Theoretical study of the optical properties of Rhodamine 6G in Ag-ethanol suspension

COMP 200

AlTrev C. Sykes, veesykes@yahoo.com, Center for Materials Research, Norfolk State University, 700 Park avenue, Norfolk, VA 23504 and Suely M. Black, smblack@nsu.edu, Department of Chemistry and Center for Materials Research, Norfolk State University, 700 Park Avenue, Norfolk, VA 23504.
It has been observed experimentally that R6G exhibits a new emission band at 612nm in solution of aggregated Ag nanoparticles. In this study, the equilibrium atomic geometry, electron energy structure, and optical properties of Rh6G dye molecules, in pure solvent and in the presence of Ag8 cluster have been obtained. Calculations of the optimal geometry of the two systems were carried out using Jaguar 4.2. The structures were obtained using the density functional theory with the B3LYP exchange-correlation functional, 3-21G* basis set, and the dielectric continuum model for methanol solvent. The first excitation energies were obtained for this structure using the 3-21G* and 6-31G* basis sets, at the B3LYP level. Gaussian 03 implementation of the ZINDO semi-empirical model was applied to that same structure, and optical transitions energies and intensities were obtained. The theoretically obtained excitation energies are compared to experimental values.