SYNTHESIS AND PHOTOCHEMISTRY OF QUANTUM-SIZE SEMICONDUCTOR PARTICLES IN SOLUTION AND IN MODIFIED LAYERS

We describe the preparation of highly monodisperse, quantum-size CdS p articles. In these samples a band splitting into discrete exciton-like states is observed. A mechanism for the excitonic fluorescence is pre sented involving shallow traps as a reservoir for electrons which fina lly recombine with free positive holes across the bandgap. Quantum-siz e CdS and PbS particles prepared in situ on highly porous, polycrystal line TiO2 electrodes work as highly efficient sensitizers. Photocurren t yields of more than 70% are reported. In the case of PbS, it is show n that an efficient electron transfer is possible only with particles in the size of the quantization regime.