Spectroscopic properties of molecular-wire/semiconductor nanocrystalline superstructures

The spectroscopic properties of new molecular-wire/nanocrystalline (NCs) su perstructures have been examined. The molecular-wires consisted of (phenyle ne)(n)-(acetylene)(n-1)-dicarboxylate conjugated chains, with a length vary ing 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 photolum inescence (PL) spectra at 1.4 K, the PL-excitation, and the time-resolved P L 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 molec ular wires and the NCs, by an exciton diffusion mechanism. Furthermore, dir ect excitation into the NCs band edge showed an unexpected red-shift, a con sequence of a molecular wires-NCs electronic interaction.