of SRB and reduction of SO4 2+ into S2-, while it blocked the precipitation between S2- and Zn2+ to control the nucleation and growth of ZnS, resulting in the formation of ZnS QDs. When the HPS concentration increased from 0.2 to 1.6 g/L, the average crystal size (ACS) of ZnS QDs dropped from 5.95 to 3.34 nm, demonstrating the controlled biosynthesis of ZnS QDs. The ZnS QDs were coated or adhered to by both HPS and proteins, which played an important role in the controlled biosynthesis of ZnS QDs. The remarkable blue shift of the narrow UV absorption peak was due to the quantum confinement effect. The sequential variation in the colour of the photoluminescence spectrum (PL) from red to yellow suggested a tunable PL of the ZnS QDs. The current work demonstrated that SRB can fabricate the formation of ZnS QDs with a controlled size and tunable PL at a high-production rate of approximately 8.7 g/(L × week) through the simple mediation of HPS, with the yield being 7.46 times the highest yield in previously reported studies. The current work is of great importance to the commercialization of the biosynthesis of ZnS QDs.

  2. Engineering Gold Nanorod-Based Plasmonic Nanocrystals for Optical Applications

    KAUST Repository

    Huang, Jianfeng

    2015-09-01

    Plasmonic nanocrystals have a unique ability to support localized surface plasmon resonances and exhibit rich and intriguing optical properties. Engineering plasmonic nanocrystals can maximize their potentials for specific applications. In this dissertation, we developed three unprecedented Au nanorod-based plasmonic nanocrystals through rational design of the crystal shape and/or composition, and successfully demonstrated their applications in light condensation, photothermal conversion, and surface-enhanced Raman spectroscopy (SERS). The “Au nanorod-Au nanosphere dimer” nanocrystal was synthesized via the ligand-induced asymmetric growth of a Au nanosphere on a Au nanorod. This dimeric nanostructure features an extraordinary broadband optical absorption in the range of 400‒1400nm, and it proved to be an ideal black-body material for light condensation and an efficient solar-light harvester for photothermal conversion. The “Au nanorod (core) @ AuAg alloy (shell)” nanocrystal was built through the epitaxial growth of homogeneously alloyed AuAg shells on Au nanorods by precisely controlled synthesis. The resulting core-shell structured, bimetallic nanorods integrate the merits of the AuAg alloy with the advantages of anisotropic nanorods, exhibiting strong, stable and tunable surface plasmon resonances that are essential for SERS applications in a corrosive environment. The “high-index faceted Au nanorod (core) @ AuPd alloy (shell)” nanocrystal was produced via site-specific epitaxial growth of AuPd alloyed horns at the ends of Au nanorods. The AuPd alloyed horns are bound with high-index side facets, while the Au nanorod concentrates an intensive electric field at each end. This unique configuration unites highly active catalytic sites with strong SERS sites into a single entity and was demonstrated to be ideal for in situ monitoring of Pd-catalyzed reactions by SERS. The synthetic strategies developed here are promising towards the fabrication of

  3. Biomolecularly capped uniformly sized nanocrystalline materials: glutathione-capped ZnS nanocrystals

    Science.gov (United States)

    Torres-Martínez, Claudia L.; Nguyen, Liem; Kho, Richard; Bae, Weon; Bozhilov, Krassimir; Klimov, Victor; Mehra, Rajesh K.

    1999-09-01

    Micro-organisms such as bacteria and yeasts form CdS to detoxify toxic cadmium ions. Frequently, CdS particles formed in yeasts and bacteria were found to be associated with specific biomolecules. It was later determined that these biomolecules were present at the surface of CdS. This coating caused a restriction in the growth of CdS particles and resulted in the formation of nanometre-sized semiconductors (NCs) that exhibited typical quantum confinement properties. Glutathione and related phytochelatin peptides were shown to be the biomolecules that capped CdS nanocrystallites synthesized by yeasts Candida glabrata and Schizosaccharomyces pombe. Although early studies showed the existence of specific biochemical pathways for the synthesis of biomolecularly capped CdS NCs, these NCs could be formed in vitro under appropriate conditions. We have recently shown that cysteine and cysteine-containing peptides such as glutathione and phytochelatins can be used in vitro to dictate the formation of discrete sizes of CdS and ZnS nanocrystals. We have evolved protocols for the synthesis of ZnS or CdS nanocrystals within a narrow size distribution range. These procedures involve three steps: (1) formation of metallo-complexes of cysteine or cysteine-containing peptides, (2) introduction of stoichiometric amounts of inorganic sulfide into the metallo-complexes to initiate the formation of nanocrystallites and finally (3) size-selective precipitation of NCs with ethanol in the presence of Na+. The resulting NCs were characterized by optical spectroscopy, high-resolution transmission electron microscopy (HRTEM), x-ray diffraction and electron diffraction. HRTEM showed that the diameter of the ZnS-glutathione nanocrystals was 3.45+/-0.5 nm. X-ray diffraction and electron diffraction analyses indicated ZnS-glutathione to be hexagonal. Photocatalytic studies suggest that glutathione-capped ZnS nanocrystals prepared by our procedure are highly efficient in degrading a test model

  4. Analysis of Zinc Sulphide (ZnS) and Cadmium Sulphide (CdS) thin ...

    African Journals Online (AJOL)

    Average optical and solid state properties of ZnS thin films include absorbance ranging from 0.049 to 0.110, transmittance 0.776 to 0.893, refractive index 1.63 to 2.02, film thickness 0.035 to 0.056μm and band gap 2.30 to 2.62 +0.05eV. For CdS thin films, the absorbance ranges from 0.067 to 0.080, transmittance 0.832 to ...

  5. Influence of Fe, Ni, and Cu Doping on the Photocatalytic Efficiency of ZnS: Implications for Prebiotic Chemistry

    CERN Document Server

    Wang, Wei

    2016-01-01

    The mineral sphalerite (ZnS) is a typical constituent at the periphery of submarine hydrothermal deposits on Earth. It has been frequently suggested to have played an important role in the prebiotic chemistry due to its prominent photocatalytic activity. Nevertheless, the need for {\\lambda} 450 nm light irradiation, the photocatalyst Zn1-xCuxS can drive the reduction of fumaric acid to produce succinic acid. Given the existence of this doped semiconductor in the hydrothermal vents on early Earth and its capability to utilize both UV and visible light, ZnS might have participated more efficiently than ever estimated in the prebiotic chemical evolution.

  6. Quinary wurtzite Zn-Ga-Ge-N-O solid solutions and their photocatalytic properties under visible light irradiation.

    Science.gov (United States)

    Xie, Yinghao; Wu, Fangfang; Sun, Xiaoqin; Chen, Hongmei; Lv, Meilin; Ni, Shuang; Liu, Gang; Xu, Xiaoxiang

    2016-01-12

    Wurtzite solid solutions between GaN and ZnO highlight an intriguing paradigm for water splitting into hydrogen and oxygen using solar energy. However, large composition discrepancy often occurs inside the compound owing to the volatile nature of Zn, thereby prescribing rigorous terms on synthetic conditions. Here we demonstrate the merits of constituting quinary Zn-Ga-Ge-N-O solid solutions by introducing Ge into the wurtzite framework. The presence of Ge not only mitigates the vaporization of Zn but also strongly promotes particle crystallization. Synthetic details for these quinary compounds were systematically explored and their photocatalytic properties were thoroughly investigated. Proper starting molar ratios of Zn/Ga/Ge are of primary importance for single phase formation, high particle crystallinity and good photocatalytic performance. Efficient photocatalytic hydrogen and oxygen production from water were achieved for these quinary solid solutions which is strongly correlated with Ge content in the structure. Apparent quantum efficiency for optimized sample approaches 1.01% for hydrogen production and 1.14% for oxygen production. Theoretical calculation reveals the critical role of Zn for the band gap reduction in these solid solutions and their superior photocatalytic acitivity can be understood by the preservation of Zn in the structure as well as a good crystallinity after introducing Ge.

  7. Ionic liquids-mediated interactions between nanorods

    Science.gov (United States)

    Yu, Zhou; Zhang, Fei; Huang, Jingsong; Sumpter, Bobby G.; Qiao, Rui

    2017-10-01

    Surface forces mediated by room-temperature ionic liquids (RTILs) play an essential role in diverse applications including self-assembly, lubrication, and electrochemical energy storage. Therefore, their fundamental understanding is critical. Using molecular simulations, we study the interactions between two nanorods immersed in model RTILs at rod-rod separations where both structural and double layer forces are important. The interaction force between neutral rods oscillates as the two rods approach each other, similar to the classical structural forces. Such oscillatory force originates from the density oscillation of RTILs near each rod and is affected by the packing constraints imposed by the neighboring rods. The oscillation period and decay length of the oscillatory force are mainly dictated by the ion density distribution near isolated nanorods. When charges are introduced on the rods, the interaction force remains short-range and oscillatory, similar to the interactions between planar walls mediated by some protic RTILs reported earlier. Nevertheless, introducing net charges to the rods greatly changes the rod-rod interactions, e.g., by delaying the appearance of the first force trough and increasing the oscillation period and decay length of the interaction force. The oscillation period and decay length of the oscillatory force and free energy are commensurate with those of the space charge density near an isolated, charged rod. The free energy of rod-rod interactions reaches local minima (maxima) at rod-rod separations when the space charges near the two rods interfere constructively (destructively). The insight on the short-range interactions between nanorods in RTILs helps guide the design of novel materials, e.g., ionic composites based on rigid-rod polyanions and RTILs.

  8. Porphyrin coordination polymer nanospheres and nanorods

    Science.gov (United States)

    Wang, Zhongchun; Shelnutt, John A.; Medforth, Craig J.

    2013-09-10

    A porphyrin coordination polymer nanostructure comprising a network of pyridyl porphyrin molecules and coordinating metal ions coordinatively bound through the pyridyl groups. In some embodiments, the porphyrins are metalloporphyrins. A variety of nanostructures are formed by the network polymer, including nanospheres, polygonal nanostructures, nanorods, and nanofibers, depending on a variety of factors including coordination metal ion, porphyrin type, metal of the metalloporphyrin, and degree of agitation during nanostructure formation. Reduction of coordinating metal ions may be used to form metal nanoparticles on the coordination polymer nanostructure.

  9. Porphyrin coordination polymer nanospheres and nanorods

    Science.gov (United States)

    Wang, Zhongchun; Shelnutt, John A.; Medforth, Craig J.

    2012-12-04

    A porphyrin coordination polymer nanostructure comprising a network of pyridyl porphyrin molecules and coordinating metal ions coordinatively bound through the pyridyl groups. In some embodiments, the porphyrins are metalloporphyrins. A variety of nanostructures are formed by the network polymer, including nanospheres, polygonal nanostructures, nanorods, and nanofibers, depending on a variety of factors including coordination metal ion, porphyrin type, metal of the metalloporphyrin, and degree of agitation during nanostructure formation. Reduction of coordinating metal ions may be used to form metal nanoparticles on the coordination polymer nanostructure.

  10. In vitro toxicity studies of polymer-coated gold nanorods

    Energy Technology Data Exchange (ETDEWEB)

    Rayavarapu, Raja G; Petersen, Wilma; Manohar, Srirang; Van Leeuwen, Ton G [Biomedical Photonic Imaging Group, MIRA Institute for Biomedical Technology and Technical Medicine, Faculty of Science and Technology, University of Twente, PO Box 217, 7500AE Enschede (Netherlands); Hartsuiker, Liesbeth; Otto, Cees [Medical Cell Biophysics, MIRA Institute for Biomedical Technology and Technical Medicine, Faculty of Science and Technology, University of Twente, PO Box 217, 7500AE Enschede (Netherlands); Chin, Patrick; Van Leeuwen, Fijs W B [Division of Diagnostic Oncology, Netherlands Cancer Institute, 1066 CX Amsterdam (Netherlands); Janssen, Hans, E-mail: S.Manohar@utwente.nl [Division of Cell Biology, The Netherlands Cancer Institute, 1066 CX Amsterdam (Netherlands)

    2010-04-09

    We evaluated cellular responses to polymer-treated gold nanorods, which were synthesized using the standard wet-chemistry method that utilizes hexadecyltrimethylammonium bromide (CTAB). The nanorod dispersions were coated with either polystyrene sulfonate (PSS) or polyethylene glycol (PEG). Two sizes of nanorods were tested, with optical responses peaking at 628 and 773 nm. The cells were from mammary adenocarcinoma (SKBR3), Chinese Hamster Ovary (CHO), mouse myoblast (C2C12) and Human Leukemia (HL60) cell lines. Their mitochondrial function following exposure to the nanorods were assessed using the MTS assay. We found PEGylated particles to have superior biocompatibility compared with PSS-coated nanorods, which showed substantial cytotoxicity. Electron microscopy showed no cellular uptake of PEGylated particles compared with their PSS counterparts. PEGylated gold nanorods also exhibited better dispersion stability in the presence of cell growth medium; PSS-coated rods tended to flocculate or cluster. In the case of the PSS particles, toxicity correlated with surface area across the two sizes of nanorods studied.

  11. Using a precursor in lamellar structure for the synthesis of uniform ZnS nanocrystals

    KAUST Repository

    Xu, Xinjiang

    2011-11-12

    Uniform ZnS nanocrystals of about 15 nm were prepared through a low temperature hydrothermal approach by treating Zn-PhPO nanosheets with Na 2S aqueous solution. Both the precursor and the final product were studied by the means of X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The photo-luminescent spectrum of the synthesized ZnS nanocrystals showed their good crystalline nature. Based on this study, the precursor structure-controlling effect was discussed, and in addition, the relevant factors possibly affecting the particle formation and the growth possessed were applied in the discussion to interpret the transformation mechanism. Further research showed that both the structure characters of the precursors and the mass transportation which occurred during the synthesis greatly affected the morphology and organization state of the final products. This research may provide some facts on the structure-controlling approaches along with a general method for the preparation of uniform sulfide nanocrystals. © Springer Science+Business Media B.V. 2011.

  12. Hugoniot and Pressure Induced Phase Changes in ZnS: A Theoretical Study.

    Science.gov (United States)

    Jyoti, G.; Joshi, K. D.; Gupta, Satish C.

    2001-06-01

    ZnS is known to transform from the ambient zinc blende structure (B3) to rocksalt structure (B1)around 12-16 GPa. In recent measurements upto 135 GPa, Uchino et al. (J.Phys. Chem. Solids 60, 827, 1999) observe anomaly in the Hugoniot behaviour between 75 to 99 GPa and associate it with melting and decomposition. Desgreniers et al. (Phy.Rev.B 61, 8726, 2000), however, report transformation of B1 phase to Cmcm structure at 96 GPa static pressure. In the present study we have calculated the Hugoniot of ZnS and analysed the stability of its various phases using ab initio FP-LAPW method. We correctly find the B3 to B1 phase change around 16 GPa. Around 96 GPa the rocksalt phase is higher in energy than the Cmcm phase, in agreement with Desgreniers et al. The distortion in B1 unit cell and fractional co-ordinates leading to the stability of Cmcm phase at 96 GPa is computed. Due to the high temperatures generated around these high pressures under shock conditions, one can not, however, rule out the possibility of shock induced melting . The calculated Hugoniot and the isotherm agree very well with the experimental data. The bulk moduli derived from the theoretical isotherm for the B3 and B1 phase are 71.26 and 112.84 GPa, respectively. Its pressure derivative for the two phases is 4.52 and 3.92.

  13. Surface modification of ZnS films by applying an external magnetic field in vacuum chamber

    Science.gov (United States)

    Ehsani, M. H.; Zarei Moghadam, R.; Rezagholipour Dizaji, H.; Kameli, P.

    2017-09-01

    In this paper, ZnS films were prepared using pulsed laser deposition technique in vacuum chamber in the presence and absence of an external magnetic field. The applied magnetic field effects on optical properties and film growth conditions were studied. For this reason, morphological, structural and optical properties of the grown films have been investigated by atomic force microscopy, field emission scanning electron microscopy, x-ray diffraction and UV-vis spectroscopy analysis techniques. The structural studies revealed that the ZnS films deposited at 200 °C crystallized in hexagonal structure. The results showed the improvement of the film crystallinity upon grain size increment and the surface morphology modification resulted from applying an external magnetic field. Using the UV-vis spectroscopy data, absorption coefficient (α), refractive index (n) and extinction coefficient (k) of the samples were calculated. The band gap energy (E g) and Urbach energy were also calculated by Tauc, ASF and DASF methods. The results show that by applying magnetic field, the band gap and Urbach energies reduced, due to improvement in the film crystallinity. For describing the magnetic field effect, a simulation of applied magnetic field effect on vapor flux in vacuum chamber was performed using Multi-Physics COMSOL package.

  14. CdS and ZnS quantum dots embedded in hyaluronic acid films

    Energy Technology Data Exchange (ETDEWEB)

    Khachatryan, G.; Khachatryan, K. [Department of Chemistry, Agricultural University, Balicka 122, 30-149 Krakow (Poland); Stobinski, L. [Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 48/52, 01-224 Warsaw (Poland); Faculty of Materials Science and Engineering, Warsaw University of Technology, Woloska 141, 02-507 Warszawa (Poland)], E-mail: lstob@ichf.edu.pl; Tomasik, P.; Fiedorowicz, M. [Department of Chemistry, Agricultural University, Balicka 122, 30-149 Krakow (Poland); Lin, H.M. [Department of Materials Engineering, Tatung University, Taipei 104, Taiwan, ROC (China)

    2009-07-29

    An in situ synthesis of ZnS and CdS quantum dots (QDs) in an aqueous solution of sodium hyaluronate (Hyal) produced foils emitting light on excitation with a UV light. The wavelength of emission was only slightly QDs size and more QDs concentration dependent and reached up to {approx}320 nm in the case of ZnS and {approx}400-450 nm in the case of CdS. Nanoparticles remained as non-agglomerated 10-20 nm nanoclusters. CdS/Hyal and ZnS/Hyal-QDs biocomposites were characterized using photoluminescence (PL), IR spectrometric techniques, and Transmission Electron Microscopy (TEM). The absolute molecular weights, radii of gyration, R{sub g}, and thermodynamic properties of the obtained foils are given. Electric resistivity studies performed for the hyaluronic foil in the 100-1000 V range have revealed that the hyaluronate foil has very weak conducting properties and QDs only insignificantly affect those properties as QDs practically did not interact with the foil. Size exclusion chromatography showed a decrease in the molecular weight of the hyaluronate after generation of QDs in its solution, particularly in the lower molecular fraction of the hyaluronate. The generation of CdS QDs was more destructive for the polysaccharide matrix.

  15. Optimizing ZnS/6LiF scintillators for wavelength-shifting-fiber neutron detectors

    Energy Technology Data Exchange (ETDEWEB)

    Crow, Lowell [ORNL; Funk, Loren L [ORNL; Hannan, Bruce W [ORNL; Hodges, Jason P [ORNL; Riedel, Richard A [ORNL; Wang, Cai-Lin [ORNL

    2016-01-01

    In this paper we compare the performance of grooved and flat ZnS/6LiF scintillators in a wavelength shifting-fiber (WLSF) detector. Flat ZnS/6LiF scintillators with the thickness L=0.2-0.8 mm were characterized using photon counting and pulse-height analysis and compared to a grooved scintillator of approximately 0.8 mm thick. While a grooved scintillator considerably increases the apparent thickness of the scintillator to neutrons for a given coating thickness, we find that the flat scintillators perform better than the grooved scintillators in terms of both light yield and neutron detection efficiency. The flat 0.8-mm-thick scintillator has the highest light output, and it is 52% higher compared with a grooved scintillator of same thickness. The lower light output of the grooved scintillator as compared to the flat scintillator is consistent with the greater scintillator-WLSF separation and the much larger average emission angle of the grooved scintillator. We also find that the average light cone width, or photon travel-length as measured using time-of-flight powder diffraction of diamond and vanadium, decreases with increasing L in the range of L=0.6-0.8 mm. This result contrasts with the traditional Swank diffusion model for micro-composite scintillators, and could be explained by a decrease in photon diffusion-coefficient or an increase in micro-particle content in the flat scintillator matrix for the thicker scintillators.

  16. Photonic nanorods with magnetic responsiveness regulated by lattice defects.

    Science.gov (United States)

    Ma, Huiru; Tang, Kai; Luo, Wei; Ma, Lin; Cui, Qian; Li, Wei; Guan, Jianguo

    2017-03-02

    Herein, we use experiments and numerical simulations to demonstrate a novel class of magnetically responsive photonic crystals (MRPCs) based on photonic nanorods which exhibit multiple optical properties in a magnetic field (H) due to their fixed photonic nanorods and H-tunable lattice defects. As an example, superparamagnetic Fe 3 O 4 @polyvinyl pyrrolidone (PVP)@SiO 2 photonic nanorods were fabricated through a polyacrylic acid-catalysed hydrolysis-condensation reaction of γ-mercaptopropyltrimethoxysilane around chain-like PC templates formed by monodispersed Fe 3 O 4 @PVP particles under H. For the as-proposed MRPCs, with increasing H, the photonic nanorods firstly experience in situ rotational orientation along the H direction, followed by alignment and connection into long parellel nanochains via the spaces between the ends of adjacent photonic nanorods (named lattice defects). As the number and size of the lattice defects changes with H, the MRPCs exhibit visible red-shifts and blue-shifts of their diffraction wavelengths in addition to monotonous enhancement of their diffraction peaks. These optical properties are very different from those of previously reported MRPCs. The diversity of the structural colors and brightness of these MRPCs with H is also closely dependent on the applied time of H, the concentration of the photonic nanorods, and the structural parameters of the nanorods, including nanorod length and interparticle distance. Due to the difficult duplication of their various optical properties as well as their easy fabrication and low cost, MRPCs based on photonic nanorods are suitable for wide applications in forgery protection and information encryption.

  17. Synthesis and characterization of ZnS with controlled amount of S vacancies for photocatalytic H2 production under visible light.

    Science.gov (United States)

    Wang, Gang; Huang, Baibiao; Li, Zhujie; Lou, Zaizhu; Wang, Zeyan; Dai, Ying; Whangbo, Myung-Hwan

    2015-02-25

    Controlling amount of intrinsic S vacancies was achieved in ZnS spheres which were synthesized by a hydrothermal method using Zn and S powders in concentrated NaOH solution with NaBH4 added as reducing agent. These S vacancies efficiently extend absorption spectra of ZnS to visible region. Their photocatalytic activities for H2 production under visible light were evaluated by gas chromatograph, and the midgap states of ZnS introduced by S vacancies were examined by density functional calculations. Our study reveals that the concentration of S vacancies in the ZnS samples can be controlled by varying the amount of the reducing agent NaBH4 in the synthesis, and the prepared ZnS samples exhibit photocatalytic activity for H2 production under visible-light irradiation without loading noble metal. This photocatalytic activity of ZnS increases steadily with increasing the concentration of S vacancies until the latter reaches an optimum value. Our density functional calculations show that S vacancies generate midgap defect states in ZnS, which lead to visible-light absorption and responded.

  18. Observation of plasmon line broadening in single gold nanorods

    Science.gov (United States)

    Qiu, Le; Larson, Timothy A.; Smith, Danielle; Vitkin, Edward; Modell, Mark D.; Korgel, Brian A.; Sokolov, Konstantin V.; Hanlon, Eugene B.; Itzkan, Irving; Perelman, Lev T.

    2008-10-01

    Attempts to realize the important potential of gold nanorods as extremely bright molecular markers have been limited by the broad spectroscopic linewidths usually observed. We identify the origin of this broadening as inhomogeneous broadening due to the extreme sensitivity of the surface plasmon resonance to the nanorod aspect ratio. Using confocal light scattering spectroscopic microscopy, we observed the narrow homogeneously broadened plasmon lines of single gold nanorods and obtained the first quantitative measurements of this homogeneous broadening. We show that homogeneous broadening can be predicted from first principals.

  19. Facile Hydrogen Evolution Reaction on WO3Nanorods

    Directory of Open Access Journals (Sweden)

    Rajeswari Janarthanan

    2007-01-01

    Full Text Available AbstractTungsten trioxide nanorods have been generated by the thermal decomposition (450 °C of tetrabutylammonium decatungstate. The synthesized tungsten trioxide (WO3 nanorods have been characterized by XRD, Raman, SEM, TEM, HRTEM and cyclic voltammetry. High resolution transmission electron microscopy and X-ray diffraction analysis showed that the synthesized WO3nanorods are crystalline in nature with monoclinic structure. The electrochemical experiments showed that they constitute a better electrocatalytic system for hydrogen evolution reaction in acid medium compared to their bulk counterpart.

  20. Temperature dependence of exciton peak energies in ZnS, ZnSe, and ZnTe epitaxial films

    Science.gov (United States)

    Pässler, R.; Griebl, E.; Riepl, H.; Lautner, G.; Bauer, S.; Preis, H.; Gebhardt, W.; Buda, B.; As, D. J.; Schikora, D.; Lischka, K.; Papagelis, K.; Ves, S.

    1999-10-01

    High-quality ZnS, ZnSe, and ZnTe epitaxial films were grown on (001)-GaAs-substrates by molecular beam epitaxy. The 1s-exciton peak energy positions have been determined by absorption measurements from 2 K up to about room temperature. For ZnS and ZnSe additional high-temperature 1s-exciton energy data were obtained by reflectance measurements performed from 300 up to about 550 K. These complete E1s(T) data sets are fitted using a recently developed analytical model. The high-temperature slopes of the individual E1s(T) curves and the effective phonon temperatures of ZnS, ZnSe, and ZnTe are found to scale almost linearly with the corresponding zero-temperature energy gaps and the Debye temperatures, respectively. Various ad hoc formulas of Varshni type, which have been invoked in recent articles for numerical simulations of restricted E1s(T) data sets for cubic ZnS, are discussed.

  1. Dispersion of the second-order nonlinear susceptibility in ZnTe, ZnSe, and ZnS

    DEFF Research Database (Denmark)

    Wagner, Hans Peter; Kühnelt, M.; Langbein, Wolfgang Werner

    1998-01-01

    We have measured the absolute values of the second-harmonic generation (SHG) coefficient \\d\\ for the zinc-blende II-VI semiconductors ZnTe, ZnSe, and ZnS at room temperature. The investigated spectral region of the fundamental radiation lambda(F) ranges from 520 to 1321 nm using various pulsed...

  2. Effects of Various Parameters on Structural and Optical Properties of CBD-Grown ZnS Thin Films: A Review

    Science.gov (United States)

    Sinha, Tarkeshwar; Lilhare, Devjyoti; Khare, Ayush

    2018-02-01

    Zinc sulfide (ZnS) thin films deposited by chemical bath deposition (CBD) technique have proved their capability in a wide area of applications including electroluminescent and display devices, solar cells, sensors, and field emitters. These semiconducting thin films have attracted a much attention from the scientific community for industrial and research purposes. In this article, we provide a comprehensive review on the effect of various parameters on various properties of CBD-grown ZnS films. In the first part, we discuss the historical background of ZnS, its basic properties, and the advantages of the CBD technique. Detailed discussions on the film growth, structural and optical properties of ZnS thin films affected by various parameters, such as bath temperature and concentration, deposition time, stirring speed, complexing agents, pH value, humidity in the environment, and annealing conditions, are also presented. In later sections, brief information about the recent studies and findings is also added to explore the scope of research work in this field.

  3. Solar light driven enhanced photocatalytic degradation of brilliant green dye based on ZnS quantum dots

    Science.gov (United States)

    Kaur, Sharanjit; Sharma, Shelja; Umar, Ahmad; Singh, Surinder; Mehta, S. K.; Kansal, Sushil Kumar

    2017-03-01

    Herein, we report the successful synthesis, detailed characterization and solar-light driven photocatalytic degradation of zinc sulfide (ZnS) quantum dots. The ZnS quantum dots were synthesized in high yield by co-precipitation method using sodium dodecyl sulfate as a stabilizing agent. The as-synthesized ZnS quantum dots were characterized in detail in terms of their morphological, structural, compositional, thermal and optical properties. The detailed characterizations confirmed that the synthesized quantum dots are well-crystalline, possessing cubic phase of zinc blende structure, pure and exhibiting good optical properties. The synthesized quantum dots were further used as potential photocatalyst for the photocatalytic degradation of brilliant green dye under solar-light irradiation which exhibited 88% degradation. The process parameters, such as pH and catalyst dose, for the photocatalytic degradation of brilliant green dye was elaborately examined in order to evaluate the highest degradation rate of targeted dye. Further, the experimental data were fitted well in the pseudo-first order kinetic model. Finally, a possible mechanism for the photocatalytic degradation of brilliant green dye by ZnS quantum dots was also suggested.

  4. High figure-of-merit p-type transparent conductor, Cu alloyed ZnS via radio frequency magnetron sputtering

    Science.gov (United States)

    Maurya, Sandeep Kumar; Liu, Ya; Xu, Xiaojie; Woods-Robinson, Rachel; Das, Chandan; Ager, Joel W., III; Balasubramaniam, K. R.

    2017-12-01

    p-type transparent conducting Cu alloyed ZnS thin films from Cu{x} Zn{1-x} S targets (x = 0.1 , 0.2, 0.3, 0.4, and 0.5) were deposited on glass substrates via radio frequency sputtering. x-ray diffraction and TEM–SAED analysis show that all the films have sphalerite ZnS as the majority crystalline phase. In addition, films with 30% and 40% Cu show the presence of increasing amounts of crystalline Cu2S phase. Conductivity values  ⩾400 S cm-1 were obtained for the films having 30% and 40% Cu, with the maximum conductivity of 752 S cm-1 obtained for the film with 40% Cu. Temperature dependent electrical transport measurements indicate metallic as well as degenerate hole conductivity in the deposited films. The reflection-corrected transmittance of this Cu alloyed ZnS (40% Cu) film was determined to be  ⩾75% at 550 nm. The transparent conductor figure of merit (ΦTC ) of the Cu alloyed ZnS (40% Cu), calculated with the average value of transmittance between 1.5 to 2.5 eV, was  ≈276 μS .

