Synthesis,structural and optical characterization of Ni-doped ZnO nanoparticles

Nanocrystalline Zn_1−x Ni _x O (x = 0.00, 0.02, 0.04, 0.06, 0.08) powders were synthesized by a simple sol–gel autocombustion method using metal nitrates of zinc, nickel and glycine. Structural and optical properties of the Ni-doped ZnO samples annealed at 800 °C are characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive analysis using X-rays (EDAX), UV–visible spectroscopy and photoluminescence (PL). X-ray diffraction analysis reveals that the Ni-doped ZnO crystallizes in a hexagonal wurtzite structure and secondary phase (NiO) was observed with the sensitivity of XRD measurement with the increasing nickel concentration (x ≥ 0.04). The lattice constants of Ni-doped ZnO nanoparticles increase slightly when Ni²⁺ is doped into ZnO lattice. The optical absorption band edge of the nickel doped samples was observed above 387 nm (3.20 eV) along with well-defined absorbance peaks at around 439 (2.82 eV), 615(2.01 eV) and 655 nm (1.89 eV). PL measurements of Ni-doped samples illustrated the strong UV emission band at ~3.02 eV, weak blue emission bands at 2.82 and 2.75 eV, and a strong green emission band at 2.26 eV. The observed red shift in the band gap from UV–visible analysis and near band edge UV emission with Ni doping may be considered to be related to the incorporation of Ni ions into the Zn site of the ZnO lattice.     

Properties of nanocrystalline zinc oxide thin films prepared by thermal decomposition of electrodeposited zinc peroxide

Zinc peroxide thin films were electrodeposited from aqueous solution at room temperature using H₂O₂ as the oxidation agent. Nanocrystalline zinc oxide thin films were then obtained from thermal decomposition of zinc peroxide thin films. The grain sizes of ZnO through thermal decomposition of ZnO₂ at 200 °C, 300 °C and 400 °C were estimated from the peak width of ZnO(110) obtained from X-ray diffraction and were 6.3 nm, 9.1 nm and 12.9 nm, respectively. The optical properties of zinc oxide thin films have been studied. The photoluminescence results indicate that ZnO thin films have low Stokes blue shift (about 110 meV) and low oxygen vacancies.     

Synthesis of Er-doped ZnO nanoparticle/organic hybrid from metal-organics

An Er-doped ZnO nanoparticle/organic hybrid was synthesized in situ from zinc acrylate (ZA) and erbium acetate (EA) using methylhydrazine. Nano-sized Er-doped ZnO particles were formed in an organic matrix by hydrolysis and polymerization of ZA–EA at 80 °C. The crystallinity of the Er-doped ZnO particles in the hybrid was dependent upon the hydrolysis temperature and water amount. Analysis by transmission electron microscopy and energy dispersive X-ray analyzer revealed that crystalline ZnO nanoparticles doped with Er were dispersed in the organic matrix. The hybrid film sandwiched between fused silica plates was highly transparent. The Er-doped ZnO particle/organic hybrid showed a photoluminescence peak at 0.81 eV (1.54 μm) attributed to the transition of Er³⁺ ions.     

Synthesis of manganese–zinc ferrite by powder mixing using ferric oxide from a steel mill acid recovery unit

With the aim of producing fine-grained manganese–zinc (Mn–Zn) ferrite at the end of a calcination process at moderate temperatures, this study consisted, at first, of an “electrochemically designed” powder mixing by wet-ball milling a mixture of manganese (MnO₂), zinc (ZnO), and iron (Fe₂O₃ granules produced by an acid recovery unit of a Brazilian steelmaker, milled to fine sizes using alkaline media) –based raw materials. This mixing/milling resulted in improved size reduction when compared to milling without any alkali addition. Further, noticeable size reduction was achieved when elemental Zn was used in place of ZnO, especially when ammonia was used as the medium. Calcination of the alkaline-milled mixture of MnO₂ + ZnO + Fe₂O₃ at 1200 °C allowed obtaining well-crystallized single-phase Mn–Zn ferrite, whereas calcination of the MnO₂ + ZnO + Fe₂O₃ mill-mixed in 100% NH₄OH at 1200 °C produced the highest saturation magnetization in the as-calcined state.     

