AVS 50th International Symposium
    Applied Surface Science Monday Sessions
       Session AS-MoA

Paper AS-MoA7
Size Dependency of Structural, Optical, and Photocatalytical Properties of TiO@sub 2@ Nanoparticles

Monday, November 3, 2003, 4:00 pm, Room 324/325

Session: Nanotube and Nanoparticle Characterization
Presenter: W. Li, University of Delaware
Authors: W. Li, University of Delaware
S.I. Shah, University of Delaware
S. Lin, University of Delaware
C. Ni, University of Delaware
C.-P. Huang, University of Delaware
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Polycrystalline TiO2 anatase nanoparticles with different average sizes (12, 17, 23 nm) were synthesized by metallorganic chemical vapor deposition (MOCVD). The particle sizes were determined by x-ray diffraction and transmission electron microscopy. The specific surface areas varied between 50 and 150 m2/gm, as measured by Brunauer-Emmett-Teller (BET) method. The size effects on the thermodynamic stability of TiO2 was analyzed by annealing samples in the temperature range of 700 to 800 oC. Only anatase to rutile phase transformation occurred. The transformation rate was accelerated with the decrease of initial particle size. The activation energy was calculated from the XRD data. The activation energy decreased from 298.85 to 180.28 kJ/mol as the initial anatase particle size decreased from 23 to 12 nm. Photoabsorption measurements showed a red shift of the absorption edges with the decrease in the particle size down to 17 nm. Below this particle size, a blue shift was observed. Photodegradation of 2-chlorophenol solutions under ultraviolet irradiation showed 17 nm sample had the highest photoreactivity. This result will be discussed on the basis of size related difference of light absorption efficiency, active surface area, and lifetime of charge carriers.