  5. Effects of Various Parameters on Structural and Optical Properties of CBD-Grown ZnS Thin Films: A Review

    Science.gov (United States)

    Sinha, Tarkeshwar; Lilhare, Devjyoti; Khare, Ayush

    2017-10-01

    Zinc sulfide (ZnS) thin films deposited by chemical bath deposition (CBD) technique have proved their capability in a wide area of applications including electroluminescent and display devices, solar cells, sensors, and field emitters. These semiconducting thin films have attracted a much attention from the scientific community for industrial and research purposes. In this article, we provide a comprehensive review on the effect of various parameters on various properties of CBD-grown ZnS films. In the first part, we discuss the historical background of ZnS, its basic properties, and the advantages of the CBD technique. Detailed discussions on the film growth, structural and optical properties of ZnS thin films affected by various parameters, such as bath temperature and concentration, deposition time, stirring speed, complexing agents, pH value, humidity in the environment, and annealing conditions, are also presented. In later sections, brief information about the recent studies and findings is also added to explore the scope of research work in this field.

  6. [Synthesis and photoluminescent properties of core/shell structure ZnS : Mn/SiO2 nanocrystals].

    Science.gov (United States)

    Jiang, Dai-Xun; Cao, Li-Xin; Liu, Wei; Su, Ge; Qu, Hua; Sun, Yuan-Guang; Dong, Bo-Hua

    2010-03-01

    Mn-doped ZnS nanopatricles synthesized by solvothermal method were successfully coated with SiO2 shells of various thicknesses by hydrolysis reaction of tetraethyl orthosilicate (TEOS). The samples were characterized by X-ray diffraction (XRD), transmission electron microscopy images (TEM), X-ray photoelectron spectroscopy (XPS) and the room temperature photoluminescence (PL) spectra. When the ZnS : Mn nanoparticles were coated with SiO2 shells, an obvious increase in particle size and a clear shell of SiO2 can be observed. The XPS measurement also gave the evidence for the core/shell structure of ZnS : Mn/SiO2 nanoparticles. Because the surface modification effect and the decrease in luminescent centers effect are concurrent in the SiO2 shells, the Mn emission intensity first increased and then decreased with the thickening of the SiO2 shell. The intensity, which attained its maxium at 5 shell thickness, was as 7 times as that for the bare ZnS : Mn nanoparticles.

  7. Controlled synthesis of Eu2+ and Eu3+ doped ZnS quantum dots and their photovoltaic and magnetic properties

    Directory of Open Access Journals (Sweden)

    Sabit Horoz

    2016-04-01

    Full Text Available Eu-doped ZnS quantum dots (QDs have been synthesized by wet-chemical method and found to form in zinc blende (cubic structure. Both Eu2+ and Eu3+ doped ZnS can be controllably synthesized. The Eu2+ doped ZnS QDs show broad photoluminescence emission peak around 512 nm, which is from the Eu2+ intra-ion transition of 4f6d1 – 4f7, while the Eu3+ doped samples exhibit narrow emission lines characteristic of transitions between the 4f levels. The investigation of the magnetic properties shows that the Eu3+ doped samples exhibit signs of ferromagnetism, on the other hand, Eu2+ doped samples are paramagnetic of Curie-Weiss type. The incident photon to electron conversion efficiency is increased with the Eu doping, which suggests the QD solar cell efficiency can be enhanced by Eu doping due to widened absorption windows. This is an attractive approach to utilize benign and environmentally friendly wide band gap ZnS QDs in solar cell technology.

  8. Magnetic core-shell ZnFe2O4/ZnS nanocomposites for photocatalytic application under visible light.

    Science.gov (United States)

    Yoo, Pil Sun; Amaranatha Reddy, D; Jia, YueFa; Bae, Sang Eun; Huh, Seong; Liu, Chunli

    2017-01-15

    Magnetic core-shell ZnFe2O4/ZnS composites were synthesized through a two-step chemical process including the hydrothermal and the co-precipitation methods. The structural characterization revealed that the composites consisted of a layer of ZnS clusters on the surface of ZnFe2O4 nanoparticles. The band gap energy of the composite was estimated to be 2.2eV through the Kubelka-Munk plot, implying the possible application as a photocatalyst under the visible light radiation. The improved photocatalytic efficiency of the ZnFe2O4/ZnS composites was confirmed through the photocatalytic degradation of Methyl Orange. The increased absorption of the visible light and the enhanced separation of the electron-hole pairs due to the relative energy band positions in ZnFe2O4 and ZnS are considered as the main advantages. Additionally, the moderate magnetization of the ZnFe2O4 core insured the easy magnetic collection of the composite materials without affecting the photocatalytic performance. Our results showed that ZnFe2O4-based nanocomposites could be used as an effective and magnetic retrievable photocatalyst. Copyright © 2016 Elsevier Inc. All rights reserved.

  9. Controlled synthesis of Eu2+ and Eu3+ doped ZnS quantum dots and their photovoltaic and magnetic properties

    Science.gov (United States)

    Horoz, Sabit; Yakami, Baichhabi; Poudyal, Uma; Pikal, Jon M.; Wang, Wenyong; Tang, Jinke

    2016-04-01

    Eu-doped ZnS quantum dots (QDs) have been synthesized by wet-chemical method and found to form in zinc blende (cubic) structure. Both Eu2+ and Eu3+ doped ZnS can be controllably synthesized. The Eu2+ doped ZnS QDs show broad photoluminescence emission peak around 512 nm, which is from the Eu2+ intra-ion transition of 4f6d1 - 4f7, while the Eu3+ doped samples exhibit narrow emission lines characteristic of transitions between the 4f levels. The investigation of the magnetic properties shows that the Eu3+ doped samples exhibit signs of ferromagnetism, on the other hand, Eu2+ doped samples are paramagnetic of Curie-Weiss type. The incident photon to electron conversion efficiency is increased with the Eu doping, which suggests the QD solar cell efficiency can be enhanced by Eu doping due to widened absorption windows. This is an attractive approach to utilize benign and environmentally friendly wide band gap ZnS QDs in solar cell technology.

  10. DFT plus U studies of Cu doping and p-type compensation in crystalline and amorphous ZnS

    NARCIS (Netherlands)

    Pham, Hieu H.; Barkema, Gerard T.; Wang, Lin-Wang

    2015-01-01

    Zinc sulfide is an excellent candidate for the development of a p-type transparent conducting material that has great demands in solar energy and optoelectronic applications. Doping with Cu is one potential way to make ZnS p-type while preserving its optical transparency for the solar spectrum;

  11. Templating gold nanorods with liquid crystalline DNA

    Science.gov (United States)

    De Sio, Luciano; Annesi, Ferdinanda; Placido, Tiziana; Comparelli, Roberto; Bruno, Vincenzo; Pane, Alfredo; Palermo, Giovanna; Curri, Maria Lucia; Umeton, Cesare; Bartolino, Roberto

    2015-02-01

    A liquid crystalline, negatively charged, whole-genome DNA is exploited to organize positively charged gold nanorods (GNRs) by means of electrostatic interaction. A mesoscopic alignment of the composite system along a preferred direction is obtained by casting a droplet of the DNA-nanorods solution onto an untreated glass substrate. Gel electrophoresis analysis enables evaluating the effective electric charge of the system, thus minimizing the DNA fragmentation. Polarized optical microscopy, combined with transmission and scanning electron microscopy, shows that, up to 20% in weight of GNR solution, the system exhibits both a long range order, induced by the liquid crystalline phase of the DNA, and a nanoscale organization, due to the DNA self-assembly. These evidences are confirmed by a polarized spectral analysis, which also points out that the optical properties of GNRs strongly depend on the polarization of the impinging probe light. The capability to organize plasmonic nanoparticles by means of DNA material represents a significant advance towards the realization of life science inspired optical materials.

  12. Structural, optical and magnetic properties of Sn doped ZnS nano powders prepared by solid state reaction

    Science.gov (United States)

    Kumar, K. Chaitanya; Rao, N. Madhusudhana; Kaleemulla, S.; Rao, G. Venugopal

    2017-10-01

    Tin doped ZnS powders (Zn1-xSnxS, x = 0.00, 0.02, 0.05&0.08) were synthesized by a simple Solid state reaction and were characterized by Powder X-ray diffractometer (XRD), UV-Vis-NIR diffuse reflectance spectrophotometer, fluorescence spectrophotometer, scanning electron microscope (SEM) and vibrating sample magnetometer (VSM). The XRD studies revealed that no change in crystal structure was observed by the substitution of Sn into ZnS lattice. The crystallite size was calculated by Scherrer's formula and found that the crystallize size of Sn doped ZnS powders were in the range of 35-45 nm. From the diffused reflectance spectra, the band gap values of Zn1-xSnxS powders were estimated, and they were found to be in the range of 3.53-3.58 eV. The pure ZnS particles showed higher optical absorption in visible region than that of Sn doped ZnS nano particles. The Photoluminescence (PL) spectra of Zn1-xSnxS powders were recorded in the range of 400-700 nm with an excitation wavelength of 360 nm. The Zn1-xSnxS powders exhibited ferromagnetism at low temperature (100 K) and super paramagnetism at room temperature (300 K). The strength of magnetization increased with increase of Sn doping concentration from 0.015 emu/g to 0.18 emu/g, when x increased from 0.00-0.05.

  13. Laser-assisted synthesis, and structural and thermal properties of ZnS nanoparticles stabilised in polyvinylpyrrolidone

    Energy Technology Data Exchange (ETDEWEB)

    Onwudiwe, Damian C. [Chemical Resource Beneficiation (CRB) Research Focus Area, North-West University, Private Bag X6001, Potchefstroom 2520 (South Africa); Krüger, Tjaart P.J. [Department of Physics, University of Pretoria, Private Bag X20, Hatfield 0028 (South Africa); Jordaan, Anine [Laboratory for Electron Microscopy, CRB Research Focus Area, North-West University, Private Bag X6001, Potchefstroom 2520 (South Africa); Strydom, Christien A., E-mail: christien.strydom@nwu.ac.za [Chemical Resource Beneficiation (CRB) Research Focus Area, North-West University, Private Bag X6001, Potchefstroom 2520 (South Africa)

    2014-12-01

    Graphical abstract: - Highlights: • Zinc sulphide (ZnS) nanoparticles were synthesised by laser irradiation. • The structural and morphological properties of the prepared samples were analysed. • Larger particles were obtained by using Na{sub 2}S instead of TAA as the sulphur source. • Phonon softening and line broadening of the peaks were observed. • Size reduction occurred in the samples obtained from both sources. - Abstract: Zinc sulphide (ZnS) nanoparticles have been synthesised by a green approach involving laser irradiation of an aqueous solution of zinc acetate (Znac{sub 2}) and sodium sulphide (Na{sub 2}S·9H{sub 2}O) or thioacetamide (TAA) in polyvinylpyrrolidone (PVP). The structural and morphological properties of the prepared samples were analysed using a transmission electron microscope, TEM, a high resolution transmission electron microscope, HRTEM, X-ray diffraction, and Raman spectroscopy. The thermal properties were studied using a simultaneous thermal analyser (SDTA). Better dispersed and larger particles were obtained by using sodium sulphide (Na{sub 2}S) instead of TAA as the sulphur source. X-ray diffraction (XRD) analyses and Raman measurement show that the particles have a cubic structure, which is usually a low temperature phase of ZnS. There were phonon softening and line broadening of the peaks which are attributed to the phonon confinement effect. The average crystallite size of the ZnS nanoparticles estimated from the XRD showed a reduction in size from 13.62 to 10.42 nm for samples obtained from Na{sub 2}S, and 9.13 to 8.16 nm for samples obtained from TAA, with an increase in the time of irradiation. The thermal stability of PVP was increased due to the incorporation of the ZnS nanoparticles in the matrices. The absorption spectra showed that the nanoparticles exhibit quantum confinement effects.

  14. Interactions of aqueous amino acids and proteins with the (110) surface of ZnS in molecular dynamics simulations

    Energy Technology Data Exchange (ETDEWEB)

    Nawrocki, Grzegorz; Cieplak, Marek [Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw (Poland)

    2014-03-07

    The growing usage of nanoparticles of zinc sulfide as quantum dots and biosensors calls for a theoretical assessment of interactions of ZnS with biomolecules. We employ the molecular-dynamics-based umbrella sampling method to determine potentials of mean force for 20 single amino acids near the ZnS (110) surface in aqueous solutions. We find that five amino acids do not bind at all and the binding energy of the remaining amino acids does not exceed 4.3 kJ/mol. Such energies are comparable to those found for ZnO (and to hydrogen bonds in proteins) but the nature of the specificity is different. Cysteine can bind with ZnS in a covalent way, e.g., by forming the disulfide bond with S in the solid. If this effect is included within a model incorporating the Morse potential, then the potential well becomes much deeper—the binding energy is close to 98 kJ/mol. We then consider tryptophan cage, a protein of 20 residues, and characterize its events of adsorption to ZnS. We demonstrate the relevance of interactions between the amino acids in the selection of optimal adsorbed conformations and recognize the key role of cysteine in generation of lasting adsorption. We show that ZnS is more hydrophobic than ZnO and that the density profile of water is quite different than that forming near ZnO—it has only a minor articulation into layers. Furthermore, the first layer of water is disordered and mobile.

  15. Investigation on one-pot hydrothermal synthesis, structural and optical properties of ZnS quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Nirmala Jothi, N.S. [Department of Physics, Loyola College, Chennai 600 034 (India); Joshi, Amish G. [CSIR – National Physical Laboratory, Dr. K.S. Krishnan Road, New Delhi 110 012 (India); Jerald Vijay, R. [Department of Physics, Saveetha School of Engineering, Saveetha University, Chennai 602105 (India); Muthuvinayagam, A. [Department of Physics, Loyola College, Chennai 600 034 (India); Sagayaraj, P., E-mail: psagayaraj@hotmail.com [Department of Physics, Loyola College, Chennai 600 034 (India)

    2013-02-15

    The advantage of hydrothermal synthesis of semiconductor quantum dots (QDs) over the control of particles size, morphology and stability is reported here. In a typical synthesis procedure, the zinc and sulfur precursor molar ratio of 1:3 was used in an aqueous solution at 150 °C. The cubic phase of ZnS with average particles size of 5 nm was confirmed and estimated from the X-ray diffraction (XRD) analysis. The composition and purity of the sample were analyzed from (energy dispersive-ray analysis) EDAX and (X-ray photoelectron spectroscopy analysis) XPS spectra. The absorption spectrum shows the large shift in the absorption band over 90 nm due to the quantum confinement of carriers. The emission spectrum of quantum dots carry more evidence on the presence of shallow trap, deep trap in the band gap of the material responsible for weak emission in the spectral region of 450–500 nm. High resolution transmission electron microscope and scanning electron microscope studies reveal the structural and morphological features of ZnS with slightly distorted spherical morphology. We found that the coordinating ability of solvent strongly influences the reaction process and morphology of the products. - Graphical abstract: TEM and HRTEM images of pure ZnS quantum dots by a facile hydrothermal technique. (iii, iv) HRTEM images of one dimensional ZnS with lattices fringe. Highlights: ► Preparation of high quality ZnS quantum dots reported. ► Low cost wet chemical method employed. ► Structural, optical and morphological studies performed.

  16. Growth and structure analysis of tungsten oxide nanorods using environmental TEM.

    Science.gov (United States)

    Tokunaga, Tomoharu; Kawamoto, Tadashi; Tanaka, Kenta; Nakamura, Naohiro; Hayashi, Yasuhiko; Sasaki, Katsuhiro; Kuroda, Kotaro; Yamamoto, Takahisa

    2012-01-25

    WO3 nanorods targeted for applications in electric devices were grown from a tungsten wire heated in an oxygen atmosphere inside an environmental transmission electron microscope, which allowed the growth process to be observed to reveal the growth mechanism of the WO3 nanorods. The initial growth of the nanorods did not consist of tungsten oxide but rather crystal tungsten. The formed crystal tungsten nanorods were then oxidized, resulting in the formation of the tungsten oxide nanorods. Furthermore, it is expected that the nanorods grew through cracks in the natural surface oxide layer on the tungsten wire.

  17. Enhanced Photoluminescence in Acetylene-Treated ZnO Nanorods

    National Research Council Canada - National Science Library

    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

    2016-01-01

    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...

  18. Novel nanorods based on PANI / PEO polymers using electrospinning method

    Science.gov (United States)

    Al-Hazeem, Nabeel Z.; Ahmed, Naser M.; Matjafri, M. Z.; Sabah, Fayroz A.; Rasheed, Hiba S.

    2016-07-01

    In this work, we fabricated nanorods by applying an electric potential on poly (ethylene oxide) (PEO) and polyaniline (PANI) as a polymeric solution by electrospinning method. Testing was conducted on the samples by field emission scanning Electron microscope (FE-SEM), X-ray diffraction (XRD) and Photoluminescence. And the results showed the emergence of nanorods in the sample within glass substrate. Diameters of nanorods have ranged between (52.78-122.40)nm And a length of between (1.15 - 1.32)μm. The emergence of so the results are for the first time, never before was the fabrication of nanorods for polymers using the same method used in this research.

  19. Novel nanorods based on PANI / PEO polymers using electrospinning method

    Energy Technology Data Exchange (ETDEWEB)

    Al-Hazeem, Nabeel Z., E-mail: nabeelnano333@gmail.com [Nano-Optoelectronics Research and Technology Laboratory, School of Physics, Universiti Sains Malaysia, 11800 USM, Penang (Malaysia); Ministry of Education, the General Directorate for Educational Anbar (Iraq); Ahmed, Naser M.; Matjafri, M. Z. [Nano-Optoelectronics Research and Technology Laboratory, School of Physics, Universiti Sains Malaysia, 11800 USM, Penang (Malaysia); Sabah, Fayroz A. [Nano-Optoelectronics Research and Technology Laboratory, School of Physics, Universiti Sains Malaysia, 11800 USM, Penang (Malaysia); Department of Electrical Engineering, College of Engineering, Al-Mustansiriya University, Baghdad (Iraq); Rasheed, Hiba S. [Nano-Optoelectronics Research and Technology Laboratory, School of Physics, Universiti Sains Malaysia, 11800 USM, Penang (Malaysia); Department of Physics, College of Education, Al-Mustansiriya University, Baghdad (Iraq)

    2016-07-06

    In this work, we fabricated nanorods by applying an electric potential on poly (ethylene oxide) (PEO) and polyaniline (PANI) as a polymeric solution by electrospinning method. Testing was conducted on the samples by field emission scanning Electron microscope (FE-SEM), X-ray diffraction (XRD) and Photoluminescence. And the results showed the emergence of nanorods in the sample within glass substrate. Diameters of nanorods have ranged between (52.78-122.40)nm And a length of between (1.15 – 1.32)μm. The emergence of so the results are for the first time, never before was the fabrication of nanorods for polymers using the same method used in this research.

  20. Morphological and Electrochemical Properties of Crystalline Praseodymium Oxide Nanorods

    Directory of Open Access Journals (Sweden)

    Shamshi Hassan M

    2010-01-01

    Full Text Available Abstract Highly crystalline Pr6O11 nanorods were prepared by a simple precipitation method of triethylamine complex at 500°C. Synthesized Pr6O11 nanorods were uniformly grown with the diameter of 12–15 nm and the length of 100–150 nm without any impurities of unstable PrO2 phase. The Pr6O11 nanorod electrodes attained a high electrical conductivity of 0.954 Scm−1 with low activation energy of 0.594 eV at 850°C. The electrochemical impedance study showed that the resistance of electrode was significantly decreased at high temperature, which resulted from its high conductivity and low activation energy. The reduced impedance and high electrical conductivity of Pr6O11 nanorod electrodes are attributed to the reduction of grain boundaries and high space charge width.

  1. Inducing multiple functionalities in ZnS nanoparticles by doping Ni{sup +2} ions

    Energy Technology Data Exchange (ETDEWEB)

    Dixit, Namrata; Anasane, Nishant [Physical and Polymer Research Laboratory, Department of Chemistry, Faculty of Science, The Maharaja Sayajirao University of Baroda, Vadodara 390 002, Gujarat (India); Chavda, Mukesh [Department of Applied Physics, Polytechnic, The Maharaja Sayajirao University of Baroda, Vadodara 390 002, Gujarat (India); Bodas, Dhananjay [Center for Nanobio Sciences, Agharkar Research Institute, Pune 411 004 (India); Soni, Hemant P., E-mail: drhpsoni@yahoo.co.in [Physical and Polymer Research Laboratory, Department of Chemistry, Faculty of Science, The Maharaja Sayajirao University of Baroda, Vadodara 390 002, Gujarat (India)

    2013-06-01

    Graphical abstract: Figure shows spherical ZnS nanoparticle (light red) containing Ni as dopant ions (light green inside) exhibiting both optical (straight lines) as well as magnetic (elliptical field lines) activities simultaneously. Highlights: ► A simple method has been adopted to synthesize Ni{sup +2} doped ZnS nanoparticles. ► The enhancing and quenching of the PL intensity depended upon ‘purity of the phase’. ► The change in packing of the molecules in ZnS NPs directly depended on concentration of dopant. ► Magnetic and optical properties were found to be dopant dependent (e.g. Ni{sup +2} ions). ► Proper choice of solvent for synthesis shows a marked effect on magnetism. - Abstract: In this study, we propose that it is possible to induce multiple functionalities such as optical activity, electrical conductance and magnetism in single ZnS/Ni nanoparticles and exploit the same by only changing the external stimuli such as magnetic field, wavelength of light, electric field etc. Such type of material finds great significance in the field of electronics as well as in bioimaging. For the purpose, we have synthesized cubic ZnS:Ni{sup 2+} nanoparticles (NPs) using a simple wet-chemical method. Synthesized ZnS:Ni{sup 2+} NPs had been characterized by X-ray diffraction pattern (XRD) and energy dispersive X-ray (EDX) analysis. The amounts of Ni and Zn in the material were determined by inductively coupled plasma-atomic emission spectroscopy (ICP-AES). Morphology of the NPs is studied by transmission electron microscopy (TEM). Optical studies are carried out using UV–visible (UV–Vis) and Photoluminescence (PL) spectroscopies. Quantum efficiency of the material was also computed. The enhancement and quenching of the PL intensity are correlated with the ‘purity of the phase’. It is observed that change in packing of the molecules of the host material directly depended on concentration of dopant ion. The thermal study of the material was carried out

  2. Novel Organo-Soluble Optically Tunable Chiral Hybrid Gold Nanorods

    Science.gov (United States)

    2014-12-04

    soluble porphyrin mixed monolayer-protected GNRs, porphyrin Zn, Cu and Mg complex monolayer-protected GNRs, and organo-soluble perylene thiol monolayer...254 nm for 0 (blue), 5 min (pink), 10 min (yellow), 15 min (green), and 20 min (red). Organo-soluble porphyrin mixed monolayer-protected gold...nanorods were, for the first time, synthesized and characterized. The resulting gold nanorods (GNRs) encapsulated by both porphyrin thiol and alkyl thiol

  3. High value of ferroelectric polarization in BFO nanorods

    Science.gov (United States)

    Bandyopadhyay, S. K.; Dutta, Nabanita; Rana, Subhasis; Sen, Pintu; Himanshu, A. K.; Chakraborty, P. K.

    2014-04-01

    Significantly high value of polarization is obtained in multiferroic Bismuth Ferrite (BFO) in form of nanorods protruding out. These were developed on porous Anodised Alumina (AAO) templates using wet chemical technique. Diameters of nanorods vary in the range from 10-100 nm. The high value of polarization is attributed to the nanostructure. There is no leakage current in P-E loop observed at various fields and frequencies.

  4. High capacitance in BiFeO3 nanorod structure

    Science.gov (United States)

    Rana, Subhasis; Dutta, Nabanita; Bandyopadhyay, S. K.; Sen, Pintu; Himanshu, A. K.

    2014-04-01

    A remarkably high value of specific capacitance of 450 F/g is observed through electrochemical measurements in the electrode made of multiferroic Bismuth Ferrite (BFO) in the form of nanorods protruding out. These were developed on porous Anodised Alumina (AAO) templates using wet chemical technique. Diameters of nanorods are in the range of 20-100 nm. The high capacitance is attributed to the nanostructure. The specific capacitances are constant after several cycles of charge-discharge.

  5. Fabrication, Conductive Properties and Photocatalytic Application of Silver Nanorods

    Science.gov (United States)

    Chen, Yi-Hsun; Liu, Pai-Chung; Lin, C. B.

    2017-07-01

    This study proposes a process for fabricating silver nanorods used in conductive circuits and photocatalytic applications. In this process, UV-irradiated silver chloride nanoparticles are added to ethylene glycol solution containing polyvinyl pyrrolidone (PVP) and silver nitrate at 120 °C. With the seed crystal synthesis method, this process yielded a solution containing silver nanowires with an aspect ratio (AR) of approximately 1055 after 12 h. Aluminum foam was then placed in this solution, and the solution was stirred using a magnetic stirrer at 400 rpm. After 4 days, this process yielded a solution of silver nanorods with an AR of approximately 130. After completely washing away any PVP on the surface of the silver nanorods, a conductive ethanol ink containing 25 wt.% silver nanorods was prepared, and a conductive layer approximately 3 μm thick was applied on a glass slide. Measurements obtained using a four-point probe indicated that this layer had a sheet resistance of approximately 0.012 Ω/sq. Furthermore, a conductive ethanol ink containing 26 wt.% silver nanorods was used in a pen to draw conductive circuits on Bristol board and matte paper; the resulting sheet resistances were 132 and 0.018 Ω/sq, respectively. Finally, a visible-light-responsive photocatalyst consisting of silver nanorods dispersed over the Ag@AgCl film (Ag@AgCl/Ag nanorods; AR = 25) was synthesized through heterogeneous precipitation. The photocatalytic activity of the Ag@AgCl film can be further improved by the addition of silver nanorods.

  6. Pure wurtzite GaP nanowires grown on zincblende GaP substrates by selective area vapor liquid solid epitaxy

    Science.gov (United States)

    Halder, Nripendra N.; Kelrich, Alexander; Cohen, Shimon; Ritter, Dan

    2017-11-01

    We report on the growth of single phase wurtzite (WZ) GaP nanowires (NWs) on GaP (111) B substrates by metal organic molecular beam epitaxy following the selective area vapor–liquid–solid (SA-VLS) approach. During the SA-VLS process, precursors are supplied directly to the NW sidewalls, and the short diffusion length of gallium (or its precursors) does not significantly limit axial growth. Transmission electron microscopy (TEM) images reveal that no stacking faults are present along a 600 nm long NW. The lattice constants of the pure WZ GaP obtained from the TEM images agree with values determined previously by x-ray diffraction from non-pure NW ensembles.

  7. Intersubband absorption of p-type wurtzite GaN/AlN quantum well for fiber-optics telecommunication

    Science.gov (United States)

    Park, Seoung-Hwan; Ahn, Doyeol; Park, Chan-Yong

    2017-11-01

    The intersubband transition of wurtzite (WZ) p-type GaN/AlN quantum well (QW) structures grown on GaN substrate was investigated theoretically using the multiband effective-mass theory. The peak value of the TE-polarization absorption spectrum is found to be similar to that of the TM-polarization absorption spectrum. The absorption coefficients for TE- and TM-polarizations are mainly attributed to the absorption from the ground state (m1 = 1) because holes are mainly confined in ground states near the band-edge in an investigated range of the carrier density. We observe that a transition wavelength of 1.55 μm can be obtained for the QW structure with a relatively thin (˜16 Å) well width. Thus, we expect that a p-type WZ AlN/GaN heterostructure is applicable for a photodetector application for fiber-optic communications with normal incidence of wave.

  8. Intraband relaxation time in wurtzite InGaN quantum-well lasers and comparison with experiment

    CERN Document Server

    Park, S H

    1999-01-01

    The intraband relaxation time for wurtzite (WZ) 3.5-nm In sub 0 sub . sub 1 sub 5 Ga sub 0 sub . sub 8 sub 5 N/In sub 0 sub . sub 0 sub 2 Ga sub 0 sub . sub 9 sub 8 N quantum well (QW) lasers is investigated theoretically. The results are also compared with those obtained from fitting the experimental data with a non-Markovian gain model with many-body effects. An intraband relaxation time of 25 fs is obtained from the comparison with experiment, which is in reasonably good agreement with the calculated value of 20 fs at the subband edge. These values are significantly shorter than those (40 - 100 sf) reported for zinc-blende crystals, such as InP and GaAs. This is because the hole effective masses of GaN are larger than those of GaAs and InP.

