The fluorescence of conjugated polyelectrolytes (CPEs) is quenched with very high efficiency by small molecule quenchers with opposite charges. This effect has been referred to as amplified quenching or superquenching. We study the profound correlation between the fluorescence quenching efficiency, CPE chain aggregation (induced by the addition of either Ca2+ or H2O to methanol solution), and quencher molecular size. We propose that the superlinear Stern-Volmer quenching behavior typically observed in CPE-quencher systems arises due to quencher-induced aggregation of the CPE chains.
Effect of aggregation of PPE on amplified quenching
Ref: (1) Jiang, H.; Zhao, X.; Schanze, K. S. "Amplified Fluorescence Quenching of a Conjugated Polyelectrolyte Mediated by Ca2+." Langmuir 2006, 22, 5541-5543.
(2) Jiang, H.; Zhao, X.; Schanze, K. S. "Effects of Polymer Aggregation and Quencher Size on Amplified Fluorescence Quenching of Conjugated Polyelectrolytes." Langmuir 2007, 23, 9481-9486.
Aggregation of PPE in MeOH with the addition of
H2O (Top) or Ca2+ (Bottom)