Search Results (8)

The synthesis and characterization of ZnO/TiO₂, SiO₂/TiO₂, Al₂O₃/TiO₂, and Al_1.9Co_0.1O₃/TiO₂ core/shell nanoparticles (NPs) is reported. The NPs were used for photocatalytic degradation of brilliant blue E-4BA under UV and visible light irradiation, monitored by high-performance liquid chromatography and UV-vis absorption spectroscopy. The size of the NPs ranged from 10 to 30 nm for the core and an additional 3 nm for the TiO₂ shell. Al₂O₃/TiO₂ and Al_1.9Co_0.1O₃/TiO₂ showed superior degradation under UV and visible light compared to ZnO/TiO₂ and SiO₂/TiO₂ with complete photodecomposition of 20 ppm dye in 20 min using a 10 mg/100 mL photocatalyst. The “Co-doped” Al_1.9Co_0.1O₃/TiO₂ NPs show the best performance under visible light irradiation, which is due to increased absorption in the visible range. DFT-calculated band structure calculations confirm the generation of additional electronic levels in the band gap of γ-Al₂O₃ through Co³⁺ ions. This indicates that Co-doping enhances the generation of electron–hole pairs after visible light irradiation. Full article

This review addresses the importance of Zn for obtaining multifunctional materials with interesting properties by following certain preparation strategies: choosing the appropriate synthesis route, doping and co-doping of ZnO films to achieve conductive oxide materials with p- or n-type conductivity, and finally adding polymers in the oxide systems for piezoelectricity enhancement. We mainly followed the results of studies of the last ten years through chemical routes, especially by sol-gel and hydrothermal synthesis. Zinc is an essential element that has a special importance for developing multifunctional materials with various applications. ZnO can be used for the deposition of thin films or for obtaining mixed layers by combining ZnO with other oxides (ZnO-SnO₂, ZnO-CuO). Also, composite films can be achieved by mixing ZnO with polymers. It can be doped with metals (Li, Na, Mg, Al) or non-metals (B, N, P). Zn is easily incorporated in a matrix and therefore it can be used as a dopant for other oxidic materials, such as: ITO, CuO, BiFeO_3, and NiO. ZnO can be very useful as a seed layer, for good adherence of the main layer to the substrate, generating nucleation sites for nanowires growth. Thanks to its interesting properties, ZnO is a material with multiple applications in various fields: sensing technology, piezoelectric devices, transparent conductive oxides, solar cells, and photoluminescence applications. Its versatility is the main message of this review. Full article

A_yB_1−yC_xFe_2−xO₄ (C=Ho,Gd,Al) ferrite powders have been synthesized by the sol-gel combustion route. The X-ray diffraction of the CoHo_xFe_2−xO₄ (x = 0~0.08) results indicated the compositions of single-phase cubic ferrites. The saturation magnetisation of CoHo_xFe_2−xO₄ decreased by the Ho³⁺ ions, and the coercivity increased initially and then decreased with the increase of the calcination temperature. The Mössbauer spectra indicated that CoHo_xFe_2−xO₄ displays a ferrimagnetic behaviour with two normal split Zeeman sextets. The magnetic hyperfine field tends to decrease by Ho³⁺ substitution owing to the decrease of the A–B super-exchange by the paramagnetic rare earth Ho³⁺ ions. The value of the quadrupole shift was very small in the CoHo_xFe_2−xO₄ specimens, indicating that the symmetry of the electric field around the nucleus is good in the cobalt ferrites. The absorption area of the Mössbauer spectra changed with increasing Ho³⁺ substitution, indicating that the substitution influences the fraction of iron ions at tetrahedral A and octahedral B sites. The X-ray diffraction of Mg_0.5Zn_0.5C_xFe_2−xO₄(C=Gd,Al) results confirmed the compositions of single-phase cubic ferrites. The variation of the average crystalline size and lattice constant are related to the doping of gadolinium ions and aluminum ions. With increasing gadolinium ions and aluminum ions, the coercivity increased and the saturation magnetization underwent a significant change. The saturation magnetization of AlMg_0.5Zn_0.5FeO₄ ferrite reached a minimum value (M_S= 1.94 mu/g). The sample exhibited ferrimagnetic and paramagnetic character with the replacement with Gd³⁺ ions, that sample exhibited paramagnetic character with the replacement with Al³⁺ ions, and the isomer shift values indicated that iron is in the form of Fe³⁺ ions. Full article

