Au-Pt bimetallic nanoparticles formation via viologen-mediated reduction on polymeric nanospheres

Poly(vinylbenzyl chloride) nanospheres prepared via emulsion polymerization were surface functionalized with viologen moieties. Several methods were investigated to achieve the desired high surface concentration of viologen moieties with minimal aggregation of the nanospheres. The viologen-functionalized nanospheres were used for photoinduced reduction of gold ions and platinum ions, either individually, simultaneously or sequentially, to result in the formation of well-distributed Au-Pt nanoparticles of a few nanometers on the surface of the nanospheres. UV-visible absorption spectroscopy and XPS analyses of these bimetallic nanoparticles were carried out. The reaction time and the sequence of the reduction process play an important role in determining the composition of the bimetallic nanoparticles. High-resolution transmission electron microscopy analysis reveals the highly crystalline nature of the bimetallic nanoparticles.