PHOTOELECTROCHEMICAL BEHAVIOR OF BI2S3 NANOCLUSTERS AND NANOSTRUCTURED THIN-FILMS

Quantized semiconductor nanoclusters of Bi2S3 are prepared in acetonit rile by reacting BiI3 with H2S or Na2S. Both preparation methods yield stable colloids with particle diameters of less than or equal to 5 nm . Excitation with a 355-nm laser pulse results in transient bleaching in the 400-500-nm region. This process is followed by the formation of S-surf(-) with a difference absorption maximum around 540 nm. This we attribute to the chemical changes associated with the hole-trapping p rocess. A composite thin film electrode comprised of SnO2/Bi2S3 nanocr ystallites has been prepared by sequential deposition of SnO2 and Bi2S 3 films onto an optically transparent electrode, and its photoelectroc hemical behavior has been studied. The thin film is photoactive in the visible and near-IR and exhibits an incident photon to photocurrent e fficiency (IPCE) of similar to 15% at 400 nm.