Title

Adventures n Dimerization: An Exploration of Intermolecular Forces

Poster Number

4

Format

Poster Presentation

Abstract/Artist Statement

One of the oldest synthetic dyes, Rhodamine 6G was used in the first flashlamp-pumped dye laser as well as the first continuous-wave dye laser. Applications today utilize its fluorescing capabilities in biochemical research, and its photophysical properties in modern dye lasers. However, Rhodamine 6G in solution readily forms dimers, which affect laser efficiency. This investigation seeks to understand what kinds of intermolecular forces cause dimerization of this dye in aqueous solution. Utilizing visible spectroscopy, absorbance spectra of Rhodamine 6G in aqueous solution were studied as a function of temperature. As temperature increases, the monomer to dimer ratio increases, indicating that dimer formation is exothermic. Using DATAN software algorithms to analyze the change in monomer to dimer absorbance spectra ratios from 20 to 80 °C, the equilibrium constant for the process at 25°C is found to be about 5 x 103 which corresponds to an approximate G° of -20 kJ/mol. Utilizing this data, a constant H° from 20 to 80 °C is found to be about -40 kJ/mol, in agreement with the expectation that dimer formation is exothermic. The value of G° is similar in energy to weak bond formation, implying that a combination of electrostatic and van der Waals forces are what drive Rhodamine 6G to dimerize. Furthermore, literature on Rhodamine 6G structure suggests the existence of two different dimer conformations, whose forces are in agreement with our findings. Future studies of these structures are the key to minimizing their existence and thereby optimizing laser efficiency.

Location

DeRosa University Center, Ballroom B

Start Date

2-5-2009 1:00 PM

End Date

2-5-2009 3:00 PM

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May 2nd, 1:00 PM May 2nd, 3:00 PM

Adventures n Dimerization: An Exploration of Intermolecular Forces

DeRosa University Center, Ballroom B

One of the oldest synthetic dyes, Rhodamine 6G was used in the first flashlamp-pumped dye laser as well as the first continuous-wave dye laser. Applications today utilize its fluorescing capabilities in biochemical research, and its photophysical properties in modern dye lasers. However, Rhodamine 6G in solution readily forms dimers, which affect laser efficiency. This investigation seeks to understand what kinds of intermolecular forces cause dimerization of this dye in aqueous solution. Utilizing visible spectroscopy, absorbance spectra of Rhodamine 6G in aqueous solution were studied as a function of temperature. As temperature increases, the monomer to dimer ratio increases, indicating that dimer formation is exothermic. Using DATAN software algorithms to analyze the change in monomer to dimer absorbance spectra ratios from 20 to 80 °C, the equilibrium constant for the process at 25°C is found to be about 5 x 103 which corresponds to an approximate G° of -20 kJ/mol. Utilizing this data, a constant H° from 20 to 80 °C is found to be about -40 kJ/mol, in agreement with the expectation that dimer formation is exothermic. The value of G° is similar in energy to weak bond formation, implying that a combination of electrostatic and van der Waals forces are what drive Rhodamine 6G to dimerize. Furthermore, literature on Rhodamine 6G structure suggests the existence of two different dimer conformations, whose forces are in agreement with our findings. Future studies of these structures are the key to minimizing their existence and thereby optimizing laser efficiency.