Hexagonal Zincite Structure Research Articles

Beta particle excited thermoluminescence of new ZnO:Ce phosphors

This work reports on the beta particle excited thermoluminescence (TL) of ZnO:Ce phosphors, synthesized through a controlled chemical precipitation reaction followed by thermal annealing at 900 °C in an air atmosphere during 24 h. The successful obtention of crystalline hexagonal zincite structure was confirmed by X-Ray diffraction. By milling ZnO:Ce powder precipitated during the reaction before carrying out the thermal annealing, there are improved reproducibility and enhanced TL features of interest for dosimetry. Ce doping strongly increases the TL sensitivity and leads to a simpler glow curve shape. The TL – dose response exhibits a linear behavior at least up to 128 Gy. The sensitivity of the synthesized ZnO:Ce is ca. 103 times greater than that of undoped ZnO. The TL fades 22% two days after radiation exposure, and then it becomes negligible.

SYNTHESIS OF SILVER (Ag) DOPED ZINC OXIDE (ZnO) NANOPARTICLES AS EFFICIENTPHOTOCATALYTIC ACTIVITY FOR DEGRADATION METHYLENE BLUE DYE

Zinc oxide (ZnO) and silver doped zinc oxide (Ag-ZnO) nanoparticles were prepared using zinc nitrates as oxidizers, glycine and citric acid as fuels as solution combustion synthesis (SCS) at 500°C. X-ray diffraction (XRD) pattern demonstrates the presence of Ag+ in the hexagonal zincite structure of ZnO. The average crystalline size of the particles of ZnO and Ag-ZnO were found to 47 nm and 74 nm respectively. From the Fourier transform infrared (FTIR) spectrum, the composition of Ag doped ZnO confirmed Ag-Zn-O stretching vibration at 510 cm-1. The UV-Visible absorption spectra results showed that synthesized ZnO and Ag-ZnO nanoparticles exhibited UV-visible absorption peaks at 370 nm, corresponds to a band gap of 3.24 eVand 3.08 eV respectively. Based on the above characterization techniques, the incorporation of silver affects the structural and optical behaviour of ZnO nanoparticles. The ZnO nanoparticles were observed that the particles are spherical morphologies. EDAX spectrum indicates no other elemental presence in the synthesized nanoparticle. The present work illustrate the Ag-ZnO nanoparticles as a photo-catalyst to decompose contaminants in the presence of UV light. The photo-catalytic activity of ZnO samples were investigated by UV- irradiation of methylene blue solution in a photocatalytic setup. The resulting mixtures were irradiated with UV light for a period of 45 mins. Based on results, the photocatalytic activity of Ag-ZnO nanoparticles were enhanced by the addition of Ag in pure ZnO nanoparticles. Ag doped ZnO nanoparticles showed higher photocatalytic activity efficiency than pure ZnO nanoparticles.

Synthesis, Characterization, Optical and Electrical Properties of Citrate Mediated Terbium Doped ZnO Nanoparticles for Multifunctional Applications

Terbium doped ZnO nanoparticles were synthesized via co-precipitation method using sodium citrate as a capping agent to study optical and electrical properties. The crystalline structure and the unit cell parameters were refined by the Reitveld analysis, infers that the nanomaterials crystallized in hexagonal zincite structure. The calculated grain size using Scherrer’s equation and the Williamson hall plot is found to be similar in values. Ensuing particle gives green emission due to the transitions from the excited 5D4 to the lower 4f energy levels. From the dielectric study, it is confirmed that the synthesized nanocrystal is useful for higher frequency applications.

Thermoluminescence of ZnO:Na phosphors exposed to beta particle irradiation

In this work, the thermoluminescence (TL) characterization of pellet-shaped ZnO:Na phosphors synthesized through a controlled chemical reaction followed by thermal annealing at 900 °C in air is reported. X-Ray diffraction patterns reveal ZnO hexagonal zincite structure for the samples, some of which were exposed to beta particle irradiation in the dose range from 0.08 to 2048 Gy in order to study their TL features. The synthesized ZnO:Na samples are more than 200 times more sensitive than ZnO samples synthesized by the same method, and present a 0.02 (1/50) sensitivity relative to the TLD-100 dosimeter.

Characterization of nanostructured ZnO grown by linear sweep voltammetry

Highly transparent and well aligned ZnO nanorods (NRs) have been synthesized by linear sweep voltammetry (LSV) on fluorine doped tin oxide (FTO) glass substrates. The effect of electrodeposition parameters such as sweep rate and number of cycles was investigated by scanning electron microscopy (SEM), X-ray diffraction, photoluminescence (PL) and UV–visible spectroscopy. The deposited ZnO NRs show hexagonal zincite structure and a high transmittance up to 95% in the near infrared and part of the visible region. The density, the orientation and the optical properties of ZnO NRs were strongly affected by the type of the sweep rate, and this was related to the nucleation mode involved in each case.