  9. Al{sub 4}SiC{sub 4} wurtzite crystal: Structural, optoelectronic, elastic, and piezoelectric properties

    Energy Technology Data Exchange (ETDEWEB)

    Pedesseau, L., E-mail: laurent.pedesseau@insa-rennes.fr, E-mail: jacky.even@insa-rennes.fr; Even, J., E-mail: laurent.pedesseau@insa-rennes.fr, E-mail: jacky.even@insa-rennes.fr; Durand, O. [Fonctions Optiques pour les Technologies de l’Information, FOTON UMR 6082, CNRS, INSA de Rennes, 35708 Rennes (France); Modreanu, M. [Tyndall National Institute, University College Cork, Lee Maltings, Cork (Ireland); Chaussende, D.; Sarigiannidou, E.; Chaix-Pluchery, O. [LMGP, CNRS, Université Grenoble Alpes, 38000 Grenoble (France)

    2015-12-01

    New experimental results supported by theoretical analyses are proposed for aluminum silicon carbide (Al{sub 4}SiC{sub 4}). A state of the art implementation of the density functional theory is used to analyze the experimental crystal structure, the Born charges, the elastic properties, and the piezoelectric properties. The Born charge tensor is correlated to the local bonding environment for each atom. The electronic band structure is computed including self-consistent many-body corrections. Al{sub 4}SiC{sub 4} material properties are compared to other wide band gap wurtzite materials. From a comparison between an ellipsometry study of the optical properties and theoretical results, we conclude that the Al{sub 4}SiC{sub 4} material has indirect and direct band gap energies of about 2.5 eV and 3.2 eV, respectively.

  10. Growth of wurtzite InP/GaP core-shell nanowires by metal-organic molecular beam epitaxy

    Science.gov (United States)

    Halder, Nripendra N.; Kelrich, Alexander; Kauffmann, Yaron; Cohen, Shimon; Ritter, Dan

    2017-04-01

    We report on the selective area vapor-liquid-solid (SA-VLS) growth of InP/GaP core shell nano-wires (NWs) by metal organic molecular beam epitaxy. Wurtzite crystal structure of the core InP was transferred to the GaP shell through layer by layer radial growth which eliminated bending of the NWs in random directions. Low growth temperature restricted surface segregation and kept the shell free from indium. Strain in the GaP shell was partially relaxed through formation of periodic misfit dislocations. From the periodicity of Moiré fringes and splitting of the fast-Fourier-transform of the transmission electron micrographs, the radial and axial strain were determined as 4.5% and 6.2%, respectively.

  11. Picosecond spin relaxations of acceptor-bound exciton and A-band free exciton in wurtzite GaN

    Energy Technology Data Exchange (ETDEWEB)

    Tackeuchi, A.; Otake, H.; Fujita, T.; Kuroda, T. [Department of Applied Physics, Waseda University, Tokyo 169-8555 (Japan); Chinone, T.; Liang, J.H.; Kajikawa, M. [Stanley Electric Company, Ltd., Edanishi 1-3-1, Aoba, Yokohama 225-0014 (Japan)

    2006-07-01

    The spin relaxation process of acceptor-bound excitons in wurtzite GaN is observed by spin-dependent pump and probe reflectance measurement with subpicosecond time resolution. The time evolutions measured at 15-50 K have a single exponential component corresponding to the electron spin relaxation time of 1.40-1.14 ps. These spin relaxation times are slightly longer than those of the A-band free excitons of 0.47-0.25 ps in GaN at 150-225 K. The spin relaxation time is found to be proportional to T{sup -0.175}, where T is the temperature. This weak temperature dependence indicates that the main spin relaxation mechanism is the Bir-Aronov-Pikus process. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  12. Envelope-function analysis of wurtzite InGaN/GaN quantum well light emitting diodes

    Science.gov (United States)

    Xiao, D.; Kim, K. W.; Zavada, J. M.

    2004-07-01

    Fundamental electrical and optical properties of strained wurtzite InGaN/GaN-based quantum-well light-emitting diodes are calculated based on the Rashba-Sheka-Pikus Hamiltonian in the vicinity of the Γ point. It is found that the strain and the strain-induced piezoelectric field significantly alter the subband structure and determines the output intensity of the nitride quantum well light emitting diodes. For the case with high In composition (≳0.2), the calculation also supports the possibility of strain relaxation in the quantum well. Coupled with an optimized set of parameters, our theoretical model provides an excellent agreement with the available experimental data over a wide range of In composition (0-0.5).

  13. Structural and electronic properties of wurtzite MgZnO and BeMgZnO alloys and their thermodynamic stability

    Science.gov (United States)

    Gorczyca, I.; Teisseyre, H.; Suski, T.; Christensen, N. E.; Svane, A.

    2016-12-01

    Structural and electronic properties of MgZnO and BeMgZnO alloys are studied by the ab-initio Density Functional Theory method. Large band gap bowings are found for both kinds of alloys. The total energies as functions of the lattice constants are calculated and used to determine the ranges of composition in which the alloys are stable in the wurtzite structure. It is shown that the addition of 6% of Be can already help in stabilization of the MgZnO alloy in the wurtzite structure. The band gap can reach 7 eV for the wurtzite BexMg0.5Zn0.5-xO alloys with x approaching 0.5 and about 5.0 eV for Be0.125MgxZn0.875-xO type alloys for x approaching 0.6. Varying the alloy composition according to the presented stabilization diagram showing ranges of the x, y, for which BexMgyZn1-x-yO is stable in the wurtzite phase, one may tune band gaps over a wide spectral range, which provides flexibility in band gap engineering.

  14. Thermal Conductivity of Wurtzite Zinc-Oxide from First-Principles Lattice Dynamics--a Comparative Study with Gallium Nitride.

    Science.gov (United States)

    Wu, Xufei; Lee, Jonghoon; Varshney, Vikas; Wohlwend, Jennifer L; Roy, Ajit K; Luo, Tengfei

    2016-03-01

    Wurtzite Zinc-Oxide (w-ZnO) is a wide bandgap semiconductor that holds promise in power electronics applications, where heat dissipation is of critical importance. However, large discrepancies exist in the literature on the thermal conductivity of w-ZnO. In this paper, we determine the thermal conductivity of w-ZnO using first-principles lattice dynamics and compare it to that of wurtzite Gallium-Nitride (w-GaN)--another important wide bandgap semiconductor with the same crystal structure and similar atomic masses as w-ZnO. However, the thermal conductivity values show large differences (400 W/mK of w-GaN vs. 50 W/mK of w-ZnO at room temperature). It is found that the much lower thermal conductivity of ZnO originates from the smaller phonon group velocities, larger three-phonon scattering phase space and larger anharmonicity. Compared to w-GaN, w-ZnO has a smaller frequency gap in phonon dispersion, which is responsible for the stronger anharmonic phonon scattering, and the weaker interatomic bonds in w-ZnO leads to smaller phonon group velocities. The thermal conductivity of w-ZnO also shows strong size effect with nano-sized grains or structures. The results from this work help identify the cause of large discrepancies in w-ZnO thermal conductivity and will provide in-depth understanding of phonon dynamics for the design of w-ZnO-based electronics.

  15. Thermal Conductivity of Wurtzite Zinc-Oxide from First-Principles Lattice Dynamics – a Comparative Study with Gallium Nitride

    Science.gov (United States)

    Wu, Xufei; Lee, Jonghoon; Varshney, Vikas; Wohlwend, Jennifer L.; Roy, Ajit K.; Luo, Tengfei

    2016-01-01

    Wurtzite Zinc-Oxide (w-ZnO) is a wide bandgap semiconductor that holds promise in power electronics applications, where heat dissipation is of critical importance. However, large discrepancies exist in the literature on the thermal conductivity of w-ZnO. In this paper, we determine the thermal conductivity of w-ZnO using first-principles lattice dynamics and compare it to that of wurtzite Gallium-Nitride (w-GaN) – another important wide bandgap semiconductor with the same crystal structure and similar atomic masses as w-ZnO. However, the thermal conductivity values show large differences (400 W/mK of w-GaN vs. 50 W/mK of w-ZnO at room temperature). It is found that the much lower thermal conductivity of ZnO originates from the smaller phonon group velocities, larger three-phonon scattering phase space and larger anharmonicity. Compared to w-GaN, w-ZnO has a smaller frequency gap in phonon dispersion, which is responsible for the stronger anharmonic phonon scattering, and the weaker interatomic bonds in w-ZnO leads to smaller phonon group velocities. The thermal conductivity of w-ZnO also shows strong size effect with nano-sized grains or structures. The results from this work help identify the cause of large discrepancies in w-ZnO thermal conductivity and will provide in-depth understanding of phonon dynamics for the design of w-ZnO-based electronics. PMID:26928396

  16. Synthesis and Tribological Properties of WSe2Nanorods

    Directory of Open Access Journals (Sweden)

    Yang Jinghai

    2008-01-01

    Full Text Available Abstract The WSe2nanorods were synthesized via solid-state reaction method and characterized by X-ray diffractometer, TEM, and HRTEM. The results indicated the WSe2compounds had rod-like structures with diameters of 10–50 nm and lengths of 100–400 nm, and the growth process of WSe2nanorods was discussed on the basis of the experimental facts. The tribological properties of WSe2nanorods as additives in HVI500 base oil were investigated by UMT-2 multispecimen tribotester. Under the determinate conditions, the friction coefficient of the base oil containing WSe2nanorods was lower than that of the base oil, and decreased with increasing mass fraction of WSe2nanorods when it was <7 wt.%. Moreover, the base oil with the additives was rather suited to high load and high rotating speed. A combination of rolling friction, sliding friction, and stable tribofilm on the rubbing surface could explain the good friction and wear properties of WSe2nanorods as additives.

  17. In Vivo Toxicity Studies of Europium Hydroxide Nanorods in Mice

    Science.gov (United States)

    Patra, Chitta Ranjan; Abdel Moneim, Soha S.; Wang, Enfeng; Dutta, Shamit; Patra, Sujata; Eshed, Michal; Mukherjee, Priyabrata; Gedanken, Aharon; Shah, Vijay H; Mukhopadhyay, Debabrata

    2009-01-01

    Lanthanide nanoparticles and nanorods have been widely used for diagnostic and therapeutic applications in biomedical nanotechnology due to their fluorescence properties and pro-angiogenic to endothelial cells, respectively. Recently, we have demonstrated that europium (III) hydroxide [EuIII(OH)3] nanorods, synthesized by the microwave technique and characterized by several physico-chemical techniques, can be used as pro-angiogenic agents which introduce future therapeutic treatment strategies for severe ischemic heart/limb disease, and peripheral ischemic disease. The toxicity of these inorganic nanorods to endothelial cells was supported by several in vitro assays. To determine the in vivo toxicity, these nanorods were administered to mice through intraperitoneal injection (IP) everyday over a period of seven days in a dose dependent (1.25 to 125 mgKg−1day−1) and time dependent manner (8–60 days). Bio-distribution of europium elements in different organs was analyzed by inductively coupled plasma mass spectrometry (ICPMS). Short-term (S-T) and long-term (L-T) toxicity studies (mice sacrificed on day 8 and 60 for S-T and L-T, respectively) show normal blood hematology and serum clinical chemistry with the exception of a slight elevation of liver enzymes. Histological examination of nanorod treated vital organs (liver, kidney, spleen and lungs) showed no or only mild histological changes that indicate mild toxicity at the higher dose of nanorods. PMID:19616569

  18. ZnO nanorods: growth mechanism and anisotropic functionalization

    Science.gov (United States)

    Pacholski, Claudia; Kornowski, Andreas; Weller, Horst

    2004-10-01

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

  19. Structural and Thermal Studies of ZnS and CdS Nanoparticles in Polymer Matrices

    Directory of Open Access Journals (Sweden)

    Jejenija Osuntokun

    2016-01-01

    Full Text Available We report the synthesis and structural studies of ZnS and CdS nanoparticles in polyvinylpyrrolidone (PVP, poly(vinyl alcohol (PVA, and poly(methyl methacrylate (PMMA matrices. The metal sulfides/polymer nanocomposites were characterized by X-ray diffraction (XRD, Fourier transform infrared spectroscopy, electronic spectroscopy (UV-Vis, transmission electron microscopy (TEM, and thermogravimetric analysis (TGA. The particle sizes as calculated from the absorption spectra were in agreement with the results obtained from TEM and XRD data. They showed metal sulfides nanoparticles in the polymers matrices with average crystallite sizes of 1.5–6.9 nm. The TGA results indicate that incorporation of the nanoparticles significantly altered the thermal properties of the respective polymers with ZnS/PVA and CdS/PVA nanocomposites displaying higher thermal stability than the other polymer nanocomposites.

  20. Fabrication of TiO2/ZnS nanocomposites for solar energy mediated photocatalytic application

    Science.gov (United States)

    Prasannalakshmi, P.; Shanmugam, N.

    2017-03-01

    In the present work, we demonstrate the photocatalytic properties of nanosized TiO2, and different levels of ZnS-loaded TiO2/ZnS composites, for the degradation of the organic dyes brilliant green (BG), and methylene blue (MB) under solar light irradiation. For this process, TiO2 and the composites were synthesized by a sol-gel method. Further, the prepared products were subjected to structural, optical, and morphological characterizations. The results of the photocatalytic activity imply that for the samples studied, TiO2 loaded with an optimum level of zinc (0.25 M), and sulfur (0.5 M) is better able to actively degrade both BG and MB, due to its enhanced BET surface area, reduced band gap, and low charge transfer resistance.

  1. Polytypism in ZnS, ZnSe, and ZnTe: First-principles study

    KAUST Repository

    Boutaiba, F.

    2014-06-23

    We report results of first-principles calculations based on the projector augmented wave (PAW) method to explore the structural, thermodynamic, and electronic properties of cubic (3C) and hexagonal (6H, 4H, and 2H) polytypes of II-VI compounds: ZnS, ZnSe, and ZnTe. We find that the different bond stacking in II-VI polytypes remarkably influences the resulting physical properties. Furthermore, the degree of hexagonality is found to be useful to understand both the ground-state properties and the electronic structure of these compounds. The resulting lattice parameters, energetic stability, and characteristic band energies are in good agreement with available experimental data. Trends with hexagonality of the polytype are investigated.

  2. Crystallographic and optical studies on Cr doped ZnS nanocrystals

    Directory of Open Access Journals (Sweden)

    M. R. Bodke

    2014-09-01

    Full Text Available Chromium doped ZnS nanocrystals with pure and 10% compositions were synthesized by chemical co-precipitation route. Samples were characterized by X-ray diffraction (XRD technique, Fourier transforms infrared spectroscopy (FTIR and UV-Visible spectrometer. Lattice parameter 'a' decreases and grain size increases with increasing Cr concentration. XRD study shows that both the samples have cubic structure. Grain size increases due to ionic radius. The functional groups and chemical species of Cr doped ZnO samples were determined using FTIR data. UV-Vis study revealed that red shift is clearly observed in absorption band. Surface morphology of pure and 10% Cr doped samples was investigated by SEM technique and it is confirmed that images exibit cubic form of the samples. Using EDS, percentage of chemical compositions of material recorded.

  3. Single-material multilayer ZnS as anti-reflective coating for solar cell applications

    Science.gov (United States)

    Salih, Ammar T.; Najim, Aus A.; Muhi, Malek A. H.; Gbashi, Kadhim R.

    2017-04-01

    Multilayer Zinc Sulfide (ZnS) is a promising low cost antireflective coating for solar cell applications, in this work; thin films with novel structure containing cubic and hexagonal phases were successfully deposited by thermal evaporation technique with three different layers. XRD analysis confirms the existence of both phases and high specific surface area. AFM analysis reveals that films with three layers have lower roughness and average grain size than other films. The optical measurements obtained by UV-vis, the calculated values of refractive index and reflectivity using some well known refractive index-band gap relations indicate that thin films with triple layer TL-ZnS have lower refractive index and reflectivity than other films, empirical equations were suggested and show the quantum confinement effects on band gap and reflectivity.

  4. Harmonic generation by atomic and nanoparticle precursors in a ZnS laser ablation plasma

    Energy Technology Data Exchange (ETDEWEB)

    Oujja, M.; Lopez-Quintas, I.; Benítez-Cañete, A.; Nalda, R. de; Castillejo, M., E-mail: marta.castillejo@iqfr.csic.es

    2017-01-15

    Highlights: • Plume species in infrared ns laser ablation of ZnS studied by low-order harmonic generation. • Different spatiotemporal properties of harmonics from atoms and nanoparticles. • Results compared with calculations of optical frequency up-conversion in perturbative regime. - Abstract: Harmonic generation of a driving laser propagating across a laser ablation plasma serves for the diagnosis of multicomponent plumes. Here we study the contribution of atomic and nanoparticle precursors to the generation of coherent ultraviolet and vacuum ultraviolet light as low-order harmonics of the fundamental emission (1064 nm) of a Q-switched Nd:YAG laser in a nanosecond infrared ZnS laser ablation plasma. Odd harmonics from the 3rd up to the 9th order (118.2 nm) have been observed with distinct temporal and spatial characteristics which were determined by varying the delay between the ablation and driving nanosecond pulses and by spatially scanning the plasma with the focused driving beam propagating parallel to the target. At short distances from the target surface (≤1 mm), the harmonic intensity displays two temporal components peaked at around 250 ns and 10 μs. While the early component dies off quickly with increasing harmonic order and vanishes for the 9th order, the late component is notably intense for the 7th harmonic and is still clearly visible for the 9th. Spectral analysis of spontaneous plume emissions help to assign the origin of the two components. While the early plasma component is mainly constituted by neutral Zn atoms, the late component is mostly due to nanoparticles, which upon interaction with the driving laser are subject to breakup and ionization. With the aid of calculations of the phase matching integrals within the perturbative model of optical harmonic generation, these results illustrate how atom and nanoparticle populations, with differing temporal and spatial distributions within the ablation plasma, contribute to the nonlinear

  5. Mn-doped ZnS quantum dots for the determination of acetone by phosphorescence attenuation

    Energy Technology Data Exchange (ETDEWEB)

    Sotelo-Gonzalez, Emma; Fernandez-Argueelles, Maria T. [Department of Physical and Analytical Chemistry, University of Oviedo, Avda. Julian Claveria 8, E-33006 Oviedo (Spain); Costa-Fernandez, Jose M., E-mail: jcostafe@uniovi.es [Department of Physical and Analytical Chemistry, University of Oviedo, Avda. Julian Claveria 8, E-33006 Oviedo (Spain); Sanz-Medel, Alfredo, E-mail: asm@uniovi.es [Department of Physical and Analytical Chemistry, University of Oviedo, Avda. Julian Claveria 8, E-33006 Oviedo (Spain)

    2012-01-27

    Highlights: Black-Right-Pointing-Pointer Colloidal Mn:ZnS QDs exhibiting intense and long-lasting phosphorescence were synthesized and exhaustively characterized. Black-Right-Pointing-Pointer Several experimental factors that influence classical phosphorescence do not modify the Mn:ZnS QDs phosphorescence emission. Black-Right-Pointing-Pointer Mn:ZnS QDs have been applied for phosphorescence-based acetone determination. Black-Right-Pointing-Pointer A mechanism has been proposed to explain acetone quenching effect on QDs phosphorescence. - Abstract: Quantum dot (QD) nanoparticles (NPs) are increasingly used as highly valuable fluorescent biomarkers and as sensitive (bio)chemical probes. Interestingly, if certain metal impurities are incorporated during the NPs synthesis, phosphorescent QDs with analytical potential can be obtained. We report here the synthesis of colloidal manganese-doped ZnS nanoparticles which have been surface-modified with L-cysteine that exhibit an intense room temperature phosphorescence (RTP) emission in aqueous media even in the presence of dissolved oxygen (i.e. sample deoxygenation is not needed). An exhaustive RTP photoluminescent and morphological characterization of the synthesized QDs and their potential for development of phosphorescent analytical methodologies is described. Application to analytical control of acetone ('model analyte' from the ketones family) in water and urine samples is carried out by measuring the QDs phosphorescence quenching rate. The observed results showed a high selectivity of Mn{sup 2+}-doped ZnS QDs towards acetone. The linear range of the developed methodology turned out to be at least up to 600 mg L{sup -1} with a detection limit (DL) for acetone dissolved in aqueous medium of 0.2 mg L{sup -1}. The developed methodology was finally applied for acetone determination in different spiked water and urine samples, and the recoveries fall in the range of 93-107%.

  6. Properties of In–N codoped p-type ZnO nanorods grown through a two-step chemical route

    Energy Technology Data Exchange (ETDEWEB)

    Duta, M.; Mihaiu, S.; Munteanu, C. [Institute of Physical Chemistry “Ilie Murgulescu”, Romanian Academy, 202 Splaiul Independentei, 060021 Bucharest (Romania); Anastasescu, M., E-mail: manastasescu@icf.ro [Institute of Physical Chemistry “Ilie Murgulescu”, Romanian Academy, 202 Splaiul Independentei, 060021 Bucharest (Romania); Osiceanu, P.; Marin, A.; Preda, S. [Institute of Physical Chemistry “Ilie Murgulescu”, Romanian Academy, 202 Splaiul Independentei, 060021 Bucharest (Romania); Nicolescu, M., E-mail: mnicolescu2006@yahoo.com [Institute of Physical Chemistry “Ilie Murgulescu”, Romanian Academy, 202 Splaiul Independentei, 060021 Bucharest (Romania); Modreanu, M. [Tyndall National Institute, University College, Cork (Ireland); Zaharescu, M.; Gartner, M. [Institute of Physical Chemistry “Ilie Murgulescu”, Romanian Academy, 202 Splaiul Independentei, 060021 Bucharest (Romania)

    2015-07-30

    Highlights: • p-Type ZnO film codoped with In, N on glass substrate was obtained. • The films were prepared by sol–gel followed by hydrothermal method. • Influence of annealing regimes on opto-electrical properties was studied. • Thin films morphology consists of interconnected, randomly oriented nanorods. • 3.31 × 10{sup 17} cm{sup −3}carrier concentration and 85% transmission were obtained at 500 °C. - Abstract: By codoping with a donor–acceptor pair through a two-step chemical method we have succeed to obtain p-type ZnO thin films on glass. Firstly, a thin undoped ZnO seed layer was deposited by sol–gel method followed by the deposition of In–N codoped ZnO film obtained through the hydrothermal technique. The influence of post-deposition annealing temperature (100 °C, 300 °C and 500 °C) on the samples was investigated from a structural, chemical, morphological and optoelectrical point of view. X-ray diffractometry (XRD), infrared ellipsometry and X-ray photoelectron spectroscopy (XPS) analyses have confirmed the codoped nature of the ZnO thin films. The XRD pattern analysis has established the films have wurtzite nanocrystalline structure, the crystallite sizes varying between 10 nm and 13 nm with the annealing temperature. Continuous and homogenous films with nanorods surface morphology has been obtained, as visualized by scanning electron microscopy measurements. Hall Effect measurements have established that all samples, regardless of annealing temperature, showed p-type conduction due to the successful incorporation of nitrogen in the film, with the highest carrier concentration registered at 500 °C. This is in good correlation with the nitrogen content in the films as revealed from XPS. In all samples, the XPS depth profiling has shown a nitrogen gradient with higher elemental concentration at the surface.

  7. Shape and size effects in the optical properties of metallic nanorod

    NARCIS (Netherlands)

    Kooij, Ernst S.; Poelsema, Bene

    2006-01-01

    The influence of size and geometrical shape on the optical properties of randomly oriented metallic nanorods is investigated using the discrete dipole approximation (DDA). Our calculations provide a benchmark for an accurate characterisation of nanorod suspensions by frequently used optical

  8. Optical properties and toxicity of undoped and Mn-doped ZnS semiconductor nanoparticles synthesized through the aqueous route

    Science.gov (United States)

    Labiadh, Houcine; Sellami, Badreddine; Khazri, Abdelhafidh; Saidani, Wiem; Khemais, Said

    2017-02-01

    Undoped and Mn-doped ZnS nanoparticles were synthesized at 95 °C in basic aqueous solution using the nucleation-doping strategy. Various samples of the Mn:ZnS NPs with 5, 10 and 20% of Mn dopant have been prepared and characterized using X-ray diffraction, energy-dispersive X-ray analysis, high resolution electron microscopy and photoluminescence (PL) measurements. When increasing the concentration of manganese Mn, the photoluminescence intensity gradually decreases. The PL spectra of the Mn-doped ZnS nanoparticles at room temperature exhibit both, the 450 nm blue defect-related emission and the 592 nm orange Mn2+ emission. It is vital to obtain NPs that meet the application requirements, however their environmental toxicity needs to be investigated. In this study, the induction of oxidative stress within the digestive gland of the Ruditapes decussatus organism (clam) is described. Antioxidant enzyme activities (superoxide dismutase (SOD) and catalase (CAT)) as well as malondialdehyde (MDA) levels have been determined in the digestive gland after exposure to 100 μg/L of ZnS, ZnS:Mn (5%), ZnS:Mn (10%) and ZnS:Mn (20%). The nanomaterials studied exhibit different responses in the digestive gland. Undoped Mn-ZnS has no effect on the markers considered, showing the limited interaction between this nanoparticle and the cells of the test organisms. In contrast, Mn-doped ZnS increases the activities of SOD and CAT and the level of MDA species, although this toxicity is highly dependent on the chemical properties of the material. These findings provide ideas for future considerations of ZnS nanoparticles, as well as information on the interaction between these materials and an aquatic environment. These data are the first evidence available of the formation of ZnS NPs using aqueous method and are an indication of the importance of knowing the biological target of the NPs when testing their potential impact on environmental model organisms.

  9. The effect of water molecules on the thiol collector interaction on the galena (PbS) and sphalerite (ZnS) surfaces: A DFT study

    Energy Technology Data Exchange (ETDEWEB)

    Long, Xianhao [School of Chemistry and Chemical Engineering, Guangxi University, Nanning 530004 (China); Chen, Ye, E-mail: fby18@126.com [College of Resources and Metallurgy, Guangxi University, Nanning 530004 (China); Chen, Jianhua, E-mail: jhchen@gxu.edu.cn [School of Chemistry and Chemical Engineering, Guangxi University, Nanning 530004 (China); College of Resources and Metallurgy, Guangxi University, Nanning 530004 (China); Xu, Zhenghe; Liu, Qingxia [Department of Chemical and Materials Engineering, University of Alberta, Edmonton, AB T6G 2V4 (Canada); Du, Zheng [National Supercomputing Center in Shenzhen, Shenzhen 518055 (China)

    2016-12-15

    Highlights: • Water adsorption has a greater effect on the electron distribution of ZnS surface than PbS surface. • Water adsorption decreases the reactivity of ZnS surface atoms but improves that of PbS. • Thiol collectors cannot interact with the hydrated ZnS surface. • The hydration has little influence on the interaction of thiol collectors with PbS surface. - Abstracts: In froth flotation the molecular interaction between reagents and mineral surfaces take place at the solid liquid interface. In this paper, the effect of water molecule on the three typical thiol collectors (xanthate, dithiocarbomate and dithiophosphate) interactions at the galena (PbS) and sphalerite (ZnS) surfaces has been studied adopting density functional theory (DFT). The results suggests that the presence of water molecule shows a greater influence on the electron distribution of ZnS surface than PbS surface, and reduce the reactivity of ZnS surface atoms but improves the reactivity of PbS surface atoms during the reaction with xanthate. Water adsorption could also reduce the covalent binding between Zn and S atoms but have little influence on Pb-S bond. In the presence of water, xanthate, dithiocarbomate (DTC) and dithiophosphate (DTP) could not adsorb on the sphalerite surface. And for galena (PbS) surface, the interaction of DTP is the strongest, then the DTC and the interaction of xanthate is the weakest. These results agree well with the flotation practice.

  10. Nanotubes, nanorods and nanowires having piezoelectric and/or pyroelectric properties and devices manufactured therefrom

    Science.gov (United States)

    Russell, Thomas P [Amherst, MA; Lutkenhaus, Jodie [Wethersfield, CT

    2012-05-15

    Disclosed herein is a device comprising a pair of electrodes; and a nanotube, a nanorod and/or a nanowire; the nanotube, nanorod and/or nanowire comprising a piezoelectric and/or pyroelectric polymeric composition; the pair of electrodes being in electrical communication with opposing surfaces of the nanotube, nanorod and/or a nanowire; the pair of electrodes being perpendicular to a longitudinal axis of the nanotube, nanorod and/or a nanowire.

  11. Fabrication and characterization of nanorod solar cells with an ultrathin a-Si:H absorber layer

    NARCIS (Netherlands)

    Kuang, Y.; van der Werf, C.H.M.; Houweling, Z.S.|info:eu-repo/dai/nl/251874486; Di Vece, M.|info:eu-repo/dai/nl/248753355; Schropp, R.E.I.|info:eu-repo/dai/nl/072502584

    2011-01-01

    In this paper, we present a three-dimensional nanorod solar cell design. As the backbone of the nanorod device, density-controlled zinc oxide (ZnO) nanorods were synthesized by a simple aqueous solution growth technique at 80 °C on ZnO thin film pre-coated glass substrate. The as-prepared ZnO

  12. Effect of sample producing conditions on the thermoluminescence properties of ZnS thin films developed by spray pyrolysis method

    CERN Document Server

    Yazici, A N; Bedir, M

    2003-01-01

    In this work, the effect of thin film production conditions (substrate temperature and ratio of starting material) was studied on the intensity of thermoluminescence (TL) signal and TL emission spectrum of ZnS samples that were grown by spray pyrolysis method. It was observed that the intensity of TL signal increases with increasing the substrate temperature (T sub s) and reaches a maximum point at the substrate temperature of 500 deg. C with a high ratio of ZnCl sub 2 salt solutions. Secondly, it was observed that the energy level of trap present in ZnS samples is not single-level but instead has a distribution of energy levels. The type of the trap distribution is probably an exponential distribution. However, the distribution of energy levels approaches to single energy level with increasing substrate temperature.

