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Synthesis and Characterization of Structural and Photocatalytic Properties of Ag-TiO2 Nano-Coatings

Mehdizadeh Dehkordi, Arash | 2009

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 39324 (04)
  4. University: Sharif University of Technology
  5. Department: Physics
  6. Advisor(s): Taghavinia, Nima
  7. Abstract:
  8. Titanium dioxide has covered a wide range of applications as a semiconductor photocatalyst. TiO2 is an indirect, 3.2 eV band gap semiconductor which can be stimulated using UV light. Improving the quick electron-hole recombination rate, we can enhance the photocatalytic efficiency of this semiconductor. One of the approaches in hand is to use noble metals in connection to TiO2. Among noble metals, due to its plasmonic and anti-bacterial properties and ease of preparation, silver would serve as a perfect candidate. The mechanism for photocatalytic enhancement in Ag-TiO2 structures lies behind the fact that silver can trap the photogenerated electron of TiO2 and inhibit the electron-hole recombination, hence improving the photocatalytic efficiency. In this work, Ag-TiO2 composite thin films were fabricated. First, TiO2 thin film with 150 nm thickness is deposited on glass substrate using dip-coating method, and then silver nanoparticles are loaded on TiO2 surface using photoreduction method. Optical characterization of the thin films was performed and plasmonic absorbance of silver nanoparticles was detected. SEM micrographs show that the silver nanoparticles on TiO2 matrix cover a broad distribution with sizes in the range 20-100 nm, depending on the time required for silver deposition, and a variety of shapes most of which are spherical. Results indicate that surface roughness increases gradually upon increase in the silver content of the samples. XPS spectra prove the presence of metallic silver species on the surface. Enhancement of photocatalytic behavior of Ag-TiO2 thin films was examined using Methylene Blue photodegradation test. Hydrophilic property of coatings was also considered upon Ag addition. The effect of heat treatment on the Ag-TiO2 thin films and silver diffusion phenomenon were studied in this research. Prepared Ag-TiO2 thin films show multicolour photochromic behavior as well
  9. Keywords:
  10. Nanothin Film ; Photocatalyst ; Silver Nanoparticles ; Titanium Dioxide ; Nano Layers ; Multicolour Photochromism

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