Solvent Effects on the Spectroscopy of Dyes

Abstract

Linear solvation energy relationships (LSERs) were used to quantify the intermolecular interactions between solvents and two organic dyes - di-8-ANEPPS and RH-237. LSERs evaluate the sensitivity of a dye's wavelength of maximum absorbance or emission to solvent acidity (alpha), basicity (beta), polarity/polarizability (pi*), and excess polarizability (delta). The quantification of the sensitivity of a dye to these parameters (alpha, beta, pi*, and delta) allows for the characterization of the dye's ability to interact through dipole-dipole, dispersion, and hydrogen bonding interactions. To develop these relationships required the use of UV -visible and fluorescence spectroscopy to measure the wavelengths of maximum absorbance and emission of the dyes. The results of di-8-ANEPPS show that solvent basicity, acidity and polarity/polarizability affect the spectroscopy of the dye, meaning di-8-ANEPPS is polar and can accept and donate hydrogen bonds in solution. Similar results were found for RH-237. The results, however, are difficult to interpret because nonpolar solvents could not be incorporated in the LSERs due to solubility limitations. Work is currently in progress on Coumarin 30. The long-term goal of the research is to use the dyes to study surfactants in order to enhance oil recovery from reservoirs.