In this work, the potential of Ni1 − xCoxFe2O4 (x = 0.0, 0.3, 0.5, 0.7, 1) bifunctional nanocomposites as nanocarriers in drug delivery systems and electrode material in supercapacitors was investigated. The nanocomposites were successfully synthesized by a simple and eco-friendly thermal treatment method using rosemary leaf extract, avoiding the need for harmful reducing or capping agents. The investigation into the cytotoxicity of ternary blended transition nanoferrite, employed as quercetin (Que) nanocarriers (NCs) in drug delivery systems, was conducted using the MTT assay. The cell viability ranged from 20% to 37% at the highest concentration (60 μg/ml) against cancer cells and resulting in a cytotoxicity of 35% to 43% against HEK 293-T cell line. By cyclic voltammetry (CV) characterizations, we also demonstrated the excellent performance as electrode material for supercapacitors of the as-prepared mixed ternary-transition-metal ferrites. The NiCF73 sample (Ni0.7Co0.3Fe2O4) had a better specific capacitance value at 2 mV/s scan rate equal to 2014 F/g. The results showed that by controlling the biocompatibility and electrochemical properties of Ni1 − xCoxFe2O4 nanocomposites, their performance in various practical applications in the biomedical field, as well as in wastewater treatment and water desalination applications, can be improved.
