Silver nanoparticles-loaded carboxymethyl cellulose nanocomposites: structural, morphological, optical, dielectric, and antibacterial properties

Abstract

Multifunctional nanocomposites were prepared by incorporating varying loadings of silver nanoparticles (Ag NPs) into a sodium carboxymethyl cellulose (CMC) matrix using the solution casting technique. The films produced were systematically examined for their structural, morphological, optical, dielectric, and antibacterial characteristics. XRD confirmed the formation of crystalline Ag phases within the predominantly amorphous CMC matrix. FTIR shows changes indicating a shift in the local chemical environment of CMC functional groups, suggesting interactions between the oxygen-containing groups of CMC and the Ag nanoparticles, as well as a disruption of the native hydrogen bonding network of the polymer matrix. TEM examination revealed statistically distributed quasi-spherical Ag nanoparticles with an average diameter of around 38 nm, whereas FESEM/EDX indicated the presence of Ag particles with different sizes, including clustered structures. UV–Vis diffuse reflectance analysis indicated a notable reduction in the optical band gap as the concentration of silver NPs increased. The refractive index dispersion of the CMC/Ag nanocomposites strongly depended on Ag loading. The highest refractive index values (1.26–1.60) were obtained for 1 wt.% Ag, followed by 3 wt.% and 6 wt.%, whereas the lowest values (1.06–1.14) were observed for 9 wt.% Ag. Dielectric measurements revealed an increase in conductivity with increasing Ag concentration, and the charge transport mechanism followed the Correlated Barrier Hopping (CBH) model. Furthermore, the CMC/Ag nanocomposites exhibited enhanced antibacterial activity against both Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria, with inhibitory efficacy increasing with increasing Ag NP concentration. These results illustrate the synergistic effect of Ag nanoparticles and the CMC matrix on the physicochemical characteristics of the nanocomposites, making them promising candidates for optoelectronic, dielectric, and biological applications.