Fluorescence quenching experiments in a restricted reaction space: The effect of ionic strength on the reaction rate and on the distribution of ions around a polyelectrolyte
Conference
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OSTI ID:141710
- Univ. of Texas, Austin, TX (United States)
Time resolved and steady-state fluorescence quenching experiments have been performed for 9-ethanol anthracene (9-EA) covalently bound to a polymer of polymethacrylic acid (PMA). The loading was low enough to give on average less than one chromophore per polymer. Solutions of this polymer (9-EA-PMA) were basified with KOH to a pH of 11 in water to yield a deprotonated polymer. The quencher was Tl{sup +}(from TiNO{sub 3}). The source for extra ionic strength was K{sup +} (from KNO{sub 3}). Quenching experiments were performed as a function of the quencher concentration and the ionic strength. The quencher concentration ranged from 0-5 mM and the ionic strength ranged from 2-100 mM. At each ionic strength a Stern-Volmer analysis was performed on both the steady-state and time resolved data. From these results there was no indication of static quenching. However, due to the negative curvature of the Stern-Volmer plots the authors postulate that some of the chromophores are inaccessable to the quenchers. Experiments were also performed using Cu{sup ++} (Cu(NO{sub 3}){sub 2}) as a quencher. Positive curvature in the Stern-Volmer plots were obtained as well as indications of static quenching. Positive curvature in the Stern-Volmer plots were obtained as well as indications of static quenching. Simulations are in progress using a Poisson-Boltzmann distribution for the ionic atmosphere around the polyelectrolyte and the Smoluchowski equation for the diffusive motion of the quenchers. Progress in fitting the above kinetic quenching data to a molecular level will be described.
- OSTI ID:
- 141710
- Report Number(s):
- CONF-930304--
- Country of Publication:
- United States
- Language:
- English
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