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Abstract
Titanium dioxide (TiO2) composites has been utilized for many applications, such as air and water purification. Polyvinyl alcohol (PVA) is considered as one of most attractive polymers due to its excellent properties of low cost, high hydrophilicity, processability, good film-forming and excellent physical properties. The research on PVA/TiO2 composites will open up exciting possibilities with both advantages of excellent photocatalysis of TiO2 and special chemical and physical properties of PVA.
Because seldom researches were done to discuss the temperature dependence property of PVA/TiO2 composites, it is necessary to detect the change of properties with different annealing temperatures. In detail, the present work prepared PVA/TiO2 nanocomposite thin films by sol-gel dip coating on polished fused SiO2 substrates, followed by annealing separately at 100 oC, 180 oC and 260 oC for 4 h under nitrogen. Then the mineralogical, surface compositional, optical, microstructural and photocatalytic properties were investigated in this project. Laser Raman microspectroscope (Raman) and X-Ray diffraction (XRD) were tested, which showed the enhanced anatase with increasing temperature. The Fourier transform infrared spectroscopy (FTIR) showed the presence of PVA. X-ray photoelectron spectroscopy (XPS) indicated the occurrence of Ti4+ → Ti3+ conversion. Band-gap change of the thin films were obtained by using UV-Vis spectrophotometry (UV-Vis). Finally, the scanning electron microscope (SEM) showed appearance of enlarged cracking with increasing temperature. The photocatalysis testing was also done with degradation of Methyl Blue (MB) solution in 24 h and it showed at 180 oC, thin films showed the best performance.
With the in-depth research, the enhanced photocatalytic performance of nanostructured TiO2 thin films through combined effects of polymer conjugation and Mo-doping. Based on prevous research, the annealing temperature of 180 oC was chosen. Different extents of Mo-doping in the range of 0.00-0.20 wt% (0-0.0010 at%) were used for the doping of the PVA/TiO2 nanoparticulate thin films. The similar testing strategy with the first project were used. The XRD showed 0.10 wt% films had the best crystallinity. Raman and FT-IR data confirmed the presence of polymer with conjugation structure. XPS alsoshowed Ti4+ → Ti3+ conversion. UV-Vis analysis data showed the 0.10 wt% Mo-doped films had the narrowest band gap. SEM showed increasing doping level would enlarge the cracking on the surface. The photocatalysis testing showed 0.10 wt% Mo-doped films had the highest photocatalytic efficiency.
Overall, the project is doing some research on the effect of temperature and doping on PVA/TiO2 composites thin films. It is believed that this topic deserves to be studied further and has a great impact.