Zinc oxide (ZnO) is used widely in electrical and optical applications due to its wide band gap and also semiconductor properties. In the present study ZnO and Al doped (Al/Zn ratio equals to 6 wt. %) nanofibers (NFs) were synthesized by electrospinning method and post calcination at different temperatures 250, 300 and 400 ˚ C. The effect of dopant on microstructure, crystallography, functional molecule groups, and photoluminescence behavior of ZnO NFs were studied by means of scanning electron microscopy (SEM), X-ray diffraction pattern (XRD), Fourier-transform infrared spectroscopy (FTIR), and photoluminescence spectroscopy (PL), respectively. Results showed that the average diameter of ZnO NFs was increased from 131 to 468 nm after calcination. XRD analysis indicated that the hexagonal wurtzite ZnO was formed in both samples. Also it confirmed that the Al dopant was incorporated into ZnO NFs. Comparison of FTIR spectra showed that the Al doping caused to shift the Zn-O band to higher frequencies and also construct the stronger bonds inside the ZnO lattice. PL results also revealed that the Al doping enhanced the optical properties. It is because that the point defects issued by Al doping create lower energy levels for transferring the electrons from conduction band to valence band.

Germanium nanostructures were generated in the post annealed germanium oxide thin films. Visible and near infrared photoluminescence bands were observed in the samples annealed at 350°C and 400°C, respectively. These different luminescence ranges are attributed to the presence of the defects in oxide matrix and quantum confinement effect in the germanium nanostructures, respectively. Decay time and temperature dependence of the luminescence for different bands were investigated, which confirmed our idea about the origin of the luminescence.

Zinc oxide is a semiconductor which has photo-catalyst properties and could be used for degradation of organic materials. In this research silver doped zinc oxide nanoparticles were synthesized using Pechini sol-gel method in order to investigate its photo-catalyst properties. Nanoparticles show good photo-catalyst properties due to high surface area to volume ratio and adding of noble metals to semiconductor decreases recombination of electron-hole. Samples with different weight percentages of silver (0. 6, 1. 8, 3. 1 and 6. 2) were synthesized. Samples were characterized by UV-Visible spectroscopy, X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), Field Emission Scanning Electron Microscope (FESEM), Energy-Dispersive X-ray spectroscopy and Photo luminance Spectroscopy. Photo-catalyst properties of samples were analyzed by degradation of methylene blue. Results showed that Ag doping decreased the particle size of samples and the sample containing 1. 8% Ag had maximum rate in degradation of methylene blue solution and this was coincidence with PL results. Adding of Ag to ZnO decreased recombination rate of electron-hole in oxide and therefore increased photo-catalyst properties of samples or degradation rate of solutions. To confirm the decolorization repeatability of the synthesized samples, three photocatalytic cycles were performed on the sample containing 1. 8wt% of silver. It was observed that the decolorization efficiency of sample was not significantly reduced, and it is indicate that the synthesized catalyst is stable and functional.