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Effects of Charge and Structure of Hyaluronic Acid on the Luminescence Quenching in Aqueous Solution
Author(s) -
Kluge Thomas,
Masuda Akiko,
Yamashita Koichi,
Ushida Kiminori
Publication year - 1998
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1998.tb02543.x
Subject(s) - chemistry , aqueous solution , ruthenium , quenching (fluorescence) , photochemistry , reaction rate constant , excited state , kinetics , luminescence , fluorescence , catalysis , materials science , organic chemistry , physics , optoelectronics , quantum mechanics , nuclear physics
The quenching of electronically excited Ru(bpy) 3 2+ (bpy = Tris‐2,2′‐bipyridine) by methylviologen (MV) and ferricyanide (FC) in aqueous solutions of hyaluronic acid (HA) was studied. The structural and viscosity changes occuring with increasing HA concentration were found to influence the photophysical and photochemical properties of the sensitizer. Different kinetic models had to be used for the quenchers studied. The kinetics of the quenching of *Ru(bpy) 3 2+ by MV can be described by the pseudophase model, which indicates that the rate for the exchange of the quencher between the microdroplets is higher than that for the excited state decay of the Ruthenium complex. In contrast, the quenching by the negatively charged quencher, FC, can be described by the Infelta‐Tachiya equation, which indicates that the distribution of this quencher on the aqueous microdroplets is of the Poisson type and there is no exchange of quencher molecules during the lifetime of the sensitizer. The lifetimes of the excited Ruthenium complex, the unimolecular constants for its quenching by FC and the average concentration of the aqueous microdroplets increase with increasing HA concentration, reflecting the change in the solution structure during the transition from semidilute to concentrated regions. For MV no significant dependence of the quenching constant on the HA content of the solution was found. The reaction behavior of charged reactants in HA solution depends strongly on the sign of the charge.