  13. Effect of Post-Synthesis Treatments on the Properties of ZnS Nanoparticles: An Experimental and Computational Study

    Directory of Open Access Journals (Sweden)

    Balantseva Elena

    2015-09-01

    Full Text Available This work deals with the characterization of ZnS NanoParticles (NP, prepared by precipitation employing thioacetamide as sulfur source at different reaction time length. The attention is focused on the modification induced on structural, surface and electronic properties of ZnS NP by post-synthesis treatments. These were aimed at removing from the samples surface adsorbed reactants, by washing or thermal treatments, both in air or vacuum. The effect of these parameters is followed by X-Ray Diffraction (XRD, Transmission Electron Microscopy (TEM, Fourier Transform InfraRed (FTIR, gas-volumetric and ThermoGravimetric Analysis (TGA. Moreover, the effect of nanostructuration on the semiconducting material band gap is evaluated by Diffuse Reflectance UV-Vis (DR UV-Vis spectroscopy. Density Functional Theory (DFT calculations have been employed to clarify the role of the adsorbed reactants on the surface stability and to assess the relationship between particle size and band gap value.

  14. Impact of pulse duration in high power impulse magnetron sputtering on the low-temperature growth of wurtzite phase (Ti,Al)N films with high hardness

    Energy Technology Data Exchange (ETDEWEB)

    Shimizu, Tetsuhide, E-mail: simizu-tetuhide@tmu.ac.jp [Division of Human Mechatronics Systems, Graduate School of System Design, Tokyo Metropolitan University, 6-6, Asahigaoka, Hino-shi, 191-0065 Tokyo (Japan); Teranishi, Yoshikazu; Morikawa, Kazuo; Komiya, Hidetoshi; Watanabe, Tomotaro; Nagasaka, Hiroshi [Surface Finishing Technology Group, Tokyo Metropolitan Industrial Technology Research Institute, 2-4-10, Aomi, Kohtoh-ku, 135-0064 Tokyo (Japan); Yang, Ming [Division of Human Mechatronics Systems, Graduate School of System Design, Tokyo Metropolitan University, 6-6, Asahigaoka, Hino-shi, 191-0065 Tokyo (Japan)

    2015-04-30

    (Ti,Al)N films were deposited from a Ti{sub 0.33}Al{sub 0.67} alloy target with a high Al content at a substrate temperature of less than 150 °C using high power impulse magnetron sputtering (HIPIMS) plasma. The pulse duration was varied from 60 to 300 μs with a low frequency of 333 Hz to investigate the effects on the dynamic variation of the substrate temperature, microstructural grain growth and the resulting mechanical properties. The chemical composition, surface morphology and phase composition of the films were analyzed by energy dispersive spectroscopy, scanning electron microscopy and X-ray diffraction, respectively. Mechanical properties were additionally measured by using a nanoindentation tester. A shorter pulse duration resulted in a lower rate of increase in the substrate temperature with an exponentially higher peak target current. The obtained films had a high Al content of 70–73 at.% with a mixed highly (0002) textured wurtzite phase and a secondary phase of cubic (220) grains. Even with the wurtzite phase and the relatively high Al contents of more than 70 at.%, the films exhibited a high hardness of more than 30 GPa with a relatively smooth surface of less than 2 nm root-mean-square roughness. The hardest and smoothest surfaces were obtained for pulses with an intermediate duration of 150 μs. The differences between the obtained film properties under different pulse durations are discussed on the basis of the grain growth process observed by transmission electron microscopy. The feasibility of the low-temperature synthesis of AlN rich wurtzite phase (Ti,Al)N films with superior hardness by HIPIMS plasma duration was demonstrated. - Highlights: • Low temperature synthesis of AlN rich wurtzite phase (Ti,Al)N film was demonstrated. • 1 μm-thick TiAlN film was deposited under the temperature less than 150 °C by HIPIMS. • High Al content with highly (0002) textured wurtzite phase structure was obtained. • High hardness of 35 GPa were

  15. In vivo photothermal tumour ablation using gold nanorods

    Science.gov (United States)

    de Freitas, L. F.; Zanelatto, L. C.; Mantovani, M. S.; Silva, P. B. G.; Ceccini, R.; Grecco, C.; Moriyama, L. T.; Kurachi, C.; Martins, V. C. A.; Plepis, A. M. G.

    2013-06-01

    Less invasive and more effective cancer treatments have been the aim of research in recent decades, e.g. photothermal tumour ablation using gold nanorods. In this study we investigate the cell death pathways activated, and confirm the possibility of CTAB-coated nanoparticle use in vivo. Nanorods were synthesized by the seeding method; some of them were centrifuged and washed to eliminate soluble CTAB. The MTT cytotoxicity test was performed to evaluate cytotoxicity, and the particles’ viability after their synthesis was assessed. Once it had been observed that centrifuged and washed nanorods are harmless, and that nanoparticles must be used within 48 h after their synthesis, in vivo hyperthermic treatment was performed. After irradiation, a tumour biopsy was subjected to a chemiluminescence assay to evaluate membrane lipoperoxidation, and to a TRAP assay to evaluate total antioxidant capacity. There was a 47 ° C rise in temperature observed at the tumour site. Animals irradiated with a laser (with or without nanorods) showed similar membrane lipoperoxidation, more intense than in control animals. The antioxidant capacity of experimental animal tumours was elevated. Our results indicate that necrosis is possibly the cell death pathway activated in this case, and that nanorod treatment is worthwhile.

  16. Collective Plasmonic Properties in Few-Layer Gold Nanorod Supercrystals.

    Science.gov (United States)

    Hamon, Cyrille; Novikov, Sergey M; Scarabelli, Leonardo; Solís, Diego M; Altantzis, Thomas; Bals, Sara; Taboada, José M; Obelleiro, Fernando; Liz-Marzán, Luis M

    2015-10-21

    Gold nanorod supercrystals have been widely employed for the detection of relevant bioanalytes with detection limits ranging from nano- to picomolar levels, confirming the promising nature of these structures for biosensing. Even though a relationship between the height of the supercrystal (i.e., the number of stacked nanorod layers) and the enhancement factor has been proposed, no systematic study has been reported. In order to tackle this problem, we prepared gold nanorod supercrystals with varying numbers of stacked layers and analyzed them extensively by atomic force microscopy, electron microscopy and surface enhanced Raman scattering. The experimental results were compared to numerical simulations performed on real-size supercrystals composed of thousands of nanorod building blocks. Analysis of the hot spot distribution in the simulated supercrystals showed the presence of standing waves that were distributed at different depths, depending on the number of layers in each supercrystal. On the basis of these theoretical results, we interpreted the experimental data in terms of analyte penetration into the topmost layer only, which indicates that diffusion to the interior of the supercrystals would be crucial if the complete field enhancement produced by the stacked nanorods is to be exploited. We propose that our conclusions will be of high relevance in the design of next generation plasmonic devices.

  17. Highly Uniform Epitaxial ZnO Nanorod Arrays for Nanopiezotronics

    Directory of Open Access Journals (Sweden)

    Nagata T

    2009-01-01

    Full Text Available Abstract Highly uniform and c-axis-aligned ZnO nanorod arrays were fabricated in predefined patterns by a low temperature homoepitaxial aqueous chemical method. The nucleation seed patterns were realized in polymer and in metal thin films, resulting in, all-ZnO and bottom-contacted structures, respectively. Both of them show excellent geometrical uniformity: the cross-sectional uniformity according to the scanning electron micrographs across the array is lower than 2%. The diameter of the hexagonal prism-shaped nanorods can be set in the range of 90–170 nm while their typical length achievable is 0.5–2.3 μm. The effect of the surface polarity was also examined, however, no significant difference was found between the arrays grown on Zn-terminated and on O-terminated face of the ZnO single crystal. The transmission electron microscopy observation revealed the single crystalline nature of the nanorods. The current–voltage characteristics taken on an individual nanorod contacted by a Au-coated atomic force microscope tip reflected Schottky-type behavior. The geometrical uniformity, the designable pattern, and the electrical properties make the presented nanorod arrays ideal candidates to be used in ZnO-based DC nanogenerator and in next-generation integrated piezoelectric nano-electromechanical systems (NEMS.

  18. Air annealing induced transformation of cubic CdSe microspheres into hexagonal nanorods and micro-pyramids

    Energy Technology Data Exchange (ETDEWEB)

    Kale, Rohidas B., E-mail: rb_kale@yahoo.co.in [Department of Physics, Institute of Science, Mumbai 400032, M.S. (India); Lu, Shih-Yuan, E-mail: sylu@mx.nthu.edu.tw [Department of Chemical Engineering, National Tsing-Hua University, Hsin-Chu 30013, Taiwan (China)

    2015-08-15

    Highlights: • Nanocrystalline CdSe thin films were deposited using inexpensive CBD method. • Air annealing induced structural and interesting morphological transformation. • The as-deposited CdSe thin films showed a blue shift in its optical spectra. • The films showed a red shift in their optical spectra after annealing. - Abstract: CdSe thin films have been deposited onto glass substrates using a chemical bath deposition method at relatively low temperatures (40 °C). The precursors used for the deposition of the thin films are cadmium nitrate hexahydrate, freshly prepared sodium selenosulfate solution and aqueous ammonia solution as a complex as well as pH adjusting reagent. In order to study the influence of air annealing on their physicochemical properties, the as-deposited CdSe thin films were further annealed at 200 °C and 400 °C for 3 h in air atmosphere. Significant changes in the morphology and photonic properties were clearly observed after the thermal annealing of the CdSe thin films. The as-deposited CdSe films grow with the cubic phase that transforms into mixed cubic and hexagonal wurtzite phase with improved crystalline quality of the films after the air annealing. Morphological observation reveals that the as-deposited thin films grow with multilayer that consists of network or mesh like structure, uniformly deposited on the glass substrate over which microspheres are uniformly distributed. After air annealing, CdSe nanorods emerged from the microspheres along with conversion of few microspheres into micro-pyramids. The UV–visible study illustrates that the as-deposited thin film shows blue shifts in its optical spectrum and the spectrum was red-shifted after annealing the CdSe thin films. The band gap of the CdSe thin films were found to be decreased after the thermal treatment.

  19. Acetone sensing of multi-networked WO3-NiO core-shell nanorod sensors

    Science.gov (United States)

    Choi, Seungbok; Lee, Jae Kyung; Lee, Woo Seok; Lee, Chongmu; Lee, Wan In

    2017-10-01

    WO3-NiO core-shell nanorods were synthesized by thermal evaporation of a mixture of WO3 and graphite powders and immersion of the synthesized WO3 nanorods in an 20 mM of nickel(II) acetate tetrahydrate (Ni(OCOCH3)2·4H2O) solution followed by UV irradiation and annealing. Subsequently, multi-networked nanorod sensors were fabricated by connecting these nanostructures with electrodes. The sensing properties of pristine WO3 nanorod and WO3-NiO core-shell nanorod sensors toward acetone were examined. Subsequently, multi-networked nanorod sensors were fabricated by connecting these nanostructures with electrodes. The WO3-NiO core-shell nanorod sensor exhibited a stronger response to acetone gas and shorter response/recovery times than the pristine WO3 nanorod sensor. The pristine WO3 nanorods showed responses of approximately 1.36 to 200 ppm of CH3COCH3 at 300 °C. On the other hand, the WO3-NiO core-shell nanorods showed responses of 4.4 to the same concentration of CH3COCH3 at the same temperature. The core-shell nanorods exhibited response and recovery times of 51 s and 59 s, respectively for 200 ppm of CH3COCH3. On the other hand, the pristine WO3 nanorods exhibited response and recovery times of 51 s and 59 s, respectively, for the same concentration of CH3COCH3. NiO coating enhanced the selectivity of the WO3 nanorods for acetone as well as the sensitivity of the WO3 nanorods. The underlying mechanism of the enhanced response of the WO3-NiO core-shell nanorod sensor is also discussed in detail.

  20. Origin of Photoluminescence and XAFS Study of (ZnS)1-x(AgInS2)x Nanocrystals.

    Science.gov (United States)

    Rao, M Jagadeeswara; Shibata, Tomohiro; Chattopadhyay, Soma; Nag, Angshuman

    2014-01-02

    Donor-Acceptor transition was previously suggested as a mechanism for luminescence in (ZnS)1-x(AgInS2)x nanocrystals. Here we show the participation of delocalized valence/conduction band in the luminescence. Two emission pathways are observed: Path-1 involves transition between a delocalized state and a localized state exhibiting higher energy and shorter lifetime (∼25 ns) and Path-2 (donor-acceptor) involves two localized defect states exhibiting lower emission energy and longer lifetime (>185 ns). Surprisingly, Path-1 dominates (82% for x = 0.33) for nanocrystals with lower x, in sharp difference with prior assignment. Luminescence peak blue shifts systematically by 0.57 eV with decreasing x because of this large contribution from Path-1. X-ray absorption fine structure (XAFS) study of (ZnS)1-x(AgInS2)x nanocrystals shows larger AgS4 tetrahedra compared with InS4 tetrahedra with Ag-S and In-S bond lengths 2.52 and 2.45 Å respectively, whereas Zn-S bond length is 2.33 Å along with the absence of second nearest-neighbor Zn-S-metal correlation.

  1. Preparation and Characterization of ZnS, CdS and HgS/Poly(methyl methacrylate Nanocomposites

    Directory of Open Access Journals (Sweden)

    Johannes Z. Mbese

    2014-09-01

    Full Text Available The synthesis and characterization of ZnS/PMMA (poly(methyl methacrylate, CdS/PMMA and HgS/PMMA nanocomposites are presented. Hexadecylamine (HDA-capped ZnS, CdS and HgS nanoparticles were synthesized using dithiocarbamate single molecule precursors at 180 °C. FTIR (Fourier transform infrared spectroscopy spectra measurement confirmed the dispersion of the metal sulfide nanoparticles in the PMMA matrices to form the metal sulfides/PMMA nanocomposites. Powder X-ray diffraction confirmed the presence of the amorphous PMMA in the nanocomposites. The ZnS and HgS particles were indexed to the cubic phase, while the HgS particles correspond to the hexagonal phase. Thermogravimetric analyses showed that the metal sulfide nanocomposites are thermally more stable than their corresponding precursor complexes. The TEM (Transmission electron microscope analyses revealed that the ZnS nanoparticles have a particle size of 3–5 nm; the crystallite size of the CdS nanoparticles is 6–12 nm, and HgS nanoparticles are 6–12 nm.

  2. Synthesis and characterization of Zn{sub 3}P{sub 2}/ZnS core/shell nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Sun, T.; Wu, P.C. [State Key Laboratory for Mesoscopic Physics and School of Physics, Peking University, Beijing 100871 (China); Guo, Z.D. [Beijing National Laboratory for Molecular Sciences, State Key Lab of Rare Earth Materials Chemistry and Applications, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871 (China); Dai, Y.; Meng, H.; Fang, X.L. [State Key Laboratory for Mesoscopic Physics and School of Physics, Peking University, Beijing 100871 (China); Shi, Z.J. [Beijing National Laboratory for Molecular Sciences, State Key Lab of Rare Earth Materials Chemistry and Applications, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871 (China); Dai, L., E-mail: lundai@pku.edu.c [State Key Laboratory for Mesoscopic Physics and School of Physics, Peking University, Beijing 100871 (China); Qin, G.G., E-mail: qingg@pku.edu.c [State Key Laboratory for Mesoscopic Physics and School of Physics, Peking University, Beijing 100871 (China)

    2011-05-23

    Fully-surrounded Zn{sub 3}P{sub 2}/ZnS core/shell nanowires (NWs) were synthesized for the first time via a two-step method: a catalyst free chemical vapor deposition followed by a low-pressure vulcanization process. Field emission scanning electron microscopy, high-resolution transmission electron microscopy, and high-angle angular dark field scanning transmission electron microscopy were used to characterize the morphologies, crystal structure, and element composition of the core/shell NWs. The band structure analysis demonstrates that the Zn{sub 3}P{sub 2}/ZnS core-shell NW type-II heterostructures have bright potential in photovoltaic nanodevice applications. The core/shell NW growth method used here can be extended to other material system. - Highlights: Fully-surrounded Zn{sub 3}P{sub 2}/ZnS core/shell NWs were synthesized via a two-step method. The structure of core/shell can be controlled. The core/shell NW growth method used can be extended to other material system. The band structure analysis shows the core-shell NWs have type-II heterostructure.

  3. Influence of the Polyvinyl Pyrrolidone Concentration on Particle Size and Dispersion of ZnS Nanoparticles Synthesized by Microwave Irradiation

    Directory of Open Access Journals (Sweden)

    Nayereh Soltani

    2012-09-01

    Full Text Available Zinc sulfide semiconductor nanoparticles were synthesized in an aqueous solution of polyvinyl pyrrolidone via a simple microwave irradiation method. The effect of the polymer concentration and the type of sulfur source on the particle size and dispersion of the final ZnS nanoparticle product was carefully examined. Microwave heating generally occurs by two main mechanisms: dipolar polarization of water and ionic conduction of precursors. The introduction of the polymer affects the heating rate by restriction of the rotational motion of dipole molecules and immobilization of ions. Consequently, our results show that the presence of the polymer strongly affects the nucleation and growth rates of the ZnS nanoparticles and therefore determines the average particle size and the dispersion. Moreover, we found that PVP adsorbed on the surface of the ZnS nanoparticles by interaction of the C–N and C=O with the nanoparticle’s surface, thereby affording protection from agglomeration by steric hindrance. Generally, with increasing PVP concentration, mono-dispersed colloidal solutions were obtained and at the optimal PVP concentration (5%, sufficiently small size and narrow size distributions were obtained from both sodium sulfide and thioacetamide sulfur sources. Finally, the sulfur source directly influences the reaction mechanism and the final particle morphology, as well as the average size.

  4. Influence of the polyvinyl pyrrolidone concentration on particle size and dispersion of ZnS nanoparticles sythesized by mcrowave iradiation.

    Science.gov (United States)

    Soltani, Nayereh; Saion, Elias; Erfani, Maryam; Rezaee, Khadijeh; Bahmanrokh, Ghazaleh; Drummen, Gregor P C; Bahrami, Afarin; Hussein, Mohd Zobir

    2012-09-27

    Zinc sulfide semiconductor nanoparticles were synthesized in an aqueous solution of polyvinyl pyrrolidone via a simple microwave irradiation method. The effect of the polymer concentration and the type of sulfur source on the particle size and dispersion of the final ZnS nanoparticle product was carefully examined. Microwave heating generally occurs by two main mechanisms: dipolar polarization of water and ionic conduction of precursors. The introduction of the polymer affects the heating rate by restriction of the rotational motion of dipole molecules and immobilization of ions. Consequently, our results show that the presence of the polymer strongly affects the nucleation and growth rates of the ZnS nanoparticles and therefore determines the average particle size and the dispersion. Moreover, we found that PVP adsorbed on the surface of the ZnS nanoparticles by interaction of the C-N and C=O with the nanoparticle's surface, thereby affording protection from agglomeration by steric hindrance. Generally, with increasing PVP concentration, mono-dispersed colloidal solutions were obtained and at the optimal PVP concentration (5%), sufficiently small size and narrow size distributions were obtained from both sodium sulfide and thioacetamide sulfur sources. Finally, the sulfur source directly influences the reaction mechanism and the final particle morphology, as well as the average size.

  5. Transparent nanocrystalline ZnO and ZnO:Al coatings obtained through ZnS sols

    Science.gov (United States)

    Kolobkova, E. V.; Evstropiev, S. K.; Nikonorov, N. V.; Vasilyev, V. N.; Evstropyev, K. S.

    2017-11-01

    Thin and uniform ZnO and ZnO:Al coatings were prepared on glass surfaces by using film-forming colloidal solutions containing small ZnS nanoparticles and polyvinylpyrrolidone as a polymer stabilizer. Film-forming ZnS sols were synthesized in the mixed water-propanol-2 solutions by chemical reaction between zinc nitrate and sodium sulfide. The addition of modifying component such as Al(NO3)3 into the film-forming solutions allows one to obtain thin and uniform ZnO:Al coatings. An increase in the sodium sulfide content in film-forming solutions leads to the growth of light absorption in the UV. The evolution of a coating material at all technological stages from the ZnS sols up to the transparent ZnO and ZnO:Al2O3 coatings (the latter kind being denoted further, in accord with a common practice, by ZnO:Al) was studied using the optical spectroscopy, XRD analysis, DSC-TGA, and SEM methods. The chemical processes of decomposing salts and the polymer occur by heating the intermediate composite ZnS/polyvinylpyrrolidone coatings in the 280-500 °C temperature range. Experimental data show that the ZnO and ZnO:Al coatings prepared consist of the slightly elongated oxide nanoparticles. These coatings fully cover the glass surface and demonstrate a high transparency in the UV and visible.

  6. Low-temperature self-limiting atomic layer deposition of wurtzite InN on Si(100)

    Energy Technology Data Exchange (ETDEWEB)

    Haider, Ali, E-mail: ali.haider@bilkent.edu.tr, E-mail: biyikli@unam.bilkent.edu.tr; Kizir, Seda; Biyikli, Necmi, E-mail: ali.haider@bilkent.edu.tr, E-mail: biyikli@unam.bilkent.edu.tr [National Nanotechnology Research Center (UNAM), Bilkent University, Bilkent, Ankara 06800 Turkey (Turkey); Institute of Materials Science and Nanotechnology, Bilkent University, Bilkent, Ankara 06800 Turkey (Turkey)

    2016-04-15

    In this work, we report on self-limiting growth of InN thin films at substrate temperatures as low as 200 °C by hollow-cathode plasma-assisted atomic layer deposition (HCPA-ALD). The precursors used in growth experiments were trimethylindium (TMI) and N{sub 2} plasma. Process parameters including TMI pulse time, N{sub 2} plasma exposure time, purge time, and deposition temperature have been optimized for self-limiting growth of InN with in ALD window. With the increase in exposure time of N{sub 2} plasma from 40 s to 100 s at 200 °C, growth rate showed a significant decrease from 1.60 to 0.64 Å/cycle. At 200 °C, growth rate saturated as 0.64 Å/cycle for TMI dose starting from 0.07 s. Structural, optical, and morphological characterization of InN were carried out in detail. X-ray diffraction measurements revealed the hexagonal wurtzite crystalline structure of the grown InN films. Refractive index of the InN film deposited at 200 °C was found to be 2.66 at 650 nm. 48 nm-thick InN films exhibited relatively smooth surfaces with Rms surface roughness values of 0.98 nm, while the film density was extracted as 6.30 g/cm{sup 3}. X-ray photoelectron spectroscopy (XPS) measurements depicted the peaks of indium, nitrogen, carbon, and oxygen on the film surface and quantitative information revealed that films are nearly stoichiometric with rather low impurity content. In3d and N1s high-resolution scans confirmed the presence of InN with peaks located at 443.5 and 396.8 eV, respectively. Transmission electron microscopy (TEM) and selected area electron diffraction (SAED) further confirmed the polycrystalline structure of InN thin films and elemental mapping revealed uniform distribution of indium and nitrogen along the scanned area of the InN film. Spectral absorption measurements exhibited an optical band edge around 1.9 eV. Our findings demonstrate that HCPA-ALD might be a promising technique to grow crystalline wurtzite InN thin films at low substrate

  7. Low-temperature self-limiting atomic layer deposition of wurtzite InN on Si(100

    Directory of Open Access Journals (Sweden)

    Ali Haider

    2016-04-01

    Full Text Available In this work, we report on self-limiting growth of InN thin films at substrate temperatures as low as 200 °C by hollow-cathode plasma-assisted atomic layer deposition (HCPA-ALD. The precursors used in growth experiments were trimethylindium (TMI and N2 plasma. Process parameters including TMI pulse time, N2 plasma exposure time, purge time, and deposition temperature have been optimized for self-limiting growth of InN with in ALD window. With the increase in exposure time of N2 plasma from 40 s to 100 s at 200 °C, growth rate showed a significant decrease from 1.60 to 0.64 Å/cycle. At 200 °C, growth rate saturated as 0.64 Å/cycle for TMI dose starting from 0.07 s. Structural, optical, and morphological characterization of InN were carried out in detail. X-ray diffraction measurements revealed the hexagonal wurtzite crystalline structure of the grown InN films. Refractive index of the InN film deposited at 200 °C was found to be 2.66 at 650 nm. 48 nm-thick InN films exhibited relatively smooth surfaces with Rms surface roughness values of 0.98 nm, while the film density was extracted as 6.30 g/cm3. X-ray photoelectron spectroscopy (XPS measurements depicted the peaks of indium, nitrogen, carbon, and oxygen on the film surface and quantitative information revealed that films are nearly stoichiometric with rather low impurity content. In3d and N1s high-resolution scans confirmed the presence of InN with peaks located at 443.5 and 396.8 eV, respectively. Transmission electron microscopy (TEM and selected area electron diffraction (SAED further confirmed the polycrystalline structure of InN thin films and elemental mapping revealed uniform distribution of indium and nitrogen along the scanned area of the InN film. Spectral absorption measurements exhibited an optical band edge around 1.9 eV. Our findings demonstrate that HCPA-ALD might be a promising technique to grow crystalline wurtzite InN thin films at low substrate temperatures.

  8. Electrostatic built-in fields in wurtzite III-N nanostructures: Impact of growth plane on second-order piezoelectricity

    Science.gov (United States)

    Patra, Saroj K.; Schulz, Stefan

    2017-10-01

    In this work we present a detailed analysis of the second-order piezoelectric effect in wurtzite III-N heterostructures, such as quantum wells and quantum dots, grown on different substrate orientations. Our analysis is based on a continuum model using a here derived analytic expression for the second-order piezoelectric polarization vector field as a function of the incline angle θ to the wurtzite c axis. This expression allows for a straightforward implementation in existing quantum well and quantum dot codes. Our calculations on III-N quantum well systems reveal that especially for semipolar structures with high incline angle values (55∘≤θ ≤80∘ and 105∘≤θ ≤120∘ ), second-order piezoelectricity noticeably contributes to the overall electric built-in field. For instance, in an InGaN/GaN multiple quantum well system with 22% In, the electric field increases by approximately 20% due to second-order piezoelectricity. Overall, when including second-order piezoelectric effects in the calculation of electric fields in GaN/AlN and InGaN/GaN quantum well systems an improved agreement between our theory and experimental literature data is observed. When studying quantum dots, at least for the here considered model geometry and growth planes, we observe that for GaN/AlN structures second-order effects are of secondary importance. The situation is different for non-c -plane In0.2Ga0.8N /GaN quantum dots. For example, inside a nonpolar In0.2Ga0.8N /GaN dot the built-in potential arising from second-order piezoelectricity is comparable in magnitude to the built-in potential originating from spontaneous and first-order piezoelectric polarization, but opposite in sign. This feature leads to a change in the built-in potential profile both in and around the In0.2Ga0.8N /GaN quantum dot structure, which in general is relevant for electronic and optical properties of these systems.

  9. Hierarchical mordenite zeolite nano-rods bundles favourable to bulky molecules

    Science.gov (United States)

    Dai, Guang; Hao, Wenming; Xiao, Huan; Ma, Jinghong; Li, Ruifeng

    2017-10-01

    Hierarchical mordenite zeolite nano-rods bundles were successfully synthesized by a novel approach of using organosilane functioned fumed silica as silicon source. The organic moiety linked on the surface of fumed silica inhibits the growth of zeolite crystal into large size, leading to the nano-rods assembled bundles. The mordenite nanorods bundles exhibited significantly improved mesitylene adsorption capacity compared with the conventional mordenite. As a catalyst, the hierarchical mordenite nanorods bundles showed remarkable catalytic performance in the benzylation of mesitylene by benzyl chloride, due to the efficient diffusion rate and improved accessibility of the active sites in the hierarchical mordenite nanorods bundles.

  10. Tailored Au nanorods: optimizing functionality, controlling the aspect ratio and increasing biocompatibility

    Energy Technology Data Exchange (ETDEWEB)

    Cai Xiaoqing; Wang, Cheng-Liang; Chen, Hsiang-Hsin; Chien, Chia-Chi; Lai Shengfeng; Chen Yiyun; Hua, Tzu-En; Kempson, Ivan M; Hwu, Y [Institute of Physics, Academia Sinica, Nankang, Taipei 115, Taiwan (China); Yang, C S [Center for Nanomedicine, National Health Research Institutes, Miaoli, Taiwan (China); Margaritondo, G, E-mail: phhwu@sinica.edu.tw [Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne (Switzerland)

    2010-08-20

    Monodisperse gold nanorods with high aspect ratio were synthesized by x-ray irradiation. Irradiation was first used to stimulate the creation of seeds. Afterward, nanorod growth was stimulated either by chemical reduction or again by x-ray irradiation. In the last case, the entire process took place without reducing agents. The shape of the final products could be controlled by modulating the intensity of the x-ray irradiation during the seed synthesis. In turn, the nanorod aspect ratio determines the absorption wavelength of the nanorods that can thus be optimized for different applications. Likewise, the aspect ratio influences the uptake of the nanorods by HeLa cells.

  11. Enhanced luminescence of ZnO:RE{sup 3+} (RE=Eu, Tb) nanorods by Li{sup +} doping and calculations of kinetic parameters

    Energy Technology Data Exchange (ETDEWEB)

    Pal, Partha P., E-mail: phys.ppal@gmail.com; Manam, J.

