Spectroscopic Properties of Molecular-Wire/Semiconductor Nanocrystalline Superstructures

Abstract

The spectroscopic properties of new molecular-wire/nanocrystalline (NCs) superstructures have been examined. The molecular-wires consisted of (phenylene)n−(acetylene)n-1−dicarboxylate conjugated chains, with a length varying between 1.9 nm and 3.3 nm. The NCs component consisted of either PbS or CdS, with an average diameter ranging between 2.0 and 5.0 nm. The photoluminescence (PL) spectra at 1.4 K, the PL-excitation, and the time-resolved PL measurements showed a typical quantum size effect of the individual NCs, and additional collective effects of the superstructure. Simulation of the luminescence decay processes suggested an energy transfer between the molecular wires and the NCs, by an exciton diffusion mechanism. Furthermore, direct excitation into the NCs band edge showed an unexpected red-shift, a consequence of a molecular wires-NCs electronic interaction.