Reaction of platinum nanocatalyst with the ferricyanide reactant to produce prussian blue analogue complexes

Abstract

The field of catalysis with colloidal nanoparticles is in its infancy. The question of whether the catalysis occurs on the surface of the nanoparticle (thus heterogeneous) or homogeneously in solution using a complex made by the nanoparticle is now being debated. Thus, the molecular mechanism of nanocatalysis has not yet been studied in detail. The first step in this effort is to study the molecular mechanism of the reaction of each reactant with the nanoparticle. This letter is an effort in this direction. A great deal of research has used platinum nanoparticles (PtNPs) to catalyze electron-transfer reactions such as that between thiosulfate and hexacyanoferrate III. We monitored this reaction in detail using optical, Raman, and IR spectroscopies. By increasing the reaction time, two sequential dominant species are formed. The first one is found to have spectral signatures of a Prussian blue analogue with a structure of K[Pt IIFe IIICN) 6]. With increasing time, the intensity of the spectrum of this complex is found to decrease, whereas a spectrum similar to that of a complex having the structure of [Pt IVFe II(CN 6) increased. A mechanism for the formation of these metal-mixed valency Prussian blue analogues is given. © 2007 American Chemical Society.