Of Mn (2 +) Of Eu (3 +) Doping Of Zns Luminescence Properties

Nanoscience have been drawn considerable interest and physicaly investigated all over the world. The nanoparticles have different properties compared with bulk materials such as quantum size effect, surface effect, the dieletric confinement etc. The intrinsic optical properties of nanoparticles have been thoroughly studied. The optical properties of semiconductor nanoparticles doped with activator elements such as ZnS:Mn2+ which was first prepared in 1993 led to a new stage of investigation of optical characteristics of nanoparticles . In this thesis, we studied optical properties of Eu3+ and Mn2+ doped ZnS nanocrystallites. The new results are as follows:1. ZnS: Mn2+ ethanol colloids were synthesized and dispersed into PVB film .The luminescence enhancement of Mn2+ was observed after ultraviolet irradiation. We consider that surface state act as quenching centers. With the irradiation, the surface state decreases and therefore luminescence of Mn2+ increases. Reduction of quenching centers is the result of chemical change by obtaining energy from ZnS excited by UV light. Life time of Mn2+ in nano-ZnS was measured and was found to be close to that of the bulk materials.Therefore the quenching centers quench the exciton but not the Mn2+ ion self.2. The increasing curves are different in film and ethanol colloids because there is diffusion process of quenching centers in colloids. The decay curve of quenching centers is non-exponential. 3. Nano-ZnS: Mn2+ dispersed in PVB film has the same enhancement after exposure in solar light. The material has potential on measuring the dosage of UV irradiation of solar light.4. The nanoparticles of ZnS: Eu3+ were synthesized for the first time. The energy transfer process between the ZnS host and the Eu3+ ions was observed form the excitation spectra. Site-select spectra indicate that the Eu3+ in nanoparcles formed two kinds of luminescence centers with different branch ratios of 5D0-7FJ. The ratio of varied with different excitation.5. The luminescence enhancement of Eu3+ was also observed after ultraviolet irradiation but was weaker than the ZnS:Mn2+ and the branch ratio of 5D0-7F0 increased after irradiation. It indicates probably the contribution from the centers in the surface of nanoparticles increased.6. In monitoring the emission of 5D1-7FJ, the excitation spectra shows that there is only one line corresponding to 5D2 energy state. We consider above 5D2 state there is an intermediate state through which the energy from the higher state is transferred to 5D0 state. That the fluorescence ratio of 5D1-7FJ is higher than that of free Eu3+ ions exhibits the small relaxation rate between 5D2 and 5D1 states, probably due to unusual phonon mode distribution in nanoparticles.