Web Release Date: October 19,
Hierarchically Assembled Porous ZnO Nanoparticles: Synthesis, Surface Energy, and Photocatalytic Activity
and
NEAT ORU and Peter A. Rock Thermochemistry Laboratory, University of California at Davis, One Shields Avenue, Davis, California 95616, and Laboratory of Inorganic Materials Chemistry, University of Namur (FUNDP), 61 rue de Bruxelles, B-5000 Namur, Belgium
Received May 2, 2007
Revised Manuscript Received July 25, 2007
Abstract:
We show an effective experimental method to prepare hierarchically porous zinc oxide (ZnO) spherical
nanoparticles through a self-assembly pathway using surface-modified colloidal ZnO nanocrystallites as
the building blocks and P-123 copolymers as the template in aqueous solution. Copolymers are thoroughly
removed by Soxhlet extraction with ethanol and calcination at 400 
C. The final products have been
characterized by X-ray powder diffraction (XRD) pattern, scanning electron microscopy (SEM),
transmission electron microscopy (TEM), high-resolution TEM (HRTEM), and photoluminescence (PL)
spectroscopy. On the basis of calorimetric measurements reported separately, the surface enthalpy (
) of
the hydrated porous ZnO is 1.42 ± 0.21 J/m2, in good agreement with that of ZnO nanoparticles. The
calorimetric results support the presence of self-assembled ZnO nanocrystallites in the nanoporous ZnO.
Photocatalytic activitiy of porous ZnO nanoparticles has been tested on the photodegradation of phenol
under ambient condition, indicating that porous ZnO nanoparticles show superior activity to TiO2
nanoparticles (PC-500).
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