Studies on the natural fluorescence of wool and wool grease
The principal aims of the work were to further the current knowledge of the natural fluorescence of wool and wool wax, to characterise the species responsible and to thoroughly investigate the light induced changes. The natural visible fluorescence of Merino fibres was found to vary along the length of the fibre, from highly fluorescent tips to barely fluorescent roots. It would appear that the same species' are responsible for the fluorescence at the tip and root. An increased level of fluorescence was observed when the disulphide bonds of cystine were oxidised to cysteic acid residues, due to the removal of the quenching disulphide bond. Each of the morphological components examined (cuticle, cortex and cell membrane complex) were fluorescent. Chemical bleaching treatments caused an increase in the fluorescence intensity of the components, with the same emitting species being responsible as in the nonbleached. Fluorescent lamps and laser irradiation were used to investigate the (different) effects of UV and blue light upon the fluorescence intensity of wool. UV irradiation caused a rapid increase in intensity which was accompanied by a definite protective effect being exhibited by the wool yolk. The enhancement of the white appearance in photobleached wool is not due to the production of UV absorbing species which exhibit blue fluorescence, but to the destruction of yellow Coloured residues. Northlight fluorescent lamps led to no change in the level of fluorescence whereas blue laser light caused a decrease. The level of natural fluorescence decreased when wool, embedded in immersion oil or glycerol, was irradiated with UV light. The effect of four reducing agents on wool was investigated:in the presence of UV irradiation, blue light irradiation and in the dark. The agents fell into two groups. The first group (Rongalit C and sodium hypophosphite) had little effect on their own but in the presence of irradiation retarded the effect of light. The second group (BlankitD andt hiouread ioxide)h ada n effect on their own and upon irradiation acted as photosensitisers causing extensive photobleaching. The difference between the two groups was attributed to the pH of the solutions used. The whitenin gobserved was (generally)d uet o the destruction of visible absorbing chromophore rsather than to the production of UV absorbing chromophore which exhibit blue fluorescence. Wool yolk is highly fluorescent. The amount of wool yolk/intensity of wool yolk fluorescence was found to vary along a Merino wool fibre from 'zero' at the tips to intense at the roots. The fluorescence of wool grease consists of two components - 'grease' and chlorophyll. The 'grease' fluorescence reveals the presence of a number of chromophores/components. An attempt to isolate these was only partly successful. Chlorophyll could be detected in all the wool greases examined. Weathering was found to result ultimately in a decrease in the fluorescence intensity arising from both the 'grease' and chlorophyll components. UV irradiation revealed that complex photochemical reactions were occurring. The role of wool yolk in the photoyellowing of wool in nature was investigated. Using special conditions no migration of fluorescent probes (models for photosensitisers) into the wool structure could be observed. The 'swelling' solvent, toluene/methanol (9: 1) was found to act as a photosensitiser.