Preparation Of TiO₂ Thin Films On Optical Fiber By Electrostatic Self-assembling And Investigation On Their Photocatalytic Activities

TiO₂ colloids were produced by dispersion TiO₂ power in aquatic solution. The effects of preparation technics and processing parameters to the stability of TiO₂ colloid were investigated by microscopic-electrophorety instrument and transmission electron microscope (TEM). TiO₂ nano-particles were assembled on optic fibers by electrostatic self-assembly method. The raw materials used for assembling were TiO₂ colloid, anionic surfactant sodium lauryl sulfate (SDS) and cationic surfactant palmityl trimethyl ammonium chloride (CTAC). Then SDS[/CTAC/TiO₂]n and CTAC[/SDS /TiO₂]n with several layers were produced. The effects of optical fiber cleaning, pH of colloid and concentration of surfactants on self-assembly process were investigated by scanning electron microscope (SEM). The photocatalysis degradation to methyl orange of TiO₂ film on optic fibers was also studied initially.The results showed that the isoelectric point of TiO₂ colloid is 6.8. Annealing was good for the dispersion of TiO₂ nano-paricles. Ball milling was needed to break the cluster formed during annealing. The stable TiO₂ colloid with positive charge was prepared on conditions that the ratio of solid to liquid was 2% and the pH was 3; the stable TiO₂ colloid with negative charge was obtained on conditions that the ratio of solid to liquid was 2% , the pH was 3 and the concentration of PAA-NH4 was 0.8‰.The films can be well formed on optic fibers by electrostatic self-assembly method using CTAC and SDS; to forming well-distributed, ordered and compact SDS [/CTAC/TiO₂]n and CTAC[/SDS/TiO₂]n compound films, the optic fibers were completely cleaned by ultrasonic and washed by distilled water after every dipping, the pH of TiO₂ colloid were adjusted at 3 and 9, the solid concentration of TiO₂ colloid was 2%, the concentration of surfactant was around itself critical micelle concentration (cmc) and the sediment time is 300s; The quality control of first thin film had important effect on assembly of multilayer films; the thickness of films could be controlled by the layers of the films using electrostatic self-assembly method, the thickness of every layer is about 30nm in theory, but the thickness in fact was thicker than in theory because of some degree cluster of particles; the photocatalysis degradation to methyl orange of TiO₂ film on optic fibers was better than TiO₂ film on glass slide.