The past decade has seen many improvements in the synthesis and characterization of nanometer-sized metal particles which have interesting potential applications in various fields, such as catalysis, optics and electronics. These nano-objects are almost exclusively stabilized by thiolate molecules, which limit their grown and allow their recovery as powders that can be re-dissolved. When particles are capped by bifunctional molecules, they can react with incoming molecules (over-grafting reactions) in order to modify their crown and then their characteristics. It is of special interest to follow the evolution of nanoparticles properties induced by crown modifications. Whereas most of the papers describing such an approach deal with gold nanoparticles, the present work reports on platinum nanoparticles.
We synthesized 4-mercaptoaniline functionalized platinum particles of 2 nm diameter and we reacted them with 2-thiophenecarbonyl chloride. The derivatized particles were dissolved in DMSO and gave long term stable solutions. The Langmuir-Blodgett technique was then used to build up stable Langmuir films and Langmuir-Blodgett films. The latter were build up on various substrates which allowed characterization by IR, XRD, TEM, XPS.
The electrocatalytical behaviour of the ultra-thin films towards oxygen reduction were investigated in acidic medium. It revealed a direct activity without any previous activation treatment in spite of the presence of the organic shell at the surface of the particles. Furthermore, using XPS we evidenced that the organic crown was not significantly destroyed upon prolonged cycling.
These preliminary results open a way to the study of original and versatile platinum based nanocomposites and suggest interesting potentialities in term of application to fuel cells.