Templated Preparation And Photoluminescence Of Composite Structure TiO₂Nanotube Arrays

Recently, environment and energy issues have become hot topics worldwide,Among them, running short of fossil fuel energy and environmental pollution areserious problems: ultilizing solar energy directly as a light source becomes an idealtechnology for environmental pollution improvement and clean energyproduction.Since1972, Fujishma et al. have found that continued oxidation of TiO2electrode after irradiation can produce water via the reduction reaction.Semiconductor photocatalytic materials, e.g. Titanium dioxide (TiO2) attractedintensive interests. TiO2is an important wide band gap semiconductor materials, andwidely used in photoluminescence, hydrogen production by water splitting,photocatalytic degradation, dye sensitized solar cell (DSSC) has a broad applicationprospect. In comparison with TiO2films, TiO2nanotube has large specific surfacearea, which is expected to improve the catalytic performance of the material.⑴This dissertation systematically studied the influence of experimentalconditions on the structural parameters of anodic aluminum oxide (AAO) template.Besides electrolyte, the concentration and temperature of electrolyte can affect thestructure of AAO. The anodic oxidation voltage is also a key factor for controllingthe pore spacing. The pore spacing increases with oxidation voltage in a linearrelationship. The pore-opening time has a great impact on the pore size of AAO,which provides an additional way to tune the pore diameter.⑵The dissertation further presents a new method for preparation of TiO2nanotubes: we use AAO as a template to prepare large area uniform and orderly TiO2nanotube arrays by direct current deposition. The tube wall becomes thick to fill thepores with deposition time. Finally, the orifice closed completely. The as preparedTiO2nanotubes by electrodeposition are amorphous, and can be further crystallizedby annealing. The structure and the morphology of TiO2nanotube arrays arecharacterized by SEM, XRD and TEM, As a result, the nanotubes undergo different morphology under different annealing temperature ranging from350~750℃:almost no morphology change is observed when annealed at low temperature of350℃. However, at the high temperature of750℃, the nanotube arrays are almostcompletely collapse to form the dense rutile phase structure. The crystallization ofTiO2nanotubes increase with the annealing temperature (350~750℃), In contrast,"red edge" effect in PL also decreased with the increase of annealingtemperature.Finally, the photoluminescence intensity is increased to reach amaximum at550℃. With the annealing temperature of550℃, thephotoluminescence intensity decreases with the time, together with a blue shift of thePL emission.⑶Using the CdS particles to modify the macroporous TiO2nanotubes:theexperimental results indicate that the CdS particles distribute uniformly in thenanotubes in a stable status, which could find potential applications inphotocatalysis, etc..