Synthesis of relatively monodisperse ZnO nanocrystals from a precursor zinc 2,4-pentanedionate

Monodisperse ZnO nanoparticles were successfully prepared through the decomposition of zinc acetylacetonate precursor in oleylamine. The samples were characterized by transmission electron microscope, X-ray diffraction and infrared spectroscopy. The particle size and morphology could be modified through tuning the reaction temperature, reaction period and concentration of zinc acetylacetonate. The grain size of monodisperse ZnO could be obtained at 205 and 300 °C for 1 h with 1:100 molar ratio of acetylacetonate and oleylamine, respectively. The average grain size of ZnO nanoparticles increased and the shape of ZnO particles varied with the reaction period prolonging or reaction temperature increasing. Some ZnO particles had self-aggregated into a belt using a solution of 1:10 molar ratio of zinc acetylacetonate and oleylamine at 250 °C for 1 h. The oleylamine plays an important role in preventing aggregation of ZnO nanoparticles.     

Synthesis of deer horn-like and spherical ZnO nanoparticles by microwave decomposition of bis(2-pyridinethiol <Emphasis Type="Italic">N</Emphasis>-oxide)zinc using factorial and Taguchi experimental designs

Deer horn-like and spherical nanoparticles of ZnO have been prepared via microwave heating (MWH) of Bis (2-pyridinethiol N-oxide) Zinc (II) [BPTZ] complex. The product was characterized by XRD, SEM, LLS, BET, FTIR and chemical analysis. The 2³ factorial and the Taguchi L ₄ designs were used for factors effect estimation and determination of optimum conditions for spherical ZnO nanoparticle synthesis. The three main factors considered were power of microwave, temperature of pyrolysis and time of thermal decomposition. The time of pyrolysis had the most influence on the average particle size and the size distribution of product. The average particle size for the spherical ZnO at optimum conditions was found to be 16 nm and the particle range was 16 ± 13 nm.     

Low temperature dielectric studies of zinc oxide (ZnO) nanoparticles prepared by precipitation method

Using zinc nitrate as a precursor and NaOH starch as a stabilizing agent, hexagonal zinc oxide (ZnO) nanoparticles has been synthesized by precipitation method. The transmission electron microscopy (TEM) images show particles of nearly uniform spherical size of around 40 nm. The infrared spectroscopy (FT-IR) measurement reveals the peak at 500 cm^?1, corresponding to the Zn–O bond. Dielectric studies of ZnO nanoparticles show frequency dependence dielectric anomaly at low temperature (85–300 K). Results reveal that the capacitance and loss tangent decrease with the frequency while these parameters improve with the increasing of temperature. The increase of a.c. conductivity with the temperature indicates that the mobility of charge carriers is responsible for hopping and electronic polarization in ZnO nanoparticles.     

Low temperature fabrication of ZnO-whey protein isolate nanocomposite

Nanocrystalline zinc oxide (ZnO) particles coated with whey protein isolate (WPI) were fabricated in the weak basic aqueous solution condition at near room temperature. The X-ray diffraction and transmission electron microscopy measurements confirmed the nanoscaled composite structure of ZnO-WPI. The average composite granules size was about 300 nm and the embedded ZnO nanoparticles were uniform and monodisperse with an average diameter of 65 nm.     

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.     

Fabrication of pure ZnO nanoparticles by polymerization method

ZnO nanoparticles have received enormous attention due to their wide range of application such as diodes, ultraviolet-protection films, catalysts, sensors, ceramics and solar energy transformation parts. In the current research, ZnO nanoparticles were prepared by polymer decomposition. Synthesized ZnO nanoparticles were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and transition electron microscopy (TEM) and size distribution of these particles was investigated. Narrow size distribution of particles with a diameter of 20–30 nm and the regular distribution of ZnO nanoparticles were attributed to the application of poly amidoxime polymer. The results show that the polymer thermal decomposition technique is a feasible method for production of ZnO nanoparticles.     

Low-temperature fabrication of porous and transparent ZnO films with hybrid structure by self-hydrolysis method

Porous, transparent and controllable ZnO nanoparticulate films were fabricated by self-hydrolysis of zinc salts in its crystalline water without any additions at 65 °C by an evaporating acetone solvent. The crystallite size of ZnO nanoparticles was about 30 nm, and the thickness of the nanoparticle film was controllable by simply changing the coating times. ZnO nanoparticulate films in thickness of 500 nm showed a high transmittance (>90%) in the visible range and widen bandgap (3.35 eV). The c-axis oriented ZnO nanoarray film was fabricated by a subsequent heterogeneous nucleation and growth in an aqueous solution. As-grown ZnO hybrid films showed a good transmittance (>85%) in the visible range.     

