Evaluation of photoexcitation energy transfer in lignophenol

Abstract

Although lignopheols, which are linear-typed lignin derivative macromolecules with only small amount of random conjugations, showed light-beige appearances in powders and brown in solutions, almost no absorbance in visible light region > 400 nm. These appearances were produced by relaxation processes such as fluorescence influenced by inter-/intramolecular interactions. Differences in peaks between UV-Vis and excitation spectra strongly implied that there are widespread and multi-stepped relaxation processes. Analyses of energy transfers in the lignophenols compared to damaged alkali lignins with rich conjugations using ketones as energy acceptors were carried out by Stern-Volmer analysis. It is found that there are multi-stepped energy transfers in lignin macromolecules via located conjugations by comparison between UV-Vis and excitation spectra and by analyses of synchro fluorescence spectra. Especially hardwood lignophenol showed highest ability for energy transfers twice larger than softwood lignophenols.