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
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.