Study On Photoluminescence Of ZnO Nanoparticles And Random Laser Material With Ultralow Threshold

ZnO is a wide bandgap oxide semiconductor, which is the promising luminescent nanomaterial. Water-soluble ZnO quantum dots (QDs) with strong blue emission (quantum yield of 76%) was synthesized through a simple solution route using oleic acid (OA) as surface modifier. The stability originates from the surface-bonded OA molecules. The water-soluble of such QDs is provided by the hydroxyl groups on their surface come from diethanolamine (DEA). Based on series control experiments, the strong blue emission is suggested to arise from the formation of surface ZnO/oleic acid complexes.Uniform ZnO nanoparticles embedded in lipophilic polymethyl methacrylate (PMMA) matrix were prepared in detail with unbalanced sol-gel route. Fourier Transform Infrared (FTIR) confirms partial ester groups of R-COOCH3 in PMMA are hydrolyzed to form carboxylic ion groups during the sol-gel reaction, which chemisorbs on the surface of ZnO nanoparticles to eliminate the surface defects, thus ZnO nanoparticles in PMMA matrix exhibits complete ultraviolet (UV) emissions, while emissions in visible region are fully quenched.ZnO nanostructures with uniform size were synthesized by confining the reaction of Zn(NO₃)₂ and DEA in reverse microemulsion system composed with CCl4-AOT-Water. It's found that the ratio of [DEA]/[Zn²⁺] is decisive on the morphology and photoluminescence of ZnO nanostructures. The templating role of reverse micelles for producing the ZnO nanostructure is directly observed under TEM. It's proved the growth of nanorods under the restriction of reverse micelles follows the Ostwald mechanism.The isotropic and spherical ZnO were synthesized in Zn²⁺-TEA-IPA solution with low temperature hydrothermal method based on the oriented attachment (OA) mechanism. The formation of single-crystal ZnO microsphere is a kinetic dominated growth process. ZnO quasi-spheres can emit strong ultraviolet light and weak blue light. Maleic anhydride modified PS (m-PS) templet was prepared according to emulsion polymerization process. With the m-PS as core, the m-PS/ZnO core-shell structures were synthesized by a low temperature hydrothermal route. The growth mechanism of the m-PS/ZnO core-shell is investigated intensively. Single-crystal ZnO with hollow and polyhedral structure is obtained after calcination at 500°C. Single crystal cup can emit strong ultraviolet light and weak green light.It's experimentally demonstrated the random laser emission can be realized in reverse microemulsion system with ordinary xenon lump (the pump intensity is～μW/cm²) in AOT-CCl4-Water system. The pump threshold intensity is 109 magnitudes lower than that in common random laser. By introducing ZnO QDs in reverse micelles, the emission intensity could be 3 times than that of without ZnO QDs under the same pump intensity.