Preparation And Photoluminescence Study Of Nano-and Micro-ZnO

In the thesis, the basic properties, preparation and research survey of ZnO material were summarized. This experiment mainly involved two parts, undoping and doping ZnO. The undoping ZnO were prepared by two methods: One kind of methods was two-step microwave-assisted method for spherical powder, the other was solution-phase method synthesized ZnO quantum dots(QDS). Doping of ZnO were prepared by introduced the rare earth element Eu³⁺ and mental Pb²⁺ with a particular focus on the photo-luminescence properties of as-prepared product. The results of study are listed as follows:(1) This paper attempted a new application of microwave-assisted technology in the preparation of sub-micro spherical ZnO which growth mechanism was discussed. The PL spectrum showed that there have two main peaks at 420nm and 470nm respectively. Violet emission peak position located at 420nm was assigned to the radiative recombination of electrons in a donor intrinsic zinc(Zni) and holes from the valence band. The blue one at 470nm was combined of electrons from the shallow donor oxygen vacancy transited to the zinc vacancy, recombination of trapped electrons and holes from the valence band or radiative recombination of electrons in conductive band and acceptors ionized zinc vacancy.(2) ZnO:Eu³⁺ was synthesized by sol-gel method. The photoluminescence peak located at 592nm and 615nm. The influence of different Eu³⁺ concentration at same excited energy on emissive intensity difference between ⁵D₀—⁷F₁ and ⁵D₀—⁷F₂ were discussed. The results show that when the concentration of Eu³⁺ was 1at.%, the distribution of two energy level was equal. When the concentration of Eu³⁺ was 3at.%, the distribution of energy to ⁵D₀—⁷F₂ was up to maxim.(3) Employing combustion method, the metal ions Pb²⁺ doped ZnO were synthesized. Synthesized condition on blue photoluminescence property of ZnO:Pb²⁺ was discussed. The optimized experimental conditions for the preparation of ZnO:Pb were that the ratio of citric acid and znic accetate was 4:1 (in molar), flux and zinc acetate was 1:100, the combustion temperature was above 700°C, respectively.Violet emission located at 420nm was assigned to the radiative recombination of electrons in a donor Zni and holes from the valence band. The blue one 470nm was attributed to charge transition between metal cations and ligand.(4) ZnO and quantum dots was also prepared by solution-phase methods. The influence of experiment conditions such as the ratio of Zn²⁺ to OH^- and the reactant concentration on product size were analyzed by the PL-PLE.