Creating nanoparticles at the right time and the right place

Researchers from Professor Christoph Weder’s Polymer Chemistry and Materials group have developed a metallosupramolecular polymer that, when activated with the right stimulus, allows the formation of platinum nanoparticles when and where needed within a material. The polymer can serve as the basis for creating nanocomposites that contain metallic particles in patterns that can be created on demand.

Nanocomposites that contain metallic nanoparticles are particularly interesting because they combine the functional, structural, and mechanical properties of their two components, the polymer matrix and the metallic filler, and are useful for applications that range from catalysis to soft electronics. Gaining spatial control over the nanoparticle incorporation is useful, for example, to confine catalytic sites or create electrically conducting pathways. This approach enables the highly targeted formation of platinum nanoparticles at a designated time and place within the material, rather than randomly or all at once. “The precise placement and distribution of the nanoparticles is important for the performance of devices, but very challenging to control,” says group leader Dr. Stephen Schrettl. In a paper that was just featured on the cover of the influential Journal of the American Chemical Society, the AMI researchers show that this can be achieved by the controlled decomposition of a so-called metallosupramolecular polymer.

Until now, attempts to create nanocomposites with non-randomly placed nanoparticles were met with limited success. The AMI researchers, however, have managed to solve this problem by synthesizing a polymer that contains complexes of individual platinum atoms. These complexes are stable at ambient conditions, but they can be dissociated upon heating or exposure to ultraviolet light. The platinum atoms released in this process assemble into platinum nanoparticles whenever and wherever they are needed, without additional reagents or the formation of byproducts. This approach was exploited to create flexible films with well-defined platinum-containing areas or patterns with a resolution down to 10 µm. “We picked platinum for this study, because it is electrically conductive and also serves as catalyst for many chemical reactions” explains Schrettl.  “The method that we developed now enables us to control where and when the nanoparticles are formed, and we demonstrated that this allows one to ‘write’ electrically conductive pathways into an otherwise insulating object or to create objects that contain catalytically active spots,” adds Schrettl.

For this study, the researchers focused on metallosupramolecular polymers with platinum complexes but the concept promises to be readily applicable to different metals and systems that allow production of the corresponding nanocomposites.

Reference: Olaechea, L.M.; Montero de Espinosa, L.; Oveisi, E.; Balog, S.; Sutton, P.; Schrettl, S.; Weder, C. Spatially Resolved Production of Platinum Nanoparticles in Metallosupramolecular PolymersJournal of the American Chemical Society, 2020, 142 (1), 342-348