| The physical and chemical properties of titania (titanium dioxide, TiO2) have been intensively studied for decades. As a relatively inexpensive semiconductor with nontoxicity, long-term stability and chemical inertness in aqueous solutions, TiO2 shows great prospects as photocatalyst, in particular, for the degradation of organic pollutants in aqueous solutions. The intrinsic wide-band-gap of TiO2 (band gap=3.2 eV) and high recombination rate are to be solved, which limit the further improvement of photocatalytic activity using solar energy. In addition, the exploitation of powder TiO2 is not beneficial to recycling use, more importantly, induces possible second pollution. Based on the above key influence factors, much effort has been made, such as, the doping of nonmetal elements, the doping of noble metal, binary or multiple combined semiconductor and surface sensitization, which can effectively improve the solar-driven photocatalytic activity of TiO2The sensitivity toward surface enhanced Raman scattering (SERS) and UV-cleanable property of Ag/TiO2 thin films were then investigated. In the SERS tests, the target analyte (Rhodamine 6G) was first adsorbed onto the Ag/TiO2 thin films as the probe analyte, this was followed by the measurements of Raman intensity and SERS maps. Thereafter, the thin films adsorbed with target analyte was cleaned and regenerated/recovered upon UV irradiation in water, and the removal of target analyte was attributed to photodegradation property of anatase-phase TiO2. This study suggested that the Ag/TiO2 thin films would be promising as reproducible photocatalyst and reproducible SERS applications. Surrounding the direction of the modification of TiO2 and SERS substrates, our mainly works are listed below:(1) Well-oriented TiO2 nanobelts (NBs) decorated with Ag nanoparticles on Ti foils were prepared by hydrothermal corrosion, subsequently annealing treatment, and successive ionic layer adsorption reaction (SILAR) technique. The ultraviolet-visible (UV-vis) absorption spectra show that the Ag nanoparticles deposited on the TiO; NBs surfaces can induce the red-shift of absorption edge and exhibits a broad absorption band in the visible region, which extends the scope of absorption spectrum and help to improve the photocatalytic degradation efficiency. The photocatalytic experiment results reveal that Ag-decorated TiO2 NBs possess higher photocatalytic activities toward methyl orange than pure. The experimental results showed that the detection limit of rhodamine 6G on Ag/TiO2 NBs composite substrates can reach as low as 10-7mol/L. The composites showed excellent recyclable photodegradation abilities and SERS substrates.(2)WO3-TiO2 nanowires (WO3-TWS) on Ti foils were prepared using simple hydrothermal treatment approach, wet impregnation and subsequent annealing treatment sequently. Ag nanoparticles were successfully decorated on the obtained WO3-TWS by successive ionic layer adsorption reaction (SILAR) technique. The ultraviolet-visible (UV-vis) absorption spectra showed that the Ag-WO3 nanoparticles deposited on the TiO2 nanowires surfaces could induce the red-shift of absorption edge and exhibits a broad absorption band in the visible region, which extends the scope of absorption spectrum and help to improve the photocatalytic degradation efficiency. The photocatalytic experiment results revealed that Ag-W03-TWS possess higher photocatalytic activities toward methyl orange than pure TiO2 nanowires. The degradation efficiency of 95.6% after 10 cycles indicated that the as-prepared Ag-WO3-TWS composite photocatalysts exhibite excellent long-time recyclable ability for the degradation of contaminants. The experimental results showed that the detection limit of rhodamine 6G on Ag-WO3-TWS composite substrates can reach as low as 10-7mol/L. The composites also showed excellent recyclable SERS substrates.(3) The controllable of one-dimensional TiO2 nanobelts decorated with Bi2WO6 nanocrystals based on Ti foils was reported using two-step hydrothermal treatment method. X-ray photoelectron spectroscopy measurement results exhibited the binding energies changes of Ti and 0 elements, implying the generation of semiconductor heterojunction structure of Bi2WO6/TiO2 nanocrystals onto the surface of TiO2 nanobelts. The photocatalytic experiment results revealed that Bi2WO6/TiO2 composites possess higher photocatalytic activities toward methyl orange than pure TiO2 nanobelts and exhibited excellent long-time recyclable ability for the degradation of contaminants.(4) The{001} facets of anatase TiO2 is much more reactive than the thermodynamically more stable{101} facets. We reported the assembly of nanoplates and{200}Bi2WO6 plate-like particles using hydrothermal method. TiO2 sheets are mainly dominated by{001} facets; while Bi2WO6 sheets are mainly dominated by{200} facets via the control of PH value in the solution. The composites show higher photocatalytic activities compared with P25. |
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