Chitosan Films with Morphology Modified by Cellulose Nanofibers Investigated by SERS Spectroscopy

In this study, it was investigated chitosan (CHIT) films in the presence or absence of cellulose nanofibers (CNF) and silver nanoparticles (AgNP), whose chemical interactions involving metallic surfaces were characterized by surface-enhanced Raman scattering (SERS) spectroscopy. Changes in the morphology were analyzed through atomic force microscopy (AFM) and scanning electron microscopy (SEM). SEM and AFM micrographs revealed that the incorporation of CNF significantly altered CHIT films, leading to changes in the polymer topography and surface texture due to intimal interactions between CNF and the CHIT matrix. Raman spectra of CHIT and CNF/CHIT films showed similar profiles, reflecting comparable molecular structures of both modified biopolymers. However, SERS spectra of both films, after recovering with AgNP, demonstrated distinct spectral profiles. Innovatively, density functional theory (DFT) calculations of an oligomer model for CHIT were employed to assign the vibrational modes observed in the SERS spectra, which allowed identify key interactions between CHIT moieties and AgNP surfaces. SERS results revealed that chemical adsorption of CHIT on AgNP surfaces occurs through interactions of glycosidic oxygen and amino groups. Such findings provide insights into the structural and chemical behavior of this nanocomposite, highlighting its potential for advanced biological applications.