Reversed double-beam photoacoustic spectroscopic analysis of photoinduced change in absorption of cellulose fibres.

Photoabsorption properties of cellulose fibres under continuous and modulated irradiation were investigated in situ by the use of reversed double-beam photoacoustic spectroscopy (RDB-PAS). This photoacoustic (PA) measurement enabled observation of ultraviolet- and visible light-induced, electron trap filling, and reductive change on the surface of the fibres. Energy-resolved measurements and analysis of the kinetics of photoinduced de-excitation suggested that electrons that accumulated in the different cellulose crystalline phases had moderate reactivity toward molecular oxygen. Saturation limits of the intensities of the PA and RDB-PAS signals under de-aerated conditions in the presence of surface-adsorbed methanol were estimated for softwood and hardwood cellulose samples. The results suggest that the RDB-PAS technique is a feasible method for the estimation of the electron trap distribution, which is a potential measure of the density of crystalline cellulose defects.

Properties of ultrasound extracted bicomponent lignocellulose thin films.

Agricultural and forest residues obtained after harvesting are promising renewable sources, suitable as a source of pulp for cellulose nanocrystal manufacturing. Cavitation-assisted softening of the lignin-carbohydrate matrix offers sample opportunity for cellulose fibril liberation and degradation of amorphous cellulose. The present work addresses cavitation assisted cellulose fibril and crystal liberation and film forming properties of the supernatant phase of treated agricultural and forest residues. The effectiveness of this method has been evaluated according to crystallinity indices and hydrogen bond energies, as measured by FT-IR analysis. It has been observed that the use of cavitation increased the crystallinity and caused partial removal and degradation of the lignin matrix. Overall, it appears that considerable improvement of crystallinity can be obtained from agricultural and forest residues through the use of cavitation.