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.     

Microstructure of nanoscale zinc oxide crystallites

Nanosized ZnO particles were prepared using a simple precipitation method. First, hydrozincite was obtained by adding Na₂CO₃ aqueous solutions with different concentrations to a zinc acetate precursor, previously dissolved in ethanol. We observed that the starting concentration of the precursors and the water content used for the hydrolysis influenced the size of the hydrozincite particles. The formation of the ZnO nanoparticles began after heating the hydrozyncite to 200 °C, and even when heating to 600 °C nanosized ZnO particles of 20-50 nm were obtained without agglomeration. The morphology and crystallinity of the obtained solids were characterized using XRD, SEM and TEM.     

Direct synthesis of monodispersed ZnO nanoparticles in an aqueous solution

Monodispersed ZnO nanoparticles with mesopores were successfully prepared via a simple route through the transformation of Zn(NH₃)₄²⁺ precursor in the presence of sodium oleate and hydrazine at 80 °C with the pH of 8.5. Hydrazine and sodium oleate were used to control the size at 30-60 nm and to improve dispersion properties of ZnO nanoparticles. The samples were characterized by TEM, XRD, IR and TG-DTA, and the results suggest that the grains are composed of ZnO and a small quantity of oleate. The oleate plays an important role in preventing the ZnO nanoparticles from aggregating.     

Effect of the annealing temperature on transparency and conductivity of ZnO:Al thin films

Highly aluminum-doped zinc oxide (ZnO:Al) films were grown by rf-magnetron sputtering at low temperature from aerogel nanoparticles and characterized by structural, electrical and optical techniques. Nanoparticles with a size of about 30 nm were synthesized by sol–gel method using supercritical drying in ethyl alcohol and annealed at different temperatures with different gas atmospheres. The ZnO films were polycrystalline textured, preferentially oriented along the (002) crystallographic direction normal to the film surface. The films show within the visible wavelength region an optical transmittance of more than 90% and low electrical resistivity of 10^− 3 Ω cm at room temperature.     

Small angle neutron scattering and photoluminescence property of wet chemistry process synthesised ZnO nanoparticles

We report the synthesis of zinc oxide (ZnO) nanoparticles from aqueous solution at 25°C and subsequent heating of the solution at 115°C by the suitable selection of the solution chemistry and the control of the alkaline conditions. The structure of the synthesised ZnO particles was studied by X-ray diffraction (XRD), confirming the formation of Wurtzite structure. The optical property of synthesised ZnO nanoparticles is investigated through room temperature photoluminescence (PL) measurement. The PL of ZnO nanoparticles shows a strong UV emission band at approximately 385 nm, a blue–green band at approximately 473 nm and a very weak green band at approximately 554 nm, although polydispersity of the sample shows no presence on the PL spectrum. Small angle neutron scattering is used to determine the size and the size distribution of ZnO nanoparticles. The SANS data analysis and model fitting predict the size as about 18–20 nm, which is closely matched with XRD and transmission electron microscopy results with Gaussian distribution.     

Optical and electrical properties of aluminum-doped zinc oxide nanoparticles

Aluminum-doped zinc oxide nanopowders were prepared using a surfactant assisted complex sol–gel method, and were characterized using inductively coupled plasma, X-ray diffraction, scanning electron microscopy/energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and UV–Vis spectroscopy. Al was effectively doped into the ZnO matrix with concentrations up to 6.00 atomic ratio percents (at.%). X-ray diffraction results revealed that all of the nanoparticles had a pure hexagonal wurtzite structure free of any impurities when annealing temperature was below 1273 K. The optical band gap of the nanopowders, which was affected by the Al-doping concentration, reached a maximum of 3.43 eV when ZnO was doped with 4.00 at.% Al. The effect of post-annealing temperature and vacuum conditions on the resistivities of the Al-doped ZnO nanoparticles was also investigated. And the lowest volume resistivity (1.2 Ω cm) was achieved by annealing the Al-doped ZnO nanoparticles in a vacuum at 1173 K for 2 h.     

