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Ryan's Project Page - RISE Summer 2008 |
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Intern: Ryan Chan, Materials Chemistry, Brown University
Mentor: Nick Strandwitz
Faculty Supervisor: Galen Stucky
Department: Materials |
NOBLE METAL CATALYSIS IN NANOPARTICLE YOLK-METAL OXIDE SHELL ARCHITECTURE
Gold nanoparticles have shown promising properties for use in fuel cell, automotive, and industrial catalysis,
exhibiting catalytic activity similar to platinum at nearly half the cost. The nanoparticles’ size and high surface-areato-
volume ratio cause them to exhibit catalytic properties not seen in the bulk phase. However, performance and
durability are highly dependent upon the support utilized as well as the nanoparticle size. Huang and Schüth have
developed a novel support architecture consisting of a nanoparticle core enclosed in a porous metal oxide shell,
synthesized through a three step process: hydrophilic gold nanoparticles are encased in silica through a Stöber
method synthesis, covered in metal oxides using a solution phase reaction, and finally immersed in basic solution to
remove the silica spacing layer (Fig. 1). The porous shell provides superior separation of the nanoparticles while
simultaneously preventing sintering; the nanoreactors retain nearly 100% catalytic ability even after calcinations at
1073K. The charge and chemical functionality of the gold nanoparticle surface are presumably important parameters
for subsequent coatings in metal oxides. Herein we focus on controlling the synthesis of the silica shell, exploring
the effects of cationic, anionic, and neutral ligands as well as varying the Stöber reaction conditions. We report
successful synthesis of monodisperse, 75-200nm Au@SiO2 spheres with 5-8nm Au nanoparticle cores. This
architecture is easily replicable for many types of ligand-stabilized, hydrophilic nanoparticles, overcoming a
significant hurdle in the application of nanoparticle catalysis.
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