    2014-01-15

    Lithium co-doped ZnO:Eu{sup 3+} and ZnO:Tb{sup 3+} nanophosphors were prepared by co-precipitation method and the effect of Li{sup +} co-doping was systematically studied by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), UV-Vis-NIR reflectance, Photoluminescence (PL) spectroscopy and Thermoluminescence (TL) studies. XRD pattern shows typical peak pattern for hexagonal wurtzite structure and matches JCPDS card no. 79-0206. A shift of the (1 0 1) peak towards the lower angle in Li{sup +} co-doped samples can be observed showing the increase of lattice constant for the incorporation of Li{sup +} ions in the lattice sites. The present samples are found to be consisting of nanorods of diameter 60–90 nm as revealed by the SEM image. The FTIR pattern shows the enhancement of peak intensity for the ZnO in the Li{sup +} co-doped samples. The diffuse reflectance study shows red shift of the absorption edges in Li{sup +} co-doped ZnO:Eu{sup 3+} and Li{sup +} co-doped ZnO:Tb{sup 3+}. PL study reveals that a very small amount of Li{sup +} is very effective for charge compensation and for producing lattice defect to enhance the rare-earth related emissions, whereas a little excess of Li{sup +} brings oxygen vacancies, which leads to luminescence quenching. The prominent peaks of the TL glow curves of Li{sup +} co-doped ZnO:RE{sup 3+} samples are found to be increased than that of ordinary ZnO:RE{sup 3+} samples. The peaks are also shifted towards the lower temperature from the peaks of ZnO:RE{sup 3+} due to the Li{sup +} co-doping. The TL glow curves of the Li{sup +} co-doped ZnO:RE{sup 3+} samples are found to obey first order kinetics. The samples are found to be very useful in thermoluminescence dosimetry. -- Highlights: • Effect of Li{sup +} co-doping on ZnO:RE{sup 3+}(RE=Eu,Tb) nanorods were studied. • Formation of nanorods confirmed by SEM and TEM image. • No major change in XRD peak pattern on Li

  12. Ultrasound-assisted degradation of organic dyes over magnetic CoFe2O4@ZnS core-shell nanocomposite.

    Science.gov (United States)

    Farhadi, Saeed; Siadatnasab, Firouzeh; Khataee, Alireza

    2017-07-01

    Magnetic CoFe2O4@ZnS core-shell nanocomposite was successfully synthesized via one-step hydrothermal decomposition of zinc(II) diethanoldithiocarbamate complex over CoFe2O4 nanoparticles at low temperature of 200°C. The obtained nanocomposite was characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, UV-Vis spectroscopy, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, magnetic measurements, and Brunauere-Emmette-Teller. The results confirmed the formation of CoFe2O4@ZnS nanocomposite with the average crystallite size of 18nm. The band gap of 3.4eV was obtained using UV-vis absorption of CoFe2O4@ZnS nanocomposite, which made it a suitable candidate for sono-/photo catalytic processes. This nanocomposite was applied as a novel sonocatalyst for the degradation of organic pollutants under ultrasound irradiation. The results showed complete degradation of methylene blue (MB) (25mg/L) within 70min in the presence of CoFe2O4@ZnS nanocomposite and H2O2 (4mM). The trapping experiments indicated that OH radicals are the main active species in dye degradation. In addition, sonocatalytic activity of the CoFe2O4@ZnS nanocomposite was higher than those of pure ZnS and CoFe2O4, showing that the combining ZnS with magnetic CoFe2O4 could be an excellent choice to improve its sonocatalytic activity. The nanocomposite could be magnetically separated and reused without any observable change in its structure and performance even after five consecutive runs. Copyright © 2017 Elsevier B.V. All rights reserved.

  13. Infrared transmissive and rain-erosion resistant performances of GeC/GaP double-layer thin films on ZnS substrates

    Science.gov (United States)

    Li, Yang-Ping; Wang, Ning; Che, Xing-Sen; Chen, Hai-Bo; Liu, Zheng-Tang

    2013-01-01

    GeC/GaP double layer films were deposited on ZnS substrates with radio frequency magnetron sputtering for infrared antireflective and protective purposes. Infrared transmissive and rain erosion resistant performances of the films were studied. Results show that the refractive index of the GaP films is similar to that of bulk GaP and a low refractive index of about 1.78 was obtained for GeC films. The average transmittance of GeC/GaP/ZnS over 8-11.5 μm rises by more than 4% in comparison with that of the uncoated ZnS. After rain erosion, some parts of the GeC layer were sputtered off, with discrete pits formed and the sub-layer GaP film exposed on the bottom of the pits. When the thickness of the GaP film was small, cracks were created by rain erosion on the surface of the exposed GaP films; yet the cracks disappeared with increasing the thickness of the sub-layer GaP. The damages to the uncoated ZnS surface caused by rain erosion are cracks. The lateral border of the cracks was peeled with increasing the rain erosion time. Infrared transmittance of both coated and uncoated ZnS fell after rain erosion, but the fall in infrared transmittance of uncoated ZnS was larger than that of coated ZnS, indicating the GeC/GaP films can protect the ZnS substrate from rain erosion.

  14. Pseudodirect to Direct Compositional Crossover in Wurtzite GaP/InxGa1–xP Core–Shell Nanowires

    KAUST Repository

    Gagliano, L.

    2016-11-29

    Thanks to their uniqueness, nanowires allow the realization of novel semiconductor crystal structures with yet unexplored properties, which can be key to overcome current technological limits. Here we develop the growth of wurtzite GaP/InGaP core-shell nanowires with tunable indium concentration and optical emission in the visible region from 590 nm (2.1 eV) to 760 nm (1.6 eV). We demonstrate a pseudodirect (δ-δ) to direct (δ-δ) transition crossover through experimental and theoretical approach. Time resolved and temperature dependent photoluminescence measurements were used, which led to the observation of a steep change in carrier lifetime and temperature dependence by respectively one and 3 orders of magnitude in the range 0.28 ± 0.04 ≤ x ≤ 0.41 ± 0.04. Our work reveals the electronic properties of wurtzite InGaP.

  15. Mechanistic study of ZnO nanorod array electrodeposition

    Energy Technology Data Exchange (ETDEWEB)

    El Belghiti, H.; Pauporte, T.; Lincot, D. [Laboratoire d' Electrochimie et Chimie Analytique, UMR7575, Ecole Nationale Superieure de Chimie de Paris-Universite Paris 6 (France)

    2008-10-15

    The growth of ZnO nanorods by electrodeposition from oxygenated aqueous mixture of zinc chloride and potassium chloride is studied experimentally as a function of the deposition time, zinc concentration and the substrate. These parameters influence markedly the characteristics of the deposits (rod density, aspect ratio, orientation). A mechanistic model is presented in order to explain the formation of ZnO nanorod arrays by electrodeposition. The model is based on the effect of zinc concentration on the interfacial pH at the electrode surface and then on the charged stable zinc species able to react with the growing film. The charge of the complex seems to be the key parameter which stops the lateral growth and then significantly increases the aspect ratio of the single crystalline nanorods. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  16. Fourier Transform Surface Plasmon Resonance (FTSPR) with Gyromagnetic Plasmonic Nanorods.

    Science.gov (United States)

    Jung, Insub; Yoo, Haneul; Jang, Hee-Jeong; Cho, Sanghyun; Lee, Kyungeun; Hong, Seunghun; Park, Sungho

    2018-02-12

    An unprecedented active and dynamic sensing platform based on a LSPR configuration that is modulated by using an external magnetic field is reported. Electrochemically synthesized Au/Fe/Au nanorods exhibited plasmonically active behavior through plasmonic coupling, and the middle ferromagnetic Fe block responded to a magnetic impetus, allowing the nanorods to be modulated. The shear force variation induced by the specific binding events between antigens and antibodies on the nanorod surface is used to enhance the sensitivity of detection of antigens in the plasmonics-based sensor application. As a proof-of-concept, influenza A virus (HA1) was used as a target protein. The limit of detection was enhanced by two orders of magnitude compared to that of traditional LSPR sensing. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Fabrication and Photocatalytic Properties of ZnSe Nanorod Films

    Directory of Open Access Journals (Sweden)

    Jiajia Yin

    2016-01-01

    Full Text Available ZnSe nanorod films grown on fused quartz glass substrates via a simple two-step synthesis protocol were demonstrated to be environmentally safe and effective recyclable photocatalysts. These films showed greatly enhanced photocatalytic activity compared to pulsed laser deposition ZnSe films in the degradation of methyl orange dye solutions. The well-crystalized ZnSe nanorods had a length of 15 µm and a diameter of 200 nm and were densely grown on the substrate. The morphology, crystal structure, crystal phase, and photophysical properties of the ZnSe nanorod films were investigated using field-emission scanning electron microscopy (FE-SEM, UV-Vis spectroscopy, X-ray diffraction (XRD, transmission electron microscopy (TEM, and high resolution transmission electron microscopy (HRTEM.

  18. Tin Oxide Nanorod Array-Based Electrochemical Hydrogen Peroxide Biosensor

    Directory of Open Access Journals (Sweden)

    Liu Jinping

    2010-01-01

    Full Text Available Abstract SnO2 nanorod array grown directly on alloy substrate has been employed as the working electrode of H2O2 biosensor. Single-crystalline SnO2 nanorods provide not only low isoelectric point and enough void spaces for facile horseradish peroxidase (HRP immobilization but also numerous conductive channels for electron transport to and from current collector; thus, leading to direct electrochemistry of HRP. The nanorod array-based biosensor demonstrates high H2O2 sensing performance in terms of excellent sensitivity (379 μA mM−1 cm−2, low detection limit (0.2 μM and high selectivity with the apparent Michaelis–Menten constant estimated to be as small as 33.9 μM. Our work further demonstrates the advantages of ordered array architecture in electrochemical device application and sheds light on the construction of other high-performance enzymatic biosensors.

  19. Surface singularities of nanorod laden droplets in magnetic field

    Science.gov (United States)

    Kornev, Konstantin; Tokarev, Alexander; Lee, Wah-Keat

    2013-11-01

    Magnetic nanorods are attractive materials enabling assembly, ordering, control, and reconfiguration of different magnetic lattices within milliseconds in milliTesla magnetic fields. In this talk we will show a new physical principle of self-assembly of magnetic nanorods into singular cusps at the droplet surface. These singularities can be formed on demand not deforming the entire droplets by taking advantage of the magneto-static interactions between nanorods in non-uniform magnetic field. Using X-ray phase contrast imaging and scaling analysis we will explain the behavior of magnetic nematics and their interactions with the droplet surface. The authors are grateful for the financial support of the National Science Foundation through Grant EFRI 0937985, and of the Air Force Office of Scientific Research through Grant FA9550-12-1-0459.

  20. Towards a Reproducible Synthesis of High Aspect Ratio Gold Nanorods

    Directory of Open Access Journals (Sweden)

    Susanne Koeppl

    2011-01-01

    Full Text Available The seed-mediated method in presence of high concentrations of CTAB is frequently implemented in the preparation of high aspect ratio gold nanorods (i.e., nanorods with aspect ratios of 5 or more; however, the reproducibility has still been limited. We rendered the synthesis procedure simpler, decreased the susceptibility to impurities, and improved the reproducibility of the product distribution. As a result of the high aspect ratios, longitudinal plasmon absorptions were shifted up to very high absorption maxima of 1955 nm in UV-vis-NIR spectra (since this band is completely covered in aqueous solution by the strong absorption of water, the gold species were embedded in poly(vinyl alcohol films for UV-vis-NIR measurements. Finally, the directed particle growth in (110 direction leads to the conclusion that the adsorption of CTAB molecules at specific crystal faces accounts for nanorod growth and not cylindrical CTAB micelles, in agreement with other observations.

  1. Controlled synthesis of PbTe nanorods and nanotubes.

    Science.gov (United States)

    Liu, Xiaoyan; Chen, Feihu; Jin, Yong; Qian, Yitai

    2013-01-01

    A hydrothermal route has been developed to synthesize lead telluride (PbTe) nanostructures through the reaction between Pb(CH3COO)2 and Na2TeO3. When the surfactant poly(vinyl pyrrolidone) (PVP) was introduced into the solution, uniform PbTe nanorods with a diameter of about 30 nm could be prepared, while absent of PVP, PbTe nanotubes could be synthesized. Furthermore, some interesting Y-, V-, crisscross-shaped PbTe nanotubes were reported for the first time. The resulting materials were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and high-resolution TEM (HRTEM). Two different mechanisms are identified to explain the formation of the nanorods and nanotubes herein. A surfactant-assisted oriental attachment mechanism is explained to describe the formation of PbTe nanorods, whereas, we deduce PbTe nanotubes follow a self-generated template route.

  2. Cr2O3 nanoparticle-functionalized WO3 nanorods for ethanol gas sensors

    Science.gov (United States)

    Choi, Seungbok; Bonyani, Maryam; Sun, Gun-Joo; Lee, Jae Kyung; Hyun, Soong Keun; Lee, Chongmu

    2018-02-01

    Pristine WO3 nanorods and Cr2O3-functionalized WO3 nanorods were synthesized by the thermal evaporation of WO3 powder in an oxidizing atmosphere, followed by spin-coating of the nanowires with Cr2O3 nanoparticles and thermal annealing in an oxidizing atmosphere. Scanning electron microscopy was used to examine the morphological features and X-ray diffraction was used to study the crystallinity and phase formation of the synthesized nanorods. Gas sensing tests were performed at different temperatures in the presence of test gases (ethanol, acetone, CO, benzene and toluene). The Cr2O3-functionalized WO3 nanorods sensor showed a stronger response to these gases relative to the pristine WO3 nanorod sensor. In particular, the response of the Cr2O3-functionalized WO3 nanorods sensor to 200 ppm ethanol gas was 5.58, which is approximately 4.4 times higher that of the pristine WO3 nanorods sensor. Furthermore, the Cr2O3-functionalized WO3 nanorods sensor had a shorter response and recovery time. The pristine WO3 nanorods had no selectivity toward ethanol gas, whereas the Cr2O3-functionalized WO3 nanorods sensor showed good selectivity toward ethanol. The gas sensing mechanism of the Cr2O3-functionalized WO3 nanorods sensor toward ethanol is discussed in detail.

  3. Reconfigurable assemblies of shape-changing nanorods.

    Science.gov (United States)

    Nguyen, Trung Dac; Glotzer, Sharon C

    2010-05-25

    Reconfigurable nanostructures represent an exciting new direction for materials. Applications of reversible transformations between nanostructures induced by molecular conformations under external fields can be found in a broad range of advanced technologies including smart materials, electromagnetic sensors, and drug delivery. With recent breakthroughs in synthesis and fabrication techniques, shape-changing nanoparticles are now possible. Such novel building blocks provide a conceptually new and exciting approach to self-assembly and phase transformations by providing tunable parameters fundamentally different from the usual thermodynamic parameters. Here we investigate via molecular simulation a transformation between two thermodynamically stable structures self-assembled by laterally tethered nanorods whose rod length is switched between two values. Building blocks with longer rods assemble into a square grid structure, while those with short rods form bilayer sheets with internal smectic A ordering at the same thermodynamic conditions. By shortening or lengthening the rods over a short time scale relative to the system equilibration time, we observe a transformation from the square grid structure into bilayer sheets, and vice versa. We also observe honeycomb grid and pentagonal grid structures for intermediate rod lengths. The reconfiguration between morphologically distinct nanostructures induced by dynamically switching the building block shape serves to motivate the fabrication of shape-changing nanoscale building blocks as a new approach to the self-assembly of reconfigurable materials.

  4. Structural, optical and ion sensing properties of 2-mercaptoethanol capped Mn-doped ZnS nanocrystals

    Science.gov (United States)

    Deka, Kuldeep; Kalita, Manos P. C.

    2017-11-01

    Zn1-xMnxS (x = 0.005, 0.01, 0.015, 0.02) nanocrystals were synthesized by a chemical route at room temperature. 2-mercaptoethanol was used as capping agent for the nanocrystals. The crystallite sizes (band gaps) have been found to be about 3.5 nm (3.8 eV) for all the Mn-doped ZnS nanocrystals. The photoluminescence spectra exhibit a broad emission centred at 410 nm which has been attributed to the presence of various defects in ZnS nanocrystals and a highly intense yellow emission at 578 nm due to the 4T1 - 6A1 transition of the Mn2+ dopant. The intensity of the yellow emission has been found to be maximum for the 1.5% Mn-doped ZnS nanocrystals. The possibility of the nanocrystals for ion sensing viz. Fe2+, Co2+, Ni2+ and Mn2+ through photoluminescence quenching of the yellow emission of the 1.5% Mn-doped ZnS nanocrystals has been investigated. The intensity of the yellow emission has been found to be highly sensitive to the presence of the ions. The limit of detection for the Fe2+, Co2+, Ni2+ and Mn2+ has been found to be 5 μM, 10 μM, 0.5 nM and 1 nM, respectively. For particular high concentration ranges which are different for the different ions, the well-known Stern-Volmer linear relationship between F0/F (F0 and F are the photoluminescence intensities without and with ions) and ion concentration has been found to be obeyed. In case of Ni2+ and Mn2+, in the very low concentration ranges, plots between F0/F and logarithm (concentration) have been found to be linear. The 2-mercaptoethanol capped Mn-doped ZnS nanocrystals thus have the potential for development of phosphorescence sensor for detection of extremely low concentration of ions, particularly Ni2+ and Mn2+.

  5. Synthesis of binary bismuth-cadmium oxide nanorods with sensitive electrochemical sensing performance

    Energy Technology Data Exchange (ETDEWEB)

    Wen, Yong [Xinjiang Univ., Xinjiang (China). School of Civil Engineering and Architecture; Pei, Lizhai; Wei, Tian [Anhui Univ. of Technology, Anhui (China). School of Materials Science and Engineering

    2017-07-15

    Binary bismuth-cadmium oxide nanorods have been synthesized by a simple hydrothermal process without templates and additives. X-ray diffraction and high-resolution transmission electron microscopy reveal that the nanorods possess single crystalline tetragonal Bi{sub 2}CdO{sub 4} phase. Scanning electron microscopy and transmission electron microscopy images show that the length and diameter of the nanorods are 20-300 nm and 5-10 μm, respectively. The formation of the binary bismuth-cadmium oxide nanorods is closely related to the hydrothermal parameters. The electrochemical sensing performance of the binary bismuth-cadmium oxide nanorods has been investigated using the nanorods as glassy carbon electrode modifiers. The detection limit is 0.19 μM with a linear range of 0.0005-2 mM. The nanorod-modified glassy carbon electrode exhibits good electrocatalytic activity toward L-cysteine and great application potential for electrochemical sensors.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-02-01

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

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

    Science.gov (United States)

    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/CH3NH3PbI3 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/CH3NH3PbI3 with the longest ZnO nanorods.

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

    Science.gov (United States)

    Abdulsattar, Mudar Ahmed

    2015-09-01

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

  9. Dynamical properties and their strain-dependence of ZnSe(ZnSe:N: Zinc-blende and wurtzite

    Directory of Open Access Journals (Sweden)

    Dandan Wang

    2014-06-01

    Full Text Available The lattice dynamical properties of ZnSe and ZnSe with substitutional N incorporation(ZnSe:N are investigated in both the zinc-blend(ZB and wurtzite(WZ structures using first-principles calculations. The optical phonon modes of ZB-ZnSe at the Γ-point locate at 250 cm−1 for LO and 213 cm−1 for TO. The characteristic E2 phonon modes at about 50 cm−1 and the E1 and another E2 phonon modes around 200 cm−1 of WZ-ZnSe are suggested to be the fingerprint for distinguishing the two polytypes of ZnSe. For substitutional N incorporated ZnSe, the N incorporation introduces three new high energy modes above 500 cm−1, and the splitting of them is much larger in the WZ phase than that in ZB phase. The strain dependence of phonon frequency which could be useful for corresponding spectroscopic strain characterization are also studied. The simple linear dependence is determined for ZB-ZnSe, while the situation for WZ-ZnSe looks more complicated.

  10. Compression-induced phase transition of GaN bulk from wurtzite phase to five-fold coordination hexagonal phase

    Science.gov (United States)

    Qian, Yu; Shang, Fulin; Wan, Qiang; Yan, Yabin

    2017-09-01

    The phase transformation of GaN bulk from the Wurtzite phase (WZ) to the hexagonal phase (HX) is studied by molecular dynamics simulation. The mechanical response and atomic structural evolution of transition are analyzed in detail. In addition, the loading rate effect on the phase transition is determined, that is, the phase transition ratio declines with a decrease of the strain rate. The WZ GaN bulk completely transforms into the HX phase in the case of compression at an ultrahigh strain rate. However, at a relatively slower strain rate, the HX phase of GaN partly nucleates and the untransformed regions are proved to be elastic deformed regions. Combined with an energy analysis, two atomic movement modes are recognized as the inducements for the phase transition and formation of elastic deformed regions. The first mode, which is responsible for the formation of elastic deformed regions, is an atomic sliding motion along the c {0001} planes. The second mode is a radial stretching atomic motion. The radial stretching motion, which requires a lot of energy, induces the WZ-HX phase transition. Moreover, the phase transition is affected drastically by the rise of temperature.

  11. Thermal expansions in wurtzite AlN, GaN, and InN: First-principle phonon calculations

    Science.gov (United States)

    Xu, Li-Chun; Wang, Ru-Zhi; Yang, Xiaodong; Yan, Hui

    2011-08-01

    Using the first-principle phonon calculations under the quasiharmonic approximation, thermal expansions in III-nitrides with wurtzite AlN, GaN, and InN are reported. The results showed that it is different for each thermal expansion of three III-nitrides at low temperatures, which is consistent with their Grüneisen parameters as the function of temperature. Below 50 K, negative thermal expansions occur in InN, while GaN and AlN follow the rule of positive thermal expansion. To seek the origin of positive/negative thermal expansion distinction, the mode Grüneisen parameters and the phonon spectra are investigated. They indicate that different low-frequency phonon vibration modes correspond to the change of thermal expansions. Below 5 THz, the significant weighted negative values of mode Grüneisen parameters, caused by the weakening of mixing-mode constituted with two transverse acoustic (TA) modes and a small overlapped part of optical modes, directly lead to the negative thermal expansion at low temperatures.

  12. Effect of (1010) crystal orientation on electronic properties of wurtzite GaN/AlGaN quantum-well

    CERN Document Server

    Park, S H

    2000-01-01

    The electronic properties of a (1010)-oriented wurtzite (WZ) GaN/AlGaN quantum well (QW) are investigated using the multiband effective-mass theory. These results are compared with those of a (0001)-oriented WZ GaN/AlGaN QW with the piezoelectric (PZ) effect taken into account. For the (0001)-oriented structure, the optical matrix element is significantly reduced with increasing the well thickness due to the PZ electric field. This means that, in the (0001)-oriented structure, a QW structure with a thinner well thickness is desirable to obtain better laser characteristics. For the (1010)-oriented structure, it is found that the average hole effective masses are largely reduced compared to those for the (0001)-oriented structure. Also, the (1010)-oriented structure shows a much larger optical matrix element for g'-polarization due to the crystal orientation effect. These results suggest that the (1010)-oriented QW structures show improved characteristic compared to the (0001)-oriented QW structure with the PZ ...

  13. Calculation of the electron and hole impact ionization rate for wurtzite AlN and GaN

    Science.gov (United States)

    Li, G. R.; Qin, Z. X.; Luo, G. F.; Shen, B.; Zhang, G. Y.

    2010-11-01

    The interband impact ionization transition rate (IIR) of electrons and holes in wurtzite GaN and AlN is calculated using full local density approximation (LDA) band structures under the scissor approximation. The IIR of AlN is first calculated and the results show a large difference between the IIR of electrons and holes. The IIR of electrons grows from zero to 1014 at energies of ~6.6-10 eV, while the IIR of holes is zero below 12.2 eV. The difference is interpreted by the energy gap between the sixth and the seventh valence bands. Analysis shows that it is hard for holes in AlN to tunnel through the large energy gap between the sixth and the seventh valence bands; as a result, holes can hardly get enough energy for impact ionization in the electrical field of several MV cm-1. This indicates that AlN is a good material for avalanche photodetectors of controllable gain, low noise and wide bandwidth with a cutoff wavelength of 210 nm. To further facilitate Monte Carlo simulation, the AlN and GaN IIR are fitted to the Keldysh formula.

  14. Piezoelectric Field Enhanced Second-Order Nonlinear Optical Susceptibilities in Wurtzite GaN/AlGaN Quantum Wells

    Science.gov (United States)

    Liu, Ansheng; Chuang, S.-L.; Ning, C. Z.; Woo, Alex (Technical Monitor)

    1999-01-01

    Second-order nonlinear optical processes including second-harmonic generation, optical rectification, and difference-frequency generation associated with intersubband transitions in wurtzite GaN/AlGaN quantum well (QW) are investigated theoretically. Taking into account the strain-induced piezoelectric (PZ) effects, we solve the electronic structure of the QW from coupled effective-mass Schrodinger equation and Poisson equation including the exchange-correlation effect under the local-density approximation. We show that the large PZ field in the QW breaks the symmetry of the confinement potential profile and leads to large second-order susceptibilities. We also show that the interband optical pump-induced electron-hole plasma results in an enhancement in the maximum value of the nonlinear coefficients and a redshift of the peak position in the nonlinear optical spectrum. By use of the difference-frequency generation, THz radiation can be generated from a GaN/Al(0.75)Ga(0.25)N with a pump laser of 1.55 micron.

  15. Spontaneous polarization effects on electronic and optical properties of wurtzite GaN/AlGaN quantum well lasers

    Energy Technology Data Exchange (ETDEWEB)

    Park, Seoung Hwan [Catholic University of Taegu-Hyosung, Kyeongsan (Korea, Republic of)

    2001-04-01

    The spontaneous (SP) and piezoelectric (PL) polarization effects on the electronic and the optical properties of wurtzite (WZ) GaN/AlGaN quantum well (QW) lasers are investigated. It is shown that the transition energies have a significant dependence on both the well and the barrier widths. The theoretical transition energies agree very well width the experimental results for several Al compositions and barrier widths. The estimated SP polarization constant for AlN ranges from -0.040 to -0.050 C/m{sup 2}, which is smaller than the value (-0.081 C/m{sup 2}) predicted by using a previous theory. It is found that the optical gain for the self-consistent (SC) model is substantially smaller than that for the flat-band (FB) model. In particular, in the case of a QW structure with a thick well width, the reduction in the optical gain is dominantly due to a larger spatial separation between the electron and the hole wave functions. These results suggest that a QW structure with a thin well width below 30 A is desirable for QW lasers. On the other hand, it is observed that the optical gain is a weak function of the barrier width.

  16. Electronic band structure of wurtzite InN around the fundamental gap in the presence of biaxial strain

    Energy Technology Data Exchange (ETDEWEB)

    Bhattacharyya, Jayeeta; Ghosh, Sandip [Department of Condensed Matter Physics and Material Science, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005 (India)

    2007-02-15

    We present results of a theoretical study of the electronic band structure of wurtzite InN films under biaxial strain in the C-plane (0001) and in planes that correspond to non-polar orientations such as the A-plane (11 anti 20) and the M-plane (1 anti 100). The calculations are performed under the k.p perturbation theory approach using the Bir-Pikus Hamiltonian. The results show that the fundamental bandgap of InN shifts by 30 meV (14 meV) for isotropic tensile (compressive) strain in the C -plane with out-of-plane contraction (dilation) of 0.2%. For films of non-polar orientations, the c-axis lies in the film plane and the strain is expected to be different between directions parallel and perpendicular to c. Such anisotropic strain give rise to valence band mixing which results in dramatic changes in the optical polarization properties as evidenced by the calculated oscillator strengths of the interband transitions. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  17. Band gaps of wurtzite Sc{sub x}Ga{sub 1−x}N alloys

    Energy Technology Data Exchange (ETDEWEB)

    Tsui, H. C. L.; Moram, M. A. [Department of Materials, Imperial College London, Exhibition Road, London SW7 2AZ (United Kingdom); Goff, L. E. [Department of Materials, Imperial College London, Exhibition Road, London SW7 2AZ (United Kingdom); Department of Physics, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE (United Kingdom); Rhode, S. K. [Department of Materials Science and Metallurgy, University of Cambridge, Charles Babbage Road, Cambridge CB3 0FS (United Kingdom); Pereira, S. [CICECO and Dept. Physics, Universidade de Aveiro, 3810-193 Aveiro (Portugal); Beere, H. E.; Farrer, I.; Nicoll, C. A.; Ritchie, D. A. [Department of Physics, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE (United Kingdom)

    2015-03-30

    Optical transmittance measurements on epitaxial, phase-pure, wurtzite-structure Sc{sub x}Ga{sub 1−x}N films with 0 ≤ x ≤ 0.26 showed that their direct optical band gaps increased from 3.33 eV to 3.89 eV with increasing x, in agreement with theory. These films contained I{sub 1}- and I{sub 2}-type stacking faults. However, the direct optical band gaps decreased from 3.37 eV to 3.26 eV for Sc{sub x}Ga{sub 1−x}N films, which additionally contained nanoscale lamellar inclusions of the zinc-blende phase, as revealed by aberration-corrected scanning transmission electron microscopy. Therefore, we conclude that the apparent reduction in Sc{sub x}Ga{sub 1−x}N band gaps with increasing x is an artefact resulting from the presence of nanoscale zinc-blende inclusions.

  18. Modelling of Packed Co Nanorods for Hard Magnetic Applications

    Directory of Open Access Journals (Sweden)

    Toson P.

    2014-07-01

    Full Text Available We present a numerical algorithm based on the bullet physics library to generate densely packed (39% - 41% structures of high-aspect-ratio nanorods for finite element micromagnetic simulations. The coercivities µ0Hc of the corresponding Cobalt nanorod structures vary between 0.50T and 0.67T, depending on the overall orientation of nanorods, which is in good agreement with experimental results. The simulations make it possible to estimate the coercivity loss due to incoherent reversal processes (27% as well as the gain due to shape anisotropy (59%. Our calculations show permanent magnets consisting of packed Co nanorods with an energy density product (BHmax of 83kJ/m3. We estimate that this value can be increased to 103kJ/m3 by increasing the packing density from 40% to 45%. Another way to optimize (BHmax is the usage of novel materials. By varying the anisotropy constant K1 and the saturation polarisation JS we found lower limits for these parameters to reach a certain energy density product. To increase (BHmax to 160 kJ/m3, K1 and JS have to be in the order of 450kJ/m3 and 2.25T, respectively. The thermal stability of this approach was verified by elastic band calculations. Cobalt nanorods with a diameter of 10nm and a height of 50nm are thermally stable at room temperature, but problematic at 900K. Doubling the nanorods' height to 100nm increases that limit considerably.

