The influence of annealing temperature on the structure, morphologies and optical properties of ZnO nanoparticles (original) (raw)
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Annealing effects on photoluminescence of ZnO nanoparticles
Materials Letters, 2013
In this study, the effects of annealing temperature on photoluminescence (PL) of ZnO nanoparticles were studied. ZnO was annealed at various temperatures between 600 and 900 1C. The X-ray diffraction (XRD) results demonstrated that grain size increased with increase of annealing temperature. As the annealing temperature increased from 600 to 800 1C, the intensities of both UV peak and that of green luminescence (GL) enhanced monotonously but reduced at 900 1C. The enhancement in the UV peak intensity is attributed to the decrease of grain boundaries and surface states; whereas, the remarkable improvement in the GL is assigned to the out-diffusion of oxygen from the sample up to 800 1C. It supports that GL is induced by the singly ionized oxygen vacancies. These oxygen vacancies are saturated due to the finiteness of the defects at 800 1C. So, it is speculated that the deterioration of GL intensity at 900 1C is due to the evaporation of Zn which is predominant at temperatures higher than 850 1C.
Effects of annealing temperature on morphologies and optical properties of ZnO nanostructures
Superlattices and Microstructures, 2008
Electroplated depositions of Sm were prepared using a vertical well-type electrodeposition unit with an aqueous ammonium acetate electrolyte system, with an average deposition yield just over 87%. The depositions were analyzed for morphology and thickness by scanning electron microscopy (SEM) and chemical composition by energy dispersion X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) before and after firing. The depositions were fired at 125-700°C, while varying the heating rate from 0.5 to 10°C/min in either an oxidizing or reducing atmosphere. A heating rate of 10°C/min was slow enough to prevent disruption of the deposition morphology during firing. A gas sweep enhanced the removal of any organic substituents, with an oxidizing environment being more advantageous than a reducing environment.
Effect of annealing temperature on the optical properties of ZnO nanoparticles
In this work, ZnO films were prepared by drop casting technique. The films were deposited on quartz substrates under different annealing time (15,30,45 and 60 min.) at a constant temperature (800 °C). The optical properties were achieved by measuring the absorbance and transmittance spectra in the wavelength range (200-900) nm. It was found that the absorbance decreases while transmission increases as the annealing time increases, while the reflectance decreases as the annealing time increases. The optical measurements indicate the kind of transition which was a direct allowed with an average band gap energies lie between 3.3 eV and 3.54 eV with the change of annealing time.
The influence of calcination temperature on optical properties of ZnO nanoparticles
THE 8TH NATIONAL PHYSICS SEMINAR 2019, 2019
ZnO nanoparticles (NPs) have synthesized by sol-gel with different calcination temperatures. Scanning electron microscopy (SEM) shows that the morphology of ZnO NPs has large aggregation. Then, X-ray diffraction (XRD) technique confirmed that the XRD pattern of ZnO NPs has polycrystalline wurtzite structure. The crystallite size in (002) plane at a calcination temperature of 200 o C, 400 o C, 600 o C are 9.28 nm, 12.60 nm, 20.11 nm, respectively. The intensity of observed peaks increases when the calcination temperature is higher. The room temperature UV-Vis absorbance of ZnO NPs indicate that the higher calcination temperature cause absorption peak shifted to longer wavelength and the bandgap energy lower. Optical photoluminescence properties confirmed that the UV emission coincides with the green emissions which correspond to the electron transition from the bottom conduction band to Vo, Vzn, and Ozn level. As a result, all the samples of the ZnO NPs have single broad emission in the range of 330 nm-550 nm with the peak at the UV wavelength of 375 nm. Nevertheless, the PL pattern is not linearly with increasing calcination temperature.
Advanced Materials Research, 2013
Intensive and innovative research is focused on the preparation of various nanostructured materials especially nanostructured metal oxides as applicable to number of applications.The present work mainly emphasis a single step synthesis of ZnO nanoparticles by employing surfactant free forced condensation method. Surface morphology of the sample was precisely controlled by varying the calcination conditions. Investigation on the structure, surface and composition of ZnO nanoparticles is of both fundamental interest and technological importance. X-ray diffraction (XRD) analysis reviled that the ZnO nanoparticles exhibits crystalline with the preferential orientation along (1 0 0) plane. SEM image shows the nanoparticles are in the range of 75 to 150 nm with spherical shape. The room temperature PL spectra of ZnO particles exhibited strong ultraviolet photoluminescence around 380 nm at room temperature.
