الفهرس 
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Abstract
In this thesis, Novel, high-purity, mono-doped and multi-doped nano-structured derived from barium stannate (BaSnO3), copper oxide (CuO) and titanium oxide (TiO2) were synthesized by two different methods; sol-gel and coprecipitation approaches. The as-prepared metal oxides were calcined at 1150, 500 and 600 oC respectively. The doping technique played a crucial role in enhancing the magnetic and electrical properties that are suitable for using in electronic applications. It also successfully achieved proper control of the band gap values of prepared metal oxides to obtain high energy conversion efficiency suitable for photonic and photocatalytic applications. The effect of incorporation of such metal-ions on the structural, optical, dielectric, magnetic properties and the photocatalytic activity of the synthesized oxides were thoroughly investigated.
This thesis contains three main chapters, the outlines can be summarized as follows:
The first chapter (Introduction): This chapter is comprised of two sections. The first section provides a general overview of metal oxide semiconductors (MOS) and multifunctional metal oxides, including their potential uses in future data and energy storage technologies such as spintronics. It also highlights the dielectric properties of MOS and explores the effects of mono and multi-doping on their properties. In addition, one of the current worldwide hot topics, wastewater treatment, and the different solutions employed to address this critical problem have also been overviewed, with a particular focus on the photocatalytic technique. The second section is dedicated to a literature review of recent reports related to metal oxides under study barium stannate (BaSnO3), copper oxide (CuO) and titanium oxide (TiO2). It also explored the effects of doping and multidoping on the characteristics of these materials, with a focus on how these modifications can enhance their structural, optical, electrical, magnetic, and photocatalytic activities.
The second chapter (Experimental): This chapter demonstrates the different synthetic methods employed to prepare the nanostructured metal oxides and the chemicals used in this study. Sol gel technique was used to synthesize dilute magnetic semiconductor structures with the formula of BaSn0.96-XZr0.04MXO3 (M = Mn, Fe, Co, x = 0, 0.02) followed by calcination 1150 °C. On the other hand, the coprecipitation technique was successfully implemented to obtain variable and dilute multidoped compositions composed of CuO, Cu0.97Cr0.01Mn0.01Fe0.01O, Cu0.97Mn0.01Fe0.01Ni0.01O, and Cu0.97Mn0.01Co0.01Ni0.01O powders. The coprecipitation method was also used for enhancing the optical and photo-response of TiO2 through successful multi-doping techniques of TiO2, to obtain visible-light photoactive materials (Ti0.97Li0.015Mo0.015O2), (Ti0.97 Mg0.015Mo0.015O2) and (Ti0.97Al0.015Mo0.015O2). It also presents the different characterization techniques employed to explore the obtained structural, morphological, magnetic, dielectric and optical properties of the produced oxides. In addition, the optimized conditions employed during the photocatalytic degradation of the dyes and the models used to investigate the rate constants of the reaction were described. Appling the prepared photocatalysts for the treatment of two different dyes (Congo red and solo chrome) as case studies under the solar illumination environment have been also investigated. This chapter was also pointed out to explain the basic principles and techniques used for the characterization of the prepared samples such as: XRD, SEM-EDX, TEM, FT-IR, UV−vis, Diffuse reflectance (DR), Vibrating-sample magnetometer (VSM) and Hioki LCR.
The third chapter (Results and Discussion):
This chapter was concerned with the characterization of synthesized nano-structured barium stannate (BaSnO3), copper oxide (CuO) and titanium oxide (TiO2). The effect of mono and multi-doping on the structural, optical, electrical, magnetic, and photocatalytic activities was reported. This chapter is divided into three sections:
In the first section, variable and dilute multi-doped compositions composed of BaSnO3 samples were attained through the sol-gel technique. Zr and/or Mn, Fe or Co ions were employed as dopants to induce room temperature ferromagnetic nature into the perovskite BaSnO3 for high-performance information applications. Dilute magnetic semiconductor structures with the formula of BaSn0.96-XZr0.04MXO3 (M = Mn, Fe, Co, x = 0, 0.02) have been synthesized. The Mono-phase of cubic BaSnO3 structure without any impurities was recorded for all compositions via X-ray diffraction technique. The detected relation between dopants ionic size and BaSnO3 crystal dimensions supports the substitution process of Sn4+-site. Extended visible band state absorption tails were formed in BaSn0.94Zr0.04Mn0.02O3 and BaSn0.94Zr0.04Co0.02O3 samples, owing to 3d-orbitals of Mn and Co ions. Upon the addition of Zr and/or Mn, Fe or Co ions, high refinement of BaSnO3 morphology from inhomogeneous large grains to well distribute small ones was seen. Magnetically, 4wt% Zr4+ ions displayed the ability to induce full-saturated spin ferromagnetic order with saturation magnetization of 1.16 emu/g, retentivity of 0.11 emu/g and coercivity of 147 Oe. The addition of Zr/Co ions also stimulates full-saturated spin ferromagnetic order with saturation magnetization of 1.36 emu/g, retentivity of 0.17 emu/g and coercivity of 149 Oe. The pronounced ferromagnetic character could be assigned to that the empty 4d-Zr4+ ions show high ability in reversing the diamagnetic nature of BaSnO3 to a ferromagnetic one through interaction with oxygen vacancies. It seems that the interaction of the outer 4d-shell of Zr and 3d-orbital of Co with the oxygen vacancies into BaSnO3 lattice supports a strong magnetic exchange. Through looking into the previous studies on magnetic properties of BaSnO3, the recorded saturation magnetization of 4wt% Zr and 4wt% Zr+ 2 wt% Co ions are remarkable values for single nonmagnetic dopant and nonmagnetic + magnetic as dual dopants, respectively.
