Ultrahigh Vacuum Instrumentation for Scanning Probe Microscopy Studies of Noble Metal
Catalysts at the Nanoscale
Satoru Emori, Brian James, Jimmy Vo
Mentor: Regina Ragan
Catalytic activity is dependent on the electronic properties of the materials involved, as a
catalytic reaction involves transfer of electrons between the catalyst, the substrate, and the
reacting species. For instance, although bulk gold is catalytically inert, gold nano-clusters of
diameter approximately 3 nm on titanium dioxide substrates exhibit excellent catalytic activity,
partly due to perturbation of electronic properties from quantum sized effects. Such altered
electronic properties of nanometer-sized materials can be investigated with scanning probe
microscopy techniques, which can measure atomic and molecular structure and local electronic
properties. Thus, scanning probe microscopy studies can elucidate interactive phenomena
between the catalyst and the reacting species at the molecular level, including electron transfer
and preferential attachment sites. However, obtaining quantitative data for these nanoscale
phenomena requires an ultrahigh vacuum (UHV) condition to minimize contamination in the
characterization environment. To deposit the reacting species on catalyst samples at a controlled
rate, a UHV chamber equipped with a precision leak valve has been designed and assembled.
After successful preliminary testing, the chamber has been integrated into an existing UHV
system with sample preparation and scanning probe microscopy capabilities. This integrated
instrumentation allows preparation, deposition, and nanoscale characterization of catalysts to be
conducted seamlessly. From the fundamental understanding of catalysis at the nanoscale, more
efficient and economical catalysts may be developed for such applications as decomposition of
organic compounds and production of hydrogen for fuel cells.