The effects of oxygen-catalysed and heat treatment on the precipitation synthesised ZnO nanoparticles

Nanocrystalline ZnO particles prepared by precipitation method from Zn and I₂ reaction with oxygen as catalyst were investigated. The addition of diethanolamine (DEA) as capping agent and fast pyrolysis treatment at 550, 700 and 850?°C were also characterised and elaborated. Compact and small spherical particles were observed for ZnO synthesised with O₂ catalysed whilst, uneven surface, fewer dense packing particles and macropore structures were observed for ZnO prepared without excess of O₂. It was shown that diffusion of O₂ has improved the structural and photoluminescence behaviour of the prepared ZnO nanoparticles. ZnO synthesised with O₂-catalysed exhibited better crystalline and leaned towards a pure state as shown by shifting of PL peak to higher energy of pure ZnO while, sample prepared without excess of O₂ exhibits poor crystalline and decreasing of the energy band gap with respect to increment of calcination temperatures. Single violet emission was observed in all samples synthesised with excess of O₂ whereby the highest intensity was obtained by calcining at 850?°C with photon energy at 2.95 eV. In contrast to sample with excess of O₂, ZnO calcined without excess of O₂ at 850?°C displays violet and green emission with energy at 2.93 eV and 2.35 eV, respectively.     

Microwave-assisted hydrothermal synthesis of zinc oxide particles starting from chloride precursor

Zinc oxide (ZnO) was synthesized using a microwave assisted hydrothermal (MAH) process based on chloride/urea/water solution and under 800 W irradiation for 5 min. In the bath, Zn²⁺ ions reacted with the complex carbonate and hydroxide ions to form zinc carbonate hydroxide hydrate (Zn₄CO₃(OH)₆·H₂O), and the conversion from Zn₄CO₃(OH)₆·H₂O to ZnO was synchronously achieved by a MAH process. The as-prepared ZnO has a sponge-like morphology. However, the initial sponge-like morphology of ZnO could change to a net-like structure after thermal treatment, and compact nano-scale ZnO particles were finally obtained when the period of thermal treatment increased to 30 min. Pure ZnO nanoparticles was obtained from calcination of loose sponge-like ZnO particles at 500 °C. The analysis of optical properties of these ZnO nanoparticles showed that the intensity of 393 nm emission increased with the calcination temperature because the defects were reduced and the crystallinity was improved.     

Facile preparation of Ag/ZnO nanoparticles via photoreduction

Ag/ZnO nanoparticles can be obtained via photocatalytic reduction of silver nitrate at ZnO nanorods when a solution of AgNO₃ and nanorods ZnO suspended in ethyleneglycol is exposed to daylight. The mean size of the deposited sphere like Ag particles is about 5 nm. However, some of the particles can be as large as 20 nm. The ZnO nanorods were pre-prepared by basic precipitation from zinc acetate di-hydrate in the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide. They are about 50–300 nm in length and 10–50 nm in width. Transmission electron microscopy (TEM), energy-dispersive X-ray analysis (EDS), X-ray powder diffraction (XRD), UV–Vis spectroscopy, X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) were used to characterize the resulting Ag/ZnO nanocomposites.     

Fabrication and growth mechanism of hexagonal zinc oxide nanorods via solution process

This article presents, the fabrication of perfectly hexagonal zinc oxide nanorods performed via solution process using zinc nitrate hexahydrate (Zn(NO₃)₂·6H₂O) and hexamethylenetetramine (HMT) at various concentrations of i.e. 1 × 10⁻³ to 10 × 10⁻² M in 50 mL distilled water and refluxed at 100 °C for 1 h. We used HMT because it acts as a template for the nucleation and growth of zinc oxide nanorods, and it also works as a surfactant for the zinc oxide structures. The X-ray diffraction patterns clearly reveal that the grown product is pure zinc oxide. The diameters and lengths of the synthesized nanorods lie in the range of 200–800 nm and 2–4 μm, respectively as observed from the field emission scanning electron microscopy (FESEM). The morphological observation was also confirmed by the transmission electron microscopy (TEM) and clearly consistent with the FESEM observations. The chemical composition was analyzed by the FTIR spectroscopy, and it shows the ZnO band at 405 cm⁻¹. On the basis of these observations, the growth mechanism of ZnO nanostructures was also proposed.     