  19. Performance Improvement of GaN-Based Flip-Chip White Light-Emitting Diodes with Diffused Nanorod Reflector and with ZnO Nanorod Antireflection Layer

    Directory of Open Access Journals (Sweden)

    Hsin-Ying Lee

    2014-01-01

    Full Text Available The GaN-based flip-chip white light-emitting diodes (FCWLEDs with diffused ZnO nanorod reflector and with ZnO nanorod antireflection layer were fabricated. The ZnO nanorod array grown using an aqueous solution method was combined with Al metal to form the diffused ZnO nanorod reflector. It could avoid the blue light emitted out from the Mg-doped GaN layer of the FCWLEDs, which caused more blue light emitted out from the sapphire substrate to pump the phosphor. Moreover, the ZnO nanorod array was utilized as the antireflection layer of the FCWLEDs to reduce the total reflection loss. The light output power and the phosphor conversion efficiency of the FCWLEDs with diffused nanorod reflector and 250 nm long ZnO nanorod antireflection layer were improved from 21.15 mW to 23.90 mW and from 77.6% to 80.1% in comparison with the FCWLEDs with diffused nanorod reflector and without ZnO nanorod antireflection layer, respectively.

  20. Sensing based on the motion of enzyme-modified nanorods

    DEFF Research Database (Denmark)

    Bunea, Ada-Ioana; Pavel, Ileana-Alexandra; David, Sorin

    2015-01-01

    Asymmetric modification with an enzyme confers nanorods an enhanced diffusive motion that is dependent on the concentration of the enzyme substrate. In turn, such a motion opens the possibility of determining the concentration of the enzyme substrate by measuring the diffusion coefficient of nano...... media. Based on the obtained results we are confident that our motion-based approach to sensing can be developed to the point where different nanorods in a mixture simultaneously report on the concentration of different compounds with good temporal and spatial resolution....

  1. Far-Infrared Absorption of PbSe Nanorods

    KAUST Repository

    Hyun, Byung-Ryool

    2011-07-13

    Measurements of the far-infrared absorption spectra of PbSe nanocrystals and nanorods are presented. As the aspect ratio of the nanorods increases, the Fröhlich sphere resonance splits into two peaks. We analyze this splitting with a classical electrostatic model, which is based on the dielectric function of bulk PbSe but without any free-carrier contribution. Good agreement between the measured and calculated spectra indicates that resonances in the local field factors underlie the measured spectra. © 2011 American Chemical Society.

  2. Uptake, translocation, and toxicity of gold nanorods in maize

    Science.gov (United States)

    Moradi Shahmansouri, Nastaran

    Nanomaterials are widely used in many different products, such as electronics, cosmetics, industrial goods, biomedical uses, and other material applications. The heavy emission of nanomaterials into the environment has motived increasing concern regarding the effects on ecosystems, food chains, and, human health. Plants can tolerate a certain amount of natural nanomaterials, but large amounts of ENMs released from a variety of industries could be toxic to plants and possibly threaten the ecosystem. Employing phytoremediation as a contamination treatment method may show promise. However a pre-requisite to successful treatment is a better understanding of the behavior and effects of nanomaterials within plant systems. This study is designed to investigate the uptake, translocation, bioavailability, and toxicity of gold nanorods in maize plants. Maize is an important food and feed crop that can be used to understand the potential hazardous effects of nanoparticle uptake and distribution in the food chain. The findings could be an important contribution to the fields of phytoremediation, agri-nanotechnology, and nanoparticle toxicity on plants. In the first experiment, hydroponically grown maize seedlings were exposed to similar doses of commercial non-coated gold nanorods in three sizes, 10x34 nm, 20x75 nm, and 40x96 nm. The three nanorod species were suspended in solutions at concentrations of 350 mg/l, 5.8 mg/l, and 14 mg/l, respectively. Maize plants were exposed to all three solutions resulting in considerably lower transpiration and wet biomass than control plants. Likewise, dry biomass was reduced, but the effect is less pronounced than that of transpiration and wet biomass. The reduced transpiration and water content, which eventually proved fatal to exposed plants, were most likely a result of toxic effect of gold nanorod, which appeared to physically hinder the root system. TEM images proved that maize plants can uptake gold particles and accumulate them in

  3. Enzyme-mimetic effects of gold@platinum nanorods on the antioxidant activity of ascorbic acid

    Science.gov (United States)

    Zhou, Yu-Ting; He, Weiwei; Wamer, Wayne G.; Hu, Xiaona; Wu, Xiaochun; Lo, Y. Martin; Yin, Jun-Jie

    2013-01-01

    Au@Pt nanorods were prepared by growing platinum nanodots on gold nanorods. Using electron spin resonance (ESR), we determined that the mechanisms for oxidation of ascorbic acid (AA) by Au@Pt nanorods and ascorbic acid oxidase (AAO) were kinetically similar and yielded similar products. In addition we observed that Au@Pt nanorods were stable with respect to temperature and pH. Using UV-VIS spectroscopy, the apparent kinetics of enzyme-mimetic activity of Au@Pt nanorods were studied and compared with the activity of AAO. With the help of ESR, we found that Au@Pt nanorods did not scavenge hydroxyl radicals but inhibited the antioxidant ability of AA for scavenging hydroxyl radicals produced by photoirradiating solutions containing titanium dioxide and zinc oxide. Moreover, the Au@Pt nanorods reduced the ability of AA to scavenge DPPH radicals and superoxide radicals. These results demonstrate that Au@Pt nanorods can reduce the antioxidant activity of AA. Therefore, it is necessary to consider the effects of using Pt nanoparticles together with other reducing agents or antioxidants such as AA due to the oxidase-like property of Au@Pt nanorods.Au@Pt nanorods were prepared by growing platinum nanodots on gold nanorods. Using electron spin resonance (ESR), we determined that the mechanisms for oxidation of ascorbic acid (AA) by Au@Pt nanorods and ascorbic acid oxidase (AAO) were kinetically similar and yielded similar products. In addition we observed that Au@Pt nanorods were stable with respect to temperature and pH. Using UV-VIS spectroscopy, the apparent kinetics of enzyme-mimetic activity of Au@Pt nanorods were studied and compared with the activity of AAO. With the help of ESR, we found that Au@Pt nanorods did not scavenge hydroxyl radicals but inhibited the antioxidant ability of AA for scavenging hydroxyl radicals produced by photoirradiating solutions containing titanium dioxide and zinc oxide. Moreover, the Au@Pt nanorods reduced the ability of AA to scavenge

  4. Synthesis, stabilisation and characterisation of rhamnolipid-capped ZnS nanoparticles in aqueous medium.

    Science.gov (United States)

    Narayanan, J; Ramji, R; Sahu, H; Gautam, P

    2010-06-01

    Capping agents stabilise the size of the nanoparticles in the range of 1-10 nm. Microbial surfactants as capping agents are beneficial replacements for chemically synthesised ones because of lower toxicity. Rhamnolipids are surfactants produced by Pseudomonas aeruginosa, having high affinity for metal ions. In this study, the authors used rhamnolipids for capping ZnS nanoparticles. The capped particles were stabilised in aqueous environment and its characteristics were studied using Fourier transform infrared spectroscopy (FT-IR), small angle X-ray scattering (SAXS), high resolution transmission electron microscopy (HR-TEM) and ultraviolet-visible spectra, fluorescence spectra. The particle Bohr radius was found to be 4.5 nm both by SAXS and HRTEM, thus proving rhamnolipid to be an effective capping agent for the synthesis of uniform nanoparticles. SAXS study not only reveals the particle size and distribution but also its self-affined agglomeration behaviour. This work is a novel method for stabilising nanoparticles in aqueous condition using biosurfactant.

  5. A rapid microwave route for the synthesis of ZnS nanoparticles

    Directory of Open Access Journals (Sweden)

    M. Salavati-Niasari

    2011-07-01

    Full Text Available ZnS  nanoparticles  were  synthesized  via  a  simple  surfactant  free microwave  route.  In  this  synthesis, thioacetamide  was  used  as sulfur  source.  The effects  of different  parameters  such  as  type of zinc precursor,  time  and  power  of  irradiation  on  the  morphology and  particle  size  of  the  products  have been  investigated.  The nanostructures  were  characterized  by  means  of  X-ray  diffraction (XRD, energy-dispersive X-ray analysis (EDX, scanning electron microscopy (SEM, Fourier transform infrared (FT-IR and photoluminescence (PL spectroscopy.

  6. Mechanisms of Polymer-Templated Nanoparticle Synthesis: Contrasting ZnS and Au.

    Science.gov (United States)

    Podhorska, Lucia; Delcassian, Derfogail; Goode, Angela E; Agyei, Michael; McComb, David W; Ryan, Mary P; Dunlop, Iain E

    2016-09-13

    We combine solution small-angle X-ray scattering (SAXS) and high-resolution analytical transmission electron microscopy (ATEM) to gain a full mechanistic understanding of substructure formation in nanoparticles templated by block copolymer reverse micelles, specifically poly(styrene)-block-poly(2-vinylpyridine). We report a novel substructure for micelle-templated ZnS nanoparticles, in which small crystallites (∼4 nm) exist within a larger (∼20 nm) amorphous organic-inorganic hybrid matrix. The formation of this complex structure is explained via SAXS measurements that characterize in situ for the first time the intermediate state of the metal-loaded micelle core: Zn(2+) ions are distributed throughout the micelle core, which solidifies as a unit on sulfidation. The nanoparticle size is thus determined by the radius of the metal-loaded core, rather than the quantity of available metal ions. This mechanism leads to particle size counterintuitively decreasing with increasing metal content, based on the modified interactions of the metal-complexed monomers in direct contrast to gold nanoparticles templated by the same polymer.

  7. Room temperature d{sup 0} ferromagnetism in ZnS nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Proshchenko, Vitaly; Horoz, Sabit; Tang, Jinke; Dahnovsky, Yuri, E-mail: yurid@uwyo.edu [Department of Physics and Astronomy/3905, University of Wyoming, 1000 E. University Avenue, Laramie, Wyoming 82071 (United States)

    2016-06-14

    Room temperature ferromagnetic semiconductors have a great deal of advantage because of their easy integration into semiconductor devices. ZnS nanocrystals (NCs), bulk, and surfaces exhibit d{sup 0} ferromagnetism at room temperature. The experiments reveal that NC ferromagnetism takes place at low and room temperatures only due to Zn vacancies (S vacancies do not contribute). To understand the mechanism of d{sup 0} ferromagnetism, we introduce the surface-bulk model of a nanocrystal, which includes both surface and bulk magnetizations. The calculations demonstrate that the surface has the higher than bulk magnetization. We find the mechanism of the ferromagnetism is due to sulfur s- and p-electrons in a tetrahedral crystal field. The bulk magnetic moment increases with Zn vacancy concentration at small concentrations and then goes down at larger concentrations. A surface magnetic moment behaves differently with the concentration. It is always a monotonically rising function. We find that the total NC magnetic moment increases with the size and concentration of Zn vacancies (only low concentrations). We also study the magnetization per unit cell where we find that it decreases for the surface and increases for bulk magnetism with the NC size.

  8. Acquired CNS lesions in fetal MRI; Erworbene ZNS-Laesionen im fetalen MRT

    Energy Technology Data Exchange (ETDEWEB)

    Reith, W.; Pogledic, I. [Universitaetsklinikum des Saarlandes, Homburg/Saar, Klinik fuer Diagnostische und Interventionelle Neuroradiologie, Homburg/Saar (Germany)

    2013-02-15

    Acquired central nervous system (CNS) lesions are often subtle; therefore, the prenatal diagnosis of these lesions is extremely important. The fetal ultrasound examination and magnetic resonance imaging (MRI) are two important imaging methods that give an insight into these types lesions. The method of choice during pregnancy is still fetal ultrasound; however, fetal MRI is important when there are certain pathologies, e.g. periventricular leukomalacia (PVL) or malformations of the vein of Galen. In this manner clinicians can plan further therapy after childbirth in advance (e.g. cerebral angiography or embolization). (orig.) [German] Die erworbenen ZNS-Laesionen sind oft subtil, und eine praezise praenatale Diagnostik ist in diesen Faellen besonders wichtig. Die fetale Sonographie und das fetale MRT koennen hierzu einen relevanten Beitrag leisten. Die Sonographie ist immer noch die Untersuchungsmethode der Wahl waehrend der Schwangerschaft. Insbesondere bei bestimmten Pathologien wie der periventrikulaeren Leukomalazie (PVL) oder einer V. -Galeni-Malformation ist das fetale MRT sehr hilfreich, um nach der Geburt die entsprechenden weitergehenden Massnahmen, wie eine zerebrale Angiographie und Embolisation, fruehzeitig zu planen. (orig.)

  9. Super Exchange-Induced Canted Ferromagnetism in Transition Metal-Doped ZnS Quantum Dots

    Science.gov (United States)

    Sharma, Lalit Kumar; Mukherjee, Samrat

    2017-02-01

    ZnS quantum dots doped with magnetic transition metal (Zn1- x TM x S; where x = 0.04, 0.08 and transition metal = Ni, Mn, Fe, Co and Cr) were synthesized using a chemical co-precipitation method. To prevent agglomeration, samples were capped with polyvinylpyrrolidone. X-ray diffraction peaks confirmed pure cubic phases of all samples. The crystallite dimensions of the samples are within the scale of 2.0-2.6 nm, which was calculated using Scherrer formula. A band gap varying from 4.1 eV to 4.24 eV was estimated from their ultraviolet-visible absorption spectroscopy. The synthesized samples show a strong blue shift in their emission spectroscopy along with emissions from inherent Zn and S point defects (interstitial and vacancy). Superconducting quantum interference device studies at 300 K reveal that all samples show room temperature canted ferromagnetism at low magnetic fields which does not saturate even up to a fields of 5 T. We study the defects as seen through emission spectroscopy and correlate with the magnetic properties of the doped semiconducting quantum dots.

  10. Synthesis of Nitrogen-Doped ZnS with Camellia Brushfield Yellow Nanostructures for Enhanced Photocatalytic Activity under Visible Light Irradiation

    Directory of Open Access Journals (Sweden)

    Gang-Juan Lee

    2013-01-01

    Full Text Available Nitrogen modified zinc sulfide photocatalysts were successfully prepared and characterized by X-ray diffraction (XRD, field emission scanning electron microscopy (FE-SEM, high-resolution transmission electron microscopy (HR-TEM, X-ray photoelectron spectroscopy (XPS, and surface area analysis. Thermal decomposition of the semisolid was carried out under nitrogen conditions at 500°C for 2 hours, and a series of nitrogen-doped ZnS photocatalysts were produced by controlling inflow flow rate of nitrogen at 15–140 mL/min. Optical characterizations of the synthesized N-doping ZnS substantially show the shifted photoabsorption properties from ultraviolet (UV region to visible light. The band gaps of nitrogen-doped ZnS composite catalysts were calculated to be in the range of 2.58~2.74 eV from the absorptions edge position. The 15N/ZnS catalyst shows the highest photocatalytic activity, which results in 75.7% degradation of Orange II dye in 5 hrs by visible light irradiation, compared with pristine ZnS and higher percentage N-doping ZnS photocatalysts.

  11. Thermal and optical characterization of biologically synthesized ZnS nanoparticles synthesized from an endophytic fungus Aspergillus flavus: A colorimetric probe in metal detection

    Science.gov (United States)

    Uddandarao, Priyanka; Balakrishnan, Raj Mohan

    2017-03-01

    Nanostructured semiconductor materials are of great importance for several technological applications due to their optical and thermal properties. The design and fabrication of metal sulfide nanoparticles with tunable properties for advanced applications have drawn a great deal of attention in the field of nanotechnology. ZnS is a potential II-IV group material which is used in hetero-junction solar cells, light emitting diodes, optoelectronic devices, electro luminescent devices and photovoltaic cells. Due to their multiple applications, there is a need to elucidate their thermal and optical properties. In the present study, thermal and optical properties of biologically synthesized ZnS nanoparticles are determined in detail with Thermal Gravimetric Analysis (TGA), Derivative Thermogravimetric Analysis (DTG), Differential Scanning Calorimeter (DSC), Diffuse Reflectance Spectroscopy (DRS), Photoluminescence (PL) and Raman spectroscopy. The results reveal that ZnS NPs exhibit a very strong quantum confinement with a significant increase in their optical band gap energy. These biologically synthesized ZnS NPs contain protein residues that can selectively bind with metal ions in aqueous solutions and can exhibit an aggregation-induced color change. This phenomenon is utilized to quantitatively measure the metal concentrations of Cu2 + and Mn2 + in this study. Further the stability of nanoparticles for the metal sensing process is accessed by UV-Vis spectrometer, zeta potential and cyclic voltammeter. The selectivity and sensitivity of ZnS NPs indicate its potential use as a sensor for metal detection in the ecosystem.

  12. Large Stokes Shift and High Efficiency Luminescent Solar Concentrator Incorporated with CuInS2/ZnS Quantum Dots.

    Science.gov (United States)

    Li, Chen; Chen, Wei; Wu, Dan; Quan, Dunhang; Zhou, Ziming; Hao, Junjie; Qin, Jing; Li, Yiwen; He, Zhubing; Wang, Kai

    2015-12-08

    Luminescent solar concentrator (LSC) incorporated with quantum dots (QDs) have been widely regarded as one of the most important development trends of cost-effective solar energy. In this study, for the first time we report a new QDs-LSC integrated with heavy metal free CuInS2/ZnS core/shell QDs with large Stokes shift and high optical efficiency. The as-prepared CuInS2/ZnS QDs possess advantages of high photoluminescence quantum yield of 81% and large Stocks shift more than 150 nm. The optical efficiency of CuInS2/ZnS QDs-LSC reaches as high as 26.5%. Moreover, the power conversion efficiency of the QDs-LSC-PV device reaches more than 3 folds to that of pure PMMA-PV device. Furthermore, the PV device is able to harvest 4.91 folds solar energy with the assistance of this new CuInS2/ZnS QDs-LSC for the same size c-Si PV cell. The results demonstrate that this new CuInS2/ZnS QDs-LSC provides a promising way for the high efficiency, nonhazardous and low cost solar energy.

  13. Band gap modulation of mono and bi-layer hexagonal ZnS under transverse electric field and bi-axial strain: A first principles study

    Science.gov (United States)

    Rai, D. P.; Kaur, Sumandeep; Srivastava, Sunita

    2018-02-01

    Density functional theory has been employed to study the electronic and mechanical properties of the monolayer and bilayer ZnS. AB stacked ZnS bilayer is found to be energetically more favorable over the AA stacked ZnS bilayer. The electronic bandgap decreases on moving from monolayer to bilayer. Application of positive transverse electric field in AA/AB stacked bilayers leads to a semiconductor to metal transition at 1.10 V/Å. Reversed polarity of electric field, on the other hand, leads to an asymmetric behavior of the bandgap for AB stacking while the behavior of the bandgap in AA stacking is polarity independent. The strong dependency of bandgap on polarity of electric field in AB stacked ZnS bilayer is due to the balancing of external field with the induced internal field which arises due the electronegativity and heterogeneity in the arrangements of atoms. The electronic structure varies with the variation of applied biaxial strain (compression/tensile). We report an increase in band gap in both single and double layers under compression up to -8.0%, which can be attributed to greater superposition of atomic orbitals (Zn-d and S-p hybridization). We expect that our results may stimulate more theoretical and experimental work on hexagonal multi-layers of ZnS employing external field (temperature, pressure, field etc.) for future applications of our present work.

  14. Optimization of the ZnS Buffer Layer by Chemical Bath Deposition for Cu(In,Ga)Se2 Solar Cells.

    Science.gov (United States)

    Jeon, Dong-Hwan; Hwang, Dae-Kue; Kim, Dae-Hwan; Kang, Jin-Kyu; Lee, Chang-Seop

    2016-05-01

    We evaluated a ZnS buffer layer prepared using a chemical bath deposition (CBD) process for application in cadmium-free Cu(In,Ga)Se2 (CIGS) solar cells. The ZnS buffer layer showed good transmittance (above 90%) in the spectral range from 300 to 800 nm and was non-toxic compared with the CdS buffer layers normally used in CIGS solar cells. The CBD process was affected by several deposition conditions. The deposition rate was dependent on the ammonia concentration (complexing agent). When the ammonia concentration was either too high or low, a decrease in the deposition rate was observed. In addition, post heat treatments at high temperatures had detrimental influences on the ZnS buffer layers because portions of the ZnS thin films were transformed into ZnO. With optimized deposition conditions, a CIGS solar cell with a ZnS buffer layer showed an efficiency of 14.18% with a 0.23 cm2 active area under 100 mW/cm2 illumination.

  15. The effect of varied pH on the luminescence characteristics of antibody-mercaptoacetic acid conjugated ZnS nanowires

    Science.gov (United States)

    Chaudhry, Madeeha; Rehman, Malik Abdul; Gul, Asghari; Qamar, Raheel; Bhatti, Arshad Saleem

    2017-11-01

    We demonstrate here that the effect of varied pH of the media on the photoluminescence (PL) properties of mercaptoacetic acid (MAA) and digoxin antibody (Ab) conjugated zinc sulphide (ZnS) nanowires. The charge-transfer kinetics from MAA to ZnS and vice versa showed a profound effect on the luminescence of ZnS defect states. The PL intensity of the ZnS defect states showed strong dependence on the value of pH with respect to the pKa of MAA. The carboxyl and thiol group of MAA in the protonated (pH pH > pKa) states resulted in the quenched PL intensity. While for pH ∼ pKa, the PL intensity was regained as there was equal probability of both protonated and deprotonated carboxyl and thiol groups. These findings indicated that pH of the environment is a key parameter for the use of MAA-Ab conjugated ZnS nanowires as an optical biomarker.

  16. Synthesis of non-aggregated nicotinic acid coated magnetite nanorods via hydrothermal technique

    Energy Technology Data Exchange (ETDEWEB)

    Attallah, Olivia A., E-mail: olivia.adly@hu.edu.eg [Center of Nanotechnology, Nile University, 12677 Giza (Egypt); Pharmaceutical Chemistry Department, Heliopolis University, 11777 El Salam, Cairo (Egypt); Girgis, E. [Solid State Physics Department, National Research Center, 12622 Dokki, Giza (Egypt); Advanced Materials and Nanotechnology Lab, CEAS, National Research Center, 12622 Dokki, Giza (Egypt); Abdel-Mottaleb, Mohamed M.S.A. [Center of Nanotechnology, Nile University, 12677 Giza (Egypt)

    2016-02-01

    Non-aggregated magnetite nanorods with average diameters of 20–30 nm and lengths of up to 350 nm were synthesized via in situ, template free hydrothermal technique. These nanorods capped with different concentrations (1, 1.5, 2 and 2.5 g) of nicotinic acid (vitamin B3); possessed good magnetic properties and easy dispersion in aqueous solutions. Our new synthesis technique maintained the uniform shape of the nanorods even with increasing the coating material concentration. The effect of nicotinic acid on the shape, particle size, chemical structure and magnetic properties of the prepared nanorods was evaluated using different characterization methods. The length of nanorods increased from 270 nm to 350 nm in nicotinic acid coated nanorods. Goethite and magnetite phases with different ratios were the dominant phases in the coated samples while a pure magnetite phase was observed in the uncoated one. Nicotinic acid coated magnetic nanorods showed a significant decrease in saturation magnetization than uncoated samples (55 emu/g) reaching 4 emu/g in 2.5 g nicotinic acid coated sample. The novel synthesis technique proved its potentiality to prepare coated metal oxides with one dimensional nanostructure which can function effectively in different biological applications. - Highlights: • We synthesize nicotinic acid coated magnetite nanorods via hydrothermal technique • Effect of nicotinic acid concentration on the nanorods properties was significant • Nanorods maintained uniform shape with increased concentration of nicotinic acid • Alterations occurred in particle size, mineral phases and magnetics of coated samples.

  17. Photoconduction properties in aligned assemblies of colloidal CdSe/CdS nanorods.

    Science.gov (United States)

    Persano, Anna; De Giorgi, Milena; Fiore, Angela; Cingolani, Roberto; Manna, Liberato; Cola, Adriano; Krahne, Roman

    2010-03-23

    We report on photoconduction and optical properties of aligned assemblies of core-shell CdSe/CdS nanorods prepared by a seeded growth approach. We fabricate oriented layers of nanorods by drop casting the nanorods from a solution on substrates with prepatterned, micrometer-spaced electrodes and obtain nanorod alignment due to the coffee stain effect. The photoconductivity of the nanorod layers can be improved significantly by an annealing process under vacuum conditions. The spectral response of the photocurrent shows distinct features that can be assigned to the electronic level structure of the core-shell nanorods and that relate well to the spectra obtained by absorption measurements. We study assemblies of nanorods oriented parallel and perpendicular to the applied electric field by the combined use of photocurrent and photoluminescence spectroscopy. We obtain consistent results which show that charge carrier separation and transport are more efficient for nanorods oriented parallel to the electric field. We also investigate the light polarization sensitivity of the photocurrent for the oriented nanorod layers and observe higher conductivity in the case of perpendicular polarization with respect to the long axis of the nanorods.

  18. Graphite/ZnO nanorods junction for ultraviolet photodetectors

    Czech Academy of Sciences Publication Activity Database

    Yatskiv, Roman; Grym, Jan; Verde, Maria

    2015-01-01

    Roč. 105, March 2015 (2015), s. 70-73 ISSN 0038-1101 R&D Projects: GA MŠk(CZ) LD14111 Institutional support: RVO:67985882 Keywords : ZnO nanorods * Graphite based junction * UV photodetector Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 1.345, year: 2015

  19. Luminescence properties of hydrothermally grown ZnO nanorods

    Czech Academy of Sciences Publication Activity Database

    Yatskiv, Roman; Grym, Jan

    2016-01-01

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

  20. Plasmonic-cavity model for radiating nano-rod antennas

    DEFF Research Database (Denmark)

    Peng, Liang; Mortensen, N. Asger

    2014-01-01

    In this paper, we propose the analytical solution of nano-rod antennas utilizing a cylindrical harmonics expansion. By treating the metallic nano-rods as plasmonic cavities, we derive closed-form expressions for both the internal and the radiated fields, as well as the resonant condition and the ......In this paper, we propose the analytical solution of nano-rod antennas utilizing a cylindrical harmonics expansion. By treating the metallic nano-rods as plasmonic cavities, we derive closed-form expressions for both the internal and the radiated fields, as well as the resonant condition...... and the radiation efficiency. With our theoretical model, we show that besides the plasmonic resonances, efficient radiation takes advantage of (a) rendering a large value of the rods' radius and (b) a central-fed profile, through which the radiation efficiency can reach up to 70% and even higher in a wide...... frequency band. Our theoretical expressions and conclusions are general and pave the way for engineering and further optimization of optical antenna systems and their radiation patterns....

  1. Detecting Casimir torque with an optically levitated nanorod

    Science.gov (United States)

    Xu, Zhujing; Li, Tongcang

    2017-09-01

    The linear momentum and angular momentum of virtual photons of quantum vacuum fluctuations can induce the Casimir force and the Casimir torque, respectively. While the Casimir force has been measured extensively, the Casimir torque has not been observed experimentally though it was predicted over 40 years ago. Here we propose to detect the Casimir torque with an optically levitated nanorod near a birefringent plate in vacuum. The axis of the nanorod tends to align with the polarization direction of the linearly polarized optical tweezer. When its axis is not parallel or perpendicular to the optical axis of the birefringent crystal, it will experience a Casimir torque that shifts its orientation slightly. We calculate the Casimir torque and Casimir force acting on a levitated nanorod near a birefringent crystal. We also investigate the effects of thermal noise and photon recoils on the torque and force detection. We prove that a levitated nanorod in vacuum will be capable of detecting the Casimir torque under realistic conditions, and will be an important tool in precision measurements.

  2. Resonances and permittivity dispersion effects in ITO nanorod arrays

    CERN Document Server

    Li, Shi-Qiang; Ketterson, John B; Chang, Robert P H

    2014-01-01

    In the nanophotonics community, there is an active discussion regarding the origin of the selective absorption/scattering of light by the resonances with nanorod arrays. Here we report a study of the resonances in ordered indium-tin-oxide (ITO) nanorod arrays from the perspective of waveguides. We discover that with only 2.4% geometrical coverage, the micron-length nanorod arrays strongly interact with light across an extra-wide band from visible to mid-infrared resulting in less than 10% transmission at the first order destructive interference. Simulations show excellent agreement with our experimental observation. Near-field profile obtained from simulation reveals the electric field is mainly localized on the surfaces of the nanorods at all the resonances. Theoretical analysis is then applied to explain the resonances and it was found that the resonances in the visible are different from those in the infrared. The former resonances are the result of the interference between guided wave and wave propagated ...

