PbSe nanocrystal network formation during pyridine ligand displacement.

Solution-phase pyridine treatment displaced oleic acid capping ligands from the surface of PbSe nanocrystals. During ligand displacement the nanostructure morphology dramatically changed from well-stabilized, individual nanocrystals to form crystallographically connected nanocrystal networks. The network morphology was governed by the diameter of the constituent nanocrystals. Larger nanocrystals showed dipolar alignment but maintained individual nanocrystal character, while smaller nanocrystals crystallographically fused along the <100> axis. Optical studies of nanocrystal thin films showed that pyridine ligand displacement quenches the nanocrystal photoluminescence. Blends of nanocrystals and conjugated polymer showed photoluminescence quenching of the polymer with increasing nanocrystal content. The extent of photoluminescence quenching was only weakly dependent on the nanocrystal size or surface chemistry, suggesting that the interaction between nanocrystal and polymer is mostly in the form of energy transfer rather than charge transfer.