Abstract
A combined theoretical and experimental approach has been applied to study the 1s electron-energy surface properties of cellulose, chitin, synthesized chitin nanorods and chitosan using density functional theory and high-resolution photoelectron spectroscopy. This allows to reliably distinguish the contributions of surface hydrocarbon impurities in the photoelectron spectra and to examine in detail the chemical states of the polysaccharide surfaces. Although a stoichiometric structure is suggested for the cellulose surface as more likely, a mechanism for possible degradation of the surface including removal of the OH group bonded to glucose ring is also contemplated. The good agreement between theoretical and experimental results allows suggesting a chitosan-like structure for the surfaces of as-prepared chitin and of chitin nanorods. In addition to the dominant concentration of amino NH2 groups on these surfaces, a small amount of acetyl amine NH2COCH3 groups is also observed on the as-prepared chitin. It is possible that protonated amino NH3+ functional groups instead of acetyl amine are present on the crystalline surface of chitin nanorods. The possible destructive role of X-ray radiation on the studied surfaces is also discussed.