In parallel to the successful synthesis of the aforementioned BaSnO3 samples, the second section reported dilute multi-doped compositions composed of CuO, Cu0.97Cr0.01Mn0.01Fe0.01O, Cu0.97Mn0.01Fe0.01Ni0.01O, and Cu0.97Mn0.01Co0.01Ni0.01O nano-powders synthesized via a coprecipitation approach. The crystal structural analysis of the synthesized compositions indicated that a high-purity mono-phase of monoclinic CuO structure was formed and also ruled out the existence of any other impurities. The Fourier-transform infrared (FT-IR) spectra demonstrated the characteristic vibrational absorption modes of the CuO structure. The transmission electron microscopy (TEM) images revealed that the pure CuO has approximately spherical nano-sized particles while Cu0.97Cr0.01Mn0.01Fe0.01O, Cu0.97Mn0.01Fe0.01Ni0.01O and Cu0.97Mn0.01Co0.01Ni0.01O powders have nano-spherical particles as well as some elongated particles. Optically, the incorporation of these transition metals blends led to the formation of long absorption tails and obvious red shifts for the band gap energy of CuO. Exactly, CuO, Cu0.97Cr0.01Mn0.01Fe0.01O, Cu0.97Mn0.01Fe0.01Ni0.01O and Cu0.97Mn0.01Co0.01Ni0.01O samples exhibited infrared band gap energies of 1.42, 1.4, 1.25 and 1.2 eV, respectively. Magnetically, at room temperature Cu0.97Mn0.01Fe0.01Ni0.01O exhibits a perfect ferromagnetic performance with high saturation magnetization of 1.15 emu/g and coercivity of 76 Oe. It seems that the multi-doping induced a robust ferromagnetic state via Cu2+-Mn+ or Mn+-Mn+ exchange interactions (M= Mn, Fe, Ni) into CuO, leading to remarkable room temperature magnetic characteristics.
The third section reported enhancing the optical and photo-response of TiO2 through successful multi-doping techniques. To attain this goal, different structures composed of pure TiO2, (Ti0.97Li0.015Mo0.015O2), (Ti0.97 Mg0.015Mo0.015O2) and (Ti0.97Al0.015Mo0.015O2) were synthesized by coprecipitation method. The XRD patterns confirmed a tetragonal structure of anatase TiO2 with some minor peaks assigned to rutile and brookite phases in the undoped sample. The (Li, Mo), (Mg, Mo) and (Al, Mo) codoped-TiO2 samples indicate that the codoping leads to formation of pure anatase phase. from UV–VIS diffuse reflectance spectra (DRS), the band gap energy and excitation wavelength of the doped and undoped TiO2 nanoparticles were identified. The samples recorded varying photocatalytic activity against the degradation of Congo red (CR) dye at high concentrations (50 ppm). The sequence of decreasing the dye-maximum absorption peak followed the following order Ti0.97Li0.015Mo0.015O2> pure TiO2> Ti0.97Al0.015Mo0.015O2≥ Ti0.97Mg0.015Mo0.015O2 which indicates that Ti0.97Li0.015Mo0.015O2 has the highest degradation efficiencies compared to the other compositions. The photocatalytic activity of the samples was also evaluated for the removal of solochrome dye with a high concentration 50 ppm. The variations of the absorption peak of SCV followed the following order Ti0.97Li0.015Mo0.015O2= Ti0.97Al0.015Mo0.015O2> Ti0.97Li0.015Mo0.015O2> pure TiO2> Ti0.97Mg0.015Mo0.015O2. Hence the Ti0.97Li0.015Mo0.015O2 showed the highest degradation efficiencies against both dyes with degradation efficiency 89 and 97% for CR and SCV dyes respectively. The enhanced photocatalytic activity was related to increase band gab, a low surface area-to-volume ratio and the high crystallinity of Ti0.97Li0.015Mo0.015O2 which is suitable for the generation of long-lived holes and reduced the rate of e−/h+ recombination. The dielectric properties of the synthesized TiO2 -powder showed that the (Li, Mo) co-doping significantly improves the dielectric constant value to reach 2430 at 50 Hz. A moderate increase in the dielectric constant was achieved owing to the insertion of Mg with Mo ions into TiO2 lattice, reaching 861 (50 Hz). In the same context, implantation of Al with Mo exhibits good influences on the dielectric constant and increases it to 1060 at a frequency of 50 Hz. The sequence in the dielectric constant enhancement follows the following order (Li, Mo) > (Al, Mo) > (Mg, Mo) > TiO2. So, the dielectric results indicated that the bi-doping of TiO2 enhanced the dielectric characteristics which is suitable for dielectric and electronic applications.