Spin coating of transparent zinc oxide films using novel precursor

The coating of transparent ZnO films using zinc 2-ethylhexanoate [Zn(OOCH(C₂H₅)C₄H₉)₂] as a novel metal organic monomer is reported. Zinc 2-ethylhexanoate is liquid at room temperature and can be spin-coated on a flat substrate without precipitation of ZnO under ambient condition. The spin-coated films were heated at different temperatures to remove unwanted organic materials from the surface. It was found that transparent ZnO films could be produced on glass substrates at low heating temperature (~400 °C). The ZnO films produced using the new monomer were free of cracks and defects. Also the ZnO films produced using the new monomer have excellent optical transmittance, mechanical properties and small surface roughness. The surface morphology and degree of crystallinity of the films coated by the new monomer were compared with these properties of ZnO films produced using zinc acetate-based sol–gels. The results clearly indicate that the novel monomer is a potential precursor for coating transparent ZnO films at low temperatures.     

Calibration of reaction parameters for the improvement of thermal stability and crystalline quality of multi-walled carbon nanotubes

The results of Raman analysis on multi-walled carbon nanotubes, prepared by catalysed chemical vapour deposition, are used as a guide for the calibration of the growth parameters, directed to improve crystalline quality and resulting thermal stability of nanotubes. Under selective growth conditions, the resistance to oxidation in air, as assessed by thermogravimetry measurements, is found to increase with the establishment of the long-range graphitic order in radial tube direction, as signalled by the Raman G′/G intensity ratio enhancement. In the range of parameters explored (synthesis temperature: 500–700 °C; growth atmosphere: 120 cc/min i-C₄H₁₀–H₂–He mixture with He at 0–25%; i-C₄H₁₀/H₂ flow ratio: 1–3; metal load and reduction temperature of Fe/Al₂O₃ catalysts: 17–40 wt%, and 500 and 700 °C, respectively), the best crystalline quality and the highest oxidative resistance are achieved by carrying out the synthesis reaction at 700 °C in 1:1:0 i-C₄H₁₀–H₂–He atmosphere over 29 wt% Fe catalysts reduced at 700 °C. An additional relevant finding is the strong correlation evidenced between results of thermogravimetry and Raman analyses, suggesting the use of Raman spectroscopy for non-destructively evaluating the thermal stability of any graphitically ordered carbon species.     

Production of opaque frits with low ZrO<Subscript>2</Subscript> and ZnO contents and their industrial uses for fast single-fired wall tile glazes

The amounts of zirconium and zinc oxides, which raise the production costs of ceramic glazes, were decreased in fast single-fired wall tile frit compositions and an industrial frit production was conducted. Opacity of the fired frit-based glazes was accomplished by compositional modifications of frits with no other nucleating agent. It was determined that the ratios of Al₂O₃/ΣR₂O, Al₂O₃/ΣRO, and Al₂O₃/B₂O₃ have significant effects on decreasing ZrO₂ and ZnO levels in the frit composition. A reduction of 25% in both zirconia and zinc oxide contents of frit batches, with respect to the reference frit (R) containing 6–10% ZrO₂ and 6–10% ZnO for a glossy white opaque wall tile glaze, was achieved in the ZD glaze consisting of 4.5–7.5% zirconia and 4.5–7.5% ZnO in its frit composition. It was concluded that zircon was the main crystalline phase of the glaze contributing the opacity. The ZD frit-based glaze has a thermal expansion coefficient value of 61.13 ± 0.32 × 10⁻⁷ °C⁻¹ at 400 °C which well matches to that of the wall tile body. TS EN ISO 10545 standard tests were also applied to the final ZD glaze. It is confirmed that the production cost of a fast single-fired wall tile glaze can be decreased by 15–20% with the successful new frit developed.     

Structure and photoluminescence of SiC/ZnO nanocomposites prepared by radio frequency alternate sputtering

SiC/ZnO nanocomposites were prepared by radio frequency alternate sputtering followed by annealing in N₂ ambient. Well-crystallized ZnO matrix was obtained after annealed at 750 °C according to X-ray diffractometer patterns. Transmission electron microscopy analyses indicated that the SiC thin layer aggregated to form SiC nanoclusters with the average size of 7.2 nm when the annealing temperature was 600 °C. When the annealing temperatures increased above 900 °C, some of the SiC nanoclusters changed into SiC nanocrystals and surfacial atoms of the SiC nanoparticles were surrounded by a layer of SiO _x (x ≤ 2) according to the Fourier transform infrared spectrums. The SiC/ZnO nanocomposites annealed at 750 °C exhibit strong photoluminescence bands ranging from 250 to 600 nm. UV light originates from the near band edge emission of ZnO and the blue emission peaked at around 465 nm (2.7 eV) may be due to the formation of emission centers caused by the defects in Si–O network, while the green-emission peak at around 550 nm (2.3 eV) may be attributed to the deep level recombination luminescence caused by the vacancies of oxygen and zinc.     

