PLD Preparation And Photoluminescence Properties Of ZnO Nanostructures

ZnO is a direct wide band gap semicondutor with many excellent properties,such as near-UV emission properties, sensing properties and bio-compatibility. Ithas been demonstrated to have a host of possible practical applications includinglight emission devices, UV detectors, gas sensors and so on. In par ticular, ZnOnanostructures were revealed recently to be excellent platforms to greatly enhancebiomolecular fluorescence signal, thus to achieve ultra-high sensitivity ofbiomolecule detection, however, up to date very few systematic studies have beenconducted. At the same time, long-term stabilty of ZnO nanomaterials in aqueoussolution was questioned due to the hydrolytic reaction of ZnO. Because of theoptical transparency, chemical inertness, biological safety and facility forbioconjugation of SiO₂, we propose that ZnO-SiO₂core-shell nanostructures havepromising application potential in biomolecule detection as platforms forfluorescence enhancement.Pulsed laser deposition （PLD） has been employed as an important method toproduce high quality ZnO, but there are few reports on the growth of ZnOnanostructures or SiO₂films by PLD at248nm. In this thesis, growth properties ofZnO nanostructures by PLD at248nm was firstly studied. ZnO thin films with the[002] orientation were produced to be served as seeding layers for the sequentialgrowth of ZnO nanostructures. Infuence of the experiemntal parameters in cludingsubstrate temperatures, oxygen pressures, laser power, and the distance between thetarget and the substrate on the growth and photoluminescence properties of ZnOnanostructures was systematically studied; and the controllable growth of ZnOnanorods was realized. Secondly, PLD growth and optical transparency propertiesof SiO₂films were explored. The thicknesses and transparency of the SiO₂filmscould be controlled well by adjusting the deposition times. At last, ZnO-SiO₂core-shell nanostructures were produced by depositing SiO₂thin films with differentthicknesses on ZnO nanostructures. Luminescent stability of the core-shellnanostructures in aqueous solutions with various pH values was studied, and thesilica shells were confirmed to improve the stability of ZnO nanostructures inaqueous solution, especially in alkaline aqueous solution.These findings should strengthen the application of ZnO nanostructures inbiomolecule sensors and improve the systematical studies on mechanism investigation and performance optimization of ZnO nanostructures as biomolecularfluorescence enhancement platform.