Spectroscopic studies of plasma-modified silver-exchanged zeolite and chitosan composites

Composite biomaterials can be formed by combining natural or synthetic, organic or inorganic materials which are exactly or partially compatible when in contact with a living organism. To greatly improve the utilization of these biomaterials, understanding its interaction with its environment or host is essential. In this work, naturally-occurring and locally-abundant materials such as zeolite (Z) and chitosan (Ch), were fabricated as a silver-exchanged zeolite/chitosan (AgZ-Ch) composite using a solvent casting approach. The composites were subsequently exposed to argon (Ar) plasma excited by a 13.56 MHz radio frequency (RF) power source. Fourier-transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and X-ray absorption spectroscopy (XAS) techniques were utilized to investigate the surface and subsurface properties of the AgZ-Ch composites. Results revealed different interactions within the bulk and on the surface of the composite. The interactions for the composite formation are dominated by the attraction of the AgZ species with the –OH and –NH2 functional groups of Ch. On the other hand, the surface composition of Ch was influenced by the etching effect of Ar with the –COCH3 termination from the Ch. This study showed that the surface layer prefers to be terminated with amine and hydroxyl groups instead of amide functional groups. The present work also demonstrated the use of plasma irradiation to tune AgZ-Ch composite surface and tailor the reactivity of the functional groups on the surface.