  3. Attachment of Quantum Dots on Zinc Oxide Nanorods

    Science.gov (United States)

    Seay, Jared; Liang, Huan; Harikumar, Parameswar

    2011-03-01

    ZnO nanorods grown by hydrothermal technique are of great interest for potential applications in photovoltaic and optoelectronic devices. In this study we investigate the optimization of the optical absorption properties by a low temperature, chemical bath deposition technique. Our group fabricated nanorods on indium tin oxide (ITO) substrate with precursor solution of zinc nitrate hexahydrate and hexamethylenetramine (1:1 molar ratio) at 95C for 9 hours. In order to optimize the light absorption characteristics of ZnO nanorods, CdSe/ZnS core-shell quantum dots (QDs) of various diameters were attached to the surface of ZnO nanostructures grown on ITO and gold-coated silicon substrates. Density of quantum dots was varied by controlling the number drops on the surface of the ZnO nanorods. For a 0.1 M concentration of QDs of 10 nm diameter, the PL intensity at 385 nm increased as the density of the quantum dots on ZnO nanostructures was increased. For quantum dots at 1 M concentration, the PL intensity at 385 nm increased at the beginning and then decreased at higher density. We will discuss the observed changes in PL intensity with QD concentration with ZnO-QD band structure and recombination-diffusion processes taking place at the interface.

  4. Synthesis and characterization of metal oxide nanorod brushes

    Indian Academy of Sciences (India)

    WINTEC

    . The length of the nanorods is. <2 μm and is not up to the thickness of the membrane suggesting the discontinuity in the structure. TEM image shown in figure 4b confirms the rod-like morphology of. MoO3. The electron diffraction pattern shown ...

  5. A Surface Acoustic Wave Ethanol Sensor with Zinc Oxide Nanorods

    Directory of Open Access Journals (Sweden)

    Timothy J. Giffney

    2012-01-01

    Full Text Available Surface acoustic wave (SAW sensors are a class of piezoelectric MEMS sensors which can achieve high sensitivity and excellent robustness. A surface acoustic wave ethanol sensor using ZnO nanorods has been developed and tested. Vertically oriented ZnO nanorods were produced on a ZnO/128∘ rotated Y-cut LiNbO3 layered SAW device using a solution growth method with zinc nitrate, hexamethylenetriamine, and polyethyleneimine. The nanorods have average diameter of 45 nm and height of 1 μm. The SAW device has a wavelength of 60 um and a center frequency of 66 MHz at room temperature. In testing at an operating temperature of 270∘C with an ethanol concentration of 2300 ppm, the sensor exhibited a 24 KHz frequency shift. This represents a significant improvement in comparison to an otherwise identical sensor using a ZnO thin film without nanorods, which had a frequency shift of 9 KHz.

  6. Facile growth of Ag@ Pt bimetallic nanorods on electrochemically ...

    Indian Academy of Sciences (India)

    An efficient transducer was constructed by the direct growth of bimetallic Ag@Pt nanorods (NRDs) on L−tryptophan functionalized electrochemically reduced graphene oxide (L−ERGO) ... On the other hand, L−ERGO nanosheets tend to facilitate an effective immobilization of low density Ag seeds (Agseeds) on its surface.

  7. Biodegradable theranostic plasmonic vesicles of amphiphilic gold nanorods.

    Science.gov (United States)

    Song, Jibin; Pu, Lu; Zhou, Jiajing; Duan, Bo; Duan, Hongwei

    2013-11-26

    We have developed surface-initiated organocatalytic ring-opening polymerization on functional nanocrystals and synthesized amphiphilic gold nanorods carrying well-defined mixed polymer brushes of poly(ethylene glycol) and polylactide. Self-assembly of the amphiphilic gold nanorods affords biodegradable plasmonic vesicles that can be destructed by both enzymatic degradation and near-infrared photothermal heating. When tagged with Raman probes, strongly coupled gold nanorods in the self-assembled vesicles give rise to highly active SERS signals. The biodegradable plasmonic vesicles exhibit a unique combination of optical and structural properties that are of particular interest for theranostic applications. We have demonstrated that bioconjugated SERS-active plasmonic vesicles can specifically target EpCAM-positive cancer cells, leading to ultrasensitive spectroscopic detection of cancer cells. Furthermore, integration of photothermal effect of gold nanorods and large loading capacity of the vesicles provides opportunities for localized synergistic photothermal ablation and photoactivated chemotherapy, which have shown higher efficiency in killing targeted cancer cells than either single therapeutic modality. The versatile chemistry of organocatalytic ring-opening polymerization, in conjugation with recent development in synthesizing functional nanocrystals with tailored optical, electronic, and magnetic properties opens the possibilities for constructing multifunctional biodegradable platforms for clinical translation.

  8. Epitaxial magnetite nanorods with enhanced room temperature magnetic anisotropy.

    Science.gov (United States)

    Chandra, Sayan; Das, Raja; Kalappattil, Vijaysankar; Eggers, Tatiana; Harnagea, Catalin; Nechache, Riad; Phan, Manh-Huong; Rosei, Federico; Srikanth, Hariharan

    2017-06-14

    Nanostructured magnetic materials with well-defined magnetic anisotropy are very promising as building blocks in spintronic devices that operate at room temperature. Here we demonstrate the epitaxial growth of highly oriented Fe3O4 nanorods on a SrTiO3 substrate by hydrothermal synthesis without the use of a seed layer. The epitaxial nanorods showed biaxial magnetic anisotropy with an order of magnitude difference between the anisotropy field values of the easy and hard axes. Using a combination of conventional magnetometry, transverse susceptibility, magnetic force microscopy (MFM) and magneto-optic Kerr effect (MOKE) measurements, we investigate magnetic behavior such as temperature dependent magnetization and anisotropy, along with room temperature magnetic domain formation and its switching. The interplay of epitaxy and enhanced magnetic anisotropy at room temperature, with respect to randomly oriented powder Fe3O4 nanorods, is discussed. The results obtained identify epitaxial nanorods as useful materials for magnetic data storage and spintronic devices that necessitate tunable anisotropic properties with sharp magnetic switching phenomena.

  9. Co-catalyst free Titanate Nanorods for improved Hydrogen ...

    Indian Academy of Sciences (India)

    Abstract. Harnessing solar energy for water splitting into hydrogen (H2) and oxygen (O2) gases in the pres- ence of semiconductor catalyst is one of the most promising and cleaner methods of chemical fuel (H2) pro- duction. Herein, we report a simplified method for the preparation of photo-active titanate nanorods catalyst.

  10. Zinc oxide nanorods functionalized paper for protein preconcentration in biodiagnostics

    Science.gov (United States)

    Tiwari, Sadhana; Vinchurkar, Madhuri; Rao, V. Ramgopal; Garnier, Gil

    2017-03-01

    Distinguishing a specific biomarker from a biofluid sample containing a large variety of proteins often requires the selective preconcentration of that particular biomarker to a detectable level for analysis. Low-cost, paper-based device is an emerging opportunity in diagnostics. In the present study, we report a novel Zinc oxide nanorods functionalized paper platform for the preconcentration of Myoglobin, a cardiac biomarker. Zinc oxide nanorods were grown on a Whatman filter paper no. 1 via the standard hydrothermal route. The growth of Zinc oxide nanorods on paper was confirmed by a combination of techniques consisting of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS,) scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDX) analysis. The Zinc oxide nanorods modified Whatman filter paper (ZnO-NRs/WFP) was further tested for use as a protein preconcentrator. Paper-based ELISA was performed for determination of pre-concentration of cardiac marker protein Myoglobin using the new ZnO-NRs/WFP platform. The ZnO-NRs/WFP could efficiently capture the biomarker even from a very dilute solution (Myoglobin diagnostic concept.

  11. Tuning the oriented deposition of gold nanorods on patterned substrates

    NARCIS (Netherlands)

    Ahmed, W.; Glass, C.; Kooij, Ernst S.; van Ruitenbeek, J.M.

    2014-01-01

    The controlled patterning of anisotropic gold nanoparticles is of crucial importance for many applications related to their optical properties. In this paper, we report that gold nanorods prepared by a seed-mediated synthesis protocol (without any further functionalization) can be selectively

  12. Antimicrobial potentials of silver colloidal (nanorods) on clinical ...

    African Journals Online (AJOL)

    Antimicrobial resistance in developing countries has long been an issue of major concern. Nanotechnology has become an eye opener for the intervention on multiple drug resistance organisms. In this study we investigated the antimicrobial potentials of Silver Nitrate (nanorods) solution used in managing infectious ...

  13. ZnS thin films grown by atomic layer deposition on GaAs and HgCdTe substrates at very low temperature

    Science.gov (United States)

    Sun, C. H.; Zhang, P.; Zhang, T. N.; Chen, X.; Chen, Y. Y.; Ye, Z. H.

    2017-09-01

    ZnS films grown on GaAs and HgCdTe substrates by atomic layer deposition (ALD) under very low temperature were investigated in this work. ZnS films were grown under several temperatures lower than 140 °C. The properties of the films were investigated with high-resolution X-ray diffraction (HRXRD), scanning electron microscope (SEM), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). The results showed the ZnS films were polycrystalline. The growth rate monotonically decreased with temperature, as well as the root mean square (r.m.s) roughness measured by AFM. XPS measurement revealed the films were stoichiometric in Zn and S.

  14. Optical and structural characterization of CdS/ZnS and CdS:Cu(2+) /ZnS core-shell nanoparticles.

    Science.gov (United States)

    Murugadoss, G; Kumar, M Rajesh

    2014-09-01

    Core-shell CdS/ZnS (Zn 0.025-0.125 M) and CdS:Cu(2+) (1%)/ZnS nanoparticles were successfully synthesized using a chemical method. X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR TEM), photoluminescence (PL) and UV/Visible (UV/Vis) techniques were used to characterize the novel CdS/ZnS and CdS:Cu(2+) /ZnS core-shell nanoparticles. All absorption peaks of the synthesized samples were highly blue-shifted from the bulk CdS and ZnS. Very narrow and symmetric PL emission was observed in the yellow region for core-shell CdS/ZnS. Furthermore, the PL emission of CdS/ZnS was tuned into orange region by incorporate the Cu ion into the core CdS lattice. Copyright © 2013 John Wiley & Sons, Ltd.

  15. Oxalic acid capped iron oxide nanorods as a sensing platform.

    Science.gov (United States)

    Sharma, Anshu; Baral, Dinesh; Bohidar, H B; Solanki, Pratima R

    2015-08-05

    A label free impedimetric immunosensor has been fabricated using protein bovine serum albumin (BSA) and monoclonal antibodies against Vibrio cholerae (Ab) functionalized oxalic acid (OA) capped iron oxide (Fe3O4) nanorods for V. cholerae detection. The structural and morphological studies of Fe3O4 and OA-Fe3O4, were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy and dynamic light scattering (DLS) techniques. The average crystalline size of Fe3O4, OA-Fe3O4 nanorods were obtained as about 29±1 and 39±1nm, respectively. The hydrodynamic radius of nanorods is found as 116nm (OA-Fe3O4) and 77nm (Fe3O4) by DLS measurement. Cytotoxicity of Fe3O4 and OA-Fe3O4 nanorods has been investigated in the presence of human epithelial kidney (HEK) cell line 293 using MTT assay. The cell viability and proliferation studies reveal that the OA-Fe3O4 nanorods facilitate cell growth. The results of electrochemical response studies of the fabricated BSA/Ab/OA-Fe2O3/ITO immunosensor exhibits good linearity in the range of 12.5-500ng mL(-1) with low detection limit of 0.5ng mL(-1), sensitivity 0.1Ωng(-1)ml(-1)cm(-2) and reproducibility more than 11 times. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

  16. Effects of Fe substitution on B3-B1 phase transition and structural, vibrational, and electronic properties of ZnS from DFT calculations

    Science.gov (United States)

    Das, Pratik Kr.; Mandal, Nibir; Arya, A.

    2017-02-01

    Naturally occurring zinc sulfide (ZnS) contains a substantial amount of iron (Fe) in its crystal structure. This study explores the possible effects of such Fe impurity on the physical properties of its two phases: B3 and B1, crystallizing in a cubic system with zinc blend (ZB, space group: F-43m) and rock salt (RS, space group: Fm-3m) structures. We have performed ab-initio calculations within density functional theory (DFT) to determine the equilibrium volumes of B3- and B1-ZnS phases, doped with Fe in varying concentrations (0% to 25%), and their corresponding lattice structures. Using the enthalpy cross-over, we determine the pressure-dependent B3 to B1 transition as a function of Fe concentration. Our DFT calculations suggest an inverse relation of the transition pressure with Fe content. For pure ZnS, the transition occurs at 17 GPa, which drops to ˜12 GPa for 25% Fe. This study also provides a first-hand analysis of the elastic constants (C11, C12, and C44) to show the effects of Fe impurity on the mechanical properties of ZnS phases. Their values generally drop due to Fe and the differences widen with increasing pressure. Fe causes large softening of C44, especially for the B1 phase. We have also performed phonon calculations to characterize the vibrational properties and explain the pressure dependent structural instability of the B3- ZnS. Finally, our calculations of the electronic structures show a transition of semi-conductor to conductor behavior of ZnS with incorporation of Fe impurity.

  17. Finite element modelling of the mechanics of discrete carbon nanotubes filled with ZnS and comparison with experimental observations

    KAUST Repository

    Monteiro, André O.

    2013-09-25

    The mechanical response to a uniaxial compressive force of a single carbon nanotube (CNT) filled (or partially-filled) with ZnS has been modelled. A semi-empirical approach based on the finite element method was used whereby modelling outcomes were closely matched to experimental observations. This is the first example of the use of the continuum approach to model the mechanical behaviour of discrete filled CNTs. In contrast to more computationally demanding methods such as density functional theory or molecular dynamics, our approach provides a viable and expedite alternative to model the mechanics of filled multi-walled CNTs. © 2013 Springer Science+Business Media New York.

  18. Effective scintillation materials based on solid solutions ZnS1–xTex and perspectives of their application

    Directory of Open Access Journals (Sweden)

    Katrunov K. A.

    2011-04-01

    Full Text Available The optimal technological regime of formation ZnS1–xTex solid solution at spacing 0,0≤х≤0,1 has been determined, and has been shown that fritting in hydrogen atmosphere results in more rapid reaction in comparison to argon due to chemical-thermal etching the ZnO layer out. Further annealing in the inert Ar atmosphere leads to the increase of the light output, to the intensive emission band formation and causes afterglow level reduction and the crystalline lattice rearrangement.

  19. Structural properties of MgF2 and ZnS in thin film and in multilayer optical coatings

    Science.gov (United States)

    Perales, F.; de las Heras, C.; Agulló-Rueda, F.

    2008-11-01

    Different techniques of x-ray diffraction line profile analysis have been used to study the microstructural parameters of the MgF2 and ZnS thin films as well as MgF/ZnS multilayers. The crystallite size and microstrain of the samples have been estimated from x-ray diffraction by applying Scherrer, Scherrer-Wilson and Williamson-Hall formulae respectively. The effects of thermal annealing at different temperatures on the structure in the material in thin films and in multilayers are studied and compared by the three mentioned relations. Although some different values have been obtained from each expression, the same temperature tendency is observed.

  20. Structural properties of MgF{sub 2} and ZnS in thin film and in multilayer optical coatings

    Energy Technology Data Exchange (ETDEWEB)

    Perales, F; Agullo-Rueda, F [Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, E-28049 Madrid (Spain); De las Heras, C [Departamento de Fisica de Materiales and Instituto Nicolas Cabrera. Facultad de Ciencias, Universidad Autonoma de Madrid, Cantoblanco, E-28049, Madrid (Spain)

    2008-11-21

    Different techniques of x-ray diffraction line profile analysis have been used to study the microstructural parameters of the MgF{sub 2} and ZnS thin films as well as MgF/ZnS multilayers. The crystallite size and microstrain of the samples have been estimated from x-ray diffraction by applying Scherrer, Scherrer-Wilson and Williamson-Hall formulae respectively. The effects of thermal annealing at different temperatures on the structure in the material in thin films and in multilayers are studied and compared by the three mentioned relations. Although some different values have been obtained from each expression, the same temperature tendency is observed.

  1. A hybrid photocatalytic system comprising ZnS as light harvester and an [Fe(2)S(2)] hydrogenase mimic as hydrogen evolution catalyst.

    Science.gov (United States)

    Wen, Fuyu; Wang, Xiuli; Huang, Lei; Ma, Guijun; Yang, Jinhui; Li, Can

    2012-05-01

    Photo opportunity: A highly efficient and stable hybrid artificial photosynthetic H(2) evolution system is assembled by using a semiconductor (ZnS) as light-harvester and an [Fe(2)S(2)] hydrogenase mimic ([(μ-SPh-4-NH(2) )(2) Fe(2) (CO)(6)]) as catalyst for H(2) evolution. Photocatalytic H(2) production is achieved with more than 2607 turnovers (based on [Fe(2)S(2)]) and an initial turnover frequency of 100 h(-1) through the efficient transfer of photogenerated electrons from ZnS to the [Fe(2)S(2)] complex. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. White Light-Emitting Diodes Based on AgInS2/ZnS Quantum Dots with Improved Bandwidth in Visible Light Communication

    OpenAIRE

    Cheng Ruan; Yu Zhang; Min Lu; Changyin Ji; Chun Sun; Xiongbin Chen; Hongda Chen; Colvin, Vicki L.; Yu, William W.

    2016-01-01

    Quantum dot white light-emitting diodes (QD-WLEDs) were fabricated from green- and red-emitting AgInS2/ZnS core/shell QDs coated on GaN LEDs. Their electroluminescence (EL) spectra were measured at different currents, ranging from 50 mA to 400 mA, and showed good color stability. The modulation bandwidth of previously prepared QD-WLEDs was confirmed to be much wider than that of YAG:Ce phosphor-based WLEDs. These results indicate that the AgInS2/ZnS core/shell QDs are good color-converting ma...

  3. N,N’-diisopropylthiourea and N,N’-dicyclohexyl-thiourea zinc(II complexes as precursors for the synthesis of ZnS nanoparticles

    Directory of Open Access Journals (Sweden)

    J. Raftery

    2010-01-01

    Full Text Available The single X-ray crystal structures of zinc (II complexes of N,N’-diisopropylthiourea and N,N’ dicyclohexylthiourea weredetermined.These complexes, similar to other alkylthioureas, were found to be effective as precursors for the preparation of hexadecylamine-capped ZnS nanoparticles. The complexes are air-stable, easy to prepare and inexpensive. They pyrolyse cleanly to give high-quality ZnS nanoparticles, which show quantum confinement effects in their absorption spectra and close to band-edge emission. Their broad diffraction patterns are typicalof nanosized particles while their transmission electronmicroscopy images showed agglomerates of needle-like platelet nanoparticles.

  4. Imidazolium ionic liquid induced one-step synthesis of -Fe2O3 nanorods and nanorod assemblies for lithium-ion battery

    Directory of Open Access Journals (Sweden)

    Shuting Xie

    2016-12-01

    Full Text Available α-Fe2O3 nanorods and nanorod assemblies are prepared via a facile one-step method with the assistance of imidazolium-based ionic liquid. The aspect ratio of synthesized nanorods is determined by the alkyl chain length of [Cnmim]+. The inter-molecular π−π interaction and intra-molecular dipole-dipole interaction among imidazole rings of [C4mim]+[PhCOO]− play critical roles in both nucleation and assembly processes of α-Fe2O3 nanorods. The α-Fe2O3 nanorod assemblies show an excellent performance in lithium-ion batteries with a reversible capacity of 1007.3 mA h g−1 at the rate of 500 mA g−1 after 150 cycles.

  5. Effects of carbon defects on ZnO nanorods directly grown on graphene

    Science.gov (United States)

    Honda, Mitsuhiro; Tokuda, Fuyuki; Ichikawa, Yo

    2017-11-01

    The correlation between carbon defects and the density of ZnO nanorods directly grown on graphene was studied. Thermal annealing was performed to vary the defect density of graphene on which ZnO nanorods were directly grown via hydrothermal synthesis. We found that ZnO nanorods were densely distributed on a highly defective graphene. Furthermore, specific defect sites were observed to provide upright ZnO nanorods. Raman spectroscopy revealed that the thermally induced defect corresponds to a carbon vacancy, which is expected to provide a reactive graphene surface where precursors can be easily attached to trigger the nucleation and further growth of ZnO nanorods. The local measurement of defects is believed to elucidate the key parameters for the growth of highly oriented ZnO nanorods.

  6. In vivo fluorescence studies of whole blood after chitosan bio-functionalized gold nanorods administration

    Energy Technology Data Exchange (ETDEWEB)

    Garabagiu, Sorina [National Institute for Research and Development of Isotopic and Molecular Technologies, 65-103 Donath, 400293 Cluj-Napoca (Romania); Pestean, Cosmin [University of Agricultural Science and Veterinary Medicine, Cluj-Napoca (Romania); Stefan, Razvan, E-mail: rstefan@usamvcluj.ro [University of Agricultural Science and Veterinary Medicine, Cluj-Napoca (Romania)

    2013-11-15

    Gold nanorods (GNR) have been prepared by a seed mediated method and then functionalized with chitosan, in order to increase their biocompatibility. The interaction of GNR with whole blood has been assessed by means of fluorescence spectroscopy. The whole blood gives rise to a fluorescence emission peak with the maximum centered at 475 nm when a 410 nm excitation wavelength has been used. In vivo assessment of the existence of nanorods in the bloodstream is proven by the increase of the whole blood fluorescence due to metal enhanced fluorescence phenomenon, which leads to an increase of fluorescence emission in the close vicinity of noble metal anisotropic nanostructures. -- Highlights: • Gold nanorods have been synthesized and bio-functionalized with chitosan. • Chitosan–gold nanorods interaction was studied by UV–vis and FTIR spectroscopy. • Bio-functionalized gold nanorods solution was injected to a rabbit. • Fluorescence studies of whole blood in the presence of gold nanorods were performed.

  7. Growth of Au@Ag core-shell pentatwinned nanorods: tuning the end facets.

    Science.gov (United States)

    Zhang, Weiqing; Goh, Hao Ying Johnny; Firdoz, Shaik; Lu, Xianmao

    2013-09-16

    Au@Ag core-shell nanorods with tunable end facets are obtained by coating Au bipyramids (BPs) with Ag. The resultant nanorods exhibit a pentatwinned crystal structure with tips terminated with either {110} or {111} facets. The control over the end facets is achieved by varying the capping agents and tuning the reduction rate of Ag. Specifically, when Ag is reduced slowly, Au@Ag nanorods with flat {110} end facets are formed with cetyltrimethylammonium bromide (CTAB) as the capping agent. If CTAB is replaced with cetyltrimethylammonium chloride (CTAC), Au@Ag nanorods with tips terminated with {111} facets are obtained. However, at a high Ag reduction rate, dumbbell-shaped Au@Ag nanorods are formed, with either CTAB or CTAC as the capping agent. The morphological evolution of the nanorods in each case is closely followed and a growth mechanism is proposed. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Microemulsion synthesis and characterization of aluminum doped ZnO nanorods

    Energy Technology Data Exchange (ETDEWEB)

    Lim, S.K.; Hwang, S.H.; Kim, S. [Division of Nano and Bio Technology, Daegu Gyeongbuk Institute of Science and Technology DGIST, Daegu 700-742 (Korea)

    2010-07-15

    Aluminium doped ZnO (AZO) nanorods were synthesized by microemulsion method with different types of surfactants. Scanning electron microscopy observations show that the ZnO nanorods have diameters around about 80 nm and lengths up to several micrometers. The room temperature photoluminescence (PL) spectrum of AZO nanorods exhibited a sharp and strong ultraviolet bandgap at 383 nm and a relatively weaker emission associated with the defect level. AZO nanorods synthesized with sodium benzene sulfonate (SBS) surfactant showed lower resistivity than aluminum doped ZnO nanorods synthesized with dodecyl benzene sulfonic acid sodium salt (DBS) surfactant. Resistivity of AZO nanorods synthesized with SBS surfactant showed 2.8 x 10{sup 3} and ohm;cm. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  9. Synthesis and Properties of Layered-Structured Mn5O8 Nanorods

    DEFF Research Database (Denmark)

    Gao, Tao; Norby, Poul; Krumeich, Frank

    2010-01-01

    Mn5O8 nanorods were prepared by a topotactic conversion of γ-MnOOH nanorod precursors in nitrogen at 400 °C. The as-prepared Mn5O8 nanorods crystallized in a monoclinic structure (space group C2/m) with unit cell dimensions a = 10.3784(2) Å, b = 5.7337(7) Å, c = 4.8668(6) Å, and β = 109.491(6)°, ...

  10. The synthesis, structure and cathodoluminescence of ellipsoid-shaped ZnGa2O4 nanorods

    Science.gov (United States)

    Liu, Baodan; Bando, Yoshio; Dierre, Benjamin; Sekiguchi, Takashi; Tang, Chengchun; Mitome, Masanori; Wu, Aimin; Jiang, Xin; Golberg, Dmitri

    2009-09-01

    We fabricated ellipsoid-shaped ZnGa2O4 nanorods using a newly-designed chemical vapor deposition (CVD) process, different from the conventional methods. The optical properties of nanorods were studied using cathodoluminescence (CL) measurements. The nanorods displayed three distinct emissions centered at 360, 450 and 550 nm. The luminescence mechanism is thoroughly discussed and explained based on a detailed structural and compositional study with a transmission electron microscope (TEM) equipped with an electron energy loss spectrometer (EELS).

  11. Stabilization of Gold Nanorods (GNRs) in Aqueous and Organic Environments by Select Surface Functionalization

    Science.gov (United States)

    2016-01-01

    ARL-TR-7581 ● JAN 2016 US Army Research Laboratory Stabilization of Gold Nanorods (GNRs) in Aqueous and Organic Environments by...7581 ● JAN 2016 US Army Research Laboratory Stabilization of Gold Nanorods (GNRs) in Aqueous and Organic Environments by Select Surface... Gold Nanorods (GNRs) in Aqueous and Organic Environments by Select Surface Functionalization 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM

  12. Fabrication and spectroscopic studies on highly luminescent CdSe/CdS nanorod polymer composites

    Directory of Open Access Journals (Sweden)

    Jana Bomm

    2010-11-01

    Full Text Available Highly luminescent nanocomposites were prepared by incorporating CdSe/CdS core/shell nanorods into different polymer matrices. The resulting nanocomposites show high transparency of up to 93%. A photoluminescence quantum efficiency of 70% was obtained, with an optimum combination of nanorod (0.05 wt % and at a UV-initiator concentration of 0.1 wt % for poly(lauryl methacrylate. Nanorods tend to agglomerate in cellulose triacetate.

  13. Enhanced sensitivity of surface plasmon resonance phase-interrogation biosensor by using oblique deposited silver nanorods

    OpenAIRE

    Chung, Hung-Yi; Chen, Chih-Chia; Wu, Pin Chieh; Tseng, Ming Lun; Lin, Wen-Chi; Chen, Chih-Wei; Chiang, Hai-Pang

    2014-01-01

    Sensitivity of surface plasmon resonance phase-interrogation biosensor is demonstrated to be enhanced by oblique deposited silver nanorods. Silver nanorods are thermally deposited on silver nanothin film by oblique angle deposition (OAD). The length of the nanorods can be tuned by controlling the deposition parameters of thermal deposition. By measuring the phase difference between the p and s waves of surface plasmon resonance heterodyne interferometer with different wavelength of incident l...

  14. Fabrications and Characterizations of ZnO/Zn1-xMgxO Nanorod Quantum Structures

    National Research Council Canada - National Science Library

    Yi, Gyu-Chul

    2007-01-01

    .... However, quantum confinement effects in nanowires/nanorod heterostructures have not been easily observed despite recent synthesis of compositionally modulated nanowire superlattices by the vapor...

  15. Structural and Optical Characteristics of γ-In2Se3 Nanorods Grown on Si Substrates

    Directory of Open Access Journals (Sweden)

    M. D. Yang

    2011-01-01

    Full Text Available This study attempted to grow single-phase γ-In2Se3 nanorods on Si (111 substrates by metal-organic chemical vapor deposition (MOCVD. High-resolution transmission electron microscopy (HRTEM and selected area electron diffraction (SAED confirmed that the In2Se3 nanorods are singularly crystallized in the γ phase. The photoluminescence of γ-In2Se3 nanorods at 15 K was referred to as free and bound exciton emissions. The bandgap energy of γ-In2Se3 nanorods at room temperature was determined to be ~1.99 eV, obtained from optical absorption.