Synthesis of porous ZnO nanostructures using bamboo fibers as templates

In this study, we fabricated ZnO nanostructures using bamboo fibers as templates. The starting material used was zinc acetate, and the nanostructures were synthesized by soaking and calcining the bamboo fibers. The fabricated nanostructures were characterized using X-ray powder diffraction (XRD) analysis, scanning electron microscopy (SEM), and ultraviolet-visible spectrophotometry. The results showed that the size of the ZnO nanoparticles was approximately 20–100 nm. When the ZnO nanoparticles were used as the catalyst in the photodegradation of methyl orange, the dye degraded by 95.98 % in 80 min. The response and recovery times of a gas sensor based on the ZnO nanoparticles were 25 and 24 s, respectively, during the detection of C₂H₅OH in a concentration of 10 ppm at 270 °C.     

Photoluminescence of ZnO nanoparticles prepared by a low-temperature colloidal chemistry method

ZnO nanoparticles have been synthesized by a low-temperature colloidal chemistry method using ethylene glycol as the reaction medium. Crystalline ZnO nanoparticles were formed at a temperature as low as 150 °C. The crystallite size of the ZnO nanoparticles ranged from 8 to 20 nm. The synthesized ZnO nanoparticles exhibited size-dependent photoluminescence. Photoluminescence of the ZnO nanoparticles depended largely on the post-annealing temperature. Both DL and UV emissions were suppressed at a lower post-annealing temperature of 300 °C; however they were recovered at a higher annealing temperature of 900 °C.     

Rapid synthesis of pure and narrowly distributed Eu doped ZnO nanoparticles by solution combustion method

Pure ZnO:Eu³⁺ nanoparticles (~ 50 nm) were prepared by a solution combustion method. ZnO and Eu₂O₃ were used as starting materials and dissolved in nitric acid. Citric acid was used as a fuel. The reaction mixture was heated at 350 °C resulting into a rapid exothermic reaction yielding pure nanopowders. The atomic weight concentration of Eu³⁺ doped in ZnO was 20%. Transmission electron microscopy (TEM) was used to study the particle size and morphology. The nanopowders were characterized for phase composition using X-ray diffractrometry (XRD). Particle size distribution (PSD) analysis of ZnO: Eu³⁺ showed particle sizes ranging from 30 to 80 nm.The photoluminescence emission spectra of ZnO:Eu³⁺ nanostructures showed a strong band emission around 618 nm when excited with 515 nm wavelength.     

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.     

The formation and UV-blocking property of needle-shaped ZnO nanorod on cotton fabric

ZnO nanoparticles were in-situ grown on SiO₂ coated cotton fabric through hydrothermal method. A following hot water treatment at 100 °C or higher could transform the morphology of the ZnO nanoparticles on the surface of cotton fabric from sphere and rod to much smaller diameter needle shape through a recrystallization process. After water treatment at 100 °C or higher, the cotton fabric was covered with approximately 24 nm diameter needle-shaped ZnO nanorod and had an excellent UV-blocking property with UV protection factor value over 50. The effects of temperature and time of hot water treatment on the size and crystalline perfection of ZnO nanorod and the UV-blocking property were also studied.     

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.     

ZnO thin films prepared by a single step sol-gel process

ZnO thin films were prepared on fused silica from a single spin-coating deposition of a sol-gel prepared with anhydrous zinc acetate [Zn(C₂H₃O₂)₂], monoethanolamine [H₂NC₂H₄OH ] and isopropanol. Crystallization annealing was performed over the range 500 to 650 °C. X-ray analysis showed that thin films were preferentially orientated along the [002] c-axis direction of the crystal. The films had a transparency of greater than 85% in the visible region for sol-gels with a zinc content of up to 0.7 M and exhibited absorption edges at ∼ 378 nm. The optical band-gap energy was evaluated to be 3.298-3.306 eV. Photoluminescence showed a strong emission centered at ca. 380 nm along with a broad yellow-orange emission centered at ca. 610 nm. Single step sol-gel thin film deposition in the film thickness range from 80 nm to 350 nm was demonstrated. The effect of sol-gel zinc concentration, film thickness and crystallization temperature on film microstructure, morphology and optical transparency is detailed. A process window for single spin coating deposition of c-axis oriented ZnO discussed.