Synthesis, Characterization, and Antibacterial Performance of Chitosan–Cinnamaldehyde Nanoparticles

Abstract

Abstract Chitosan–cinnamaldehyde biopolymer nanoparticles were synthesized via a green and facile Schiff-base approach and subsequently evaluated for their structural and antibacterial properties. Structural characterization using FTIR confirmed imine (C = N) formation, while XRD analysis revealed a noticeable reduction in crystallinity from approximately ~ 40–45% for pristine chitosan to ~ 28–32% for the modified nanoparticles, indicating disruption of the native polymer packing. The average crystallite size estimated from XRD using the Scherrer equation was found to be in the range of ~ 18–35 nm, depending on composition. SEM analysis demonstrated improved nanoparticle dispersion with reduced agglomeration after cinnamaldehyde modification. Antibacterial activity assays showed pronounced inhibitory effects against both Gram-positive and Gram-negative bacteria, with inhibition zone diameters reaching up to ~ 18–22 mm, significantly higher than those of unmodified chitosan. The enhanced antibacterial performance is likely associated with the combined effects of imine functionalization, reduced crystallinity, and improved nanoparticle dispersion. These results highlight the potential of chitosan–cinnamaldehyde nanoparticles as effective antibacterial biopolymer systems prepared via an environmentally benign strategy.