Fabrication Of Metal/TiO₂ Nanocomposites And Their Catalytic Properties

The shortage of both metal nanomaterials and Ti O2 nanomaterials can be filled up by fabrication of metal/Ti O2 nanocomposites. On one hand, the dispersity and stability of metal nanomaterials can be improved by using Ti O2 nanomaterials as carriers, which can prevent the aggregation of metal nanoparticles effectively, leading to the improvement of catalytic activity and reusability. On the other hand, the absorption range of Ti O2 can be extended to the visible region by loading with metal nanomaterials attributed to the localized surface plasmon resonance(LSPR) properties, improving the utilization efficiency of sunlight. In addition, the photogenerated electrons can be directional transferred between the heterostructure of metal/Ti O2 nanocomposites, leading to the surface charge separation, avoiding the recombination of photogenerated electrons and holes, and improving the catalytic properties of the nanocomposites.According to the research background above, we designed and fabricated some novel metal/Ti O2 nanocomposites in this thesis using anodisation, photoreduction and magnetron sputtering methods. These novel nanocomposites were applied to photoelectrochemistry, catalysis and biosensor. The main contents and results are as followed:1. Periodic Au nanoparticles/Ti O2 nanotube arrays composite was fabricated via two-step anodization and in-situ photoreduction method. This nanocomposite was used as electrode for the catalytic electrooxidation of ethanol and the effect of illumination to the electrode was investigated. The results indicated that the catalytic activities of Au/Ti O2 electrode was improved under visible light illumination due to the LSPR properties of Au nanoparticles and the surface charge separation occurred on the interface of Au/Ti O2 heterojunction. The periodic Au/Ti O2 electrode also showed a unique self-cleaning property under visible light because it had greater absorption of incident light compared to the ordinary one. On the contrary, ultraviolet light illumination had almost no influence to the catalytic activities and stability of the Au/Ti O2 electrode.2. This anodization and photoreduction method was expanded to the fabrication of non-noble metal based Cu/Cu O nanoclusters-Ti O2 nanotube arrays composite, which was applied to the reduction of 4-nirtophenol(4-NP) and other catalysis. The stability, reusability and effect of fabrication conditions were investigated. The results indicated that the concentration of Cu Cl2 had obviously effect to the morphology and catalytic activity of the catalyst. The highest rate constant of this Cu/Cu O based catalyst was 13.6×10-3 s-1, better than those based on Au, Ag and Pd fabricated in the same conditions. This catalyst also showed great stability and reusability in 7 times repeat of the 4-NP reduction. Except for 4-NP, this Cu/Cu O-Ti O2 catalyst also exhibited great catalytic activitise to other organic dyes, such as methylene blue(MB), rhodamine B(Rh B) and methyl orange(MO).3. Cu/Cu O nanowire arrays-Ti O2 nanofilm composite was fabricated by thermal oxidation and magnetron sputtering method, which was used as photocathode for photoelectrochemical water splitting. The effect of fabrication conditions like calcination temperature and calcination time of Cu mesh, sputtering time of Ti O2 were investigated. The results indicated that Cu mesh calcination at 450? for 3 h exhibited the highest photocurrent intensity. The stability of Cu/Cu O photocathode can be improved by sputtering Ti O2 onto the electrode surface as Ti O2 nanofilm can prevent the corrosion of Cu O nanowire from electrolyte. The photocurrent intensity of Cu/Cu O photocathode with Ti O2 protective layer after electrochemical stability test was 0.6 m A/cm2. It was 50 percent increase compared to that without protective layer, which was 0.4 m A/cm2.4. A novel optical waveguide(OWG) biosensor based on Ag/Ti O2 multilayer film was fabricated by magnetron sputtering method. The sensitivity and limit of detection(LOD) of Ig G were investigated. The results indicated that, the Ti O2 layer above Ag film not only can work as waveguide layer to excite the specific optical waveguide mode of surface plasmon resonance(SPR) and enhance the resolution of biosensor, but also can work as protective layer to prevent the corrosion of Ag film from electrolyte and enhance the stability of biosensor. Compared with the conventional Au based SPR biosensor, the sensitivity of our Ag based OWG biosensor was 2 times improved, the resolution was 5 times improved and the LOD of Ig G was about 7 times improved.