Photoreduction of methylene blue on cadmium sulfide powder

The relaxation of photogenerated charge carriers in cadmium sulfide powder and the reduction of surface bound methylene blue have been investigated using both picosecond multiple light scattering transients and transient band gap emission measurements. A comparison of the bleaching kinetics for adsorbed dye with near-IR absorption and band gap emission transients from the semiconductor indicate that interfacial electron transfer is driven by mobile conduction band carriers with little participation by the longer-lived weakly trapped carriers. In addition, adsorbate reduction is simulated using the diffusion equation with a surface reaction.