Colloidal stability improvement of cobalt ferrite encapsulated in carboxymethylated cashew gum

Colloidal stability in water media is a critical issue for several applications of magnetic nanoparticles (MNPs). In this work, we discuss the colloidal stability improvement of CoFe2O4 after encapsulation in carboxymethylated cashew gum (CMCG), which is a natural, biocompatible, and low-cost modified polymer. Microscopic and vibrational analyses of the obtained material CoFe2O4@CTAB@CMCG, indicated a sort of polymer-caged MNPs aggregate (mean diameter of 78 nm) in which the magnetic core is surrounded by the CTAB (hexadecyltrimethylammonium bromide) surfactant whose polar tails interact with CMCG resulting in a negatively charged layer. Such arrangement explains the colloidal stability increment as deduced from zeta potential values of − 34 mV (in water) and − 14 mV (in PBS) for CoFe2O4@CTAB@CMCG in respect to CoFe2O4@CTAB (+30 mV in water). Despite the dilution effect imparted by the non-magnetic mass of CMCG, a saturation magnetization of 70.16 emu g−1 was determined for CoFe2O4@CTAB@CMCG meaning the material maintains the magnetization after encapsulation. Our work, therefore, not only introduces a low-cost strategy in line with the awareness about environmental issues but also adds value to the cashew gum which is a typical and abundant product from the northeast region of Brazil.