Excitation Energy Transfer in Branched Dendritic Macromolecules at Low (4 K) Temperatures

To understand the mode of energy transport in branched dendritic macromolecules, the optical excitation of a dendritic core (A-DSB) at low temperature (4.2 K) was investigated. Fluorescence depolarization measurements were utilized to probe the energy-transfer processes in the branching center at several different temperatures. We found that the anisotropy decay shows an interesting trend at low temperature where depolarization times decreased and the residual anisotropy value also decreased with decreasing temperature. The very fast anisotropy decay suggests a coherent mechanism of energy transport in these systems at low temperature. The contribution of inhomogeneous broadening is suggested as an important factor in the temperature dependence of the anisotropy decay and residual value. The change in inhomogeneous linewidth is responsible for this type of anisotropy behavior.