Amplified Quenching of a Conjugated Polyelectrolyte by Cyanine Dyes

Abstract

The conjugated polyelectrolyte PPESO3 features a poly(phenylene ethynylene) backbone substituted with anionic 3-sulfonatopropyloxy groups. PPESO3 is quenched very efficiently (KSV > 10(6) M(-1)) by cationic energy transfer quenchers in an amplified quenching process. In the present investigation, steady-state and picosecond time-resolved fluorescence spectroscopy are used to examine amplified quenching of PPESO3 by a series of cyanine dyes via singlet-singlet energy transfer. The goal of this work is to understand the mechanism of amplified quenching and to characterize important parameters that govern the amplification process. Steady-state fluorescence quenching of PPESO3 by three cationic oxacarbocyanine dyes in methanol solution shows that the quenching efficiency does not correlate with the Forster radius computed from spectral overlap of the PPESO3 fluorescence with the cyanines' absorption. The quenching efficiency is controlled by the stability of the polymer-dye association complex. When quenching studies are carried out in water where PPESO3 is aggregated, changes observed in the absorption and fluorescence spectra of 1,1',3,3,3',3'-hexamethylindotricarbocyanine iodide (HMIDC) indicate that the polymer templates the formation of a J-aggregate of the dye. The fluorescence dynamics in the PPESO3/HMIDC system were probed by time-resolved upconversion and the results show that PPESO3 to HMIDC energy transfer occurs on two distinctive time scales. At low HMIDC concentration, the dynamics are dominated by an energy transfer pathway with a time scale faster than 4 ps. With increasing HMIDC concentration, an energy pathway with a time scale of 0.1-1 ns is active. The prompt pathway (tau< 4 ps) is attributed to quenching of delocalized PPESO3 excitons created near the HMIDC association site, whereas the slow phase is attributed to intra- and interchain exciton diffusion to the HMIDC.

Photo‐induced reduction of Noble metal ions to metal nanoparticles on tubular J‐aggregates

“…This value is approximately 5 orders of magnitude higher than values reported in the case of conventional bimolecular static quenching and gives clear evidence for super quenching. Similar values are obtained by other authors for dye aggregates [18] or conjugated polymers [19], and values up to 10 11 M −1 were found for conjugated polymers where gold nanoparticles were used as quenchers [33].…”

“…Nowadays, this phenomenon is often called super quenching and a significant subject of research not only in dye aggregated structures [17,18], but also in other materials such as conjugated polymers [19]. However, in most cases, the detailed molecular structure of the aggregated system is either unknown or, as in case of conjugated polymers, amorphous.…”

Study on the interaction between nitroxide free radical and conjugated polyelectrolytes by fluorimetry

“…By fitting the data with the linear equation, the Stern-Volmer quenching constant in low TEMPO concentrations range is found to be 94 mol/L. The quenching of anionic conjugated polyelectrolyte PPE-SO 3 by cationic quencher has been investigated (1,15,18,19). The Stern-Volmer constants (Ksv) for MV 2+ quenching of PPE-SO 3 were in the range 10 6 -10 7 mol/L (15).…”

“…Conjugated polyelectrolytes (CPEs) are π-conjugated polymers that feature ionic solubilizing side groups (1). These materials show many of the interesting and useful properties exhibited by π-conjugated polymers, such as high fluorescence quantum yields, unique solution behaviour, the ability to interact electrostatically with other charged species, and an extraordinarily high sensitivity to fluorescence quenchers (2).…”

Conducting polymer: silver interface, morphology and properties

“…Incorporation of the side chains having ionic groups gives rise to new properties specific for polyelectrolytes. Polymeric materials that combine electrical conductivity of semiconductors with ionic conductivity of electrolytes are regarded to as conjugated polyelectrolytes [25][26][27][28].…”