الملخص
The work in this thesis has been taken for preparation of films (NiO-SiO2) and (ZnOSiO2) nanoparticles of various concentrations and different annealing temperatures has not been studied previously by sol gel. In particular, spin coating technique which has been active research topics in recent years in nanotechnology. These films have attracted much attention and it has used in many important applications, such as catalysis, the solar cells, high-energy laser and anti-reflection coatings and optical sensors. In addition, the aim of this thesis is to study and understand the relationship between structure and optical properties of NiO-SiO2 and ZnO-SiO2 sol gel mixed oxides by measurements of X-ray diffraction (XRD), Fourier transform infrared (FT-IR) absorption, photoluminescence, Raman scattering, optical absorption, and fieldemission scanning electron microscopy (FESEM), etc. in different annealing temperatures. This thesis is divided into 5 chapters and a brief description of content in each chapter is given below.d Chapter 1 is a general introduction to sol gel technique with a specific emphasis on the properties of SiO2, NiO and ZnO material. An exhaustive review on NiO-SiO2 and ZnO-SiO2 nanocomposite thin films is also given in this chapter. Chapter 2 gives a general description on the preparation technique used for the deposition of NiO-SiO2 and ZnO-SiO2 nanocomposite thin films. A brief description of different characterization techniques used in the present work is also given. Chapter 3 describes the effect of calcinations (annealing) temperatures on the surface morphological, structural and optical properties of NiO-SiO2 nanocomposite thin films annealed at different temperatures from 200-1100 °C. Our results show that the NiO(200) diffraction peak dominates in the preset work. NiO phase appeared in the XRD patterns for all samples. In addition, FESEM micrographs and EDX analysis showed that the porous structure of the silica matrix could improve the sensitivity of these nanocomposites for gas sensing because more paths would be available for the gas molecules diffusing in the film and allowing reach the NiO reactive particle. Moreover, the newly prepared photocatalysts films have been evaluated by the determination of their photonic efficiencies for degradation of methylene. The results reveal that the photonic efficiency increases with increasing calcinations temperature up to 600 °C with the maximum photonic efficiency being 0.62 %. Chapter 4: in this chapter, ZnO-SiO2 nanocomposite thin films were prepared by sol gel technique on Si substrates. The formed films gels were annealed at different temperature for 4 hours leading to nanocomposites. For these films, the effect of annealing temperatures on the structural, surface morphological, and photoluminescence properties were studied. Our results show that the c-axis orientation of ZnO films increases by increasing annealing temperature and suggested that the ZnO(100) diffraction peak dominates in the XRD measurement. In addition, the diffraction peak's positions for all phases did not show any shift with increase in the annealing temperature, suggesting fabrication of stress-free zinc oxide-silica. We also observed agglomerates of ZnO clusters act as nucleation sites for core/shell structures by FESEM. The PL spectra exhibit few separated PL bands. Moreover, The recycling tests indicated ZnO-SiO2 films was quite stable during that liquid-solid chemical sensing since no significant decrease in sensitivity was observed even after being used repetitively for 3 times, showing a good potential in practical application.e Chapter 5 illustrates the effects of concentration on the growth, structural and photoluminescence properties of ZnO-SiO2 nanocomposite films annealed at different temperatures from 200-1100 °C. The XRD patterns showed that the hexagonal wurtzite structure of the ZnO film was formed for all the prepared samples. The newly prepared photocatalysts ZnO-SiO2 films have been evaluated by the determination of their photonic efficiencies for degradation of methylene blue. The photonic efficiencies of 10 wt% ZnOSiO2 increase from 0.9 to 2.3 % with increasing annealing temperature from 200 to 600 °C and then gradually decrease to 1.56% at 1100 °C. The results indicate that 10 wt% ZnO-SiO2 annealed at 600°C showed the highest photocatalytic activity for the MB photodegradation. Our work demonstrates the ability to reduce the working temperature as well as to increase the response of ZnO thin film as a highly efficient photocatalyst, which would be of great merit for commercialized applications.
