Loading...

Fabrication of Graphene-WO3 Nanocomposites as Photocatalyst in the Visible Light Region

Choobtashani, Mohammad | 2012

2411 Viewed
  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 43188 (04)
  4. University: Sharif University of Technology
  5. Department: Physics
  6. Advisor(s): Akhavan, Omid
  7. Abstract:
  8. WO3 is known as a photocatalyst in the visible light region, but with lower efficiency compared to more interesting semiconductor photocatalysts such as TiO2 and ZnO. Many attempts have been done to increase the efficiency of this photocatalyst by incorporating metal and metal oxide nanoparticles or recently carbon nanotubes.On the other hand, application of graphene, as an unrolled carbon nanotube, for increasing the photocatalytic activity of TiO2 and ZnO has shown positive results. Furthermore, it was reported that such semiconductor photocatalysts (and very recently WO3) can photocatalytically reduce the chemically exfoliated graphene oxide sheets under UV-vis irradiation.
    In this research, first WO3 thin films were fabricated on glass substrates by thermal evaporation and sol-gel methods. Also Hummers’ method was used to synthesize graphene oxide suspension in water. Then the prepared WO3 thin films was employed to reduce graphene oxide nanosheets under either UV or visible light irradiation. At first glance reduction of graphene oxide was judged by change in color of graphene oxide layer on WO3 thin films, from light brown to dark brown and black. Then, for precise and quantitative investigations XPS was used. By this way, it was seen that graphene oxide nanosheets have undergone a slightly more reduction on thin films synthesized by sol-gel method. It was also seen that reduction under visible light was almost the same as the reduction under UV irradiation.Next, graphene-tungsten oxide composite films were synthesized by adding a definite amount of graphene oxide suspension to the prepared WO3 sol. After drying the samples at 60 C in air for 24 h, some of thin films also annealed at 450 C in air for 30 min. The photocatalytic performance of the composite films fabricated by this method was examined in photoinactivation of bacteriophage MS2 viruses under visible light irradiation. It was seen that the composite films annealed at 450 C was able to inactivate more than 99:999% of the viruses, after 3 h visible light irradiation.Using XPS studies it was found that annealing the films at 450 C in air resulted in formation of W-C and W-O-C bonds. Finally measuring the RNA efflux of the viruses was performed to confirm the photodegradation of the viral protein capsid. AFM and TEM were used to observe graphene nanosheets and surface morphology of the thin films, and graphene-tungsten oxide composite structure, respectively.
    FTIR and Raman spectroscopy were employed for investigation and characterization of the structure of the prepared thin films
  9. Keywords:
  10. Graphine ; Tungsten Oxide ; Photocatalyst ; Bacteriophage

 Digital Object List

 Bookmark

...see more