Effect of annealing on photoluminescence of blue-emitting ZnO nanoparticles by sol–gel method
Journal of Sol-Gel Science and Technology, 2012
In this work, we investigated the influence of annealing on the crystallinity, microstructures, and photoluminescence (PL) properties of ZnO nanoparticles prepared by sol-gel method. The annealing was carried out both in air and vacuum. X-ray powder diffraction, scanning electron microscopy, and ultraviolet-visible spectroscopy were used to characterize the crystal structures, diameter, surface morphology, and PL properties of ZnO nanoparticles. It has been found that both the as-grown and annealed ZnO nanoparticles had a hexagonal wurtzite crystal structure, and their average diameter and crystallinity increased with the anneal time and temperature. Pure blue-emitting behavior was observed in all samples. The emission intensity of ZnO nanoparticles was found to be enhanced after annealing, but it was highly dependent on the annealing conditions. Optimal annealing conditions both in air and vacuum were obtained for achieving maximum emission intensity in the ZnO nanoparticles. The dependence of PL properties of the ZnO nanoparticles on the annealing conditions was discussed.
Preparation of ZnO Nanoparticles without Any Annealing and Ripening Treatment
In this contribution, Nano-sized ZnO particles were prepared by chemical route through aqueous solutions of zinc acetate dihydrate and sodium hydroxide at low temperature (50 °C). The influence of concentration and the NaOH addition flow on the crystallinity and morphology of the nanoparticles were investigated. X-Ray Diffraction results showed that the as-prepared particles were zinc oxide without any annealing and ripening treatment when the [ -OH]/[Zn 2+ ] concentration ratio was at less 2. Below this value, the structure is a mixture of zinc acetate and/or zinc hydroxide. Transmission Electron Microscopy results showed that the [ -OH] concentration determines ZnO nanoparticles morphology and the slower NaOH addition flow promotes ZnO nanoparticles growth in the c-axis. Optical characterization using reflectance measurements have shown energies in the UV-visible range.
ZnO nanoparticles (ZnO–NPs) were synthesized using sol–gel method. The structural and optical properties were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and photoluminescence (PL). In this study, the effects of annealing temperature on photoluminescence (PL) of ZnO-NPs were studied. ZnO was annealed at various temperatures between 500 and 800 °C. The X-ray diffraction (XRD) results demonstrated that grain size increased with increase of annealing temperature. The average size of the nanoparticles was determined by SEM as well as XRD data and found to be 50 nm after annealing at 800 °C. As the annealing temperature increased from 500 to 800 °C, the intensities of both UV peak and that of green luminescence (GL) enhanced monotonously. The enhancement in the UV peak intensity is attributed to the decrease of grain boundaries and surface states; whereas, the remarkable improvement in the GL is assigned to the out-diffusion of oxygen from the sample up to 800 °C. It supports that GL is induced by the singly ionized oxygen vacancies. These oxygen vacancies are saturated due to the finiteness of the defects at 800 °C.
Synthesis and microstructural properties of ZnO nanoparticles prepared by precipitation method
Renewable Energy, 2013
In this work, zinc oxide (ZnO) precursor was prepared by precipitation method from zinc nitrate and ammonium carbonate in aqueous solutions. ZnO nanoparticles were synthesized by annealing the precursor at different temperatures. The effect of the annealing temperature on the particle size and photo-luminescence (PL) properties of the synthesized ZnO nanoparticles were studied by XRD, SEM, BET, TG-DTA and PL measurements. The XRD results indicated that the synthesized ZnO nanoparticles had the pure wurtzite structure. It is found that with increasing the annealing temperature the crystalinity and particle size increases as well as the lattice parameters approaches to those of the XRD standard. The studies of the aggregation of the samples were also carried out by comparing SEM micrographs with specific surface measurements and XRD results. Finally, the room temperature PL spectra show UV emission peak in the range of 378.50e379.80 nm, which is close to the bulk ZnO.
Thermo- and Photo-annealing of ZnO Nanocrystals
Japanese Journal of Applied Physics, 2007
ZnO nanocrystals grown by chemical solution deposition have been annealed in ambient air using heat and cw He-Cd laser treatments. Both annealing processes increased markedly the visible luminescence intensity. The obtained results indicate that annealing under laser illumination results in effects comparable to those of high temperature annealing.