| Abstract: | CONCLUSION. We have provided experimental evidence demonstrating the very different behaviour of triplet states of aromatic carbonyls in lignin and in dilute solution. These differences result, we believe, from the very restricted motion within the lignin structure relative to fluid solution. By using oxygen saturated samples rather than air saturated samples, we have been able to establish for the first lime that dynamic quenching by oxygen occurs within TMP. We have also confirmed our previous results on the effect of methoxylation of phenolic hydroxyl groups within lignin. On the basis of our model studies, we suggest that the most likely explanation for this is that triplet carbonyl groups are quenched statically by hydroxyl groups within the lignin structure on timescales less than 20 ns thus reducing the amount of transient detected in our laser photolysis experiments. |
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