Fabrication of Cobalt Ferrite Nanoparticles with okra (Abelmoschus esculentus) extract in a Microwave Reactor

In recent years, metal oxide nanoparticles have been the object of study because of their unique optical, electronic, and magnetic properties. Cobalt ferrites (CoFe2O4) are materials that have high magnetocrystalline anisotropy and coercivity and are used in several applications such as contrast agents for magnetic resonance imaging, biosensors, magnetic hyperthermia, and localized drug delivery. In the present work, the functionalization of the nanoparticles was performed with bioactives from okra extract (Abelmoschus esculentus). The objective of this work is the synthesis of cobalt ferrites using cobalt nitrate, iron nitrate, and okra juice in aqueous solution in an Anton Paar Monowave 200 microwave reactor using different parameters to determine the best reaction time and volume. Five syntheses were performed using different volumes and reaction times in the G30 tube of the reactor, and the following characterizations were made: dynamic light scattering (DLS), scanning transmission electron microscopy (STEM), zeta potential, and elemental analysis. The samples were identified as AD-1, AD-2, AD-3, AD-4, and AD-5, and the parameters used in each one were as follows: in AD-1, 12 mL of volume over 40 min of reaction; in AD-2, 8 mL over 20 min; in AD-3, 6 mL over 20 min; in AD-4, 15 mL over 90 min; and in AD-5, 15 mL over 40 min, all at a temperature of 110 °C. In DLS, the average sizes of the nanoparticles were as follows: AD-1 262 nm, AD-2 233 nm, AD-3 137 nm, AD-4 535 nm, and AD-5 627 nm. For average zeta potential, the following were obtained: AD-1 32 mV, AD-2 24 mV, AD-3 15 mV, AD-4 21 mV, and AD-5 15 mV. Therefore, it is evident that the use of okra bioactives favors the formation of nanoparticles, probably due to the presence of charged groups, and the synthesis in the microwave reactor was more successful when smaller volumes and shorter times were used, as in the AD-3 sample, due to the greater homogeneity and control of this synthesis method, thus making natural okra polymers potential substitutes for synthetic polymers for the synthesis of cobalt ferrites.