ELECTRON-TRANSFER DYNAMICS IN MOS2 NANOCLUSTERS - NORMAL AND INVERTEDBEHAVIOR

The photophysics and electron transfer (ET) dynamics of quantum confin ed MoS2 nanoclusters have been studied using static and time resolved emission spectroscopy. The MoS2 nanoclusters consist of a single S-Mo- S trilayer, having diameters of similar to 2.5 or 4.5 nm. Two types of electron accepters are adsorbed on these nanoclusters: 2,2'-bipyridin e (bpy) and 4,4',5,5'-tetramethyl-2,2'-bipyridine (TMB). The ET reacti on exothermicities may be varied by changing the electron acceptor or by varying the size of the MoS2 nanocluster. TMB is harder to reduce, and thus has a smaller ET driving force than bpy. The smaller nanoclus ters have a higher energy conduction band, and thus have a larger ET d riving force. In all cases, the ET driving force may be calculated fro m bulk MoS2 properties and quantum confinement theory. Both ''normal'' and ''inverted'' behaviors are observed. A reorganization energy of 0 .40 eV is calculated from energy dependent ET rates. (C) 1996 American Institute of Physics.