A SPECTROSCOPIC STUDY OF PHOTOIRRADIATED CELLULOSE

The influence of photoirradiation on cellulose was studied by means of fluorescence, Fourier transform IR and UV-visible reflectance spectro scopy. Samples of cellulose were irradiated with the entire spectrum o f a medium pressure Hg lamp, with the light from the Hg lamp filtered through a glass filter, or selectively with monochromatic light of dif ferent wavelengths. The emission spectra of untreated cellulose sample s and of differently irradiated samples were recorded after various ex posure times. Irradiation with the unfiltered radiation from the Hg la mp caused a strong increase in the emission intensity and a gradual sh ift in the emission maximum to longer wavelengths. After irradiation f or 96 h a pronounced band at 1733 cm(-1) was seen in the diffuse refle ctance IR Fourier transform spectrum of the sample, indicating the for mation of carbonyl groups as a result of the treatment. Irradiation wi th filtered light from the Hg lamp caused a small decrease in the emis sion intensity and shifted the emission maximum from 445 to 462 nm. Ex posure of cellulose to monochromatic light of 350 nm wavelength caused a gradual fading of the fluorescence with increased exposure time and a small shift in the emission maximum to longer wavelengths. After th e sample had been allowed to stand in the dark, the emission intensity was almost completely restored to its original value, but the red shi ft of the emission maximum caused by the irradiation remained unchange d.