Tapioca starch: An efficient fuel in gel-combustion synthesis of photocatalytically and anti-microbially active ZnO nanoparticles

Zinc oxide nanoparticles were synthesized by gel-combustion method using novel bio-fuel tapioca starch pearls, derived from the tubers of Manihotesculenta. The product is characterized using various techniques. The X-ray diffraction pattern correspond to a hexagonal zincite structure. Fourier transform infrared spectrum showed main absorption peaks at 394 and 508cm−1 due to stretching vibration of Zn–O. Ultravoilet–visible spectrum of zinc oxide nanoparticles showed absorption maximum at 373nm whereas the maximum of the bulk zinc oxide was 377nm. The morphology of the product was studied using scanning electron microscopy and transmission electron microscopy. The scanning electron microscopic images showed that the products are agglomerated and porous in nature. The transmission electron microscopic images revealed spherical particles of 40–50nm in diameter. The photocatalytic degradation of methylene blue was examined using zinc oxide nanoparticles and found more efficient in sunlight than ultra-violet light due to reduced band gap. The antibacterial properties of zinc oxide nanoparticles were investigated against four bacterial strains Klebsiella aerogenes, Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aereus, where Pseudomonas aeruginosa and Staphylococcus aereus exhibited significant antibacterial activity in agar well diffusion method when compared to positive control.

Synthesis and characterization of ZnO nanoparticles by thermal decomposition of a curcumin zinc complex

ZnO nanoparticles were generated by thermal decomposition of a binuclear zinc (II) curcumin complex as single source precursor. Thermal behavior of the precursor showed a considerable weight loss at about 374°C by an exothermic reaction with a maximum weight loss rate of 14%/min. Complete decomposition of precursor was observed within 49min with a heating rate of 10°C/min. Synthesized nanoparticles have been characterized by X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy and selected area electron diffraction microscopy. Results revealed monodispersed hexagonal zincite structure with an average size of 117±4nm.

Solid State Synthesis and Characterization of Zinc Oxide (ZnO) Microflakes by [Bis(acetylacetonato)zinc(II)] and Sodium Hydroxide at Room Temperature

A novel and simple one-step solid state reaction in the presence of a suitable surfactant, sodium dodecyl sulfate (SDS), and a novel precursor, [bis(acetylacetonato)zinc(II)]; [Zn(acac)2]; has been developed to synthesize uniform zinc oxide microflakes with an average thickness of 0.3–2.4 μm. In the absence of SDS the product samples contained microrods. The formation of zinc oxide microflakes depends on the molar ratio of Zn(II)/SDS and the experimental procedure. The products were characterized by X-ray diffraction, photoluminescence spectroscopy, FT-IR spectroscopy, surface area, scanning electron microscopy and transmission electron microscopy to depict the phase and morphology. The synthesized ZnO microflakes have a hexagonal zincite structure.

Characterization of Urea versus HMTA in the Preparation of Zinc Oxide Nanostructures by Solution-Immersion Method Grown on Gold-Seeded Silicon Substrate

Zinc oxide (ZnO) nanostructures prepared by immersion method were successfully grown on gold-seeded silicon substrate using Zinc nitrate hexahydrate (Zn (NO3)2.6H2O) as a precursor, separately stabilized with non-toxic urea (CH4N2O) and hexamethylene tetraamine (HMTA). The effect of changing the stabilizer of ZnO solution on the crystal structure, morphology and photoluminescence properties of the resultant ZnO is investigated. X-ray diffraction of the synthesized ZnO shows hexagonal zincite structure. The morphology of the ZnO was characterized using Field Emission Scanning Electron Microscope (FESEM). The growth of ZnO using urea as stabilizer shows clusters of ZnO nanoflower with serrated broad petals were interestingly formed. ZnO in HMTA showed growth of nanorods. The structures has high surface area, is a potential metal oxide nanostructures to be develop for optoelectronic devices and chemical sensors. The formation of ZnO nanostructures is found to be significantly affected by the stabilizer.

The Effect of Stabiliser’s Molarity to the Growth of ZnO Nanorods

A wet chemical approach, originating from sol-gel preparation, was adopted with the intention to develop a low-temperature benign method of preparation. ZnO nanorods are successfully grown in an aqueous medium. The precursor, zinc nitrate hexahydrate (Zn(NO3)2.6H2O), is stabilized by hexamethylene tetraamine (HMTA). The effect of changing the molarity of HMTA to the structural orientation of ZnO nanorods is investigated. X-ray diffraction of the synthesized ZnO shows hexagonal zincite structure. The structural features of the nanocrystalline ZnO were studied by SEM. Structural features, surface morphology and differences in lattice orientation are seemingly influenced by varying the Zn2+: HMTA molar ratio. The formation of ZnO nanorods with blunt and sharp tips is found to be significantly affected by this ratio.