Photocatalytic activity of TiO2-capped ZnO nanoparticles

Using a combined hydrothermal and sol–gel route, TiO₂ -capped ZnO nanoparticles with an average size of 60 nm were prepared. The titania shell was amorphous with a thickness of ~10 nm. Formation of Zn₂TiO₄ phase at higher calcination temperature was noticed. Effects of Ti/Zn molar ratio and coating time on the thickness of TiO₂ shell and the photoactivity of the particles for decolorization of Methylene Blue (MB) under UV lamp irradiation (3 mW/cm²) were investigated. The nanoparticles were characterized by X-ray diffraction, transmission electron microscopy, fourier-transform infrared spectrometry (FTIR), diffuse reflectance spectroscopy (DLS), and atomic absorption spectroscopy. Analysis of the photoactivity results according to Langmuir–Hinshelwood model revealed a two-step decolorization process with a high kinetics rate at the early stage followed by a slower step. The capped nanoparticles synthesized under specific conditions exhibited higher photodecolorization yield and faster kinetics in comparison to the uncoated ZnO and P25-Degussa TiO₂ nanoparticles.     

Preparation and properties of composite particles made by nano zinc oxide coated with titanium dioxide

In this paper, composite particles of nano zinc oxide coated with titanium dioxide were prepared and characterized by TEM, XRD, XPS and FT-IR, and the properties of the composite particles for photo catalysis and light absorption were studied. Tetrabutyl titanate (TBT) was hydrolyzed in an alcoholic suspension of nano zinc oxide with diethanolamine (DEA) as an additive, resulting in a film with a thickness of 20–30 nm being coated on the surface of nano zinc oxide, and the composite particles contained ZnTiO₃ after drying and calcination. Photocatalysis capabilities of the composite particles for the degradation of phenol in an aqueous solution were greatly improved as compared with nano zinc oxide particles before coating, with pure nano ZnO and nano TiO₂ with similar average sizes, or with the mixture of nano ZnO and TiO₂ with the similar composition as the composite particles. The light absorption scope of the composite particles was enlarged when compared to nano titanium dioxide with same average size.     

Fluorescent dye encapsulated ZnO particles with cell-specific toxicity for potential use in biomedical applications

Fluorescein isothiocyanate (FITC)-encapsulated SiO₂ core-shell particles with a nanoscale ZnO finishing layer have been synthesized for the first time as multifunctional “smart” nanostructures. Detailed characterization studies confirmed the formation of an outer ZnO layer on the SiO₂–FITC core. These ~200 nm sized particles showed promise toward cell imaging and cellular uptake studies using the bacterium Escherichia coli and Jurkat cancer cells, respectively. The FITC encapsulated ZnO particles demonstrated excellent selectivity in preferentially killing Jurkat cancer cells with minimal toxicity to normal primary immune cells (18% and 75% viability remaining, respectively, after exposure to 60 μg/ml) and inhibited the growth of both gram-positive and gram-negative bacteria at concentrations ≥250–500 μg/ml (for Staphylococcus aureus and Escherichia coli, respectively). These results indicate that the novel FITC encapsulated multifunctional particles with nanoscale ZnO surface layer can be used as smart nanostructures for particle tracking, cell imaging, antibacterial treatments and cancer therapy.     

Crystallization characteristic and properties of some zinc containing soda lime silicate glasses

The crystallization behaviour of some soda lime silicate glasses modified by ZnO/CaO replacement to give the composition (Na₂O)₂·CaO_1−x ·(ZnO) _x ·3SiO₂ (x = 0, 0.2, 0.4, 0.6, 0.8 and 1.0) have been investigated using differential scanning calorimetry (DSC) and X-ray diffraction analysis (XRD). The thermal expansion coefficients and AC electrical properties in the frequency range 40 Hz–5 MHz of the obtained crystalline products were determined. Two forms of sodium calcium silicate (Na₄CaSi₃O₉ & Na₂Ca₂Si₃O₉), sodium metasilicate-Na₂SiO₃, two types of sodium zinc silicate (Na_1.31Zn_0.655Si_1.345O₄ & Na₂ZnSiO₄) and α-quartz phases were mostly developed in the crystallized glasses using various heat-treatment processes. The coefficient of thermal expansion of the obtained glass–ceramic materials are between 120 × 10⁻⁷°K⁻¹ and 168 × 10⁻⁷°K⁻¹ in the 25°–600 °C temperature range. The increase of frequency generally resulted in the increase of the conductivity and decrease the dielectric constant together with the loss tangent of the glass–ceramic materials.     

