جستجوی مقالات مرتبط با کلیدواژه « zno » در نشریات گروه « مواد و متالورژی »

Recently, there has been an increase in the ability to adjust the optical band gap and enhance the brightness of luminescence in nanophosphors that are utilized in light-emitting diodes and detectors. In this study, a dual oxide composite of erbium-doped lead tungstate/Ag-doped zinc oxide (PWO: Er/ZnO: Ag) heterostructures have been synthesized via a simple chemical method, and the structural and optical properties have been investigated. The effect of excitation wavelength (Landa Landaex) and excitation source was studied on the luminescence properties of the synthesized composite nanoparticle (NPs) at room temperature. Under UV illumination, doped nanocomposite demonstrated strong emission in the blue-green region compared to the pure sample at Landa Landaex=270-280 nm. XRD and EDX results confirmed the existence of PWO and ZnO in the dual composite structure along with the related components. The results demonstrate that mixed-dimensional heterostructures could be developed for high-performance optoelectronic devices using this method.

Li-doped ZnO thin films prepared by sol-gel spin coating method, have been studied in this research to increase the p-type ZnO layers conductivity. For this purpose, the lithium dopant concentration was changed and structural, electrical, and opti-cal properties of the layers were investigated. For structural analysis, XRD and FESEM were used. Besides, thin films electri-cal properties including resistivity and majority carriers’ type were determined. Eventually, optical properties were studied by UV-Visible and PL spectroscopy. Structural investigations showed that the single phase layers with wurtzite hexagonal structure and 40-50 nm average grain size were formed. For obtaining p-type layers and enhancing their electrical conductiv-ity, there was an optimum in moderate Li concentrations. Furthermore, regarding the optical properties, it was concluded that the band gap energy is sensitive to Li concentration and the refractive index of ZnO layer decreased with Li doping. Fi-nally, the effect of Li doping was further studied by DFT calculation. These calculations propose activation of a self-compensation mechanism by Li doping which can be responsible for decrease of the conductivity at high Li concentra-tions. In the proposed mechanism, Zni donor defect sites, accompanying LiZn sites, cause self-compensation.

Novel luminous materials are always required in solid-state light-emitting diodes and displays applications. In this regard, the current study investigated the luminescence properties of cerium-doped zinc oxide/cadmium tungstate (ZnO/CdWO4: Ce) nanocomposite particles under proton, laser, and gamma-ray excitations. The XRD results revealed the simultaneous existence of monoclinic CWO and hexagonal ZnO. Doped nanocomposite particles under proton/laser irradiations displayed significant luminescence in the blue-green region compared with the pure nanocomposite. In addition, Thermo-Luminescence (TL) study of the doped pellet showed a stronger glow peak at 350-400 °C. According to the TEM, the doped nanoparticles had an average diameter of 70-150 nanometers. The existence of Zn, O, Cd, W, and Ce elements in the composites was confirmed by the EDX technique. The obtained results showed that the produced ZnO/CWO: Ce nanocomposite particles could be promising materials to be used in optoelectronic devices.

Zinc Oxide (ZnO) nanorods and titanium dioxide (TiO2) nanostructures thin films were prepared onto glass substrates by the chemical bath deposition (CBD) method. The ZnO was structured as nanorods (NRs) while TiO2 was formed as nanoflowers plate as confirmed by Field-Emission Scanning Electron Microscope (FESEM) images. The ZnO/Fe3O4 and TiO2/Fe3O4 nanostructures thin films were prepared via drop-casting Fe3O4 NPs onto the grown ZnO and TiO2 nanostructures thin films. The diameter of Fe3O4 NPs was deposited onto ZnO NRs thin films and TiO2 nanostructures thin films was ranged from 8nm to 59nm with dominated range between 10nm to 30 nm.  The crystalline structure of prepared samples was investigated through X-ray diffraction (XRD) method. However, the particles size of Fe3O4  was estimated  by XRD as well as FESEM images was around 22 nm. The photocatalytic activity of the as-prepared ZnO/Fe3O4 and TiO2/Fe3O4 nanostructures thin films was investigated against methylene blue (MB) dye at room temperature with a pH value of 10 under different exposure time by visible light. The photodegradation rate of MB dye by ZnO/Fe3O4 and TiO2/Fe3O4 nanostructures thin films was higher than that obtained by ZnO and TiO2 nanostructures thin films. The best photodegradation rate of MB dye was 100% after exposure time of 180 min was obtained by ZnO/Fe3O4 nanostructures thin film whereas it was 82% for TiO2/Fe3O4 nanostructures thin films after exposure time of  240 min.

In this work, the ZnO/CuO nanocomposite was synthesized with two different initial pH values in an acidic media through a simple one-step and cost-efficient chemical bath precipitation method. To alter the pH value of the solution, nitric acid was added dropwise and initial pH values were 1.5 and 4.5, respectively. The crystal phase structure of the samples was investigated by X-ray diffraction analysis (XRD), indicating the formation of wurtzite structure of ZnO and monoclinic structure of CuO. Additionally, the morphological structure of the as-formed nanocomposites was studied by field emission scanning electron microscopy (FESEM). It was demonstrated that at pH = 4.5 and 1.5, ZnO nanorods/CuO nanoflakes and ZnO nanoparticles/CuO nanosheets were formed, respectively. For optical characterizations, diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) spectra were performed. The band gap energy of the as-prepared samples was calculated at 3.08 and 2.9 eV with an initial pH of 1.5 and 4.5, respectively. Furthermore, PL data revealed that the sample synthesized in pH = 4.5 exhibits a significant decrease in electron/hole recombination rate compared with that of the sample fabricated in pH = 1.5. Accordingly, the photocatalytic activity of the as-prepared samples was studied employing methylene blue (MB) under visible-light irradiation. Overall, the prepared sample at pH = 4.5 and pH = 1.5 demonstrated ~76% and ~66% photo-degradation efficiency of MB after 150 min, respectively. Finally, the role of holes and hydroxyl radicals on the degradation of MB were proposed using charge carrier scavengers.

