Photocatalytic Events of CdSe Quantum Dots in Confined Media. Electrodic Behavior of Coupled Platinum Nanoparticles

The electrodic behavior of platinum nanoparticles (2.8 nm diameter) and their role in influencing the photocatalytic behavior of CdSe quantum dots (3.4 nm diameter) has been evaluated by confining both nanoparticles together in heptane/dioctyl sulphosuccinate/water reverse micelles. The particles spontaneously couple together within the micelles via micellar exchange processes and thus facilitate experimental observation of electron transfer reactions inside the water pools. Electron transfer from CdSe to Pt is found to occur with a rate constant of 1.22 x 10(9) s(-1). With the use of methyl viologen (MV2+) as a probe molecule, the role of Pt in the photocatalytic process is established. Ultrafast oxidation of the photogenerated MV+center dot radicals indicates that Pt acts as an electron sink, scavenging electrons from MV+center dot with a rate constant of 3.1 x 10(9) s(-1). The electron transfer between MV+center dot and Pt, and a drastically lower yield of MV+center dot under steady state irradiation, confirms the ability of Pt nanoparticles to discharge electrons quickly. The kinetic details of photoinduced processes in CdSe-Pt assemblies and the electrodic behavior of Pt nanoparticles provide important information for the development of light energy conversion devices.