Preparation and optical properties of fluorescent hybrid complex of polycationic conjugated polymer and surface-functionalized ZnS nanoparticles

8-Hydroxyquinoline-5-sulfonic acid (HQS) functionalized ZnS nanoparticles (ZnS-QS NPs) with strong fluorescence emission have been successfully synthesized. The ZnS-QS NPs can form hybrid complex with cation, water-soluble conjugated polyelectrolytes (P2) via electrostatic attractions. The photophysical properties of P2/ZnS-QS NPs complexes were studied by photoluminescent (PL) and UV–vis spectroscopy. It is observed that the fluorescence resonance energy transfer and π-stacking are two competitive interactions between P2 and NPs. When the charge ratio of P2 to ZnS-QS NPs is higher, the PL intensity of P2 increases and the PL peak red-shifts due to the decrease of the repulsive force between positively charged side chains of P2 and the formation of π-stacking. For the hybrid systems with lower charge ratio of P2 to ZnS-QS NPs, the PL intensity of P2 decreases and its emission peak blue-shifts, and finally, the P2 emission is completely quenched for the hybrid systems with high NPs ratios.