Nanostructured ZnO thin films with two different dopants namely Pb and Co were prepared by a sol–gel method. The thin films have been prepared from zinc acetate, monoethanolamine and iso-propanol and then they were deposited on glass substrate by using a dip coating method. The structural, morphological, photocatalytic activity and optical absorbance of thin films were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet-visible spectrophotometer and degradation of methylene blue dye (MB). The all thin films exhibited a polycrystalline hexagonal wurtzite structure that revealed by XRD. Due to doping, the average grain size of ZnO thin film increased. All films showed a wrinkle morphology. Photocatalytic activity of thin films was evaluated in aqueous solutions of Methylene Blue (MB) under UV-light illumination. The results indicated that the photocatalytic activity of ZnO thin films increased by Pb doping, conversely Co doping reduced the photocatalytic activity in comparison with the pure ZnO films. Hence speed of degradation of methylene blue by Pb doped ZnO is higher than that of pure and Co doped ZnO.

Zinc oxide (ZnO) is used for various purposes because of its special physico-chemical properties, including large band gap, high binding energy of exciton, nontoxicity, high chemical and thermal stability, large piezoelectric constants, and wurtzite crystal structure with various and widespread applications in electronics, optoelectronics, biochemical sensing, biomedical, and energy-saving systems. This review mainly aimed to present the recent improvement in ZnO-based composite materials with utilization in energy storage systems with a specific focus on lithium-ion batteries, dye-sensitized solar cells, and supercapacitors. The first part of this paper looks at the structure and properties of ZnO and then describes some of the most common synthesizing methods of ZnO com-posites, including electrochemical, chemical, solvo/hydrothermal, and physical deposition methods. Finally, the recent advancement of ZnO-based composite materials applied in energy storage systems was discussed. ©2021 JCC Research Group

Photocatalyst nanocomposites of ZnO/bentonite clay are synthesized by Solid-state ion exchange method. Ion exchange intercalation process of clays is used to incorporate the catalyst into the basal space of the layered structure of clays. The purpose of this study is to find a new method, which is focused on simplifying and saving time to prepare ZnO-bentonite composite with photocatalyst property. The synthesis of ZnO-doped bentonite nanocomposite is accomplished by placing bentonite in a melting bath of ZnSO4 for 10, 20, 40, 60 and 90 min. The nanocomposites are characterized by morphological (SEM), optical (UV/vis reflection) and analytical (EDX) techniques. According to SEM results, after ion exchanging, the parent structure of bentonite remains and only the distance between flakes increased significantly. EDX analysis clearly suggest the success of ion exchange of the expense of Ca2+, Na+ and Mg2+ cations with Zn2+. The calculated band gap for the composites were 3.14 eV (10 min), 2.64 eV (20 min) and 2.54 eV at longer times, respectively. All the prepared composites showed acceptable degradation performances. The greatest photocatalytic activity is detected in ZnO/bentonite composite solid-state ion exchanges which lasts 60 and 90 min. Leaching test results showed that the concentrations of Zn are less than 4 mg/l between 0 and 6 h. These results indicated that the photocatalytic property of composites would last longer

Structural, electrical and optical properties of indium tin oxide or ITO (In2O3:SnO2) thin films on different substrates are investigated. A 100-nm-thick pre-deposited zinc oxide (ZnO) buffer layer is utilized to simultaneously improve the electrical and optical properties of ITO films. High purity ZnO and ITO layers are deposited with a radio frequency sputtering in argon ambient with plasma powers of 150 W and 300 W, respectively. After deposition, samples are annealed in a high vacuum furnace at 400 ˚C. The effects of ZnO-coated substrates on the crystallinity and morphological properties of ITO films are analyzed by X-ray diffractometer, field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). X-ray diffraction patterns confirm the hexagonal wurtzite type polycrystalline structure of the ZnO films. FESEM and AFM analyses indicate that the surface morphology of the ITO films is affected by the ZnO buffer layer. Results also reveal that the roughness of ITO thin films is decreased in presence of the ZnO buffer layers. It has been found that ZnO incorporation promotes the crystallization of the ITO layer reduces its resistivity without deteriorating the optical transmittance.

In this paper, polycrystalline pure zinc oxide nano structured thin films were deposited on two kinds of single crystal and polycrystalline of p and n type Si in three different substrate temperatures of 300, 400 and 500◦C by low cost APCVD method. Structural, electrical and optical properties of these thin films were characterized by X ray diffraction, two point probe method and UV visible spectrophotometer respectively. IV measurements of these heterojunctions showed that turn on voltage and series resistance will increase with increasing substrate temperature in polycrystalline Si, while in single crystal Si, turn on voltage will decrease. Although they are acceptable diodes, their efficiency as a heterojunction solar cell are so low.