Platinum Nanocrystals Show Their Best Face

A strategy for synthesizing highly dispersed metal nanoparticles can lead them to adopt a specific orientation on a substrate, which may prove useful for designing nanoparticle catalysts, researchers at Northwestern University report (Nano Lett., DOI: 10.1021/nl104263j). Subtle differences in the structure and electronic properties of one face of a metal crystal relative to another face can lead to measurable differences in the catalytic activity of nanoparticles, even though all of a crystal’s faces consist of atoms of the same element. Scientists have previously tried coaxing metal particles to expose a catalytically preferred crystal face by modifying particle shape and altering synthesis conditions. But upon extended exposure to high temperatures and reactive conditions—the norm for industrial catalysis—particle structures often change, reverting to the most stable and perhaps less catalytically active geometry. Northwestern’s James A. Enterkin, Kenneth R. Poeppelmeier, and Laurence D. Marks have now come up with one way to sidestep this problem. By growing platinum nanoparticles on SrTiO₃ “nanocuboids,” a novel high-surface-area material, the team finds that the platinum nanoparticles adopt thermodynamically stable shapes, grow only along a single crystal direction, and expose different faces than they do when supported on common polycrystalline materials such as alumina and silica.