Platinum metal nanoparticles: Investigation of shape, surface, catalysis and assembly

This work focuses on the platinum metals, in particular platinum, palladium, and rhodium. The synthesis of these metals into nanoparticles with specific shapes, as well as bimetallic alloy nanoparticles of these three metals is demonstrated in this work. These metals have long been utilized extensively in the area of catalysis. The high surface area of nanoparticles is conducive to higher catalytic efficiencies than normally seen in bulk metals. The shapes of the small structures can also be altered, thereby additionally modifying some of the metal nanoparticle properties.; Platinum nanoparticles with a high percentage of cubic (with six {lcub}100{rcub} faces), tetrahedral (consisting of four {lcub}111{rcub} faces, or truncated octahedral shapes (made up of six {lcub}100{rcub} and eight {lcub}111{rcub} faces) have been synthesized by a colloidal method (Science, 1996, 272, 1924). The shapes of the Pt nanoparticles are controlled by changing the ratio of the concentration of capping polymer (polyacrylate) to that of K₂PtCl ₄ being reduced by H₂ at room temperature. A growth mechanism is proposed which produces the different nanoparticle shapes.; The catalytic activity of different shapes of nanoparticles are compared for the electron transfer between S₂O₃2− and [Fe(CN)₆]3+. In addition, the capping material surface coverage on the nanoparticles has been determined through the use FTIR and ATR spectroscopy. The catalytic activities of the different shapes of nanoparticles can be quantified in terms of surface atoms for each shape. The tetrahedral nanoparticles are found to be between 2 and 7.5 times more catalytically active per surface atom for this electron transfer reaction.; The temperature at which the capping polymer could be removed was determined, as well as and the thermal stability of these nanoparticles with respect to shape changes and melting. The platinum nanoparticles were also self-assembled into monolayers. The addition of dodecanethiol to a dominantly cubic platinum colloidal aqueous solution capped with acrylic acid leads to self-assembled monolayers. FTIR showed that both capping materials are on the surface of the nanoparticles during the assembly process.