Title

Effects of Ionic Strength on Aqueous Solutions of Xanthene Dyes

Poster Number

44

Format

Poster Presentation

Abstract/Artist Statement

Xanthene dyes tend to aggregate even in dilute aqueous solutions causing dimer formation, or higher order aggregates, which are strongly affected by structure, concentration, ionic strength, temperature, and the presence of other organic molecules. Rhodamine 6G was studied as a function of temperature in the range of 10 - 75°C in the absence and presence of ~2.0 M aqueous sodium chloride. The presence of electrolytes clearly induces dimer formation. The DATAN (DATa ANalysis) 3.1 software was used to determine the relative amounts of monomer and dimer present in solution, and the equilibrium constant for dimerization, in the presence of electrolytes, is 8.4 x 103. The Gibbs free energy of dimer formation is -22.4 kJ/mol and a van’t Hoff plot gives a standard enthalpy of dimerization of -39.2 kJ/mol. Then the standard entropy of dimer formation is calculated to be -56.5 J/(mol*K).ar.

Location

DeRosa University Center, Ballroom B

Start Date

1-5-2010 1:00 PM

End Date

1-5-2010 3:00 PM

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May 1st, 1:00 PM May 1st, 3:00 PM

Effects of Ionic Strength on Aqueous Solutions of Xanthene Dyes

DeRosa University Center, Ballroom B

Xanthene dyes tend to aggregate even in dilute aqueous solutions causing dimer formation, or higher order aggregates, which are strongly affected by structure, concentration, ionic strength, temperature, and the presence of other organic molecules. Rhodamine 6G was studied as a function of temperature in the range of 10 - 75°C in the absence and presence of ~2.0 M aqueous sodium chloride. The presence of electrolytes clearly induces dimer formation. The DATAN (DATa ANalysis) 3.1 software was used to determine the relative amounts of monomer and dimer present in solution, and the equilibrium constant for dimerization, in the presence of electrolytes, is 8.4 x 103. The Gibbs free energy of dimer formation is -22.4 kJ/mol and a van’t Hoff plot gives a standard enthalpy of dimerization of -39.2 kJ/mol. Then the standard entropy of dimer formation is calculated to be -56.5 J/(mol*K).ar.