Effect of aromatic polymer framework on the emission and quenching of photoexcited Ru(bpy)32+ in sulfonated polymer matrixes

Abstract

The Ru(bpy)32+ complex was incorporated in a sulfonated poly(2,6-dimethyl-1,4-phenylene oxide) (SPPO) or a Nafion film (bpy: 2,2′-bipyridine; Nafion: poly(perfluoroalkylene) sulfonic acid). The photoexcited Ru(bpy)32+ in both polymer matrixes underwent concentration quenching. According to the emission lifetime of the excited Ru(bpy)32+ independent of its concentration in the polymer, the concentration quenching was concluded to occur through a static mechanism. Assuming that the luminescent probe is dispersed randomly in the polymer matrix, the center-to-center distance for the concentration quenching of the excited Ru(bpy)32+ in Nafion was estimated to be 1.1 nm. The quenching efficiency of the excited Ru(bpy)32+ in SPPO is higher than that in Nafion. When incorporating 2,6-dimethylphenol (DMP: the unit of PPO) in Nafion, the quenching efficiency increases depending on the DMP concentration indicating that the structure of PPO is the main factor to enhance the quenching. When assuming that the enhancement is principally ascribed to the mediation effect of DMP as a pathway for a long-range energy transport, the mediated quenching distance was estimated to be 2.4 nm. The mediated quenching distance in SPPO is 1.8 nm.