In this work, the main objective is to enhance the gas sensing capability through investigating the effect of Al and Mg doping on ZnO based sensors. ZnO, Mg_1% doped ZnO, Al_5% doped ZnO and (Al_5%, Mg_1%) co-doped ZnO nanoparticles (NPs) were synthesized by a modified sol-gel method. The structural characterization showed the hexagonal crystalline structure of the prepared samples. Morphological characterizations confirmed the nanometric sizes of the NPs (27–57 nm) and elemental composition investigation proved the existence of Al and Mg with low concentrations. The optical characterization showed the high absorbance of the synthesized samples in the UV range. The gas sensing performances of the synthesized samples, prepared in the form of thick films, were investigated. Sensing tests demonstrated the high influence of the Al and Mg on the sensing performances towards H₂ and CO gas, respectively. The 5A1MZO-based sensor exhibits high sensitivity and low detection limits to H₂ (<2 ppm) and CO (<1 ppm). It showed a response around 70 (at 250 °C) towards 2000 ppm H₂ and 2 (at 250 °C) towards CO. Full article

In this study, high transparent thin films were prepared by radio frequency (RF) magnetron sputtering from a conventional solid state target based on ZnO:MgO:Al₂O₃ (10:2 wt %) material. The films were deposited on glass and silicon substrates at the different working pressures of 0.21, 0.61, 0.83 and 1 Pa, 300 °C and 250 W of power. X-ray diffraction patterns (XRD), atomic force microscopy (AFM), UV-vis absorption and Hall effect measurements were used to evaluate the structural, optical, morphological and electrical properties of thin films as a function of the working pressure. The optical properties of the films, such as the refractive index, the extinction coefficient and the band gap energy were systematically studied. The optical band gap of thin films was estimated from the calculated absorption coefficient. That parameter, ranged from 3.921 to 3.655 eV, was hardly influenced by the working pressure. On the other hand, the lowest resistivity of 8.8 × 10⁻² Ω cm⁻¹ was achieved by the sample deposited at the lowest working pressure of 0.21 Pa. This film exhibited the best optoelectronic properties. All these data revealed that the prepared thin layers would offer a good capability to be used in photovoltaic applications. Full article

In this paper, ZnO and Co²⁺/Mg²⁺-doped ZnO thin films on TiAlV alloy substrates were obtained. The films were deposited by spin coating of sol-gel precursor solutions and thermally treated at 600 °C for 2 h, in air and slow cooled. The doping ions concentration was 1.0 mol%. The study’s aim was to obtain implantable metallic materials with improved biocompatibility and antibacterial qualities. The characteristics of the thin films were assessed from the point of view of microstructure, morphology, wetting properties, antibacterial activity and biological response in the presence of amniotic fluid stem cells (AFSC). The results proved that all deposited samples were nanostructured, suggesting a very good antibacterial effect and proving to be suitable supports for cellular adhesion and proliferation. All properties also depended on the doping ion nature. Full article

A series of Li(Ni_1/3Mn_1/3Co_1/3)_1−xM_xO₂ (M = Al, Mg, Zn, and Fe, x = 0.06) was prepared via sol-gel method assisted by ethylene diamine tetra acetic acid as a chelating agent. A typical hexagonal α-NaFeO₂ structure (R-3m space group) was observed for parent and doped samples as revealed by X-ray diffraction patterns. For all samples, hexagonally shaped nanoparticles were observed by scanning electron microscopy and transmission electron microscopy. The local structure was characterized by infrared, Raman, and Mössbauer spectroscopy and ⁷Li nuclear magnetic resonance (Li-NMR). Cyclic voltammetry and galvanostatic charge-discharge tests showed that Mg and Al doping improved the electrochemical performance of LiNi_1/3Mn_1/3Co_1/3O₂ in terms of specific capacities and cyclability. In addition, while Al doping increases the initial capacity, Mg doping is the best choice as it improves cyclability for reasons discussed in this work. Full article

In this study, unique core-shell aluminate spinel supports, Al@MAl₂O₄ (M = Zn, Mg, or Mn), were obtained by simple hydrothermal surface oxidation and were applied to the preparation of supported Ni catalysts for CO₂ methanation. For comparison, CO methanation was also evaluated using the same catalysts. The prepared catalysts were characterized with a variety of techniques, including N₂ physisorption, CO₂ chemisorption, H₂ chemisorption, temperature-programmed reduction with H₂, temperature-programmed desorption of CO₂, X-ray diffraction, high-resolution transmission electron microscopy, and in-situ diffuse reflectance infrared Fourier transform spectroscopy. The combination of supports with core-shell spinel structures and Ni doping with a deposition–precipitation method created outstanding catalytic performance of the Ni catalysts supported on Al@MgAl₂O₄ and Al@MnAl₂O₄ due to improved dispersion of Ni nanoparticles and creation of moderate basic sites with suitable strength. Good stability of Ni/Al@MnAl₂O₄ catalyst was also confirmed in the study. Full article