Evidence for the Participation of Singlet Oxygen in the Vat–dye Photosensitized Degradation of Cellulose

Abstract

A study has been made of the vat-dye photosensitized degradation of cellulose. Whilst the part played by the dyes in direct h ydtvgen abstraction from a cellulose substrate cannot be overlooked, it is apparent that the role played by singlet oxygen is important. The ability of a dye to produce singlet oxygen has been studied by measuring the amount of tetraphenylcyclopentadienone the dye can photooxidize. Luminescence spectroscopy has been employed in order to gain information about the excited state energies of the dye molecules, and an electron spin resonance study of the dyes in rigid media has been carried out in order to obtain information about the triplet state. formed in its high energy 'Z'g state by energy transfer from the triplet state of the dye to groundstate molecular oxygen. l t would appear that the singlet oxygen is initially