Controlled synthesis of platinum submicron and nanometric particles with novel shapes

Metal nanostructures have drawn increasing interest due to their potential uses in catalysis, biological sensors, and nanoelectronics among others. As these materials have at least one dimension between 1 nm and 100 nm, interesting properties arise due to phenomena such as quantum confinement and high surface-to-volume ratio. Platinum stands as one of the most important metals for several industrial applications. As the physicochemical properties of noble-metal nanostructures are strongly dependant upon shape and size, many efforts towards the development of reliable synthesis methods for the production of nanocrystals with well defined size and morphology have been done, including platinum. On the other hand, submicron spherical Pt powders with narrow size distribution are also needed for the electronics industry. However, colloidal synthesis of such powders is a challenging task since many of the available techniques produce fine particles in the nanoscale. Independently of the great progress that many recent techniques have shown, there is still a necessity to develop chemical methods that can tailor the morphology of Pt crystals at different scales, i.e. nano- and micro-metric. In the present report, we describe how by using a cationic polyelectrolyte (poly-diallyl dimethyl ammonium chloride) the reduction kinetics of a platinum precursor in a polyol process can be controlled. As a result, Pt particles with different morphologies and crystallinity can be produced over a large scale range.