E-mail: henrik.tylli@csc.fiABSTRACT
A clear photochromism, comprising a fairly rapid emission decrease during irradiation
at 350 nm and a slower emission recovery in the dark at room temperature was observed for
cellulose samples.
Similar behaviour was found for cotton cellulose, for cellulose immersed into water and
for microcrystalline cellulose.
The emission recovery was less efficient for samples immersed into deaerated water.
Thus, a chromophore regeneration mechanism not dependent on the availability of oxygen is
supported.
Samples of microcrystalline cellulose show a considerably faster emission recovery than
cotton cellulose.
Cellulose treated with ozone shows a more pronounced photochromism than untreated
cellulose. Thus, carbonyl and lactone type structures are likely to be involved in the
rearrangements.