Rapid Thermal Annealing of ZnO Nanocrystalline Films for Dye-Sensitized Solar Cells

Nanocrystalline ZnO thin films were prepared by the sol–gel method and annealed at 600 °C by conventional (CTA) and rapid thermal annealing (RTA) processes on fluorine-doped tin oxide (FTO)-coated glass substrates for application as the work electrode for a dye-sensitized solar cell (DSSC). ZnO films were crystallized using a conventional furnace and the proposed RTA process at annealing rates of 5 °C/min and 600 °C/min, respectively. The ZnO thin films were characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM) analyses. Based on the results, the ZnO thin films crystallized by the RTA process presented better crystallization than films crystallized in a conventional furnace. The ZnO films crystallized by RTA showed higher porosity and surface area than those prepared by CTA. The results show that the short-circuit photocurrent (J _sc) and open-circuit voltage (V _oc) values increased from 4.38 mA/cm² and 0.55 V for the DSSC with the CTA-derived ZnO films to 5.88 mA/cm² and 0.61 V, respectively, for the DSSC containing the RTA-derived ZnO films.     

Hydrothermal synthesis and luminescence properties of core-shell-structured PS@SrCO<Subscript>3</Subscript>:Tb<Superscript>3+</Superscript> spherical particles

Nanocrystalline SrCO₃:Tb³⁺ phosphor layers were coated on monodisperse and spherical polystyrene particles by a typical hydrothermal synthesis without further annealing treatment, resulting in the formation of core-shell-structured polystyrene@SrCO₃:Tb³⁺ particles. X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, photoluminescence, as well as lifetimes were employed to characterize the resulting composite particles. Under ultraviolet excitation, the polystyrene@SrCO₃:Tb³⁺ phosphors show the characteristic ⁵D₄–⁷F _J (J = 6, 5, 4, 3) emission lines with green emission ⁵D₄–⁷F₅ (544 nm) as the most prominent group. The obtained core-shell phosphors are potentially applied in fluorescent lamps.     

Synthesis and adsorption property of zinc rust of zinc hydroxynitrate

In order to clarify the formation condition of zinc rusts such as layered zinc hydroxynitrate (Zn₅(OH)₈(NO₃)₂·2H₂O: ZHN), ZnO particles were aged with aqueous Zn(NO₃)₂·6H₂O solution at 6–140 °C for 48 h. Further, adsorption of H₂O and CO₂ on ZHN was examined for simulating study of atmospheric corrosion of galvanized steel. The ZHN was formed at 6 °C and the ZnO completely disappeared, meaning the hydrolysis of ZnO particles in aqueous Zn(NO₃)₂·6H₂O solution to recrystallize as ZHN. Increasing the aging temperature improved the crystallinity of layered structure of ZHN, showing a maximum at 85 °C. The formed ZHN was hexagonal plate-like particles. The particle size was dependent of the crystallinity of layered structure of ZHN. The specific surface area of ZHN was decreased on elevating the aging temperature, showing a minimum at 85 °C. The adsorption of H₂O and CO₂ was enhanced on increasing the crystallinity of layered structure of ZHN, meaning that these molecules are adsorbed not only on particle surface but also in interlayer of ZHN. These facts infer that the preferred orientation of plate-like ZHN particles leads to the formation of compact rust layer on galvanized steel and to the enhancement of corrosion resistance.     

Fabrication of hybrid solar cells using poly(2,5-dimethoxyaniline) hexagonal structures and zinc oxide nanorods

Flower-shaped zinc oxide (ZnO) structures have been synthesized in a microwave at 180 °C for 20 min using zinc nitrate and KOH. Detailed structural and morphology observation showed that the micron-sized ZnO nano-pencils grow out of the base of the flower-shaped ZnO structures. Photoluminescence spectrum measured at room temperature showed a sharp UV emission band around 390 nm which is attributed to the radiative annihilation of excitons. The synthesized PDMA and ZnO nanopencils are highly crystalline materials with one-dimensional morphology which improves the electron charge transport in the device. A distinctive photoluminescence quenching effect was observed indicating a photo-induced electron transfer. The solar cell devices fabricated from these materials demonstrated a short circuit current density of about 0.93 μA/cm², open-circuit voltage 0.58 V, and efficiency of 0.16 %.