  16. Spectral fractionation detection of gold nanorod contrast agents using optical coherence tomography

    Science.gov (United States)

    Jia, Yali; Liu, Gangjun; Gordon, Andrew Y.; Gao, Simon S.; Pechauer, Alex D.; Stoddard, Jonathan; McGill, Trevor J.; Jayagopal, Ashwath; Huang, David

    2015-01-01

    We demonstrate the proof of concept of a novel Fourier-domain optical coherence tomography contrast mechanism using gold nanorod contrast agents and a spectral fractionation processing technique. The methodology detects the spectral shift of the backscattered light from the nanorods by comparing the ratio between the short and long wavelength halves of the optical coherence tomography signal intensity. Spectral fractionation further divides the halves into sub-bands to improve spectral contrast and suppress speckle noise. Herein, we show that this technique can detect gold nanorods in intralipid tissue phantoms. Furthermore, cellular labeling by gold nanorods was demonstrated using retinal pigment epithelial cells in vitro. PMID:25836459

  17. Fabrication of graphene/titanium carbide nanorod arrays for chemical sensor application.

    Science.gov (United States)

    Fu, Chong; Li, Mingji; Li, Hongji; Li, Cuiping; Qu, Changqing; Yang, Baohe

    2017-03-01

    Vertically stacked graphene nanosheet/titanium carbide nanorod array/titanium (graphene/TiC nanorod array) wires were fabricated using a direct current arc plasma jet chemical vapor deposition (DC arc plasma jet CVD) method. The graphene/TiC nanorod arrays were characterized by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction spectroscopy. The TiO2 nanotube array was reduced to the TiC nanorod array, and using those TiC nanorods as nucleation sites, the vertical graphene layer was formed on the TiC nanorod surface. The multi-target response mechanisms of the graphene/TiC nanorod array were investigated for ascorbic acid (AA), dopamine (DA), uric acid (UA), and hydrochlorothiazide (HCTZ). The vertically stacked graphene sheets facilitated the electron transfer and reactant transport with a unique porous surface, high surface area, and high electron transport network of CVD graphene sheets. The TiC nanorod array facilitated the electron transfer and firmly held the graphene layer. Thus, the graphene/TiC nanorod arrays could simultaneously respond to trace biomarkers and antihypertensive drugs. Copyright © 2016 Elsevier B.V. All rights reserved.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-02-28

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

  19. Growth and investigation of antifungal properties of ZnO nanorod arrays on the glass

    Energy Technology Data Exchange (ETDEWEB)

    Eskandari, M., E-mail: msnano1361@yahoo.co [Nanomaterial Research Group, Academic Center for Education, Culture and Research (ACECR) on TMU, Tehran (Iran, Islamic Republic of); Haghighi, N. [Department of physics, Tehran University, Tehran (Iran, Islamic Republic of); Ahmadi, V. [Department of Electrical Engineering, Tarbiat Modares University, Tehran (Iran, Islamic Republic of); Haghighi, F.; Mohammadi, SH.R. [Department of Mycology, Tarbiat Modares University, Tehran (Iran, Islamic Republic of)

    2011-01-01

    In this study, we have investigated the antifungal activity of ZnO nanorods prepared by the chemical solution method against Candida albicans. In the study, Zinc oxide nanorods have been deposited on glass substrates using the chemical solution method. The as-grown samples are characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). X-ray diffraction (XRD) showed zinc oxide nanorods grown in (0 0 2) orientation. The antifungal results indicated that ZnO nanorod arrays exhibit stable properties after two months and play an important role in the growth inhibitory of Candida albicans.

  20. Gold nanorod reshaping in vitro and in vivo using a continuous wave laser

    National Research Council Canada - National Science Library

    David Harris-Birtill; Mohan Singh; Yu Zhou; Anant Shah; Pakatip Ruenraroengsak; Maria Elena Gallina; George B Hanna; Anthony E G Cass; Alexandra E Porter; Jeffrey Bamber; Daniel S Elson

    2017-01-01

    Gold nanorods (GNRs) are increasingly being investigated for cancer theranostics as they possess features which lend themselves in equal measures as contrast agents and catalysts for photothermal therapy...

  1. Facile Hydrothermal Approach to ZnO Nanorods at Mild Temperature

    Directory of Open Access Journals (Sweden)

    Yang Jiao

    2013-01-01

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

  2. Growth of high aspect ratio ZnO nanorods by solution process: Effect of polyethyleneimine

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Han-Seok; Vaseem, Mohammad; Kim, Sang Gon; Im, Yeon-Ho [School of Semiconductor and Chemical Engineering, Dept. of BIN Fusion Technology, BK 21 Centre for Future Energy Materials and Devices, and Nanomaterials Processing Research Center, Chonbuk National University, Jeonju 561-756 (Korea, Republic of); Hahn, Yoon-Bong, E-mail: ybhahn@chonbuk.ac.kr [School of Semiconductor and Chemical Engineering, Dept. of BIN Fusion Technology, BK 21 Centre for Future Energy Materials and Devices, and Nanomaterials Processing Research Center, Chonbuk National University, Jeonju 561-756 (Korea, Republic of)

    2012-05-15

    High aspect ratio ZnO nanorods were grown vertically on ZnO seed layer deposited silicon, glass and polyimide substrates by a solution process at low-temperature using zinc nitrate hexahydrate and hexamethylenetetramine. We studied the effect of polyethlyeneimine (PEI) on the growth of ZnO nanorods. It was found that PEI has a prominent effect on controlling the aspect ratio of ZnO nanorods in solution. The morphological and photoluminescence properties of the ZnO nanorods were also examined with varying the growth temperature (60-90 Degree-Sign C). - Graphical abstract: With addition of polyehyleneimine (PEI) high aspect-ratio ZnO nanorods were grown. It is believed that during ZnO nanorods growth, protonized form of linear PEI molecules inhibits the lateral growth by being adsorbed on non-polar lateral planes. Thus the vertical growth is favored. Highlights: Black-Right-Pointing-Pointer A controlled growth of high aspect ratio ZnO nanorods on different substrates. Black-Right-Pointing-Pointer A prominent effect of polyethlyeneimine (PEI) on controlling the aspect ratio of ZnO nanorods in solution. Black-Right-Pointing-Pointer Precursor concentration and growth temperature effect for various aspect ratio ZnO nanorods.

  3. Enhanced sensitivity of surface plasmon resonance phase-interrogation biosensor by using oblique deposited silver nanorods

    Science.gov (United States)

    Chung, Hung-Yi; Chen, Chih-Chia; Wu, Pin Chieh; Tseng, Ming Lun; Lin, Wen-Chi; Chen, Chih-Wei; Chiang, Hai-Pang

    2014-09-01

    Sensitivity of surface plasmon resonance phase-interrogation biosensor is demonstrated to be enhanced by oblique deposited silver nanorods. Silver nanorods are thermally deposited on silver nanothin film by oblique angle deposition (OAD). The length of the nanorods can be tuned by controlling the deposition parameters of thermal deposition. By measuring the phase difference between the p and s waves of surface plasmon resonance heterodyne interferometer with different wavelength of incident light, we have demonstrated that maximum sensitivity of glucose detection down to 7.1 × 10-8 refractive index units could be achieved with optimal deposition parameters of silver nanorods.

  4. Directed assembly-based printing of homogeneous and hybrid nanorods using dielectrophoresis.

    Science.gov (United States)

    Chai, Zhimin; Yilmaz, Cihan; Busnaina, Ahmed A; Lissandrello, Charles A; Carter, David J D

    2017-11-24

    Printing nano and microscale three-dimensional (3D) structures using directed assembly of nanoparticles has many potential applications in electronics, photonics and biotechnology. This paper presents a reproducible and scalable 3D dielectrophoresis assembly process for printing homogeneous silica and hybrid silica/gold nanorods from silica and gold nanoparticles. The nanoparticles are assembled into patterned vias under a dielectrophoretic force generated by an alternating current (AC) field, and then completely fused in situ to form nanorods. The assembly process is governed by the applied AC voltage amplitude and frequency, pattern geometry, and assembly time. Here, we find out that complete assembly of nanorods is not possible without applying both dielectrophoresis and electrophoresis. Therefore, a direct current offset voltage is used to add an additional electrophoretic force to the assembly process. The assembly can be precisely controlled to print silica nanorods with diameters from 20-200 nm and spacing from 500 nm to 2 μm. The assembled nanorods have good uniformity in diameter and height over a millimeter scale. Besides homogeneous silica nanorods, hybrid silica/gold nanorods are also assembled by sequentially assembling silica and gold nanoparticles. The precision of the assembly process is further demonstrated by assembling a single particle on top of each nanorod to demonstrate an additional level of functionalization. The assembled hybrid silica/gold nanorods have potential to be used for metamaterial applications that require nanoscale structures as well as for plasmonic sensors for biosensing applications.

  5. Electronic properties of wurtzite-phase InP nanowires determined by optical and magneto-optical spectroscopy

    Science.gov (United States)

    De Luca, Marta; Polimeni, Antonio

    2017-12-01

    Thanks to their peculiar shape and dimensions, semiconductor nanowires (NWs) are emerging as building components of novel devices. The presence of wurtzite (WZ) phase in the lattice structure of non-nitride III-V NWs is one of the most surprising findings in these nanostructures: this phase, indeed, cannot be found in the same materials in the bulk form, where the zincblende (ZB) structure is ubiquitous, and therefore the WZ properties are poorly known. This review focuses on WZ InP NWs, because growth techniques have reached a high degree of control on the structural properties of this material, and optical studies performed on high-quality samples have allowed determining the most useful electronic properties, which are reviewed here. After an introduction summarizing the reasons for the interest in WZ InP nanowires (Sec. I), we give an overview on growth process and structural and optical properties of WZ InP NWs (Sec. II). In Sec. III, a complete picture of the energy and symmetry of the lowest-energy conduction and valence bands, as assessed by polarization-resolved photoluminescence (PL) and photoluminescence-excitation (PLE) studies is drawn and compared to all the available theoretical information. The elastic properties of WZ InP (determined by PL under hydrostatic pressure) and the radiative recombination dynamics of spatially direct and indirect (namely, occurring across the WZ/ZB interfaces) transitions are also discussed. Section IV, focuses on the magneto-optical studies of WZ InP NWs. The diagram of the energy levels of excitons in WZ materials—with and without magnetic field—is first provided. Then, all theoretical and experimental information available about the changes in the transport properties (i.e., carrier effective mass) caused by the ZB→WZ phase variation are reviewed. Different NW/magnetic field geometrical configurations, sensitive to polarization selection rules, highlight anisotropies in the diamagnetic shifts, Zeeman splitting

  6. Wurtzite to rocksalt phase transformation of cadmium selenide nanocrystals via laser-induced shock waves: transition from single to multiple nucleation.

    Science.gov (United States)

    Wittenberg, Joshua S; Merkle, Maxwell G; Alivisatos, A Paul

    2009-09-18

    The behavior of CdSe nanocrystals shocked to stresses of 2-3.75 GPa has been studied. Above 3 GPa a near-complete disappearance of the first excitonic feature and broadening of the low-energy absorption edge were observed, consistent with a wurtzite to rocksalt structural transformation. The transformation pressure is reduced relative to hydrostatic compression in a diamond anvil cell, and the rate increases, attributed to shock induced shear stress along the reaction coordinate. The especially rapid rate observed for a 3.75 GPa shock suggests multiple nucleation events per particle.

  7. Theoretical study of direct-current and radio-frequency breakdown in GaN wurtzite- and zinc-blende-phase MESFETs (metal-semiconductor field-effect transistors)

    Energy Technology Data Exchange (ETDEWEB)

    Farahmand, Maziar [Movaz Networks, South Norcross, GA (United States); Weber, Michael; Tirino, Louis; Brennan, Kevin F. [School of Electrical and Computer Engineering, Georgia Tech, Atlanta, GA (United States); Ruden, P. Paul [Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN (United States)

    2001-11-19

    In this paper, we present a comparison of the direct-current (DC) and radio-frequency (RF) breakdown behaviours of representative wurtzite- and zinc-blende-phase GaN MESFET structures based on a theoretical analysis. The calculations are made using a full-band ensemble Monte Carlo simulation that includes a numerical formulation of the impact ionization transition rate. Calculations of both the DC and RF breakdown voltages are presented for submicron MESFET devices made from either wurtzite- or zinc-blende-phase GaN. The devices are otherwise identical. It is found that the DC breakdown voltage in the wurtzite-phase GaN MESFET is significantly larger than that in the zinc-blende-phase device. This is due to the fact that electron heating occurs more rapidly within the zinc-blende phase than the wurtzite phase of GaN. As a consequence, avalanche breakdown occurs at higher applied field strengths and voltages in the wurtzite phase than in the zinc-blende phase of GaN. It is further found that the RF breakdown voltage of the devices increases with increasing frequency of the applied large-signal RF excitation. (author)

  8. Composition-dependent photoluminescence properties of CuInS{sub 2}/ZnS core/shell quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Hua, Jie [Key Laboratory of Functional Materials Physics and Chemistry of the Ministry of Education, Jilin Normal University, Siping 136000, Jilin (China); College of Information Technology, Jilin Normal University, Siping 136000, Jilin (China); Du, Yuwei; Wei, Qi [College of Information Technology, Jilin Normal University, Siping 136000, Jilin (China); Yuan, Xi; Wang, Jin [Key Laboratory of Functional Materials Physics and Chemistry of the Ministry of Education, Jilin Normal University, Siping 136000, Jilin (China); College of Information Technology, Jilin Normal University, Siping 136000, Jilin (China); Zhao, Jialong [Key Laboratory of Functional Materials Physics and Chemistry of the Ministry of Education, Jilin Normal University, Siping 136000, Jilin (China); Li, Haibo, E-mail: lihaibo@jlnu.edu.cn [Key Laboratory of Functional Materials Physics and Chemistry of the Ministry of Education, Jilin Normal University, Siping 136000, Jilin (China)

    2016-06-15

    CuInS{sub 2}/ZnS (CIS/ZnS) core/shell quantum dots (QDs) with various Cu/In ratios were synthesized using the hot-injection method, and their photoluminescence (PL) properties were investigated by measuring steady-state and time-resolved PL spectroscopy. The emission peak of the CIS/ZnS QDs were tuned from 680 to 580 nm by decreasing the Cu/In precursor ratio from 1/1 to 1/9. As the Cu/In ratio decreases, the PL lifetimes and PL quantum yields (QYs) of CIS/ZnS core/shell QDs increased firstly and then decreased. Two dominant radiative recombination processes were postulated to analyze composition-dependent PL properties, including the recombination from a quantized conduction band to deep defects state and donor-acceptor pair (DAP) recombination. The decrease of PL efficiency resulted from high density defects and traps, which formed at the interface between CIS core and ZnS shell due to the large off-stoichiometry composition. The PL intensity and peak energy for CIS/ZnS core/shell QDs as a function of temperature were also provided. The thermal quenching further confirmed that the PL emission of CIS/ZnS QDs did not come from the recombination of excitons but from the recombination of many kinds of intrinsic defects inside the QDs as emission centers.

  9. Highly enhanced photoluminescence of AgInS2/ZnS quantum dots by hot-injection method

    Science.gov (United States)

    Liao, Shenghua; Huang, Yu; Zhang, Ying; Shan, Xiaohui; Yan, Zhengyu; Shen, Weiyang

    2015-01-01

    Highly photoluminescent and air-stable AgInS2 quantum dots (AIS QDs) were synthesized by a hot-injection route in N2 atmosphere and dark environment. The as-synthesized AIS QDs were further capped with ZnS shell by one-pot method in order to enhance the photoluminescence (PL) intensity. The photo-electronic property and the morphology of AIS QDs and AIS/ZnS QDs were characterized by ultraviolet-visible spectroscopy (UV), PL spectroscopy and transmission electronic microscopy (TEM). The results indicated that the narrow and symmetrical PL spectra of AIS QDs was time-dependent, and the emission wavelength of AIS QDs could be tunable within 436-610 nm by altering the initial Ag/In ratios. After being capped with ZnS shell, the AIS QDs showed excellent optical characteristics, including PL QYs up to 15%. The TEM results indicated that the spherical AIS/ZnS QDs were nearly monodispersed and homogeneous with an average particle size of 8 nm. The heavy metal free and high luminous AIS/ZnS QDs have great potential in biological application.

  10. Modeling and simulation of experimentally fabricated QDSSC using ZnS as light absorbing and blocking layer

    Science.gov (United States)

    Mehrabian, Masood; Dalir, Sina

    2017-07-01

    Abstract—Two main factors which limit the power conversion efficiency of solar cells are light absorption and recombination processes. In photovoltaic (PV) devices, low energy photons cannot be absorbed and excite electrons from valance band to conduction band, hence do not contribute to the current. On the other hand, high energy photons cannot be efficiently used due to a poor match to the energy gap. Existence of charge recombination in PV devices causes the low conversion performance, which is indicated by the low open-circuit voltage ( V OC ). Using a blocking layer in system could effectively reduce the recombination of charge carriers. In this study, we simulated a solar cell with ITO/ZnO/P3HT&PCBM/Ag structure. To prevent the charge recombination, a ZnS QD layer was used which acts as a light absorbing and a recombination blocking layer in the ITO/ZnO film/ZnS QD/P3HT&PCBM/Ag structure. The simulated J- V characteristics of solar cells showed a close match with the experimental results. Simulate data showed an increase of conversion efficiency in ZnS QDSSC from 1.71 to 3.10%, which is relatively 81.28% increase.

  11. Compositional, morphological, structural, microstructural, optical, and magnetic properties of Fe, Co, and Ni doped ZnS nanoparticles

    Science.gov (United States)

    Poornaprakash, B.; Chalapathi, U.; Vattikuti, S. V. Prabhakar

    2017-04-01

    We present the compositional, morphological, structural, microstructural, optical, and magnetic properties of undoped, Fe, Co, and Ni doped ZnS diluted magnetic semiconductor nanoparticles (NPs) synthesized by chemical refluxing technique at 80 °C using Polyvinylpyrrolidone (PVP) as a stabilizer. EDS spectra confirmed the presence of Zn, Fe, Co, Ni, and S in the samples with expected stoichiometry. XRD and Raman studies revealed that all the samples exhibited cubic structure without any impurity phases. The average diameter of the particles confirmed by HRTEM studies was in the range 5-8 nm. From DRS, the estimated band-gap values were 3.92, 3.70, 3.98, and 3.76 eV for undoped, Ni, Fe, and Co doped ZnS samples, respectively. Photoluminescence studies indicated that the undoped and doped samples exhibited broad and asymmetric PL peaks covering a wide visible range. Room temperature magnetisation studies revealed that the undoped, Fe, Co, and Ni doped samples exhibited diamagnetic, paramagnetic, and ferromagnetic behaviors, respectively. The use of these ions with magnetic properties in systems doped by an innovative method and thus creating a quantum confinement effect.

  12. Highly luminescent nanostructures of CdS and ZnS prepared by microwaves heating: effect of sulphide concentration

    Energy Technology Data Exchange (ETDEWEB)

    Ortiz, Samuel; Gomez, Idalia; Elizondo, Perla [Facultad de Ciencias Quimicas, Universidad Autonoma de Nuevo Leon, Av. Universidad s/n, C.P. 66450 San Nicolas de los Garza (Mexico); Cavazos, Jose [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon, Av. Universidad s/n, C.P. 66450 San Nicolas de los Garza (Mexico)

    2010-11-15

    Nearly monodisperse and highly luminescent ZnS and CdS NPs were obtained by microwave irradiation. The ZnS and CdS NPs solutions were prepared by adding freshly prepared ZnSO{sub 4} or CdSO{sub 4} solution to a thioacetamide solution at pH 8 in the presence of sodium citrate in solution used as stabilizer. The precursors concentration were such that the sulphide ion concentrations were 3 x 10{sup -2} M, 6 x 10{sup -2} M and 8 x 10{sup -2} M, for each of these [S] concentrations the [Zn] or [Cd] content were fixed at 3 x 10{sup -2} M. NPs were prepared under microwave irradiation for 1 min at 905 W of power. The NPs samples were taken when the temperature descended to ambient temperature for further analysis. Effect of concentration of Cd and Zn ions were studied in the luminescence property. RXD, AFM, TEM and UV-Vis were used too as analytical equipment for characterization. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  13. Copper- or manganese-doped ZnS quantum dots as fluorescent probes for detecting folic acid in aqueous media

    Energy Technology Data Exchange (ETDEWEB)

    Geszke-Moritz, Malgorzata [Laboratoire Reactions et Genie des Procedes (LRGP), Nancy-University, CNRS, 1 rue Grandville, 54001 Nancy Cedex (France); Department of Pharmaceutical Technology, Poznan University of Medical Sciences, Grunwaldzka 6, 60-780 Poznan (Poland); Clavier, Gilles [PPSM, ENS Cachan, CNRS, UniverSud, 61 avenue President Wilson, 94230 Cachan (France); Lulek, Janina [Department of Pharmaceutical Technology, Poznan University of Medical Sciences, Grunwaldzka 6, 60-780 Poznan (Poland); Schneider, Raphaeel, E-mail: raphael.schneider@ensic.inpl-nancy.fr [Laboratoire Reactions et Genie des Procedes (LRGP), Nancy-University, CNRS, 1 rue Grandville, 54001 Nancy Cedex (France)

    2012-04-15

    3-Mercaptopropionic acid-capped core/shell ZnS:Cu/ZnS and ZnS:Mn/ZnS doped quantum dots (QDs) prepared through hydrothermal methods exhibit high photoluminescence intensity as well as good photostability. These water-dispersible nanoparticles exhibit high fluorescence sensitivity to folic acid due to the high affinity of the carboxylate groups and nitrogen atoms of folic acid towards the Zn surface atoms of the doped dots. Quenching of the fluorescence intensity of the QDs allows the detection of folic acid concentrations as low as 11 {mu}M, thus affording a very sensitive system for the sensing of this biologically active molecule in aqueous solution. The possible quenching mechanism is discussed. - Graphical abstract: A sensitive method for the detection of folic acid based on the fluorescence quenching of Mn- or Cu-doped ZnS quantum dots was developed. Highlights: Black-Right-Pointing-Pointer Quenching of the fluorescence intensity of doped ZnS QDs in the presence of folic acid. Black-Right-Pointing-Pointer New fluorescent sensors for folic acid. Black-Right-Pointing-Pointer Detection of folic acid concentrations as low as 11 {mu}M in aqueous solution. Black-Right-Pointing-Pointer The Perrin model and fluorescence lifetimes of ZnS:Mn QDs demonstrate a static quenching mechanism. Black-Right-Pointing-Pointer Quenching efficiency of ZnS:Cu QDs correlates with the Stern-Volmer model.

  14. Spectroscopic Properties and SEM Observations of Au-Ag Core-shell Nanorods Deposited on ITO Plates

    National Research Council Canada - National Science Library

    NIIDOME, Yasuro; TSURU, Yukiko; HAMASAKI, Yuki; NAKASHIMA, Naotoshi

    2014-01-01

      Gold-silver (Au-Ag) core-shell nanorods were deposited on ITO plates. The deposition was optimized to suppress the formation of aggregates and to control the densities of the nanorods on the ITO plates...

  15. Synthesis, characterization and photovoltaic integration of type II nanorod heterostructures

    Science.gov (United States)

    McDaniel, Hunter Y.

    Motivated by a desire to control the actions of charges within materials in new and productive ways, researchers have increasingly focused their efforts on engineering materials on the nanometer scale where the laws of quantum mechanics rule supreme. Novel properties emerge when a semiconductor crystal is prepared at sizes below the hydrogenic ground state of the material, also known as the exciton Bohr radius. In addition to effects of quantum confinement, the large fraction of surface atoms can play a significant role in determining nanocrystal properties and applications. By combining two or more nanometer scale semiconductor crystals together to form a nanocrystal heterostructure, new avenues for materials engineering are opened up as nascent properties emerge. The high fraction of surface atoms means that much larger degrees of strain are possible than in the bulk. The large fraction of interface atoms means that the heterojunction properties can dominate the properties of the entire structure. Along with engineering these novel multi component properties comes new unexplored areas of science to be investigated and understood. New techniques are needed for studying these materials that require resolution of features much smaller than the wavelength of (visible) light. Along with this research comes a responsibility to share findings with the scientific community and to pursue directions that can positively impact humanity. At the same time, we should take a long term view when judging the applications of this or any new technology as we are only beginning to understand what is possible. After an introduction to the field in chapter one where we motivate our focus on anisotropic nanocrystal heterostructures, we discuss the formation of Fe3O4/CdS structures from spherical seeds in chapter two. In chapter three we turn our focus to type II CdSe/CdTe nanorod heterostructures where the anisotropy is inherent. The type II system is of particular interest because

  16. Towards measuring quantum electrodynamic torque with a levitated nanorod

    Science.gov (United States)

    Xu, Zhujing; Bang, Jaehoon; Ahn, Jonghoon; Hoang, Thai M.; Li, Tongcang

    2017-04-01

    According to quantum electrodynamics, quantum fluctuations of electromagnetic fields give rise to a zero-point energy that never vanishes, even in the absence of electromagnetic sources. The interaction energy will not only lead to the well-known Casimir force but will also contribute to the Casimir torque for anisotropic materials. We propose to use an optically levitated nanorod in vacuum and a birefringent substrate to experimentally investigate the QED torque. We have previously observed the libration of an optically levitated non-spherical nanoparticle in vacuum and found it to be an ultrasensitive torque sensor. A nanorod with a long axis of 300nm and a diameter of 60nm levitated in vacuum at 10 (- 8) torr will have a remarkable torque detection sensitivity on the order of 10 (- 28) Nm/ √Hz, which will be sufficient to detect the Casimir torque. This work is partially supported by the National Science Foundation under Grant No.1555035-PHY.

  17. Bulk plasmon-polaritons in hyperbolic nanorod metamaterial waveguides

    Science.gov (United States)

    Vasilantonakis, Nikolaos; Nasir, Mazhar E; Dickson, Wayne; Wurtz, Gregory A; Zayats, Anatoly V

    2015-01-01

    Hyperbolic metamaterials comprised of an array of plasmonic nanorods provide a unique platform for designing optical sensors and integrating nonlinear and active nanophotonic functionalities. In this work, the waveguiding properties and mode structure of planar anisotropic metamaterial waveguides are characterized experimentally and theoretically. While ordinary modes are the typical guided modes of the highly anisotropic waveguides, extraordinary modes, below the effective plasma frequency, exist in a hyperbolic metamaterial slab in the form of bulk plasmon-polaritons, in analogy to planar-cavity exciton-polaritons in semiconductors. They may have very low or negative group velocity with high effective refractive indices (up to 10) and have an unusual cut-off from the high-frequency side, providing deep-subwavelength (λ0/6–λ0/8 waveguide thickness) single-mode guiding. These properties, dictated by the hyperbolic anisotropy of the metamaterial, may be tuned by altering the geometrical parameters of the nanorod composite. PMID:26693254

  18. Gold/polypyrrole nanorods for gas sensing application

    Science.gov (United States)

    Šetka, Milena; Drbohlavová, Jana; Vallejos, Stella; Márik, Marian; Llobet, Eduard; Hubálek, Jaromír.

    2017-06-01

    This work describes the preparation of gold/polypyrrole nanorods (AuPPy NRs) using anodized alumina oxide (AAO) template and both pulsed galvanic deposition and electropolymerization for the deposition of Au and polypyrrole (PPy) nanorods (NRs), respectively. Characterization of the whole structure after AAO etching revealed the formation of a high density of NRs along the substrate with uniform diameters of approximately 50 nm and total lengths of 700 nm, the last corresponding to 1/3 and 2/3 of the length of the Au and PPy NRs, respectively. These structures are provided of bottom/top electrodes and a heating element coupled to the backside of the substrate, and their gas sensing properties towards various concentrations of NO2 in resistive configuration are presented.

  19. Synthesis and characterization of Ag doped ZnS quantum dots for enhanced photocatalysis of Strychnine asa poison: Charge transfer behavior study by electrochemical impedance and time-resolved photoluminescence spectroscopy.

    Science.gov (United States)

    Gupta, Vinod Kumar; Fakhri, Ali; Azad, Mona; Agarwal, Shilpi

    2018-01-15

    In this study, the photocatalytic degradation of Strychnine was investigated by ZnS quantum dots and doped with silver in UV systems. ZnS and Ag-ZnS quantum dots were synthesized by chemical method and characterized by powder X-ray diffraction, transmission electron microscopy, UV-vis spectra and photoluminescence. The charge transfer process on the semicon-ductor/electrolyte interface was investigated via electrochemical impedance spectroscopy (EIS) and time-resolved photoluminescence. The average diameters of ZnS and Ag doped ZnS QDs were 3.0-5.0nm and 3.0-5.3nm, respectively. The band gap of ZnS and Ag-ZnS QDs was computed as 3.47 and 3.1eV, respectively. The surface area values of ZnS and Ag-ZnS QDs have been found as 78.25 and 89.54m2/g, respectively. The influences of key operating parameters such as initial pH, catalyst dosage, UV radiation intensity, reaction time as well as the effect of initial Strychnine concentration on mineralization extents were studied. The results of the study showed that the maximum removal efficiency of Strychnine had been achieved by un-doped and Ag-doped ZnS QDs at radiation intensity of 100W/m2, at time of 60min, pH of 3 and initial Strychnine concentration of 20mg/ml. Also the observations clearly showed that the photocatalysis process with Ag doped ZnS QDs are more effective than un-doped ZnS QDs. Copyright © 2017 Elsevier Inc. All rights reserved.

  20. Photostability and visible-light-driven photoactivity enhancement of hierarchical ZnS nanoparticles: The role of embedment of stable defect sites on the catalyst surface with the assistant of ultrasonic waves.

    Science.gov (United States)

    Mahvelati-Shamsabadi, T; Goharshadi, E K

    2017-01-01

    Zinc sulfide is a UV-active photocatalyst and it undergoes photocorrosion under light irradiation. In this work, the defect sites on ZnS nanoparticles (NPs) surfaces were induced with the help of powerful ultrasonic waves. The defect sites caused (1) suppression of photocorrosion in a large extent under UV light irradiation and (2) enhancement of visible light photo activity. The photocorrosion inhibition was induced by raising valence band (VB) position through the formation of interstitial zinc and sulfur vacancy states in the ZnS band structure and weakening of oxidative capacity of hole. The enhancement of visible light photocatalytic activity may be related to the generation of more defect energy states in the ZnS band gap. Under visible light irradiation, the electron was excited from the ZnS VB to the interstitial sulfur and zinc vacancy states before injecting into the conduction band of ZnS. Therefore, we modified the band gap of ZnS so that it acts as a visible light active photocatalyst. ZnS NPs were prepared using two different classical and ultrasound methods. The prepared ZnS using ultrasound method, exhibited more outstanding photocatalytic activity for degrading reactive black 5 (RB5) under UV and sunlight irradiation in comparison with the classical method. Details of the degradation mechanism under UV light were investigated. This work provides new insights to understanding the photocorrosion stability and visible light activity of bare ZnS photocatalyst. Copyright © 2016 Elsevier B.V. All rights reserved.