Composite magnetic properties of cobalt ferrite nanoparticles embedded in bacterial nanocellulose of different porosity levels

Abstract

A simple and novel strategy for tuning the macroporous structure of bacterial nanocellulose allows for embedding nanoparticles on the template. Here, cobalt ferrite nanoparticles were co-precipitated in-situ at two templates with different porosities. Different analytical techniques like SEM, XRD, TGA, and PPMS allow for characterizing the properties of the prepared magnetic nanocomposites. After eight months of aging at room conditions, lyophilized bacterial nanocellulose preserved the macroporous structure (porosity ∼ 46%). However, rehydration and re-lyophilization of the cellulose decrease the template porosity (∼8%). The cobalt ferrite nanoparticles, growth on high and low macroporous templates, were single-crystalline and microstrain-free. The nanoparticle's shape and mean size do not change with the porosity of the template, but the cluster size does. However, the differences in porosity on templates allow tuning the nanoparticle concentration and then its magnetic interactions (in high macroporous near 63%, and low about 43%) in the nanocomposites. Magnetic data confirm the influence of the template porosity on the magnetic particle concentration. The magnetic behavior as a temperature function (effective magnetic anisotropy constant, coercive force, and reduced remanence) is dependent on the template porosity. These dissimilarities were correlated with cluster size variations, where the differences in the aggregation modify the magnetic dipolar interactions among particles.