الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 169 |  |  |
| | | from | 169 | | |
Abstract
Summary
This thesis dealt with the synthesis of Mn-doped TiO2 nanoparticles (NPs) by Sol—gel method, as a diluted magnetic semiconductors, and their characterization.
The thesis contains four chapters, arranged as follows:
Chapter I: Introduction
This chapter is divided into two parts; The first part introduces a general introduction about the concept of nanomaterials and their classification based on many parameter e.g. dimensionality, surface morphology, chemical composition, crystalline forms, chemical nature, uniformity and agglomeration state, functionalization and applications. Physicochemical properties of nanoparticles e.g. surface area, hydrophobicity, hydrophilicity or water solubility dispersability, catalytic / photocatalytic activity, magnetic, optical and mechanical properties are introduced. The causes of the unique characteristic, e.g. randomness of energy level and increased surface to volume ratio, were also introduced. The second part discusses wide band gap semiconductor materials such as TiO2 and ZnO. Focused on TiO2 as a host of DMS.
Chapter 2: literature review
In this chapter a literature survey of recent published works and reports related to our subject of investigation which display the preparation of NPs act as DMS with characterization to examine their characteristics and ability in application as spintronics.
CHAPTER 3: Materials and methods
This chapter gives the synthetic method employed to prepare the pure TiO2 and Mn-doped TiO2 NPs, the chemicals used in preparation. It presents the different characterization techniques utilized to investigate the obtained structural, morphological, optical, PL and magnetic properties of the produced samples.
CHAPTER 4: Results and Discussion
This chapter presents in detail the obtained results and their explanations in terms of previous hypotheses and in comparison to previous published data. XRD showed the structural properties of the prepared samples and ensured the successful incorporation of the Mn dopant into the host titania-semiconductor. TEM analysis gives information about the morphology, the particle size, and d-spacing resulted from the IFFT profiles, which are all in good agreement with XRD interpretation. UV-Vis DRS analysis was used to evaluate the optical characteristics, measuring the optical band gap using Kubelka-Munk function as well as the optical absorbance of the samples. PL measurement discussed defects presence in pure titania and Mn-doped TiO2. VSM indicated ferromagnetic properties of the prepared compositions with promising potential for use in spintronics applications.
Conclusions
In conclusion, the effect of Mn-doping on phase structure, ferromagnetism and optical properties of sol–gel synthesized Ti1‒xMnxO2 nanoparticles has been investigated over a wide range of (x). XRD revealed the coexistence of anatase and rutile in pure TiO2 in the nanometer size and increase of Mn-doping concentration (x) increased the percentage of anatase and reduced that of rutile. Up to x= 0.07, no secondary phase was detected which confirmed the successful incorporation of Mn cations, Mn2+ and Mn3+, into the TiO2 nanolattice warranting the absence of metallic clusters or Mn oxides. When x= 0.1, only a minority of Mn2O3 could be detected. Additionally, increase of x resulted in a monotonic reduction of the crystallite nanosize of both of anatase and rutile. Lattice constants (”a” and ”c”) as well as unit cell volume (V) of both of anatase and rutile phases increased with increasing Mn-content.
HRTEM and IFFT profiles were employed to investigate the morphology and interplanar d-spacing of the formed nanocrystalline phases. Presence of anatase, rutile and Mn2O3 was manifested.
UV–Vis revealed, in agreement with XRD results, the presence of Mn as Mn2+ and Mn3+ ions. Also, Eopt was found to decrease significantly with increasing x.
PL emission bands in violet range (400-425 nm), blue range (425-500 nm), green range (500-565 nm), and red—far red range (600-750 nm) were recorded.
Titania nanoparticles with low x, samples 0.5Mn, 1Mn, 1.5Mn and 3Mn, exhibited RT ferromagnetism and could be promising DMS materials for spintronic applications. This RT ferromagnetic ordering, originated from the interaction between Mn ions and oxygen vacancies, has been explained in terms of the BMP model.