Interactions between Rhodamine B and wool. Analysis of luminescence quenching and energy transfer

Abstract

A reflectance technique is described for quantitatively analysing the luminescence behaviour of wool in the presence of a dye, rhodamine B. The bound dye exhibits delayed fluorescence which is sensitized by one of the two naturally occurring phosphorescent groups in wool. At low dye concentrations the phosphorescence of wool is quenched mainly by simple optical screening and radiative transfer of energy from the donor phosphorescent group to the dye, but radiationless dipole-dipole T → S transfer becomes the predominant quenching process at high dye concentrations. This process is characterized by a critical transfer distance r_o of 5·0-5·3 nm. The fluorescence of wool is quenched only slightly by rhodamine B. The results indicate that optical screening and radiative energy transfer are the most important factors in the fluorescence quenching, and that radiationless dipole-dipole S → S transfer has a negligible effect on the fluorescence.