ZnO nanotriangles: Synthesis, characterization and optical properties

Zinc oxalate, [Zn(C 2O 4)·2H 2O] was used as a precursor to prepare zinc oxide nanotriangles by thermal decomposition. The different combinations of triphenylphosphine, and oleylamine were added as surfactants to control the particle size. The products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), photoluminescence spectroscopy (PL), Fourier transform infrared (FT-IR) spectroscopy, Ultraviolet–visible (UV–vis) spectroscopy and X-ray photoelectron spectroscopy (XPS). The synthesized ZnO nanoparticles have a hexagonal zincite structure.

Preparation of ZnO nanoparticles from [bis(acetylacetonato)zinc(II)]–oleylamine complex by thermal decomposition

[Bis(acetylacetonato)zinc(II)] was used as a precursor to prepare zinc oxide nanoparticles of 12–20 nm in average diameter by thermal decomposition. The different combinations of triphenylphosphine, (C 18H 15P) and oleylamine, (C 18H 37N) were added as surfactants to control the particle size. The products were characterized by X-ray diffraction (XRD), photoluminescence spectroscopy (PL), FT-IR spectroscopy, surface area, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to depict the phase and morphology. The synthesized ZnO nanoparticles have a hexagonal zincite structure. The photoluminescence of ZnO nanoparticles was studied by exciting the sample with an ArF laser (193 nm). A strong blue-shift of the emission band of ZnO, suggesting a strong quantum size effect, is observed.

Structural and magnetic property of Co-doped–ZnO thin films prepared by pulsed laser deposition

Co-doped–ZnO thin films with the hexagonal zincite structure (wurtzite) have been synthesized on (0 0 6) Al 2O 3 sapphire substrate by pulsed laser deposition. Properties of the synthesized films are studied and the relation of the properties to its structural is reported. Single phase and highly textured Co-doped–ZnO thin films are successfully grown at relatively low temperature, 100 °C. Only single zincite (0 0 2) phase is formed and no cobalt segregation is detected. The structural, magnetic, electrical and optical properties of the deposited films were analyzed. Magnetic ordering was observed for all the films and the magnitude of the ordering is strongly dependent on the substrate temperature during deposition. Semiconductors properties of the carrier concentration and resistivity were also studied by Hall effect measurement. Both films deposited at 100 °C and 600 °C still preserve its semiconductor electron carrier density at the range of 10 21 cm −3. However, the resistivity increased with the increasing deposition temperature.

Preparation of c-axis-oriented zinc-oxide thin films and the study of their microstructure and optical properties

c-axis-oriented zinc-oxide (ZnO) thin films were prepared on microscope glass substrates by sol–gel deposition. A homogeneous and stable solution was prepared by dissolving zinc-acetate 2-hydrate (ZnAc) in 2-propanol and diethanolamine. Crystalline ZnO thin films were obtained following an annealing process at temperatures between 450°C and 550°C for 1 h. Increasing annealing temperature increased the grain size and the c-axis orientation. The X-ray diffraction analysis revealed single-phase ZnO with hexagonal zincite structure. The absorption edge analysis revealed that the optical band-gap energy for the films were between 3.26 and 3.28 eV and electronic transition was direct transition type.

Synthesis and characterization of ZnO nanoparticles assembled in one-dimensional order

ZnO nanoparticles assembled in one-dimensional order were synthesized by a template-free method. The synthesized ZnO powder have a hexagonal zincite structure. The ZnO aggregates with rod-like shapes are typically ∼1.2 μm in length and 100 nm in diameter with an aspect ratio as high as ∼12, which consist of many small nanocrystals with diameters of ∼15 nm. Longer wires connected by many hexahedral ZnO nanocrystals were obtained after calcination at the temperature over 500 °C. The formation of the rod-shaped ZnO powders is related to the existence of [Zn(NH 3) x ] 2+ complex cations.

Chemical-bath ZnO buffer layer for CuInS2 thin-film solar cells

ZnO buffer layers were grown by a chemical-bath deposition (CBD) in order to improve the interface quality in p-CuInS2 based solar cells, to improve the light transmission in the blue wavelength region, but also as an alternative to eliminate the toxic cadmium. The process consists of immersion of different substrates (glass, CIS) in a dilute solution of tetraamminezinc II, [Zn(NH2)4]2+, complex at 60–95°C. During the growth process, a homogeneous growth mechanism which proceeds by the sedimentation of a mixture of ZnO and Zn(OH)2 clusters formed in solution, competes with the heterogeneous growth mechanism. The mechanism consists of specific adsorption of a complex Zn(II) followed by a chemical reaction. The last process of growth results in thin, hard, adherent and specularly reflecting films. The characterization of the deposited CBD-ZnO layers was performed by X-ray diffraction (XRD), optical transmittance, scanning electron microscopy, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The as-deposited films on glass show hexagonal zincite structure with two preferred orientations (100) and (101). High optical transmittance up to 80% in the near-infrared and part of the visible region was observed. The low growth rate of the films on CIS suggests an atomic layer-by-layer growth process.The device parameters and performance are compared to heterojunction with a standard CdS buffer layer.