Studies On The Fabrication And Application Of Oriented Mixed Metal Oxide Films Derived From Layered Double Hydroxides

Mixed metal oxide materials exhibit unique electronic, optical, magnetic and catalytic properties that make them attractive, for example, for catalyst or catalyst supports, separation and adsorbent media, magnetic recording media. As a kind ofâ…¡-â…¥compound semiconductors with a wide and direct band gap, ZnO has become an important candidate of short-wave optoelectronic devices and UV detector. Spinel ferrites have been widely applied for gas sensor, catalyst and solid solar cells. The fabrication of ZnO/ZnFe₂O₄ films in which nanoparticles assembled in an orderly arrangement becomes a way for application practical devices.In this work, the purpose is to fabricate highly oriented and porous ZnO/ZnFe₂O₄ film using ZnFeCl-LDHs as a single inorganic precursor. The wettability and photoluminescence of ZnO/ZnFe₂O₄ film was studied. The main results are as follows:1. The ZnFeCl-LDHs particles with different Zn²⁺/Fe³⁺ molar ratio of 2, 3 and 4 prepared by a method of coprecipitation which the reaction time ,temperature and pH can be controlled present characteristics of uniform, small crystal size and hexagonal nanosheets.2. (001)-oriented ZnFeCl-LDHs films obtained on Si substrates by an evaporation method of LDHs suspensions, which favors face-to-face and edge-to-edge type interaction between individual LDHs platelets. Subsequently heating these LDHs films in air affords porous ZnO mixed with ZnFe₂O₄ films, which can be rationalized in terms of a topotactic transformation of the close-packed oxygen layers: (001) ZnFeCl-LDH→(002) ZnO + ZnFe₂O₄.The ZnO is (002) oriented in this film. The element of Zn and Fe are distributed uniformly in the fillm. The Zn²⁺/Fe³⁺ molar ratio can be controlled from 2 to 4 according to the LDHs precursor. The ZnO/ZnFe₂O₄ particle size increased from 30nm to 50nm by the calcination temperature increasing from 500℃to 900℃and it is uniform with different Zn²⁺/Fe³⁺ molar ratio but the same calcinations temperature. The chemical composition and particle size of the films can be readily tuned by the LDHs precursor.3. The wettability and photoluminescence of ZnO/ZnFe₂O₄ films were studied. It is disclosed that ZnO/ZnFe₂O₄ films modified with long chain fatty acid salts perform superhydrophobic surfaces with an contact angle about 150°and excellent sticky. Optical characterazition shows that the ZnO/ZnFe₂O₄ films exhibit strong luminescent effect. The photoluminescent spectra shows emissions with peaks at 390 nm and 469 nm when the excitation wavelength at 350nm. In summary, we developed a novel method for fabricating ZnO/ZnFe₂O₄ films. The method without the necessity for any templates, structure-directing agents or single-crystalline substrates is simple and can be widely applied for fabrication of nanostructure and functional films.